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Old 03-17-2015, 05:23 PM   #1
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Generator Question

I have recently moved to Florida and like many other people, I don't want to buy a back up generator for my house when I have a perfectly good Generac NP66G in my '95 Dolphin. The generator in my motorhome is wired for 120v, it can be wired for 240v and that's what I need for my house. Here's my question, is there any problem with my motorhome having two separate phases of 120v running through it? I cant imagine that there would be as I only have a 30A shore service and can only run one AC at a time on shore power. It seems as though I have one 30A circuit running everything (one circuit of the generator or shore power) and the second circuit of the generator is to run a second AC. The only thing that worries me is are the two circuits of the generator isolated or does the motorhome combine them? I ask because on shore power, I can only run one AC a time but I can switch back and forth between which one I am running. So obviously the circuits can cross over between AC units but they don't appear to combine?
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Old 03-17-2015, 05:45 PM   #2
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With the 30amp shore power its not enough power to support two ACs.

Not sure what you need 240VAC for your house for. A problem you can seriously encounter in trying to run two separate 120 lines for 240 is their phase. Its where the 60Hz rating comes from. With a 240VAC generator you have two 120VAC legs that are phased. End result of what you are thinking of, it you can destroy the motors of anything you apply 240 to.

I have a 5500watt generator with 30amp 240VAC plug but its over 10 years old. Other month I bought from Tractor Supply a 3500watt generator on sale for under $350 which has a 25amp plug. I need the 240VAC for my well pump.
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Old 03-17-2015, 05:47 PM   #3
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BTW, first week of June every year there is tax free purchases on hurricane supplies. Its includes generators.
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Old 03-17-2015, 05:50 PM   #4
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Most smaller Generators are dual leg 110, NOT 220. Meaning your 30A shore power will connect to one of the legs and the 2nd AC (maybe with a switch somewhere) is wired to the second leg. They are in phase with each other, so you will not get 220v across both legs. Some of the larger diesel generators are proper 220v systems.

How many breakers does your generator have? What model?
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Old 03-17-2015, 06:13 PM   #5
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This is similar to my generator http://www.bdub.net/manuals/Generac_..._66_Owners.pdf
as you can see they flip the phase of the second phase and get 240v, bit it is only by combining the two (now opposite) phases of 120v to get 240v. So, you still have two 120v legs but since one has been phase inverted you can get 240v by combining the legs as you do with house current. I would keep both 120v legs in my motorhome but I will only do this if I can be sure that they remain isolated from each other so that I do not dead short the legs together anywhere. What I don't know is if the power control center combines the two legs when the generator is running? Though that wouldn't seem logical to me. However, that would not be the first thing on my rig that I have found not to be done how I would have done it.
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Old 03-17-2015, 06:25 PM   #6
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Quote:
Originally Posted by HuntingHawk View Post
With the 30amp shore power its not enough power to support two ACs.
In the Dutch Star we just traded off we had two 13.5 heat pumps and I ran both of them quit often on 30 amps with no problems for both heat and cooling.
Now, if you had two 15.0 heat pumps your statement is probably correct, but may not be always.
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Old 03-17-2015, 06:40 PM   #7
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Quote:
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In the Dutch Star we just traded off we had two 13.5 heat pumps and I ran both of them quit often on 30 amps with no problems for both heat and cooling.
Now, if you had two 15.0 heat pumps your statement is probably correct, but may not be always.
My rig will only allow one AC unit to operate at a time on shore power, it's not a question of amperage, it is the design of the circuitry. It senses if you are running the generator or if you are plugged into shore power. If I am plugged in, it will only allow one of the two AC units to be selected at a time. That is part of the design. It will still allow me to run too many things and trip the shore power breaker. It does not sense load, it only senses which power I am using (generator or shore). Sorry if I wasn't clear. My only question is "Does my rig keep the two circuits isolated or is there a time, even if briefly, that the two circuits may combine?" as that would cause a dead short and trip the breakers on my generator.
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Old 03-18-2015, 12:34 AM   #8
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This is the backup generator I bought a few months ago when on sale for $299.99
Champion Power Equipmentâ„¢ 3500W/4000W Portable Generator - Tractor Supply Co.
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Old 03-18-2015, 08:15 AM   #9
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If your motor home is 50 amps then what you describe improperly is exactly how it likes to be fed.

Problem is odds are very high you can NOT rewire for 120/240 volt service.

STILL... Save for Electric Range, Dryer, and Central AIR...Not much in most houses needs 240 volt.. and those items... You may be anle to live without for a time..Cook in the motor home.

Do not forget a Gen-Turi for the RV or cooking inside may well be your last act.
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Old 03-18-2015, 11:18 AM   #10
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This has been brought up many times so please search the forum for much reading on the subject.

A few things...
If mh is 30 amp it is a 120 vac L1 only device so do NOT mess with that.

Most rv generators are only 120 vac L1 devices so 240 vac L1-L2 not available.

Wiring into home needs proper ats or mts with possible sub panel or other extensive rewiring to make it work.

Now...
If the generator does have an option to provide L2 and true 240 vac is available without harming the original function then it is real simple to install a 4 pole twist lock outlet in the generator bay wired directly to generator to provide standard and safe connection.

House side should be a permitted installation to insure properly engineered for your location.

Please do NOT assume ANY information on this forum is correct as it is critical that it be done to correct code in your location.

DO ask questions so you can be better prepared to get the work done and please ask here about anything that may not make sense as there are many who could translate the lingo.

The local inspectors may not be aware of how your generator works so folks here can provide information that helps you discuss that with the inspector or contractor.
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Old 03-18-2015, 05:05 PM   #11
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Quote:
Originally Posted by noslenwerdna View Post
I have recently moved to Florida and like many other people, I don't want to buy a back up generator for my house when I have a perfectly good Generac NP66G in my '95 Dolphin. The generator in my motorhome is wired for 120v, it can be wired for 240v and that's what I need for my house. Here's my question, is there any problem with my motorhome having two separate phases of 120v running through it? I cant imagine that there would be as I only have a 30A shore service and can only run one AC at a time on shore power. It seems as though I have one 30A circuit running everything (one circuit of the generator or shore power) and the second circuit of the generator is to run a second AC. The only thing that worries me is are the two circuits of the generator isolated or does the motorhome combine them? I ask because on shore power, I can only run one AC a time but I can switch back and forth between which one I am running. So obviously the circuits can cross over between AC units but they don't appear to combine?
You have a 6,600W generator. It's likely giving you 60A of 110V power (Watts = Amps x Volts). Most likely, you have L1 feeding one AC and all your other circuits, and L2 feeding your other AC and the other circuits--I base this assumption on the fact that your shore power is 30A. You probably can add a 4-pole connector to get 30A @ 220V to your house. I'd check with a Generac dealer as they will be more knowledgeable about how it's currently set up--and what if anything would need to be done--to feed it into your house. It would be a lucky break for you if it's already giving 30A 110/220V. (two legs with a neutral)





Edit: Do you have your Owner's manual? Here's the manual for the PP66G:
http://www.bdub.net/manuals/Generac_..._66_Owners.pdf
See p.32. This unit does have two separate 30A x 110V legs, combined gives you 30A x 220V, so you could give your house 30A x 110/220V if yours is set up the same.



Edited again:
https://bryantrv.com/docs2/docs/Generac_IM-NP-Q.pdf
Here's the service manual for your generator. Print and save it!
P.72 appears to have the electrical schematic for your genset. It shows 20A/110V on one leg, 30A/110V on the other for the NP66G.



ABSOLUTELY get an automatic or manual transfer switch before feeding it into your house!!

I have a 4000W Onan, I know it gives me about 36A of 110V juice..it can be rewired for 18A x 220V, but I would lose 110V capability. With only one leg, I can have 18A x 220V or 36A x 110V, but not both.
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Old 03-19-2015, 05:20 PM   #12
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MT4Runner, thank you for the manuals, especially the Diagnostic Repair manual. I have different version and the one you posted is much better! I do have all of my original manuals for my motorhome but supplemental manuals, such as the D.R. manual are awesome and appreciated.
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Old 03-19-2015, 05:42 PM   #13
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FWIW - Before I spent a lot of time or money on wiring and modifications I would want to determine two things.

First is how often I might want to run on the generator. If it's less than once a year it is probably not worth making any changes.

Second is what would I really need to run. Up where I am it's the furnace, refrigerator and freezer. Anything else is marginal. I can run those safely with an extension cord and a little creative wiring.

If I was not worrying about the house freezing I would just move into the MH or at least eat and sleep in it. Then I would have TV and radio to monitor news broadcasts and all I need to be comfortable. ;-)
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Old 03-19-2015, 06:10 PM   #14
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Nothermark;

I live out n the sticks in Northern Ohio. We lose power a couple times a year, and I'm out on the end of a small feed so we are low priority and generally are a day or two without power.

I have a small 2500 watt portable that we;ve run for days.

I have a "Suicide cord" that we would use (male plug on both ends). Pull the breakers on the main panel to the house, then plug the suicide cord into any house outlet, and the other end into the generator and backfeed the house outlets.

This would only run one phase, as other outlets were on the other phase.

A couple years ago I decided that I didn't want the wife doing this, so I ran four outlets around the house, all colored red, these are tied together and run outside to a small panel where I can plug the generator (or my MH) into to supply power to these special outlets.

The outlets are located near the furnace, refrigerator, sump pump, and home entertainment system. we just unplug the appliance s from their regular outlet and into the special red outlet.

I put a plug and regular outlet on the furnace so it can be unplugged and plugged into the special outlet during the winter.

This is easy, the wife can do it, and she knows how to start the MH genny. Usually we just move to the MH and if it looks like its going to be a while, power up the special plugs and plug the house frig and furnace into its special outlet.
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