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

[johnny]

True. But it wouldn't of been nearly as much fun to just say so up front And a word to the curious, since some have been fitted to our coaches,
particularly 23' models. Do >NOT< expect a swing motor icebox to work on a Generac 3.6RV set. It varies the frequency between 55 and 65Hz, and the
waveform is sort of garbage as well.

--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

 

[emerystora]

>
> 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

One thing that people are overlooking here is that the original Norcold 12/ / 120 volt units use a swing compressor that runs on 24 volt
AC.
So the 12 volt DC goes into an inverter unit that transforms it to 12 volt AC and then it is stepped up by a transformer in the refrigerator to 24 volts AC.

the 120 volt AC input goes through another transformer that drops it down to 24 volts AC.

If your unit is dropping out when the roof air conditioner is running then I would suspect that you have a voltage drop and the refrigerator is not able to provide the 24 volts necessary for the refrigerator and the unit is shutting down.
You might check your wiring to see if there are loose connections that are causing voltage drops.

Emery Stora
77 Kingsley
Frederick, CO

 

[a.]

> 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
I don't know about later models with the dual voltage Norcold, but the earlier (GM upfitted) models only connected the 12v power feed. And the reason
they did that was because the Onan doesn't hold 60 Hz very well. The compressor will give up forever if it runs below 59 Hz or above 61 Hz too long.
When it senses 120VAC, it will automatically switch to 120VAC. Bad if the frequency is not spot on.

If the fridge will run at 12V, and if it is wired for 12V, unplug the 120V side and you won't have to worry about the fridge shutting off unless there
is a problem with the converter or house battery bank. When it is plugged into shore power or on generator, it will run off the converter (instead of
120VAC) which should pump enough current to keep the house bank charged AND run the fridge. When in transit, it will run off the battery which will
stay charged from the 455 alternator through the isolator. Dry camping will run down the house bank in a day or two (maybe less) which is unavoidable
unless you install some solar panels or run the generator daily.

You should probably fix the frequency and/or voltage problem with the Onan (if there is one), but the swing motor compressor fridge doesn't need to be
involved. Don't rely on the Onan to run it.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"Highest price does not guarantee highest quality."

 

[jim kanomata1]

We learn by asking, that is what this community is about.
I know there are lot of people that learned things from you asking the
question.
As we say; thank you for asking.

On Thu, Sep 22, 2016 at 10:05 AM, David J. Forjan 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
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[david j. forjan]

Thanks Johnny for that detailed advice - will do.
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

 

[david j. forjan]

Thanks A. Hamilto. You make a great point. I'm covered in all scenarios with the fridge just running on 12v. Even camping off-grid, I'd still want
to run the generator every day to charge the house batteries. And with those 2 Trojans, having ~2400 watts in the pair, and the fridge using ~50
watts per hour, I can run it a long time before it causes me to re-charge those batteries, which I would do anyway, by driving or just running the
generator awhile. Can't take too long for the generator to replace the 600 watts used in every 12 hours of fridge usage. A very interesting and
effective recommendation from logical deductive reasoning you gave me. I like it. Thanks, 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

 

[RJW]

> > 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,
You hit the nail on the head, at least for the original 12VDC-120VAC reefer that I once had in my coach.

When plugged in to shore power, and the reefer on, a relay in my original 12VDC-120VAV fridge would often click on and off. This got to be pretty
annoying at times, especially at night when attempting to sleep. The only way to stop that was to disconnect it from AC power. In fact I installed an
ON/OFF switch to disconnect from AC to stop the chattering and clicking when it happened, which was most of the time. This was not a problem because
whenever I had the reefer on, I was usually plugged in or had the engine running which gave the reefer a source of DC power from the smart charger or
engine alternator. Even when dry camping, I could go a weekend without running the house battery bank down. Therefore, for me not running it on AC
power was never a problem. I ran that way until the reefer failed and I replaced it with a new absorption reefer.

I had always thought that there was an inverter in the fridge to convert AC to DC to run the swing motor.


--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com


Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator, Manny Tranny etc.

 

[john r. lebetski]

Lube both ends of the governor linkage. Meter voltage No load. Trim adjustable tension pull on governor spring to get 126 volts. Add rooftop load
and it should be at about 120V, no lower. Tweak as needed.
--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First

 

[a.]

> Thanks A. Hamilto. You make a great point. I'm covered in all scenarios with the fridge just running on 12v. Even camping off-grid, I'd still
> want to run the generator every day to charge the house batteries. And with those 2 Trojans, having ~2400 watts in the pair, and the fridge using
> ~50 watts per hour, I can run it a long time before it causes me to re-charge those batteries, which I would do anyway, by driving or just running
> the generator awhile. Can't take too long for the generator to replace the 600 watts used in every 12 hours of fridge usage. A very interesting
> and effective recommendation from logical deductive reasoning you gave me. I like it. Thanks, dave
In a thread that he started to make this one a little less convoluted, Matt Colie suggests getting a cheap (100w + or -) modified sine wave inverter
and running the 12v for the fridge to it, and then plugging the fridge AC cord into the inverter (getting the fridge 12v converter out of the
picture).

That might actually decrease its DC draw and increase the amount of time between generator starts to recharge the batteries. Modern inverters are more
efficient than the one that is built into the fridge.

That's what I would do if it won't run off of 12v. And maybe even if it will.

The goal is to feed that swing motor compressor exactly 60Hz.

For even more electrical efficiency, read this: http://www.bdub.net/Refrigeration_in_the_GMC.pdf
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"Highest price does not guarantee highest quality."