50 Amp 240V over/under voltage protection for home generator use for backup power to home

Thread Starter

Old Man Here

Joined Mar 29, 2021
3
New member here. I want to say hello to the members of this forum.
Last year I had to replace the AVR on my Generac GP15000E generator which failed, and the generator was putting out 350 volts.

I was lucky because I was doing an exercise run with 2 1500 watt ceramic heaters. One thing I always do is check the voltage and HZ before I place the generator on line.

I really like the idea of the Southwire Surge Guard 50Amp – Model 34951 to use for my 15,000 watt generator for home backup power. These units are made for the RV community.

Reading the documentation for these, it appears that the Surge Guard will not allow power to the output side to the house if the generator has a floating neutral.

The unit terminates service to the house if voltages drop below 204V or rises above 264V. It will not restore power until the voltge is in the correct range.

My neutral is bonded at the main disconnect panel at the meter. My service panel in the house, has the manual lockout transfer switch, so this requires me to have a floating neutral on the generator.

Surge Guard says the generator must have the neutral bonded in the generator before it will allow power to the RV (or my house in this case).

Is there any type of over/ under voltage device that can be used with this generator that provides the same over/under voltage protection that is rated for 50 Amps?

The only thing I can find are your typical surge suppressors that do not provide this type of protection.
 

Hymie

Joined Mar 30, 2018
991
Presumably the Surge Guard needs the Neutral grounded (not floating) in order to supply the output voltage. If this is the case, the generator Neutral could be connected to ground before it enters your home.
 

Thread Starter

Old Man Here

Joined Mar 29, 2021
3
Presumably the Surge Guard needs the Neutral grounded (not floating) in order to supply the output voltage. If this is the case, the generator Neutral could be connected to ground before it enters your home.
Hymie, thanks for the reply.
I cannot connect the Neutral to the Ground at the generator, due to the fact that the house "Main Disconnect" at the meter is the single point where the Neutral and Ground is connected.
Neutral and ground are only bonded at the point where electricity enters the home, never anywhere else.
That is why I am trying to find a device that doesn't look for the Neutral connection.

I'm looking for over/ under voltage protection without the Surge Guard Safety features for RV's which do not have a Neutral bonded electrical system like our homes do.
 

Hymie

Joined Mar 30, 2018
991
But could you not somehow make this connection – it should not affect the safety of the installation if the generator Neutral is grounded at some point outside the home, which is normal for a utility mains supply.
 

crutschow

Joined Mar 14, 2008
27,696
Why not connect the neutral point from the panel to the ground at the generator with a wire?
I don't see a problem with that.
 

sagor

Joined Mar 10, 2019
479
Portable generators (for RV) are different than home generators in terms of hookup. Home generators rely on the house neutral/ground path, and there can be one and only one "ground" in the entire home system, usually your electrical service ground. For RV, a portable generator has no house ground, and you must provide your own ground stake, or tie the neutral in the RV to the generator, which must have neutral tied to the "frame". Again, only one path to ground.
In most home generator systems, the neutral must be floating in the generator, so it relies on the house ground path as installed in your electrical system. In portable generators, there is no such neutral, and the generator chassis must provide it.
Some electrical codes may allow switching a home generator neutral away from the house neutral if the generator has its own ground system and the transfer panel also switches the neutral. This varies by location. In home systems, with a generator with a floating neutral, the neutral is not switched, it is left connected in most cases.
You cannot connect 2 different grounds in a home generator setup!! You must not, ever, connect a generator with a grounded neutral at the frame to the house neutral. Never. Pick one ground or the other (depends on generator design - floating or fixed neutral). Two neutral connections can cause ground loops and other electrical dangers. Follow the electrical codes...
Summary:
Neutral on generator bonded to frame - cannot connect to house neutral. Transfer panel must move neutral from house to generator. Generator should have a proper separate ground connected to frame.
Neutral floating on generator - neutral remains fixed to house neutral, never disconnected.

If your generator has a grounded neutral but your transfer panel has hard wired neutral to house, you have to either change generator or change transfer panel. Opposite - if generator has floating neutral and transfer moves the neutral, you will have no "ground" at all - you must change transfer panel to proper type.
 

Thread Starter

Old Man Here

Joined Mar 29, 2021
3
Portable generators (for RV) are different than home generators in terms of hookup. Home generators rely on the house neutral/ground path, and there can be one and only one "ground" in the entire home system, usually your electrical service ground. For RV, a portable generator has no house ground, and you must provide your own ground stake, or tie the neutral in the RV to the generator, which must have neutral tied to the "frame". Again, only one path to ground.
In most home generator systems, the neutral must be floating in the generator, so it relies on the house ground path as installed in your electrical system. In portable generators, there is no such neutral, and the generator chassis must provide it.
Some electrical codes may allow switching a home generator neutral away from the house neutral if the generator has its own ground system and the transfer panel also switches the neutral. This varies by location. In home systems, with a generator with a floating neutral, the neutral is not switched, it is left connected in most cases.
You cannot connect 2 different grounds in a home generator setup!! You must not, ever, connect a generator with a grounded neutral at the frame to the house neutral. Never. Pick one ground or the other (depends on generator design - floating or fixed neutral). Two neutral connections can cause ground loops and other electrical dangers. Follow the electrical codes...
Summary:
Neutral on generator bonded to frame - cannot connect to house neutral. Transfer panel must move neutral from house to generator. Generator should have a proper separate ground connected to frame.
Neutral floating on generator - neutral remains fixed to house neutral, never disconnected.

If your generator has a grounded neutral but your transfer panel has hard wired neutral to house, you have to either change generator or change transfer panel. Opposite - if generator has floating neutral and transfer moves the neutral, you will have no "ground" at all - you must change transfer panel to proper type.
Correct you are. Now back to my original question...

Is there an over/under voltage device on the market that terminates service from the generator to the house, if voltages drop below 204V or rises above 264V that will not restore power until the voltage is in the correct range? One that does not need to sense the open neutral at the generator.
If not, is it possible to construct such a device that will handle 50 Amp 240V?
 

sagor

Joined Mar 10, 2019
479
Correct you are. Now back to my original question...

Is there an over/under voltage device on the market that terminates service from the generator to the house, if voltages drop below 204V or rises above 264V that will not restore power until the voltage is in the correct range? One that does not need to sense the open neutral at the generator.
If not, is it possible to construct such a device that will handle 50 Amp 240V?
Such a function would have to be part of the generator itself, where the voltage is regulated in the first place. If you have such a device, how do you engage/disengage it without affecting the generator and what it sees as a load? That is because when you drop a load (say you detect 204V), the generator voltage will then move up with no load and re-engage your sensor/device. When the sensor enables again, you get a sudden load and voltage will drop again. This will cycle forever.
Overvoltage may be easier to detect and disconnect, as that voltage may not drop when the load is disconnected (it will increase even more). Frequency of the power (Hz) will change as well. You should be monitoring that as well.
But, to answer the question, no, I do not know of such a device, especially one that works with a generator.
 
Top