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'[EE]: AIR CONDITIONER COMPRESSOR SOFTSTART'
2008\09\15@100654 by Carl Denk

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We have a 12.5 KW standby generator, and while online and the house air
conditioner starts up, there is a brief voltage drop with lights
dimming, but not enough to have to reset clocks, while the carburetted
gasoline engine's mechanical governor opens the throttle to the demand
of the new load. Otherwise the generator handles the load fine. Looking
for a soft start controller or other way to flatten the peak. My HVAC
contractor indicates there is a kit available that includes a capacitor,
and he's checking that out with the manufacturer. Apparently the device
acts like  the capacitor on a capacitor start motor.

Here's the data on the exterior unit:
Model: Rheem RAML-036JAZ
Voltage: 220 VAC 60 hertz
Breaker: 30 amp
RLA: 15.4 AMP (running amperage)
LRA: 83 AMP (locked rotor amperage)
Scroll type compressor

I am able to build a electronic device, familiar with PIC's, not that
great with design though, in particular AC.

Thanking in advance. :)

2008\09\15@143715 by Martin

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Irrelevant question, but why do you need A/C if you're running on what
is presumably emergency power?
-
Martin

Carl Denk wrote:
{Quote hidden}

2008\09\15@150954 by Carl Denk

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If the temperature is where the house is uncomfortably warm, and a tree
branch falls across the line, or other fault, brings the utility power
down we like the air conditioning on. The main function of the generator
is to provide power for a sump pump, but we like to maintain our life
style, and not depend on external issues. The generator most of the time
runs on our natural gas well, with gasoline or propane backup, so it
doesn't cost much to run the generator,maybe we even save some money
compared to the cost per KWH. Last night the issue was moderately high
winds (peak 60 mph), last summer the trees had high growth of new
foliage, and a tree branch somewhere along the 10 miles of wire between
us and the substation got blown against the wire and the substation
breaker reset 4 times within 1/2 hour. I got tired of XP booting and
doing chkdsk. Just pulled our main service disconnect breaker and let
the generator do it's thing for 4 hours until the winds died down. The
power company has a work order to check the line.

Martin wrote:
{Quote hidden}

2008\09\15@151020 by Andre Abelian

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Where are many things that can effect.

1. where is your generator connected to? Is it on main panel?
   Just the way your main power is?
2. you need to check voltage drop on generator side what's the lowest
   It gets? When air condition is turning on
3. how thick is your generator wire ?
4. Do not believe every thing company's are saying you need to do your
   Own measurement
5. if generator side voltage drop is low that means you have wiring
problem
6. if generator side voltage is high that means it is your generator's
fault not producing enough power.
7. connect amp meter in series and volte meter measure how much is the
load
  And you can tell if your load is high or generator is weak.

Andre    





{Original Message removed}

2008\09\15@170039 by Carl Denk

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Andre Abelian wrote:
> Where are many things that can effect.
>
> 1. where is your generator connected to? Is it on main panel?
>     Just the way your main power is?
>  
Yes, there is an automatic transfer switch that transfers whole house to
generator.
> 2. you need to check voltage drop on generator side what's the lowest
>     It gets? When air condition is turning on
> 3. how thick is your generator wire ?

All wire and equipment is sized per NEC.

> 4. Do not believe every thing company's are saying you need to do your
>     Own measurement
Are you saying the data I have quoted on amperage could be inaccurate?
Or the compressor defective where it is drawing more current than claimed?
>  
> 5. if generator side voltage drop is low that means you have wiring
> problem
>  
I can hear the generator speed drop, and it shows in the frequency drop,
maybe down to 50 hertz. I don't have instruments to get an actual peak
or minimum.
> 6. if generator side voltage is high that means it is your generator's
> fault not producing enough power.
> 7. connect amp meter in series and volte meter measure how much is the
> load
>  
I don't have an ampmeter that will handle that load.
>    And you can tell if your load is high or generator is weak.
>  
Generator can handle 40 amp resistance heat in addition to misc. house
load, so I don't think it's generator being weak with 30 amp protected
compressor load. It's the few seconds that it takes the mechanical
engine governor to  open the throttle more and the engine to respond.
Other loads like 1/2 hp. pump with or without capacitor stating can
start stop without issues.
> Andre    
>
>
>
>
>
> {Original Message removed}

2008\09\16@122437 by Martin

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Carl Denk wrote:

> Generator can handle 40 amp resistance heat in addition to misc. house
> load, so I don't think it's generator being weak with 30 amp protected
> compressor load. It's the few seconds that it takes the mechanical
> engine governor to  open the throttle more and the engine to respond.
> Other loads like 1/2 hp. pump with or without capacitor stating can
> start stop without issues.


The generator takes a fixed amount of time to increase it's output as
you've guessed. My guess is that the A/C motor either has a low rotor
resistance so it's higher efficiency, but requires a huge startup
current, or it's a more typical motor but the compressor represents a
very large load upon startup at zero speed. So you need a way to reduce
the startup current or increase the immediately available current.

Perhaps you could roll together a controller that would increase the
generator RPM a little bit - half a second before the compressor is
triggered? It seems like that would be the simplest way to do it. You
would get a voltage surge but perhaps that's a bit better than a big
sag. I would think you could tune the delay time to have a minimal surge.

The harder way is to mechanically modify the generator or [hardest] is
to do something to the A/C compressor.

-
Martin

2008\09\16@123827 by Carl Denk

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I see on another thread mention of generator different connection
configurations, here's additional data on the generator:
Voltmaster
http://www.voltmasteramerica.com/products/1800-SP.htm


*MODEL*        *WATTS
1 Phase*        *KVA
1 Phase*        *MAX EFFICIENCY*        *SHAFT DIAMETER (Metric)*        *KEY
WAY (MM)*        *A*        *B*        *C*        *D*        *NET WEIGHT (KGS)*
EC12.5-1        12500        12.5        87        1.65 (42)        12        12.3(312)        20.3(516)
18.0(458)        16.1(409)        238(10


1800 RPM Single Phase

Generator type totally brushless with automatic voltage regulator
+/-1.5%, single phase, .8 power factor, Class H, bi-directional
rotation, reconnectable 12 wire, voltages 110 vac - 480 vac, 300%
overload for 20 seconds, CSA listed, frequency meter (included loose on
all models) - 50 hertz available consult factory, all models ready for
hardware connections. No circuit breakers, no receptacles.

Currently the generator is connected as Single phase 120/240 volts
Double delta connection. That can be easily changed to a Parallel
Zig-Zag connection.


Carl Denk wrote:
{Quote hidden}

>> {Original Message removed}

2008\09\16@125251 by Carl Denk

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Understand what you are saying. Say a solenoid on the generator's
throttle, maybe better a stepper motor, The generator is managed by a
TRI-PLC controller which has ability to control a stepper, relays, and
timers
1: Air conditioning thermostat signals request to PLC
2: Increase the generator speed
3: time delay, then start compressor
4: time delay, generator speed to normal

Although appears possible, and with a lot of learning curve for me, at
this point I prefer looking at generator connection configuration and
the soft start avenue. Thanks for the ideas. :)

Martin wrote:
{Quote hidden}

2008\09\16@134006 by Bob Blick

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Hi Carl,

The starting load of the air conditioner, 83 Amps, is higher than the
rating of the generator.

So it doesn't surprise me that the voltage dips when the A/C starts.

If your generator is rated for a 300% temporary overload, that does not
mean it will be producing rated voltage and frequency at that time.

Boosting the engine speed in anticipation of the air conditioner
starting is asking for trouble, please don't do it. You'll be stressing
your whole system even more.

The solutions I suggest are this:

If your HVAC contractor has a factory-approved kit that solves the
problem, do that. Or else:

Get a bigger generator.

Or just get a few small UPS units for the critical devices you have in
your house.

Cheerful regards,

Bob




On Tue, 16 Sep 2008 12:38:04 -0400, "Carl Denk" <spam_OUTcdenkTakeThisOuTspamalltel.net> said:

{Quote hidden}

--
http://www.fastmail.fm - Or how I learned to stop worrying and
                         love email again

2008\09\16@134006 by Marcel Birthelmer

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Would it be possible to modify the generator motor's flywheel to add kinetic
energy, much in the way a capacitor would store electrical energy? That way,
the increased load should not affect the frequency and output voltage so
significantly (but of course this would bring its own mechanical issues -
load on berings, etc.).
Regards,
- Marcel

On Tue, Sep 16, 2008 at 9:52 AM, Carl Denk <.....cdenkKILLspamspam@spam@alltel.net> wrote:

{Quote hidden}

> -

2008\09\16@141305 by Carl Denk

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   The drive between the engine and generator is a cog belt where the
belt and sprockets are standard off the shelf components made by more
than 2 manufacturers with taper lock sprockets. I would prefer not to
modify this area since they are standard parts readily available. Being
an emergency type piece of equipment, I have considered reliability and
quick repair to be high priority.  Also Then I do not have to address
the structural issues of shaft bending, bearing loads and harmonics.
Thanks for the input. :)

Marcel Birthelmer wrote:
{Quote hidden}

>> --

2008\09\16@141936 by Dr Skip

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Don't try anticipating the load! You will go over-voltage, and still won't
generate enough excess energy to provide for the starting. Besides UPS backups
on the critical brownout-sensitive devices, here are some creative ideas:

Since compressor startup is the issue, keep it running. Open some windows or
create vent ducting to route AC air outside instead of turning the compressor
off when at the set temp.

Or, add a buzzer or light to the thermostat such that when it goes to turn on
the compressor, it waits for a pushbutton press from you to actually close the
compressor relay (in operation during gen operation). You can determine when
the system gets jolted...

There really isn't any way to avoid this when the load is a big % of generator
capacity. They all do this. Basic physics. You need to store energy in the
system for the startup load - like a big cap in a power supply. Tough to do
with AC current though. ;) Mechanically, you could modify the compressor to use
a bigger motor and a magnetic clutch and keep the motor running, so the motor's
inertia would substitute perhaps, or a bigger gen flywheel, but then you'd need
a much bigger starter motor on the gen to turn it over!

You could also change the motor over to DC, power it with a DC supply off the
AC gen, and use big caps or battery in the supply. The other might be to
piggyback a DC motor to the compressor and use batteries to start the
compressor going, then apply AC from the gen. Use a centrifugal clutch on the
DC motor perhaps.

Just some odd thoughts....



Carl Denk wrote:
{Quote hidden}

2008\09\16@142437 by Carl Denk

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Bob Blick wrote:
> Hi Carl,
>
> The starting load of the air conditioner, 83 Amps, is higher than the
> rating of the generator.
>  
The compressor circuit is only protected with 30 amp breaker. Yes the
locked rotor current is high but only very brief period, don't know if
that startup spike goes that high. Some of the other issues with the
startup are:
1: Positive displacement pump, takes only a few turns and the pressure
is up there.
2: Pump needs to be running at near normal speed quickly where the motor
has the torque when the pressure builds. Makes slow soft start not good,
probably will lock before run.
3: Slow startup may create lubrication issues with motor.

> So it doesn't surprise me that the voltage dips when the A/C starts.
>
> If your generator is rated for a 300% temporary overload, that does not
> mean it will be producing rated voltage and frequency at that time.
>
> Boosting the engine speed in anticipation of the air conditioner
> starting is asking for trouble, please don't do it. You'll be stressing
> your whole system even more.
>  

Warning well taken. :)
> The solutions I suggest are this:
>
> If your HVAC contractor has a factory-approved kit that solves the
> problem, do that. Or else:
>  
Working on that through the HVAC contractor that did that install.
> Get a bigger generator.
>  
No, a 12.5KW for an house is big to begin with. That  is a 27 HP engine
doing everything it has if we have the electric heat on. I can run on
gasoline, and heat the whole house. :)
> Or just get a few small UPS units for the critical devices you have in
> your house.
>  
Nothing is dropping out, clocks may get a little off due to imperfect
frequency regulation over long period. We have run 26 hours straight on
generator, and it's fine.

Thanks for the input. :)

{Quote hidden}

2008\09\16@145026 by olin piclist

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Bob Blick wrote:
> If your HVAC contractor has a factory-approved kit that solves the
> problem, do that. Or else:
>
> Get a bigger generator.

Or what about screw the air conditioning during a power outage.  Do you
really need every last comfort when the power goes out?  I can see why you
might want to keep your refridgerator, well pump if you have one, etc,
operating, but the **air conditioner**!?  If you keep it to basics, even a
smaller generator would do fine.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\09\16@145851 by olin piclist

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Dr Skip wrote:
> Since compressor startup is the issue, keep it running. Open some
> windows or create vent ducting to route AC air outside instead of
> turning the compressor off when at the set temp.

That's really irresponsible, even if he's willing to pay for it.  You should
be ashamed of yourself for even suggesting it.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\09\16@150017 by Martin

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Dr Skip wrote:
> Don't try anticipating the load! You will go over-voltage, and still won't
> generate enough excess energy to provide for the starting. Besides UPS backups
> on the critical brownout-sensitive devices, here are some creative ideas:

I understand that anticipating the load could be risky, I don't
understand why you think it's a bad idea. Right now he has the line
voltage governing the speed of the engine.

When the thermostat calls for the compressor:

1. a motor contactor turns on the compressor.
2. Voltage almost instantly drops on the AC line
3. The governor pulls on the throttle (the governor is probably
overdamped too)
4. The engine vacuum drops and fuel input increases
5. Engine speed increases
6. voltage creeps back up to regulated value

Each of these steps takes time - and I probably left out a few.
Similarly is a control system for a switching power supply, say perhaps
a flyback converter. There's a big phase delay between voltage dropping
and duty cycle increasing. If you sense the load you can cut through
some of the feedback steps. I don't mean gun the engine for 5 seconds
before the A/C contactor is turned on.. I'm just saying he could design
a control system that used the thermostat as a feed-forward input.

> There really isn't any way to avoid this when the load is a big % of generator
> capacity. They all do this. Basic physics. You need to store energy in the
> system for the startup load - like a big cap in a power supply. Tough to do
> with AC current though. ;) Mechanically, you could modify the compressor to use
> a bigger motor and a magnetic clutch and keep the motor running, so the motor's
> inertia would substitute perhaps, or a bigger gen flywheel, but then you'd need
> a much bigger starter motor on the gen to turn it over!

The home A/C compressor is a sealed motor/compressor unit if it was
built in the last 25[?] years.

-
Martin

2008\09\16@150959 by Carl Denk

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The compressor is hermetically sealed, changing anything there is not
possible. The house is well insulated, and the compressor runs maybe 25%
of the time at most even on most hot humid days once the house is cooled
and dehumidified, House HVAC is zoned, so we are cooling half the house
unless visitors are occupying upstairs. Whatever happens needs to be
automatic, if we are sleeping or unavailable. Agree with storing energy
thought, the generator's belt sprocket is solid iron, maybe 12" dia. x
2" thick which is quite a mass to start with, not a lightweight aluminum
spoked sheave. Keep the brainstorming up. :)

Dr Skip wrote:
{Quote hidden}

2008\09\16@151002 by Thomas C. Sefranek

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-----Original Message-----
From: EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu [piclist-bouncesspamspam_OUTmit.edu] On Behalf Of
Olin Lathrop
Sent: Tuesday, September 16, 2008 3:00 PM
To: Microcontroller discussion list - Public.
Subject: Re: [EE]: AIR CONDITIONER COMPRESSOR SOFTSTART

Dr Skip wrote:
> Since compressor startup is the issue, keep it running. Open some
> windows or create vent ducting to route AC air outside instead of
> turning the compressor off when at the set temp.

That's really irresponsible, even if he's willing to pay for it.  You should
be ashamed of yourself for even suggesting it.

********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.
--


Olin,

I was SHOCKED to discover, when I worked at MIT Lincoln Lab.  (Annex 5) They
chilled the air continuously, and then electrically heated it back up to the
desired temperature!  WINTER and summer!

Tom

 *
 |  __O    Thomas C. Sefranek  @spam@WA1RHPKILLspamspamARRL.NET
 |_-\<,_   Amateur Radio Operator: WA1RHP
 (*)/ (*)  Bicycle mobile on 145.41MHz PL74.4

ARRL Instructor, Technical Specialist, VE Contact.
hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

2008\09\16@151311 by Martin

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Olin Lathrop wrote:
> Dr Skip wrote:
>> Since compressor startup is the issue, keep it running. Open some
>> windows or create vent ducting to route AC air outside instead of
>> turning the compressor off when at the set temp.
>
> That's really irresponsible, even if he's willing to pay for it.  You should
> be ashamed of yourself for even suggesting it.
>
>

He could reduce global warming. Everyone should point their air
conditioners outdoors!
=)
-
Martin

2008\09\16@151637 by Dr Skip

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No different from keeping the car running while waiting in a line or hundreds
of other similar techniques in common use. Based on the usage described, this
amounts to having the windows open while the A/C is on for a couple of hours a
year. There are also systems that bring in fresh outside air and introduce it
into the 'system'. Essentially the same thing, and these are commercial products.

Perhaps you'd be more comfortable with re-working the ducting and cooling
outside air and bringing it in as in the commercial systems, with the added
cost and no energy savings? Same thing, but this is easier, especially for a
couple of hours a year.

And finally, it is not irresponsible to consider all the possible solutions, it
 is only irresponsible if an irresponsible choice is taken and implemented.
Otherwise, there can be no discussion of all the choices, and in some cases,
the ordinarily 'irresponsible' choice may be the only one available in a
life-threatening situation, knowledge of which might not exist by filtering
cases in advance. Don't be afraid to talk about all the possibilities.... ;)


Olin Lathrop wrote:

>
> That's really irresponsible, even if he's willing to pay for it.  You should
> be ashamed of yourself for even suggesting it.
>
>
> ********************************************************************
> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
> (978) 742-9014.  Gold level PIC consultants since 2000.

2008\09\16@152406 by Carl Denk

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The air conditioning unit is 6 year vintage high efficiency unit, sized
for whole house, which is zoned, and able to if needed (been away from
house for a period with air off) cool the entire house in about an hour
to comfortable. I understand these high efficiency motor's starting
current is a much greater % than the running current for a regular motor.

I have been having conversation with our local power supplier, who is
offering a RF peak shaving controller for air conditioners, where I
would disconnect entirely from the grid and run off my gas well. They
aren't to the point as how to handle me. All I ask for is a dry contact.
I would have to program the PLC managing the generator, and provide a
way to transfer the automatic transfer switch with the PLC. It's an
ongoing conversation. It's a relatively small rural electric cooperative
where they know many customers and employees by first name.  All input
is welcome, and some don't see all the issues at first go around.

Olin Lathrop wrote:
{Quote hidden}

2008\09\16@152634 by Dr Skip

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See below.

Martin wrote:
> Each of these steps takes time - and I probably left out a few.
> Similarly is a control system for a switching power supply, say perhaps
> a flyback converter. There's a big phase delay between voltage dropping
> and duty cycle increasing. If you sense the load you can cut through
> some of the feedback steps. I don't mean gun the engine for 5 seconds
> before the A/C contactor is turned on.. I'm just saying he could design
> a control system that used the thermostat as a feed-forward input.

Because you can't be aware of the other loads as well. If another device drops
as it is 'anticipating', you would overvoltage. Not to mention, the throttle
isn't linear, so depending on loading, may be in different places. It's 'bump
up' would be dependent on current position as well. Not a simple task. Devices
online tend to be more sensitive to over voltage than under voltage as well, so
it's a riskier state.

If it was a system with very limited variables (loads) it could be
characterized and done, but you lose a lot of flexibility in usage too due to
the constraints you have to impose on the system.

>
>
> The home A/C compressor is a sealed motor/compressor unit if it was
> built in the last 25[?] years.

This is true. They're more theoretical ideas perhaps... ;)

However, it does lead one to other solutions, like a smaller A/C system that is
'backup A/C' that has less gen impact and could be used instead of the big A/C
when on gen, but integrated into the A/C system. The added benefit is that on
really hot days, it could boost total A/C capacity as well, if he's in a region
where A/C units have trouble keeping up in August...

2008\09\16@152903 by olin piclist

face picon face
Dr Skip wrote:
> No different from keeping the car running while waiting in a line or
> hundreds
> of other similar techniques in common use.

Just because people "commonly" do it, doesn't by itself make it a good idea.

********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\09\16@153342 by Carl Denk

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Was said:

Dr Skip wrote:
> Because you can't be aware of the other loads as well. If another device drops
> as it is 'anticipating', you would overvoltage.
>
As a new topic, that presently haven't got to the point of composing an
appropriate message, is load leveling the system that would include
pumps, freezer, refrig, etc. Not ready to attack that quite yet, so hold
thoughts for the moment.

2008\09\16@153356 by Martin

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Carl Denk wrote:
> The air conditioning unit is 6 year vintage high efficiency unit, sized
> for whole house, which is zoned, and able to if needed (been away from
> house for a period with air off) cool the entire house in about an hour
> to comfortable. I understand these high efficiency motor's starting
> current is a much greater % than the running current for a regular motor.

Hi Carl,
Consensus seems to be that anticipating the load as a feed-forward
control on your governor is "just bad" so I would increase the flywheel
weight (on the generator head)

It may actually increase the load transient response though. You
shouldn't have any issues with harmonics because it's mainly the engine
and things positively attached to the engine (not by belt..) that have
to worry about harmonics.

-
Martin

2008\09\16@153840 by Martin

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Dr Skip wrote:

> Because you can't be aware of the other loads as well. If another device drops
> as it is 'anticipating', you would overvoltage. Not to mention, the throttle
> isn't linear, so depending on loading, may be in different places. It's 'bump
> up' would be dependent on current position as well. Not a simple task. Devices
> online tend to be more sensitive to over voltage than under voltage as well, so
> it's a riskier state.

The "anticipation" is less so and more like a 50mS phase lead on turning
the generator up a little in front of the A/C turn-on. Done correctly
there shouldn't be a spike. Done incorrectly it will break things. Done
correctly will include protections. It's not "that wild" an idea.

-
Martin

2008\09\16@154954 by sergio masci

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On Tue, 16 Sep 2008, Martin wrote:

{Quote hidden}

Why not put the BIG flywheel on a seperate electric motor and use that (as
a generator) to supply current when there is a dip. I mean, isn't an
electric motor that is turning a BIG flywheel and had it's input current
cut off going to act as a generator anyway (taking energy from the
flywheel and converting it to electricty).

Regards
Sergio Masci

2008\09\16@155338 by Carl Denk

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I think the design of an anticipator is more than a little beyond my
skills. Digital design/construction at somewhat simple scale is OK, a
little analog for sensors is OK, some programming in C, Basic, MAD, and
a little assembler is OK.

Martin wrote:
{Quote hidden}

2008\09\16@155447 by Carl Denk

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I came to that conclusion myself on the throttle bit. Originally I
thought the soft start approach was the way to go, and was looking for
design info and build myself. Something along the lines of capacitor
start submersible well pumps - a capacitor, a relay the normally keeps
that cap charged, and on starting the relay has the capacitor briefly in
the circuit and the capacitor is discharged to provide some energy for
starting. The flywheel doesn't seem feasible since I would need to marry
the somewhat massive flywheel to the good sized cog sprocket that
exists. This would entail a big piece of steel, precision machining, and
then balancing the whole thing. At this point I'm waiting to hear from
the contractor whole is contacting the manfacturer (Rheem). Actually
it's not that much of a nuisance, the lights dim a little, but no
electronics drop out.

Martin wrote:
{Quote hidden}

2008\09\16@160540 by Carl Denk

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Interesting point. Instead of adding a motor, and going back to my
thoughts on load leveling, start previous to the air conditioner, a
pump, freezer, etc. and drop it off line as the compressor starts. The
item on the load leveling that's my hangup is without adding any
sensors, like a temperature at a freezer, how to detect that device
needs service by monitoring it's power line. Normally a device that
doesn't require service will be seen as high resistance, but when it
requires service, the motor resistance will be very low. I would want to
sense this resistance change and then close a relay (triac). And then
when the unit turns off detect that and open the relay. Think about it,
hold your thoughts for the moment, I'll start a thread in a few days.

sergio masci wrote:
{Quote hidden}

2008\09\16@161847 by sergio masci

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On Tue, 16 Sep 2008, Carl Denk wrote:

{Quote hidden}

I would have thought that if the motor / generator is being powered by
electricity from your gas generator, that when it sees a drop in
voltage it will resist the drop by putting out current itself.

Regards
Sergio Masci

2008\09\16@163007 by Bob Blick

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On Tue, 16 Sep 2008 15:38:00 -0400, "Martin" <KILLspammartinKILLspamspamnnytech.net> said:

> The "anticipation" is less so and more like a 50mS phase lead on turning
> the generator up a little in front of the A/C turn-on. Done correctly
> there shouldn't be a spike. Done incorrectly it will break things. Done
> correctly will include protections. It's not "that wild" an idea.

But you'd be upping the voltage to a near dead short. If at startup it
draws 83 amps at 220 volts, what's it going to draw at 260 volts? And is
that a good idea?

Basically right now he has the smallest possible generator that can run
his air conditioner. It's working just the way it should.

If anything, reduce the voltage to the air conditioner(if you can do it
without sacrificing current). That's probably what the factory "soft
start" kit attempts to do, and would be the only solution I'd advise.

Cheerful regards,

Bob

--
http://www.fastmail.fm - Email service worth paying for. Try it for free

2008\09\16@164118 by Dr Skip

picon face
I wouldn't worry about it then. After many years of 'practice' with remote and
standby gens, it sounds like you're doing quite well as is. If your goal is
something that works well while you sleep, you've got it. Adding complexity
isn't going to make life easier... ;)

One thing you can do, if you only see drops and not overages, is set your
voltage higher. Motors draw increasing current (power of 2 IIRC) as voltage
drops. The lower voltage caused by excessive current at startup exacerbates the
problem. If running at 110v or 105v, you might be able to go to 120+v. Also
measure voltage at devices to account for line loss if you want to set it to
get every last millivolt out of it. ;)

This isn't anticipating, just adjusting and setting....



Carl Denk wrote:
> it's not that much of a nuisance, the lights dim a little, but no
> electronics drop out.

2008\09\16@182059 by Carl Denk

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By adding a motor/generator set between the house and the generator, I
see 2 problems
1: A M/G set of the size needed would cost lots of $$, and that's not
within budget
2: I'm guessing at a minimum the M/G would have a maximum of 85%
efficiency, and I don't have that extra capacity. I selected the
generator/engine tight to required load, going bigger would get me into
a whole different type equipment. Although my equipment was selected for
reliability, the next step up is industrial quality as opposed to what
I'll call commercial, a big step from consumer.

sergio masci wrote:
{Quote hidden}

2008\09\16@191629 by Apptech

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> And finally, it is not irresponsible to consider all the possible
> solutions, ...

Lateral thinking must be avoided at all costs!
Stamp it out aborning !!
Hunt it down the corridors of the mind and kill it !!!
Root out fresh/new/different thought at (or before) source or it may yet
transform you !!!!
Kil ...


2008\09\16@191629 by Apptech

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> I was SHOCKED to discover, when I worked at MIT Lincoln Lab.  (Annex 5)
> They
> chilled the air continuously, and then electrically heated it back up to
> the
> desired temperature!  WINTER and summer!

I'd be shocked too to see a system like that.

When you need to chill then heat, as they do there, the "proper" way to do
it is to do counterflow heat exhange of incoming warmed air against output
cool air for the reheat, as is done in the vast majority of HVAC humidity
control systems that I've seen. It may be that they had such precise
humidity control requirements that electric heating provided control they
could not easily otherwise have obtained.



   Russell



2008\09\16@194005 by Carl Denk

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Did some Googling for "hard start" and found this kit (there are other
manufacturers) consisting of an electronic potential relay and capacitor
as an easy install. Cost $37, from Graingers, probably would have next
day. affordable even if doesn't work super! Here's the link:
http://www.supco.com/eclass.htm

probably p/n SPP7E, but need to do some research as to the actual motor
size.

Looking at the schematic in the installation manual, they show the
starting capacitor and relay as optional. I'll have open the unit and
see what's really there, my feeling is there is none!  If that's the
case, could just add a relay and capacitor, but they would cost close to
the cost of the above kit or more. Will get it open in a day or two,
it's getting dark now. The kit has some protection for the motor
windings also.

2008\09\16@212806 by Mongol Herdsman

picon face
Use some sort of "sine wave inverter with built in AC Charger" between
the generator and the home (or just the conditioner). Connect
batteries and operate it as UPS.
As example:
http://www.powermaster.com.tw/PM-8000LC.htm
Max. Surge Power 16kW


On Mon, Sep 15, 2008 at 5:06 PM, Carl Denk wrote:
{Quote hidden}

2008\09\17@011937 by Apptech

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Having read most of what's been said, I still feel that there MAY be merit
in my suggestions of adding a load to get the gas engine at peak output or
(harder dearer) adding a  rotary energy store (since also suggested by
someone else) which is a known solution in some cases.

The load addition does not interact with the existing enginer controller or
push it over voltage - just gets the motor at its peak output, or as high as
is acceptyable,  prior to compressor start. If the compressor load is say
200% for 3 seconds then, provided the system will happily tolerate 200% for
say 3+X seconds, the dummy load can ramp the motor up to this point over X
seconds then ramp off the dummy load to match the compressor profile. "Dummy
load" could included any existing load which is able to be dropped off
during this process.

If this approach does not work or places an unnaceptable load on the system
then (it seems to suggest that) there is no existing solution without
modifiying the system's energy delivery or storage kinetics.

Pre-adding a load as above requires intercepting the aircon systems switch
on signal - which would hopefully be an easy enough task (but may not be).

A UPS on the affected PC systems sounds like a cheap alternative ;-).



       Russell

2008\09\17@085955 by Carl Denk

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Yes, it would be easy to intercept the air conditioning thermostat
signal, delay it and then bring another load on line briefly. To control
that other load is more challenging, and that along with load leveling
is another topic I hope to pursue another day.

As for the inverter mentioned in another message, it's only 16kw surge,
and with the generator at 12.5kw and 300% temporary overload, I don't
think it will be adequate, plus I don't know cost but probably $100's or
even $1000 which is out of budget.

Before the day is over I hope to open the air conditioner up and see
what the motor starting area actual has. The schematic indicates several
possibilities, and depending what I find, there are several inexpensive
($35) possible.

Apptech wrote:
{Quote hidden}

2008\09\17@095912 by Martin

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Mongol Herdsman wrote:
> Use some sort of "sine wave inverter with built in AC Charger" between
> the generator and the home (or just the conditioner). Connect
> batteries and operate it as UPS.
> As example:
> http://www.powermaster.com.tw/PM-8000LC.htm
> Max. Surge Power 16kW
>


That's what I'd do, it could be the beginning of an off-grid system. Not
cheap though.
-
Martin

2008\09\17@095925 by Carl Denk

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Ok, got the air conditioner opened up, and traced all the wires and
equipment on the schematic. There is no starting relay, only the relay
for the main power to both compressor and outside fan motor. There is a
dual capacitor, labeled run capacitor, one 5 mfd  to the fan motor, and
45 mfd to the compressor. Both of the capacitors motor side go to a
separate lead, which I assume is a starting winding. In addition for
both of the motors there are both a hot lead and a return to the other
leg of the 240 volt.

From this I believe that either a hard start kit that I indicated last
night or a PTCR (Positive Temperature Coefficient resistor) motor
starting package would be helpful, and at $35 I don't have much to lose.
Here's a link to PTCR
http://www.vishay.com/thermistors/list/product-23086/

There are several pumps that use a starting relay and capacitor in the
system, and although they are only 1/2 Hp. they are not an issue.
Neither is a 1 hp air compressor, but it has an unloader to reduce
pressure prior to starting.

2008\09\17@133651 by sergio masci

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On Wed, 17 Sep 2008, Apptech wrote:

> Having read most of what's been said, I still feel that there MAY be merit
> in my suggestions of adding a load to get the gas engine at peak output or
> (harder dearer) adding a  rotary energy store (since also suggested by
> someone else) which is a known solution in some cases.
>
> The load addition does not interact with the existing enginer controller or
> push it over voltage - just gets the motor at its peak output, or as high as
> is acceptyable,  prior to compressor start.

This wasn't what I was suggesting at all with the "additional load" of the
electric motor / generator (or rotary energy store as you call it). What I
was suggesting was that the energy in the flywheel could act as a buffer
and when the AC was switched on and made a big demand on the system
effectively cutting power to the electric motor and acting as a break on
the flywheel - the flywheel would resist the break by dumping energy in
the form of electricity back into the system through the motor which would
now be acting as a generator.

Regards
Sergio Masci

2008\09\17@143519 by Dr Skip

picon face
I'm not sure I understand Sergio's solution, but I am sure the following isn't
the same thing... ;)

Put a large DC motor (for simplicity) on the drive of the gen with the
alternator head and engine - you decide best coupling. Have a battery(s) being
charged by it - run it as a dc gen. When the thermostat switches the compressor
on, switch the motor to being powered as a motor (higher input voltage) and use
it for the additional HP. You even have an incremental path to a solution:

1) While a system to cover many devices would make for a complicated control
system, you could 'manually' and statically set the parameters for the
compressor turn on - timing, E and I.

2) The motor/gen could dump into a load incrementally several seconds before
switching, causing the governor to pre-compensate (open up). The switching of
one load for another could be timed to greater precision than steppers on the
throttle. The heat to a load is only for seconds, so that's not tough.

3) If you need more ooomph still, power the motor at switch time to get a quick
boost to torque. The actual timings and amount can all be set by hand.

4) You could set up a processor or several similar control circuits as skills
allow to do the same for any other big loads you have. In the end it's a motor,
some big SCRs or relays or such and some discretes as minimum.

An add'l benefit would be having some high current DC around to play with too.
You might find it useful besides battery charging. This also doesn't mess with
tehe A/C, engine control, or other current system parts, other than a drive
belt. Should you want to disconnect it, it's a switch to the motor...


sergio masci wrote:
{Quote hidden}

2008\09\17@162143 by Carl Denk

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1: The compressor is a hermetically sealed unit, motor close coupled to
the compressor, all in a sealed container full of freon (either gas or
liquid). Suction and pressure side of pump and 3 wires are only things
that penetrate the container, and are well sealed. Altering or adding
anything to the compressor shaft is not possible.
2: Another motor/generator cost is not in budget.
3: At this time the starting relay/capacitor seems the way to go. cost
is OK, easy to install, and readily available, just have to finalize the
exact type: Hard Start Kit, Relay and capacitor, or PTCR type.
4: I don't have any use for high capacity DC  equipment, and don't see
any in the future. The gas well is our contribution to reducing grid load.

Dr Skip wrote:
{Quote hidden}

2008\09\17@165326 by Harold Hallikainen

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I kind of like the soft starting of a dummy load that someone suggested.
You could use a big light bulb as the dummy load. Slowly bring it up using
phase control. When it's at full power (about the same as the compressor
surge current), switch the light off and the compressor on. I have a
feeling that trying to soft start a compressor will result in a burned out
compressor...

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!

2008\09\17@165552 by Dr Skip

picon face
I understand all but #1. Nothing was said about modifying the compressor. Only
gauge what the effect of the boost motor would be and tweak how much and how
long it adds. The boost motor is on the gen. Just clearing it up. As you say,
it seems solved.


Carl Denk wrote:
{Quote hidden}

2008\09\17@170811 by Carl Denk

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I'm not quite read to get into that yet, the issue is sensing with the
power leads when something needs service with it's power cut, the in
order of priority give the equipment power. It wouldn't be difficult to
start a pump, freezer or other item, and cut the power as the compressor
comes on. Yes the soft start of the compressor, like my wood router,
could result in a burned out compressor which would be very bad ($$$).
The compressor's wiring schematic indicates optional starting
relay/capacitor or PTCR. The hard starting kits seem to indicate
approval by compressor manufacturers. They are basically a capacitor
with electronic relay and some additional protection built in. They are
not soft start but additional capacitor start. Google "Hard Start Kit".
There is lots of info there.

Thanks everyone for input. :)

Harold Hallikainen wrote:
{Quote hidden}

2008\09\18@041748 by Mongol Herdsman

picon face
Carl Denk wrote:
> As for the inverter mentioned in another message, it's only 16kw surge,
> and with the generator at 12.5kw and 300% temporary overload, I don't
> think it will be adequate, plus I don't know cost but probably $100's or
> even $1000 which is out of budget.

It was you who wrote in the first post:
> Breaker: 30 amp
> RLA: 15.4 AMP (running amperage)
> LRA: 83 AMP (locked rotor amperage)

83 Amp * 220 V = 18.26kW, well, slightly more than 16kW, get 20kW model.
If it is out of budget, you may spend the time to earn some cash to
increase the budget. Depending on your hourly rate it would take from
a couple of days to a couple of weeks. It is less time  than the time
to develop a unique device in a proper way. If you are smart enough to
develop the device in less than two weeks, you, probably, could earn
enough cash in less time to purchase the standard boxed solution.

Regards.

2008\09\18@132612 by Carl Denk

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This unit has been on line for 3 years, changing out the generator, next
larger is considerably more money, and engine. There is no standard
boxed version that will run gasoline, natural gas, or propane and switch
under load between fuels. The current action is a little fine tuning of
the system. The reason they specify a locked rotor amperage, is so in
the event that does occur, the circuit breaker (which normally protects
the wire, and is sized for the wire size)  is expected to open the
circuit in case of equipment failure, therefore oversizing the wire and
breaker is not an appropriate practice.

There is a 2 stage resistance heat unit on the system that draws the 83
amps for both stages. The generator's PLC shuts down the one stage if
the generator is online, and shuts down the entire resistance during
generator starting or switching fuels until the generator has stabilized
on the new fuel. The generator handles that load and at the same time
any other house loads easily.

Mongol Herdsman wrote:
{Quote hidden}

2008\09\18@134138 by Vasile Surducan

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On old days that was solved by a Y to delta switch. Starting on Y with
a lower current and switched to delta after get some speed.
Assuming the motor is tri-phased (as it should be at powers larger  than 9KW).

Vasile

On 9/16/08, Bob Blick <RemoveMEbobblickTakeThisOuTspamftml.net> wrote:
{Quote hidden}

> -

2008\09\18@143100 by Carl Denk

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The unit is hermetically sealed with neutral, run, and start leads
coming out of sealed can.

Vasile Surducan wrote:
{Quote hidden}

>> --

2008\09\18@174005 by Bob Ammerman

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>> On old days that was solved by a Y to delta switch. Starting on Y with
>> a lower current and switched to delta after get some speed.
>> Assuming the motor is tri-phased (as it should be at powers larger  than
>> 9KW).
>> Vasile

You're not going to want 3-phase in a residential installation! At least not
in the US where you generally get your choice of exactly one type of
service: 120-GND-120 single phase.

-- Bob Ammerman
RAm Systems

2008\09\19@063910 by Mongol Herdsman

picon face
Carl Denk wrote:
> This unit has been on line for 3 years, changing out the generator, next
> larger is considerably more money, and engine. There is no standard
> boxed version that will run gasoline, natural gas, or propane and switch
> under load between fuels. The current action is a little fine tuning of
> the system.

Under "boxed solution" I meant "sine wave inverter with built in AC
Charger" between
the generator and the home, not generator/engine.

Also you may consider some kind of "AC booster", that is, battery
based UPS synchronized with the generator's AC to add some tens of
amperes to its output current for some seconds. 25A or 0.5kW would be
enough, a couple of 12V sealed batteries would be ok.

2008\09\19@214136 by Josh Koffman

face picon face
On Thu, Sep 18, 2008 at 10:26 AM, Carl Denk <cdenkEraseMEspam.....alltel.net> wrote:
> This unit has been on line for 3 years, changing out the generator, next
> larger is considerably more money, and engine. There is no standard
> boxed version that will run gasoline, natural gas, or propane and switch
> under load between fuels. The current action is a little fine tuning of
<snip>

Just caught my eye...can you switch fuels under load? How does that work?

Curious :)


Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
-Douglas Adams

2008\09\20@084225 by Carl Denk

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Yes it's switches fuel under load. There is a TRI-PLC  T100MD888+ with a
EXP4040, and MD-HMI PLC (programmable logic controller) to manage
everything. It programs ladder logic, with BASIC functions embedded that
allows mathematics for the ADC, displaying pressures, voltages, and
frequencies.
1: Fuel pressure for the natural gas and propane, and the natural gas
well head pressure along with gasoline level in the generator's 16
gallon  fuel tank are monitored by the PLC.
2: Priority of fuels is programmed, and when a minimum fuel pressure or
level is reached, the fuel is switched.
3: The 16 gallon gasoline tank is automatically kept full with a
transfer pump from a nearby 175 gallon tank used for vehicles.
4: The Natural Gas well has a PIC18F1320 to monitor the well and
regulated pressures and enclosure temperature. It communicates with the
PLC via a fiber optic cable to a RS-485 network.
5: The 27 hp. Kohler carburetted engine has a gaseous fuel adapter that
sets under the carb. The gaseous fuels go through a safety valve that is
controlled by engine vacuum and starting circuit.
6: To switch fuels, one valve is closed and another is opened. The most
difficult area was programming the gasoline choke. The engine speed via
the generator's frequency is monitored, and if it gets too low, the
choke is closed for  10 seconds.
7: The only load shedding necessary during a fuel switching is 1 stage
of an electric resistance furnace (backup to the natural gas and used
rarely) is dropped off line for 60 seconds. The other stage is locked
out by the PLC since the full furnace amperage is well above the
generator's output, but the generator is able to maintain 1 stage and
anything else the house can throw at it. I do hope to install some load
shedding for major loads as part of helping the power supplies with
their peak demand.

This is an overview, I do have more detailed info that I could get together.

Josh Koffman wrote:
{Quote hidden}

2008\09\20@103646 by Peter

picon face
Carl Denk <cdenk <at> alltel.net> writes:
>
> By adding a motor/generator set between the house and the generator, I
> see 2 problems
> > I would have thought that if the motor / generator is being powered by
> > electricity from your gas generator, that when it sees a drop in
> > voltage it will resist the drop by putting out current itself.
> > Sergio Masci

That's not the way it works. You size a large (oversized) squirrel cage or
capacitor run (not just start) motor and put it on the circuit of the impulse
load. It can be fitted with a slow start resistor bank to avoid a big kick when
it starts itself. This motor spins all the time and drives a relatively large
flywheel (a few kgs go go a long way). It only draws power to overcome its
losses.

When the paralleled compressor starts it causes a grid drop that will hopefully
be suppied by the flywheel motor near it and not from the far grid. This
actually works but there may be some load factor issues (i.e. you may have to
add capacitor banks and the like). once upon a time uninterruptible power was
supplied like this to large computers, until the generators would switch online
and take the load. It's a proven although low tech method.

here is a "medium" size unit:

http://www.electricnet.com/product.mvc/\
UPS-Uninterruptible-Power-Supply-300kVA-from-0002?VNETCOOKIE=NO

and a search:

http://www.google.com/\
search?q=flywheel+uninterruptible+power+supply\
&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a


Peter


2008\09\20@141630 by Martin K

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Peter wrote:
{Quote hidden}

It seems as though there is a frequency issue. If the ACIM is running at
sync minus slip, the line frequency would have to drop to sync-(2*slip)
before the ACIM would produce usable power. Y/No/Maybe? (sync=2f/poles)
A wound rotor synchronous motor would seem to work much better though it
would be more trouble to start up.
-
Martin

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