Generator Transfer switch connection choices

[joshuabardwell]

If you look over the choices I have listed, if your main panel has a option for the interlock kit, that really is going to be the easiest and cheapest solution.

Yeah. I have checked my main service panel, and I have no breaker locations free. But I hear you can get piggyback breakers to address that problem. My current generator is 5000W continuous, so I would need something like 20 amps at 240v or 40 amps at 120. If I understand correctly a pair of 20 amp 120v breakers backfed from the generator with an interlock would do the trick. Is that right?

 

[Todd727]

Hmm... so if codes are involved, it wouldn't be possible to hook up a portable generator and then only activate circuits as needed? But if I install an interlock setup with a backfeed breaker, then that's fine? What's the logic there?

Codes are always involved.

 

[daybreak1998]

Hmm... so if codes are involved, it wouldn't be possible to hook up a portable generator and then only activate circuits as needed? But if I install an interlock setup with a backfeed breaker, then that's fine? What's the logic there?

Howdy,
"The interlock"

The interlock makes it so only 1 breaker can be on. The main panel breaker, or the generator breaker. So, you turn off the main 200amp breaker, slide the metal interlock, and now you can turn on the generator breaker.
click on the picture to see larger, then click again to zoom in.


Your panel needs to have a interlock kit for it. It usually needs the 2 top right spaces for the generator breakers. If your panel is full, a lot of times you can get half breakers to help make some room.

 

[Steave]

Hmm... so if codes are involved, it wouldn't be possible to hook up a portable generator and then only activate circuits as needed? But if I install an interlock setup with a backfeed breaker, then that's fine? What's the logic there?

Some codes don't seem logical sometimes. I would guess their thinking would be once the transfer switch was thrown if the generator isn't large enough to carry what ever load it needs it would cause a problem with the generator struggling to keep up.

Sometimes it don't make sense to me. When the power goes off things like a clothes dryer which pulls a lot of power does not start back up automatically, but a water heater that was heating at the time of power lost will try to start up when power is reapplied. If your generator is too small to restart your load and you forgot to turn off the breakers there's the potential problem.

Not all Local codes call for the permanent ginny but most do.

 

[Steave]

Yeah. I have checked my main service panel, and I have no breaker locations free. But I hear you can get piggyback breakers to address that problem. My current generator is 5000W continuous, so I would need something like 20 amps at 240v or 40 amps at 120. If I understand correctly a pair of 20 amp 120v breakers backfed from the generator with an interlock would do the trick. Is that right?

Use a 30 amp double pole breaker for the backfed breaker. Using a double pole if you get a fault on a 120 volt circuit it will trip all the power from the ginny. Much safer. Same price.

 

[hr3]

What if you do overload your generator,, It has it's own breaker to protect it's self .. As for the DPDT switch after the meter,, you need a breaker or fuses before it.. so at that point it could be DIY...

 

[TerryR]

I don't understand why I can't just put a 200A DPDT break-before-make switch in between the meter and the main panel, and have the generator plug into that.

We did exactly that when we had our house built 15 years ago, though our generator is hard-wired into the switch. The inspector didn't raise any objection, so I assume it passed local code then at least. No meter collar was required because the switch is between the meter and the main panel.

One downside is you then have no indication of when utility power is restored (unless you have nearby neighbors you can see), so we had an LED indicator wired into the utility side to tell us.

This system works great for us, but it doesn't include automatic transfer (nor is our generator auto-start) so it doesn't work while were are away.

Terry

 

[sparc]

Here's another possibility for a whole house transfer switch.

Honda HP2S Portable Power Systems: Universal Transfer Switch

 

[joshuabardwell]

Some codes don't seem logical sometimes. I would guess their thinking would be once the transfer switch was thrown if the generator isn't large enough to carry what ever load it needs it would cause a problem with the generator struggling to keep up.

I just don't see why the NEC would care if I overload and damage my own generator. I must be missing something.

 

[Agent Blue]

I wired in the ProTran 10 circuit model. Works great... no problems. Got to use it for 4 hours a couple weeks ago when the power went out. The Honda 5500 fired up instantly, never missed a beat. Great setup.