Ford F150 power boost generation

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wattruler1

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Hello all, I have installed dozens of 30 and 50 amp residential main panel generator interlocks in the last couple years here in Texas. Today I did the same for a gentleman who wanted to power his panel with his 7.2 KW power boost generator on his hybrid Ford F150. I didn't do my due diligence, even though he did mention watching some concerning videos about this, and the truck's built in GFI protection will trip since the house panel has it's neutrals and grounds bonded together. I know now the error of my ways. The homeowner was really hoping for a solution not involving a transfer panel. Newer transfer panels that open the neutral would work. At least that is what my research has told me. But then you are limited to around 6 circuits and then stuck with them. My question (finally) is could I install a 3 pole main breaker switch before the panel to break the neutral and at the same time separate the grounds and neutrals in the panel and make it a sub panel as a solution ?
 
Same issue. A system has to have a ground to neutral bond somewhere, but you can't have a ground to neutral bond downstream of a GFCI.

So if you have a gen with a GFCI output, the you need the generator bonded and a transfer switch that switches the neutral.

Jon
 
ptonsparky said:
You need a three pole transfer switch feeding a small sub. Neutral being transfered as well as hots.

Forget the 3 pole breaker. No way to guarantee it gets turned off even if it was of the type designed to switch the neutral.
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^^I second this^^
It would be bad to have something not turned off properly only to have his new truck inverter burnt out when the power came back on.
 
I would trust breakers if interlocked.

The key is that you want to switch the neutral at the same time and with the same reliability as switching the line inputs.

A pair of _interlocked_ breakers can do this.

Jon
 
Hv&Lv said:
^^I second this^^
It would be bad to have something not turned off properly only to have his new truck inverter burnt out when the power came back on.
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In terms of damaging the inverter. If I do install a 3 pole breaker at the meter to open the neutral, the interlock that I put in already on the interior main panel would still be in place so that no damage could be done to the inverter. So he would have to turn off the main inside, turn on the gen inlet breaker and also go outside and turn the 3 pole breaker off. If he did not open that outside breaker the only thing that would happen is the GFCI on the truck or any subsequent 240 volt GFCI protected gen would kick off.
Related question: The technology of a 120 v GFCI outlet or breaker is that a coil looks for a 5 mA difference between hot and neutral, correct ? Why should it matter if neutral and ground are bonded ? Why is it seemingly different for a 240 v breaker. Or is it ? Please explain. I've been an electrician for almost 50 years but clearly no engineer. Clearly. :)
 
wattruler1 said:
Related question: The technology of a 120 v GFCI outlet or breaker is that a coil looks for a 5 mA difference between hot and neutral, correct ? Why should it matter if neutral and ground are bonded ? Why is it seemingly different for a 240 v breaker. Or is it ?
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It's not different for a 240V breaker. The issue arises whenever you have a neutral-ground bond on each side of the GFCI. That allows some neutral current to return via the EGC, bypassing the GFCI, which creates a current imbalance that trips the GFCI.

Cheers, Wayne
 
wattruler1 said:
The technology of a 120 v GFCI outlet or breaker is that a coil looks for a 5 mA difference between hot and neutral, correct ? Why should it matter if neutral and ground are bonded ? Why is it seemingly different for a 240 v breaker. Or is it ? Please explain. I've been an electrician for almost 50 years but clearly no engineer. Clearly. :)
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the CT in a gfci performs basically the same function as the one in a 240 two pole breaker.
Fairfield chips are in GFCIs for logic with a pair of toroid transformers. One measures difference between hot and neutral as you stated. The other measures difference between neutral and ground. Connecting the neutral and ground downstream create false readings in the second toroid circuitry.
 
Hv&Lv said:
the CT in a gfci performs basically the same function as the one in a 240 two pole breaker.
Fairfield chips are in GFCIs for logic with a pair of toroid transformers. One measures difference between hot and neutral as you stated. The other measures difference between neutral and ground. Connecting the neutral and ground downstream create false readings in the second toroid circuitry.
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Actually the neutral to ground detection is not passive. It uses one coil to impose a voltage between downstream neutral and ground and looks for resulting current. The voltage is imposed such that it will not drive current through the upstream bond, which will always be present.
 
Todd0x1 said:
We'll probably see alot of people getting around this issue by not connecting the EGC to the truck.
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I think it has already happened. Lots of reports coming in from Florida saying that truck has been a Godsend. I also saw a video where part 1 it wouldn't work and part 2 it did. The only way would have been to remove the ground or isolate and open the neutral. Removing the ground cannot be a good idea. I think this truck and the forthcoming portable gens with 240 v GFCI protection will mean the end of interlocks and backfeeding the panel. Anybody ?? Buehler ??
 
Perhaps it will mean the return of 'delta breakers', but rather than the 3rd leg being used for a solo 3 phase load in a panel, it will be used for switching the neutral.

There is certainly a market for an easy to connect manual transfer system, and the basic mechanical interlock on a panel could be extended to switch the neutral.

-Jon
 
Todd0x1 said:
We'll probably see alot of people getting around this issue by not connecting the EGC to the truck.
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I’ve seen posts in online forums from several people doing this. It could result in a small voltage gradient between the truck chassis and home grounding system, but not likely to be a significant safety issue, IMO.
 
Todd0x1 said:
We'll probably see alot of people getting around this issue by not connecting the EGC to the truck.
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retirede said:
I’ve seen posts in online forums from several people doing this. It could result in a small voltage gradient between the truck chassis and home grounding system, but not likely to be a significant safety issue, IMO.
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I agree, but if the neutral through the cord somehow gets open circuited and there's a L-N load, then the truck chassis could be up to 120V relative to ground. The GFCI should trip is there's sufficient leakage current from the truck chassis to ground, but then you're depending on having a functional GFCI.
 
synchro said:
I agree, but if the neutral through the cord somehow gets open circuited and there's a L-N load, then the truck chassis could be up to 120V relative to ground. The GFCI should trip is there's sufficient leakage current from the truck chassis to ground, but then you're depending on having a functional GFCI.
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How so? The open end of the neutral on the load side of the break would be at 120v, but not the truck chassis. Or do I have this wrong?
 
Todd0x1 said:
How so? The open end of the neutral on the load side of the break would be at 120v, but not the truck chassis. Or do I have this wrong?
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My comment is for the case in your post #13 where the EGC is disconnected from the truck outlet to prevent the neutral from being bonded to the EGC on both sides of the GFCI, which would then cause it to trip. But because this would be done to avoid switching the neutral, the neutral on the load side of a break in the cord will remain bonded to the GES. And so both the neutral and EGC going to the truck inverter would be disconnected, leaving only the hot lines connected. For simplicity, assume that the only load is between L1 and N. Then because the neutral to the inverter is open, there will be no current through this load and therefore no voltage across it, causing L1 at the inverter to be at 0V relative to ground. This will make the neutral of the inverter, and therefore the truck chassis to which it's bonded, be at 120V relative to ground.
 
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