My “Unintelligent” backup power installation

For those interested, I thought I’d share what I’ve done. The installation shares the conduit run with power to the FCSP, so I can’t give an exact cost of the installation.
Here are the major components:
Generator cord and inlet, $62.88
Heavy duty enclosure for transfer switch, $97.97
100A 4 pole transfer switch, $43.43
Wire, $153.57


100A loadcenter used as a disconnect for the FCSP. Generator inlet attached.


With cover on.


Transfer switch mounted and wired. It switches the neutral, so there is no need to cheat and eliminate the ground to the truck.



Main panel on the right, subpanel that serves loads to be powered by the backup in the center, transfer switch on the left.

There is approximately 90’ of 1-1/2“ PVC conduit between the FCSP disconnect panel and the transfer switch. Almost 100’ of wire. I ran #8 from the inlet to the transfer switch to minimize voltage drop - about 1.5% fully loaded.

Wire to the FCSP originates in the main panel and is #1 aluminum to the disconnect. #3 copper from the disconnect to the FCSP.

I haven’t done a test of running things on the truck yet - the wife is canning tomatoes in the kitchen today, I don’t want to interrupt that process.

Slick, so instead of running the gen cord across the whole garage, it's essentially routed in the same conduit that supplies the charger. WIll you link the xfer switch?

bmwhitetx said:

Slick, so instead of running the gen cord across the whole garage, it's essentially routed in the same conduit that supplies the charger. WIll you link the xfer switch?

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What do you mean “link the transfer switch”?

Don't you find it frustrating if your critical loads panel is using well below 7.2kW, but you can't turn on any circuits from the main panel because they're isolated?

Trouble with a critical loads panel is that you can't put circuits bigger than 30A in them. Whereas I've found load management in my 200A main panel works great with the ProPower's 30A output. For example, I can still use all my regular 110V circuits (lights, etc) but ALSO power my home's heat pump AC which, whilst it's on a 60A circuit, usually uses between 2kw and 5kw, or the kitchen's electric oven. I've powered my entire home including AC for a full (hot) day from ProPower via 30A generator inlet straight to the main panel, with interlock kit of course.

Thanks for this! I've been considering doing something like this for emergency backup.
The hurtle I haven't tackled yet is being limited to 30amps on the bed outlet.
I'm hoping eventually there will be some type of product (other than the SunRun) that will work with the CCS plug to get the maximum draw so I could run the HVAC.
I've looked at getting an AC soft starter, but I'm not sure if the 30amp outlet in the bed will be enough.
Being from Florida I have to worry about Hurricanes, so having the truck as a big battery is a huge benefit.
Currently, if I need to, I just using extension cords to power some appliances.

Maquis said:

What do you mean “link the transfer switch”?

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Ha, sorry. I meant put a link to the transfer switch you got or tell us the name. I'll try not to be so succinct next time!

bmwhitetx said:

Ha, sorry. I meant put a link to the transfer switch you got or tell us the name. I'll try not to be so succinct next time!

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Sorry, I should have realized what you meant.
https://www.amazon.com/dp/B0C2KLSZP3?ref=ppx_yo2ov_dt_b_product_details&th=1

I bought a 4 pole because it was about the same price and was in stock. They now only show a 2 and 3 pole, but 3 is all you need.

petemill said:

….30A generator inlet straight to the main panel, with interlock kit of course.

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The problem with that is you can’t switch the neutral so the truck will throw a ground fault.

I actually have everything I need in the subpanel except AC. My food won’t spoil, the beer will be cold, I can cook, lights will be on, and I’ll have internet.

My main panel feeds 3 subpanels, my sauna, clothes dryers, AC and a few other things I can live without such as gas fireplace blowers, jacuzzi, bathroom floor heat, secondary bedrooms (kids are grown and gone) and the FCSP.

Maquis said:

Sorry, I should have realized what you meant.
https://www.amazon.com/dp/B0C2KLSZP3?ref=ppx_yo2ov_dt_b_product_details&th=1

I bought a 4 pole because it was about the same price and was in stock. They now only show a 2 and 3 pole, but 3 is all you need.

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That does not appear to be UL listed. Would it pass inspection?

v2h8484 said:

That does not appear to be UL listed. Would it pass inspection?

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It’s not listed. Depends on how picky the inspector is. We have no inspections here.
That’s one reason the box I mounted it in is the most expensive component. If the thing blows up or melts, it will be contained.

I couldn’t find a listed 3 pole transfer switch I liked. They were all really bulky or were built into a subpanel that was too small for my use. I’ve checked the temps on it after everything running about 6 hours and detected no heat whatsoever.

Another consideration is the fact that it’s capable of automatic operation, which means it’s designed to switch while under load. I’ll only use it manually and introduce the loads after I switch to the alternate power source - in other words, I am using it to do way less than it’s designed to do.

I’ll certainly provide an update if I have any issues with it or anything else in my setup.

What is the issue with no ground connection from the truck generator 240 outlet to the panel connection? The truck generator neutral is grounded at the main panel. That means that the "truck ground" is whatever the voltage drop of the neutral is running back from the main panel when the line currents aren't balanced. Are there safety concerns for those installations that do not connect the generator ground?

theUNSTABLE said:

I've looked at getting an AC soft starter, but I'm not sure if the 30amp outlet in the bed will be enough.

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Our small (3Ton?) Bryant Evolution V 189BNV variable speed air conditioner pulls less than 10A at 230V at maximum use with no surge current (and is relatively low noise). I think they have a heat pump version as well to combine with a furnace setup. I cannot figure out why it shows 31.4A "minimum circuit Amps" and needs a 50A circuit breaker.
Our small 3 bedroom house has a 200A Main panel and solar, but solar has to drop when generator powers house when Utility is cut off.

rraustad said:

What is the issue with no ground connection from the truck generator 240 outlet to the panel connection? The truck generator neutral is grounded at the main panel. That means that the "truck ground" is whatever the voltage drop of the neutral is running back from the main panel when the line currents aren't balanced. Are there safety concerns for those installations that do not connect the generator ground?

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The bonding of the ground and neutral legs in the main house panel is interpreted by ProPower as a ground fault. That is why the neutral has to be switched from the main panel to the sub panel the truck is feeding.

rraustad said:

What is the issue with no ground connection from the truck generator 240 outlet to the panel connection? The truck generator neutral is grounded at the main panel. That means that the "truck ground" is whatever the voltage drop of the neutral is running back from the main panel when the line currents aren't balanced. Are there safety concerns for those installations that do not connect the generator ground?

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As you say, when there is voltage drop on the neutral, the truck frame will be elevated to this voltage with reference to the house grounding system. If you have 5% voltage drop on the neutral for example, you would measure 6 volts between the truck and the house ground. Probably not a big deal.
If you have a short circuit (L to N) on one of the loads, the voltage drop could increase by several times during the split second it takes the breaker to trip. The low available fault current from the truck probably limits that effect. The code is written this way because if you have a large generator, the danger is very real. With the truck as the power source, you’re more likely to get killed by a lightning strike (pun intended ).

Maquis said:

I couldn’t find a listed 3 pole transfer switch I liked. They were all really bulky or were built into a subpanel that was too small for my use.

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I wonder if the compact size of the unlisted ones is the reason why they can't get listed for some reason (e.g. not enough arc clearance).