Community Forums

mmcl26554 · 03-24-2012, 02:22 PM

My motor home has a 7KW generator. It puts out two 120 volt circuits. One 30 amp one 20 amp. Here is what I did to use it as a standby for my home.

I found on eBay a manual triple pole double throw 30 amp switch so I could disconnect the mains and connect the generator and only one would be connected to my home at a time. This is my transfer switch and it will break before make.
Since the generator only puts out 120 volts I could not power any 240 volt circuits. I installed a sub panel and moved all my 120 volt circuits to it. I powered the sub panel through the transfer switch. Each bus in the sub panel, of which there are 2, would be connected to one of the 2 outputs of the generator. When connected to the mains each buss is connected to one 120 volt 30 amp circuit, which makes for a maximum of 60 amps available for all circuits connected to the sub panel. This is more than enough to power all 120 volt circuits in my home. The only down side of this (no 240 volt) is that the heat pump, water heater and dryer are not powered. But, all lights, refrigerator, satellite TV etc are powered.

Now to make the connection to the generator I did the following:

I installed a 30 amp socket to the generator output and connected the neutral to the ground lug and the 2 hot wires one each to the other two spades. I installed a plug on the wire to the motor home which was once connected directly to the generator. Now I can disconnect the motor home from the generator and connect the house to the generator.
I installed a 3 prong dryer socked to the motor home end of the shore power cable and attached a 3 prong dryer plug to the motor home shore power input. I also attached the same 3 prong dryer plug to the wire connected to the double throw transfer switch for the home.
Now when I want to use the motor home generator to power my house I unplug the shore power cable and plug the 30 amp plug into the generator socket and plug the dryer plug attached to the transfer switch to the other end of the shore power cable.
When I flip the transfer switch now the motor home generator is connected to my house and all my 120 volt circuits are live. Works great!
As an added bonus to this all, now that I can disconnect the motor home from the generator I can add an additional shore power plug in to run both A/C’s at the same time while on shore power. I made an adapter to connect the generator circuit to A/C #2 and use a 20 amp cord to connect it to shore power. This also works great!
Michael

woodburner · 03-24-2012, 02:35 PM

I've wanted to do the same thing and one of the warnings I've read is you have to have a switch to keep the power from back feeding into the grid from what I can garner.
You wouldn't want to mess up a lineman's day by having him think the grid is dead when he's out there trying to restore your power; was essentially the thought behind it.

mmcl26554 · 03-24-2012, 02:44 PM

That is what the triple pole double throw transfer switch, I purchased off eBay does. It was less than $20. Actually the box I mounted it in was more expensive than the switch.

However, I wonder how they deal with homeowners who have alternative power such as solar or wind and DO feed power back into the grid and the power company buys it from them.

85antique · 03-24-2012, 02:57 PM

On solar and wind generators for homes the inverters need to see a pure sine wave or they shut down to prevent back feed
I did the same thing as you except my gen is 240 volt 7200 watts

mmcl26554 · 03-24-2012, 03:09 PM

I figured there must be something like a device which shut down the alternative power feed if the mains went down.
I suppose there may be many who have adapted their motor home generator to house power standby, but I didn't see any posting about it. But, it sure is nice to have.
Michael

Matchayan · 03-24-2012, 08:45 PM

Thanks for the post I have been wanting to do this with my MH, can you tell me the exact name of the transfer switch or provide a link I would like to order one.

mmcl26554 · 03-24-2012, 08:58 PM

Higher amperage switches are also available if you want from this same company.
here is the ebay link:
eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices
Feel free to ask me any questions either by posting or PM
Michael

ARFFMAN · 03-25-2012, 09:59 AM

I live in SC and as you know wwe are prone to Hurricanes, which comes with power outages.
I have a 6.5 KW in my MH and love your idea. I have read your post with great interest.
Being a Firefighter I don't leave the Island during an evaculation. Sometimes power is disconnected by Elect. Co. ( even though, no hurricane) I understand electricity enough to respect it. Is it possible to get a diagram on your hook up of your system?

mmcl26554 · 03-25-2012, 11:08 AM

Yes, I would be happy to make up a schematic of the connections, however, it will take me some time to do it, so you can read it. I will also take pictures of things. I have never posted a graphic image on any forum, but if it is allowed here I will, I just need to figure out how to do it. But, I will make one up and post it as soon as I can.
Michael

UltraKen · 03-25-2012, 11:50 AM

I just pull the mains if I'm using the generator to power the house through my shore-line.

That eliminates any chance of back-feed.

During an ice storm that took down most power in my area I put a sign on my meter saying that the mains were disconnected and to please let me know when power was back up.

mmcl26554 · 03-25-2012, 02:45 PM

Ultraken, That would work, but it's not what's recommended. Do you have enough generator to support your whole house. With my system you could leave one light connected to the mains and when the power came back it would light.
Michael

Fiesta48 · 03-25-2012, 03:14 PM

These all seems like too much work. I have a 30A Male to 15A Female adapter for the RV then run a heavy duty cord inside to the house to run the frig/heater/fan and/or light(s) for the few times we have lost power. And remember your generator cost $4/hour now (@1 gal/Hr.) to operate.

mmcl26554 · 03-25-2012, 03:49 PM

Fiesta48. Your way certainly is less complicated and if that is what you want that's geat. In my case I like projects like this and in this project I also replaced my main breaker panel as it had one bus which had overheated and it needed replacement. Additionally, the "professional electrician" who wired my home was poorly organized and the main panel was a "rat's nest" of wires it looked awful. For me this is fun, and in the end I get a new main breaker panel, a better organized electrical wiring and an easy to connect standby power system.
Michael

mmcl26554 · 03-25-2012, 03:58 PM

For those of you who want my drawings and pictures I have them completed, however the files are to large to post here. Anyone who wants a copy please PM me you email address and I will send them. They are in a .DOC format and can be read with Microsoft word. The complete document with pictures and drawings is 6Mb and the document with drawings only is 8Kb. Let me know which you would like me to email.
Michael