House power from RV generator as back-up

Does anyone know of a way to safely supply whole house power from the 4000 Onan in case of power outage? I know I could run extension cords to alternately run the fridge, freezer, and a floor fan to circulate air from the NG fireplace.  I'd like to be able to supply power to the house thermostats and circulator pumps for the NG baseboard heat.
It looks like most backup systems are 220v, and the Onan is 110v.
Dougn

Doug,

I'm not an electrician, but I have an electronics background, do all my own electrical work, and have a pretty good handle on it. With those caveats, I'm afraid the short answer when you're talking "whole house power" is no.  You pretty well already identified the usability of the Onan to support household emergency needs. The Onan is rated to provide a total 33.3 amps at 120 volts. The realistic use would be to run a couple of extension cords plugged in to two separate 20 amp circuits on the RV.  That should allow you to tap up to 20 amps on either circuit, or theoretically 15-16 amps on both at one time, everything at 120 volts. There is no outlet on the RV that will let you pull the full 33 amps on one extension cord; a person could conceivably wire in an outlet at the transfer switch to tap the full generator output of 33 amps on one power cord, but that is still going to be at 120 volts, would be a pretty major project, and I doubt it would be worth the effort.

As you say, home backup systems are normally 240 volts, since that's the line power coming into your home. It consists of two separate 120 volt feeds or phases that each feed about half of the 120 volt circuits in your main panel, with the 240 volt circuits tapping across both phases. For backup power, that can only be supplied by a generator with a 240 volt output. Lower price 5000 watt units can be had for about $500 today, with higher wattage output units going up in price. Proper installation also would use a transfer switch to switch the input to your house main panel from the line in to the generator. You can get around that with a more simple hookup (I do), but you must know what you are doing or you will compromise safety.

You mention one objective is to supply power to "house thermostats and circulator pumps". I'm not familiar with that system (my home uses natural gas central heating), but if that circuit is 120 volt and 20 amps or less, it's possible you could tie in to the wiring for that particular circuit at your main panel and power it with an Onan extension cord. If it is a 240 volt circuit, it will require the 240 volt generator.

Mike

I agree with Mike, you are not going to have 'Whole House' generator backup off the RV.

However... if you are looking to run only the systems you named first-

""run the fridge, freezer, and a floor fan to circulate air from the NG fireplace. ""

You have a possible way to do that, and can do so to code.     

Using this 30A generator transfer switch - https://www.lowes.com/pd/Reliance-306LRK-6-Circuit-Transfer-Switch-Kit-P2/50436688 



You can safely supply up to (6) 110V circuits in your house. (The picture shows it configured for 1 220V and 4 110V, but it can be configured 110V only)
 
-Compatible with most generators that have a 20-amp or 30-amp 120/240 volt 4-wire receptacle

-Can be connected to 1-pole or 2-pole household circuits, up to 30 amps

The breaker panel would be wired into your house panel.

The 'supply receptacle' would mount outside, and be the connection point for your RV.

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On the RV itself, as Mike said, you would need a 30A supply outlet. On my 2350, the transfer switch is located in the drivers B pillar, behind the seat.  I would go into that junction box, and directly wire the RV outlet to the transfer switch input.  (The generator breakers will be the safety)  With a short connecting run to something like this:

https://www.hubbell.com/wiringdevice-kellems/en/Products/Electrical-Electronic/Wiring-Devices/Watertight-Devices/Watertight-Safety-Shroud-Twist-Lock/HBL2720SW/p/1638242




The location of the transfer switch in your rig will determine the outlet location and wiring needs.  When using the 'house powering outlet' I would turn off breakers in the coach as to eliminate any draw in there.

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Now We have a safe 30A connection to the RV generator. We have a proper generator transfer panel inside the house. Just have to link them.

https://www.homedepot.com/p/Conntek-50-ft-10-4-STW-30-Amp-125-Volt-250-Volt-4-Prong-L14-30-Transfer-Switch-Cord-Generator-Extension-Cord-20602/309291375




And now you have a 30A backup power circuit in your house that works off your RV.      Cost will depend on your abilities and other parameters the existing building and RV wiring may present.

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And for the house heating system... ""I'd like to be able to supply power to the house thermostats and circulator pumps for the NG baseboard heat.""

It looks like you and Mike both have natural gas heat, I am guessing Mike has a forced air and you have a baseboard water system.    Mike's I am guessing is 220V guaranteed.  You need to do some research... check the circulator pumps and see if they are 220V or 110V.  You didnt mention the boiler, where the NG is burned to heat the water. That usually supplies the power to the thermostats also. IF it is 110V, you are still in luck.   

If the pumps and boiler both together pull less than 30A, you can wire them in with the transfer panel above and you are up and running!  There are meters on the transfer panel that will help you monitor your power usage.  If the boiler and pumps are 220V, or require more than 30A 110V to run, another generator will be required for house heat.

I WAS a registered chimney sweep and heating specialist, but 20 years ago in Vermont. Things may have changed in that world that I am unaware of. In Florida since 1994, so very little time spent ADDING heat to a house.    Excuse any ignorance I may show there.


So it is possible to use the RV safely as a backup generator, cost is up to you and your abilities. 

Dougn

You absolutely must have some form of transfer switch that is "break before make"... That is, utility power and generator power are NEVER connected at the same time, even for an instant. 100% isolation 100% of the time.

The easiest and cheapest way to do that is via extension cords.   Unplug from the wall, plug into the generator.

For your baseboard heat, as mentioned above, it cannot be a 220v system.  If it's a single 120v line on your breaker box, then you can have an electrician wire a break before make transfer switch and wire that to an electric input box near where you store your PC.

To be honest, I am not sure the Onan can output enough power to handle the circulator pump, refrigerator and freezer all at once.

Thanks to uncle Sam, I took my stimulus check and bought a Honda 2200 generator and propane conversion kit for it (can use either gasoline or propane as fuel) along with a 30# propane tank and extension cords.

I may put a transfer switch on my gas fireplace so I can alternate between it and the freezer when needed.

Don

Thanks for the thorough replies. It looks like most of the parts will be needed whether you use a dedicated backup generator or the RV.

Volkeman, The problem  I still see is that the Transfer switch box you show has a four wire input for a 120/240 generator supply, that's where I found myself stumped.

 I have roof-top solar, and understand the need to not back-feed power without protection to the service lines.

Donc, my gas fireplace does put out a fair amount of heat, and works without electricity, except for the blower fan. I have some usb computer fans like these:
https://www.aga.org/natural-gas/delivery/how-does-the-natural-gas-delivery-system-work-/   
that I could plug into my jump-starter to help move the air. I got them because my blower fan is really noisy, the computer fans are really quiet.

I already have plenty of extension cords, so I'll go the easy route. I worry most about long-term heat loss and freezing pipes, so I 'm going to try to figure out if I can supply temporary power to the boiler and circ pump, plus, I have a side-arm water heater, be nice to have hot water also.

 

Not sure what a side-arm water heater is, but none of the water heaters I have ever had (over the last 20 years or so, ever required electricity to run.  I lost power for 3 1/2 days in Denver in the mid 90's and at least had hot water.   I can't remember what we did, if anything, for heat.

Not sure what a side-arm water heater is, but none of the water heaters I have ever had (over the last 20 years or so, ever required electricity to run.  I lost power for 3 1/2 days in Denver in the mid 90's and at least had hot water.   I can't remember what we did, if anything, for heat.

A side-arm water heater has a heat exchanger connected to the boiler, requires a circ pump.

This is a very interesting subject.

I have wondered if there was an easy way to jury-rig something.  In my head, I have wondered if this would "safely" work.

1) Flip "OFF" the main house breaker(s) to isolate the house from community power.
2) Turn off every small breaker that distributes power throughout the house.
3) Plug the PC generator into my 30amp outlet in the garage, but I wonder how to output 110V-30amps direct from the PC generator.
4) Turn on only one house-distribution breaker at any given time.
- Run our gas fired forced-air furnace until the house warms up.  The 110V power required would be only for the furnace blower.
- Flip breakers to run the kitchen fridge until it shuts off.
- Flip breakers for other purposes as needed.

Being on a private well that requires 220V, that seems to be a "bust" just like a/c, but everything else just might work.  Having our house 100% converted to LED light bulbs throughout should also make a difference.  Where we live near Chicago, the focus is more on keeping the house warm in the winter rather than cool in the summer.

Does anyone know how to output 110V-30amp from their PC generator?

Volkeman, The problem  I still see is that the Transfer switch box you show has a four wire input for a 120/240 generator supply, that's where I found myself stumped.

You just leave one disconnected, and bridge the transfer switch inside. The transfer switch is made to do that.   The outlet on the RV will have one unconnected terminal. Easy peasey. 

It looks like most of the parts will be needed whether you use a dedicated backup generator or the RV.

Well, yeah!  You are using the RV as a backup generator.    With this setup you can easily put another generator on it.

And i never knew what a side arm water heater was, thanks for the enlightenment. 

This is a very interesting subject.

I have wondered if there was an easy way to jury-rig something.  In my head, I have wondered if this would "safely" work.

1) Flip "OFF" the main house breaker(s) to isolate the house from community power.
2) Turn off every small breaker that distributes power throughout the house.
3) Plug the PC generator into my 30amp outlet in the garage, but I wonder how to output 110V-30amps direct from the PC generator.
4) Turn on only one house-distribution breaker at any given time.
- Run our gas fired forced-air furnace until the house warms up.  The 110V power required would be only for the furnace blower.
- Flip breakers to run the kitchen fridge until it shuts off.
- Flip breakers for other purposes as needed.

Being on a private well that requires 220V, that seems to be a "bust" just like a/c, but everything else just might work.  Having our house 100% converted to LED light bulbs throughout should also make a difference.  Where we live near Chicago, the focus is more on keeping the house warm in the winter rather than cool in the summer.

Does anyone know how to output 110V-30amp from their PC generator?

""Turn off every small breaker that distributes power throughout the house."" 
     TURN OFF THE BIG ONES TOO!!! THEY WILL BACKFEED ONE LEG!!!      



I outlined how to put a 30A outlet on the RV above. It will use the generator breaker, and output 30A. I used the 4 prong outlet just to make the cord easy for 2Lucky's particular setup, you can use a 3 prong for 110v if you are backfeeding the 30A outlet. Just need a custom cord. (Male 3 prong twistlock to 30A RV male)

Common 'redneck' backfeed for the house is the dryer outlet. Handles 220V 50A input. We have one that reaches the dryer from the breaker box, and it is coiled inside the box. Down in the basement is the other end of a 50' cord that connects to the generator OUTSIDE.  All breakers off, Remove box cover, unplug dryer, plug in generator cord. Turn on dryer breaker for the supply, and load breakers as needed.

Is it safe?  NO.  Do people do it? YES.     Check laws in your area.

https://coopergeneratorservices.com/generator-illegal-backfeeding-dangerous/

Backfeeding is a dangerous and possibly illegal way to power your home by connecting your generator to an appliance outlet (like a dryer outlet) and allowing electrical power to flow in reverse. Power moves backward to your electrical panel and is redistributed throughout the house.

Powering your home this way is dangerous and possibly illegal. If the main breaker is not shut off, power backfeeds to the utility lines outside your home, potentially shocking a maintenance worker. In these situations, you are responsible for injury or death, and could be criminally prosecuted.

Using backfeeding to restore power to your home is dangerous because electrical loads are not balanced. Also, unbalanced loads are inefficient and put extra strain on your generator.

The setup in our house was done before I was there, I have NEVER used it.  I know many people that do use them, however.

This is a very interesting subject.

I have wondered if there was an easy way to jury-rig something.  In my head, I have wondered if this would "safely" work.

1) Flip "OFF" the main house breaker(s) to isolate the house from community power.
2) Turn off every small breaker that distributes power throughout the house.
3) Plug the PC generator into my 30amp outlet in the garage, but I wonder how to output 110V-30amps direct from the PC generator.
4) Turn on only one house-distribution breaker at any given time.
- Run our gas fired forced-air furnace until the house warms up.  The 110V power required would be only for the furnace blower.
- Flip breakers to run the kitchen fridge until it shuts off.
- Flip breakers for other purposes as needed.

Being on a private well that requires 220V, that seems to be a "bust" just like a/c, but everything else just might work.  Having our house 100% converted to LED light bulbs throughout should also make a difference.  Where we live near Chicago, the focus is more on keeping the house warm in the winter rather than cool in the summer.

Does anyone know how to output 110V-30amp from their PC generator?

Ron,

The short answer to your basic question of "can this safely work" is yes.  But it must be done with caution and complete understanding to meet the "safely" criteria.  To begin with--it is truly "jury-rigging" as you say; and it is certainly not to code.  And any electrical modifications that fall into the category of "jury-rigging" are inherently unsafe and dangerous unless you absolutely know what you are doing.  Supplying auxiliary power to your home should absolutely be done through a transfer switch which, if properly installed, will protect your home, your auxiliary power source, and the community power line feeding your home.  However I do provide emergency power to my home safely from an auxiliary generator through a back-feed type connection, which is essentially what you describe.  In my case, it is a full 240 volts, and I energize my entire main panel.  My generator is only about a 6KW unit, so it can't carry my central air conditioning, and I do monitor loads, but everything else is operable.

Your last question of how to output the PC generator is answered in my and especially Volkeman's comments above.  You would need to tie in to the transfer switch on your PC to access the full generator output, and wire in a receptacle that will let you connect a 120 volt, 30 amp cord set to your garage outlet.  With your house main breakers switched "OFF" to isolate you from community power (absolutely critical, and the first thing to do), you would then back-feed to your main panel through the circuit breaker that feeds your garage 30 amp circuit (that breaker must be "ON").  One limitation that you may not have considered is that since you are only feeding in 120 volts, you will only energize the one side of your main panel that carries the circuit breaker for your garage circuit.  Other breakers on that side of the panel will have power, but none of the breakers on the other side of the panel will have it.  It will come down to "luck of the draw" as to which other house circuits are on that panel side.  That's the advantage of a 240 volt capable auxiliary generator--in that case, with the same back-feed process, you feed the main panel through a 240 volt breaker, which energizes both sides of the panel.  In my case, I installed a 240 volt 60 amp sub-panel in my garage for outside power and lights, and that's where I tie in the generator.  With the main breakers to my main panel switched OFF, and the 60 amp breaker to my sub-panel switched ON, my main panel has 240 volts back-fed from the sub-panel to all circuits.  My generator breaker protects that feed, but in practice, I still keep my high amperage 240 volt breakers (A/C unit, electric dryer, etc) switched OFF to prevent accidental overloads.  Even the small 6KW generator carries everything else easily (including my NG central heat blowers), so can remain pretty normal during outages.  Last usage was only about a week ago, when we had a 24-hour outage on our rural electric cooperative system, and it was nice to have normal heat and power.  In 2002 we had a severe ice storm and our outage stretched to 13 days in our rural area, that's when I first acquired the generator and established the hook-up.

Mike

Since my biggest concern over long term power outage is keeping the house warm, I think I may have a simple solution using the extension cord route.
In the attached picture you'll see the 120 wiring from the wall into a surface mount switch, which supplies power to the boiler, zone valve controller (which also controls the side-arm water heater) and the transformer for the thermostats.

Does anyone see any issue with moving the switch box over and replacing it with a wall outlet, then wiring a grounded plug and wire to supply power to the switch? I could then just unplug it from the wall and connect it to my PC. Is the power from the PC inverter or generator clean enough for the circuit board in the controller?

It looks like the two circulator pumps are .75 amp. and the controller 1.5 amp, 3 zone valves at .3 each...I could run it for hours off of the coach batteries or PC solar?

Since my biggest concern over long term power outage is keeping the house warm, I think I may have a simple solution using the extension cord route.
In the attached picture you'll see the 120 wiring from the wall into a surface mount switch, which supplies power to the boiler, zone valve controller (which also controls the side-arm water heater) and the transformer for the thermostats.

Does anyone see any issue with moving the switch box over and replacing it with a wall outlet, then wiring a grounded plug and wire to supply power to the switch? I could then just unplug it from the wall and connect it to my PC. Is the power from the PC inverter or generator clean enough for the circuit board in the controller?

It looks like the two circulator pumps are .75 amp. and the controller 1.5 amp, 3 zone valves at .3 each...I could run it for hours off of the coach batteries or PC solar?

Well, amp-wise you are looking great!   No power needed for the boiler itself? (or is that part of the controller output?)

Your idea is VERY valid! 

I would add a junction box with a 3-way switch, and a 110V male receptacle.   

Put the three way switch in the hot wire before the existing switch. Wire it so when the 3-way is one way, house power supplies the switch. The 3-way in the other position would supply the extension cord power to the existing switch. That way there would be no combination that would have you accidently connecting the generator to the house power.  The attached diagram may make this a little clearer, I only show the 'hot' wires.

Dougn,

Based on what I can garner from your photo and your description, looks like your plan will work.  Total load you identify is 4 amps, or 480 watts--very nominal by any standards; an extension cord supply should handle that easily.  I don't know what rating your main panel circuit breaker feeding that circuit carries; you may be protecting it with a higher rated breaker from the coach (20 amps), but I wouldn't think that a particular risk for a temporary service.  For permanent circuits such as this a hard-wired connection is normally preferred to a plug-in, but in this case I think the convenience of being able to quickly switch supplied power is worth any small disadvantage.  I actually did the same thing to my central gas heating blower supply for the same reason, before setting up my permanent auxiliary generator hook-up.  At my first power outage, I disconnected my furnace feed from the original hard-wired box, moved the supply to a receptacle, and installed a plug on the furnace.  Used an extension cord from my generator to give us heat until I got the permanent hook-up made.  It's worked fine for 20 years.

I don't think you need to worry about the quality of the generator/inverter power.  I think they'll be fine.  My central system uses a circuit board to control all the functions and I've never had an issue on generator.

Mike

Adding a plug in line as Mike said is a good idea also, and does make sure you cannot backfeed through the supply.      I was aiming for a little more inspector-friendly setup.

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Curious... I never did any NG burner work, they did not have NG service in our area.  The boiler/heat exchanger uses no or negligible power?  Even in forced air apps?  Being used to oil fired, there was ALWAYS current draw just to make the heat.

The 5 ton AC in our house has a blower rated 3/4 HP or 4.6 amps @ 220V.  So the blower alone is close to 1000w at full draw.   480 watts for a whole house heating system is FANTASTIC.       I cant even blow the air around our house for twice that power, much less run the heat pump or heat strips.