Home » Public Forums » GMCnet » Refrigerator doesn't work when A/C on with just generator for electricity (Refrigerator works while generator, until I turn on even one A/C unit, then is stops runnin)
| Refrigerator doesn't work when A/C on with just generator for electricity [message #307581] |
Wed, 21 September 2016 17:25  |
DavidJForjan
Messages: 65
Registered: August 2016
Location: Tularosa New Mexico
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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
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307590 is a reply to message #307581] |
Wed, 21 September 2016 19:32  |
bdub
Messages: 1578
Registered: February 2004
Location: Central Texas
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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
On Wed, Sep 21, 2016 at 5:25 PM, David J. Forjan wrote:
> 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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bdub
'76 Palm Beach/Central Texas
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307592 is a reply to message #307590] |
Wed, 21 September 2016 19:52 |
k2gkk
Messages: 4452
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What does an inverter have to do with the fridge?
Mac in OKC
Sent from my iPad
On Sep 21, 2016, at 19:45, Billy Massey wrote:
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
On Wed, Sep 21, 2016 at 5:25 PM, David J. Forjan wrote:
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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| Re: Refrigerator doesn't work when A/C on with just generator for electricity [message #307597 is a reply to message #307581] |
Wed, 21 September 2016 20:38 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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DavidJForjan wrote on Wed, 21 September 2016 18:25I 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 - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307600 is a reply to message #307590] |
Wed, 21 September 2016 20:58 |
DavidJForjan
Messages: 65
Registered: August 2016
Location: Tularosa New Mexico
Karma: 2
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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
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307603 is a reply to message #307600] |
Wed, 21 September 2016 21:04 |
bdub
Messages: 1578
Registered: February 2004
Location: Central Texas
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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@list.gmcnet.org
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
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'76 Palm Beach/Central Texas
www.bdub.net
www.gmcmhphotos.com
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www.facebook.com/groups/classicgmcmotorhomes
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307610 is a reply to message #307600] |
Wed, 21 September 2016 23:02 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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DavidJForjan wrote on Wed, 21 September 2016 21:58The 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 - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Refrigerator doesn't work when A/C on with just generator for electricity [message #307626 is a reply to message #307602] |
Thu, 22 September 2016 08:52 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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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
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| Re: Refrigerator doesn't work when A/C on with just generator for electricity [message #307631 is a reply to message #307626] |
Thu, 22 September 2016 10:23 |
DavidJForjan
Messages: 65
Registered: August 2016
Location: Tularosa New Mexico
Karma: 2
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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
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| Re: Refrigerator doesn't work when A/C on with just generator for electricity [message #307638 is a reply to message #307631] |
Thu, 22 September 2016 11:31 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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The relay is not the problem because you say it works off the 120 from Onan or shore power.
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.
[Updated on: Thu, 22 September 2016 11:34] Report message to a moderator |
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307639 is a reply to message #307600] |
Thu, 22 September 2016 11:31 |
Kosier
Messages: 834
Registered: February 2008
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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
>
> _______________________________________________
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307640 is a reply to message #307631] |
Thu, 22 September 2016 11:32 |
k2gkk
Messages: 4452
Registered: November 2009
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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@list.gmcnet.org
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
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| Re: Refrigerator doesn't work when A/C on with just generator for electricity [message #307642 is a reply to message #307581] |
Thu, 22 September 2016 11:59 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
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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
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Refrigerator doesn't work when A/C on with just generator for electricity [message #307643 is a reply to message #307639] |
Thu, 22 September 2016 12:05 |
DavidJForjan
Messages: 65
Registered: August 2016
Location: Tularosa New Mexico
Karma: 2
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Member |
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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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