Refrigerator doesn't work when A/C on with just generator for electricity

D

david j. forjan

New member
Aug 14, 2016
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I would appreciate any insight here. Seems the refrigerator won't run, with the A/C on while running generator while driving (still hot here in NM).
Refrigerator runs fine, with generator or without (off Trojan batteries), but as soon as I start one A/C unit running off the generator, the
refrigerator stops running. Something to do with inverter I'm guessing. But, I'm wondering if it's a normal state for these GMC motorhomes, or if I
have a problem unto myself.
Thank you.
dave
--
David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final Drive and pork chop for level front end, Tularosa New Mexico
 
I don't know why that would act that way, but if it's a two way frig, just
switch it from automatic to propane.

bdub

> I would appreciate any insight here. Seems the refrigerator won't run,
> with the A/C on while running generator while driving (still hot here in
> NM).
> Refrigerator runs fine, with generator or without (off Trojan batteries),
> but as soon as I start one A/C unit running off the generator, the
> refrigerator stops running. Something to do with inverter I'm guessing.
> But, I'm wondering if it's a normal state for these GMC motorhomes, or if I
> have a problem unto myself.
>
 
What does an inverter have to do with the fridge?

Mac in OKC

Sent from my iPad

I don't know why that would act that way, but if it's a two way frig, just
switch it from automatic to propane.

bdub

I would appreciate any insight here. Seems the refrigerator won't run,
with the A/C on while running generator while driving (still hot here in
NM).
Refrigerator runs fine, with generator or without (off Trojan batteries),
but as soon as I start one A/C unit running off the generator, the
refrigerator stops running. Something to do with inverter I'm guessing.
But, I'm wondering if it's a normal state for these GMC motorhomes, or if I
have a problem unto myself.

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Unsubscribe or Change List Options:
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> I would appreciate any insight here. Seems the refrigerator won't run, with the A/C on while running generator while driving (still hot here in
> NM). Refrigerator runs fine, with generator or without (off Trojan batteries), but as soon as I start one A/C unit running off the generator, the
> refrigerator stops running. Something to do with inverter I'm guessing. But, I'm wondering if it's a normal state for these GMC motorhomes, or if
> I have a problem unto myself.
> Thank you.
> dave

David,

You never said what make and model the reefer is. If it is an old No(r)cold 12 & 120, I think I know the problem.
If it is 2 or three way that is a different issue, but I might still have a guess.
If (like mine) it is a residential unit that you run with an inverter. We need to talk.

Matt
--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit
 
I think before you can give him a reasonable guess, that you need to find out what kind and type (propane, 12 volt, or 110 volt) of refrigerator he
has.

This initially sounds like a low voltage (120 volt) problem when the AC kicks in. He needs to check the voltage at the refrigerator when the AC kicks
in.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
The inverter has to come on, activate, because the A/C units are only 120V. So, the fridge is on, running off DC on the only electricity available
from the generator, I turn on the A/C units, the inverter has to come into play to change the DC current coming from the generator to AC, to power the
A/C. And so I thought maybe when the inverter comes into play, it somehow screws up the DC feed to the fridge. A big maybe, but it's a variable
dave
--
David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final Drive and pork chop for level front end, Tularosa New Mexico
 
Sorry folks for the oversight. It's the original Norcold, AC or DC but not propane
--
David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final Drive and pork chop for level front end, Tularosa New Mexico
 
Ken. You have a point. It might very well be a low voltage problem. But I figured it would be built so as to be able to run at least one A/C unit
and the fridge off the generator. The fridge can't use that much electricity?!

But, the real question is: Can other people run the fridge and the A/C while driving with the generator on, or is it my problem. does anyone else do
this successfully?
--
David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final Drive and pork chop for level front end, Tularosa New Mexico
 
The generator puts out AC voltage. GMCs do not come with "inverters". They
only come with "converters" which take some AC and turn it into DC current.

bdub

-----Original Message-----
From: Gmclist On Behalf Of David J. Forjan
Sent: Wednesday, September 21, 2016 8:59 PM
To: gmclist
Subject: Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator
for electricity

The inverter has to come on, activate, because the A/C units are only 120V. So,
the fridge is on, running off DC on the only electricity available from the
generator, I turn on the A/C units, the inverter has to come into play to change
the DC current coming from the generator to AC, to power the A/C. And so I
thought maybe when the inverter comes into play, it somehow screws up the DC
feed to the fridge. A big maybe, but it's a variable
 
> The inverter has to come on, activate, because the A/C units are only 120V. So, the fridge is on, running off DC on the only electricity
> available from the generator, I turn on the A/C units, the inverter has to come into play to change the DC current coming from the generator to AC,
> to power the A/C. And so I thought maybe when the inverter comes into play, it somehow screws up the DC feed to the fridge. A big maybe, but it's
> a variable
> dave

Thanks Dave,

Now I can help.
It is probably not just when the generator is running the A/C that the reefer quits, but let me tell you how the bow really works:

The compressor is a thing called a swing motor. It has no rotating element, but a piston that is moved back and forth because it is in resonance with
the incoming power. For this jewel to do any good, the supplied power has to be really close to the resonant frequency.
The multi-vibrator (the type oscillator) that runs it on DC has no problem with this. So, on DC it always works.
There is a relay in there that changes the power supply from DC to what ever AC is coming in.
Problem:
When the supplied AC is not close to the frequency needed for the piston to vibrate full stroke, the pump doesn't. The relay is too stupid to figure
that out when the AC it sees is too far different from the 60Hz that the pump wants the pump can't run. The only thing the pump can do is stop. The
relay doesn't care. The Generator doesn't care. And the A/C unit doesn't have a clue. But if the AC is out of tune with the spring/mass of the
compressor, they won't dance.

So, if you disconnect the AC supply, the inverter will kick back in and the reefer will be happy. You just won't be able to charge the house bank as
fast. The reefer will be much happier.

It took some doing, but I was able to tune my 4.0 to run the reefer and most anything else, but it takes so attention and futzing.

Matt
--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit
 
Yes, I ran mine for 10 hours straight going to Branson when the temp hit 100 degrees.

I am still confused as to what you have for a refrigerator. Is it 120 volt only or 120 / propane or a 120 / propane /12 vdc one?

What brand and model is it?

I am very confused with your comment on the inverter use when running on the generator.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Thank you Matt and Bdub and Ken.

My unit is the original "Norcold All-Electric Refrigerator will operate either on 12-volts DC or 120-volts AC" (from the manual). It runs fine off DC
(batteries) without generator running. It runs fine when we're hooked to outside 120v power source, even with the A/C unit on. It runs fine when the
generator is running, UNTIL I turn on either A/C unit. That's when it shuts off.
I guess my comment about inverters is wrong according to you Bdub. I assumed it uses them, but as you pointed out the systems uses converters,
although I'm surprised that a generator puts out AC power directly, and not DC power. That's a new one on me. I've only heard of engines creating DC
power natively/naturally, afterwards being converted/inverted to AC power.
I suppose Matt that you are correct. Maybe the generator (original Onan 6000w) isn't as effective anymore and the voltage varies more. And then the
fridge isn't seeing the voltage/frequency it wants. And if I understand you correctly then, the relay is the problem?
Ken, my point about inverters (or converters as Bdub is the situation), is that when the fridge is running off the generator, I thought it would be on
DC power, as I'd assumed that all engines put out DC power naturally. And so, if the fridge was running on DC power without the A/C unit on, and then
the A/C unit comes on, which only uses AC power, then some inverter/converter would have to activate changing the DC power from the generator to AC
power for the A/C. And then that changeover might be confusing the fridge.
Maybe it is the relay after all.
Thank you all for your help. And, it's encouraging to hear from you Ken that you can run both the A/C and fridge while driving with the generator
on.
I'll try to do more trouble-shooting/testing.
--
David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final Drive and pork chop for level front end, Tularosa New Mexico
 
David

See page 41 of http://www.bdub.net/manuals/X7721B.zip

Check to see that you are within spec on your Onan output. If voltage is
correct, then frequency will be also.
http://www.bdub.net/manuals/Onan/Onan6kwNH_Operator-Parts.pdf

bdub

-----Original Message-----
From: Gmclist On Behalf Of David J. Forjan
Sent: Thursday, September 22, 2016 10:24 AM

My unit is the original "Norcold All-Electric Refrigerator will operate
either on 12-volts DC or 120-volts AC" (from the manual). It runs fine off
DC (batteries) without generator running. It runs fine when we're hooked to
outside 120v power source, even with the A/C unit on. It runs fine when the
generator is running, UNTIL I turn on either A/C unit. That's when it shuts
off.
 
The relay is not the problem.
As stated earlier by Matt, the fridge compressor runs on a resonant electrical wave. The speed of the waves repeating is only variable by a few waves
per second more or less than 60 or the compressor will not ride the waves correctly and so will not pump. The electrical wave is GENERATED by the
rotation of the magnetic field in the coils of wire in the generator, which is technically an ALTERNATOR. The speed of the rotation determines the
speed of the repeating electrical waves coming out of it (and returning back to it). If the generator slows down when you turn the A/C on, the
electrical waves will not be repeating fast enough for the fridge to use. So either set it to run off it's own built in inverter that generates the
waves at the right speed all the time, pulling power from the DC side of your system, or get the generator tuned up to handle the load properly so
it's speed does not drop when loaded.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
To an electrical dummy like me, it's very simple. The swing compressor
needs 60 cycle current to run.
Adjust the Onan to produce 60 cycle current when the AC is on and you're
good to go.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "David J. Forjan"
Sent: Wednesday, September 21, 2016 9:58 PM
To:
Subject: Re: [GMCnet] Refrigerator doesn't work when A/C on with just
generator for electricity

> The inverter has to come on, activate, because the A/C units are only
> 120V. So, the fridge is on, running off DC on the only electricity
> available
> from the generator, I turn on the A/C units, the inverter has to come into
> play to change the DC current coming from the generator to AC, to power
> the
> A/C. And so I thought maybe when the inverter comes into play, it somehow
> screws up the DC feed to the fridge. A big maybe, but it's a variable
> dave
> --
> David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final
> Drive and pork chop for level front end, Tularosa New Mexico
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Your Onan (which you call a generator) is actually an ALTERNATOR and is supposed to be providing approximately 120 Volts, 60 Hertz power, virtually identical to what comes off the outside power. If your fridge dies when you are running the Onan alternator, then it is obvious that your Onan alternator is at fault!

D C "Mac" Macdonald
'76 ex Palm Beach
"The Money Pit"

________________________________
From: Gmclist on behalf of David J.Forjan
Sent: Thursday, September 22, 2016 10:24
To: gmclist
Subject: Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity

Thank you Matt and Bdub and Ken.

My unit is the original "Norcold All-Electric Refrigerator will operate either on 12-volts DC or 120-volts AC" (from the manual). It runs fine off DC
(batteries) without generator running. It runs fine when we're hooked to outside 120v power source, even with the A/C unit on. It runs fine when the
generator is running, UNTIL I turn on either A/C unit. That's when it shuts off.
I guess my comment about inverters is wrong according to you Bdub. I assumed it uses them, but as you pointed out the systems uses converters,
although I'm surprised that a generator puts out AC power directly, and not DC power. That's a new one on me. I've only heard of engines creating DC
power natively/naturally, afterwards being converted/inverted to AC power.
I suppose Matt that you are correct. Maybe the generator (original Onan 6000w) isn't as effective anymore and the voltage varies more. And then the
fridge isn't seeing the voltage/frequency it wants. And if I understand you correctly then, the relay is the problem?
Ken, my point about inverters (or converters as Bdub is the situation), is that when the fridge is running off the generator, I thought it would be on
DC power, as I'd assumed that all engines put out DC power naturally. And so, if the fridge was running on DC power without the A/C unit on, and then
the A/C unit comes on, which only uses AC power, then some inverter/converter would have to activate changing the DC power from the generator to AC
power for the A/C. And then that changeover might be confusing the fridge.
Maybe it is the relay after all.
Thank you all for your help. And, it's encouraging to hear from you Ken that you can run both the A/C and fridge while driving with the generator
on.
I'll try to do more trouble-shooting/testing.
--
David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final Drive and pork chop for level front end, Tularosa New Mexico
 
The Onan is a 'volts per hertz' setup, so if you're seeing 120 volts it will be right around 60 Hz. If it sags and doesn't recover when the A/C comes
on, the frequency is going to sag as well. Measure the voltage at a plughole when the A/C is running and see what you get. Adjust the governor per
the Onan manual if it's sagging. Be sure the governor arm isn't binding anywhere and the pivot points are free. If it still doesn't make proper
power with the A/C on, Jim Miller is Your Friend.. ask him for advice.

--johnny

--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon
 
Thank you Bdub, Terry, Matt, Ken, Gary, Mac and Jon. Thanks to you all I know just what to do, starting with checking the voltage out of the Onan,
with A/C running, and without.
Amazing that I'm at the point now that I know what to do, thanks to you all. Be well all of you. dave

--
David J. Forjan, 1977 403 26' Palm Beach, glad to have the 3.70 Final Drive and pork chop for level front end, Tularosa New Mexico
 
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