Revisiting the PTO-generator question

[Jim_W]

Just read this entire thread - whew.
I have set my house up to run from a genset if needs be, but have done something slightly different.
First, I do have a main panel and a separate smaller panel with my four "critical circuits", but between them I have a DPDT relay (break before make) in its own box. The "output" of the relay is the input to my secondary panel, and the NC contacts connect to the main panel. The NO contacts connect to a MALE plug in a weatherproof box on the side of the house where I plug in the generator. They are also connected to the coil of the relay.
So, the generator energizes the relay, which first disconnects from the main panel, and then connects to the generator. There is thus no possibility of feeding back into the grid.

The relay does not switch neutral, just the two "hot" wires. Neutral is connected to ground in the main panel. The code here (Ontario) tells you to use a four wire cable from the generator i.e. keep its ground and neutral separate so that when connected to the house, it gets grounded at the panel. Grounding both the generator and the panel raises the possibility of ground loops, which are to be avoided.

Anyway, it's safe regardless of who hooks up a generator, which was my main concern. Having said that, this arrangement does not seem to be covered in the code anywhere. I don't know if I violated it but all the individual parts are CSA approved.....

 

[Egon]

Trev:
Again days late as I have just driven across Canada again. But back to your idea. It will work. In one of the plants I worked in that was the exact way the switch was done. I had the privilage of designing a lock out system so the main power was off before the generator was put on line.
Egon

 

[Spencer]

Wow, I guess my buddy did me a bigger favor than I thought. That 400 amp triple pole double throw switch cost more than $5,000 at Graingers. Maybe I should sell it and get a 200 amp?

 

[Trev]

Spencer..

Wow! Any idea how much for a 200 amp? Your buddy got any of those lying around? /w3tcompact/icons/grin.gif

Hey, one last question guys: suppose, in an emergency situation, you end up having to backfeed someone's dryer plug. Say the circuit is rated for 30 amps. If you accidentally exceed that, will the breaker take care of it? If not, is there some way I can monitor load? All I have on the generator is voltage and frequency meters. I have no idea how many amps are being pulled at any given time. Is there an easy way to measure this.. perhaps some kind of meter that hooks between the generator and the plug you are using? Or perhaps I could somehow wire in a 30-amp circuit breaker right into my cord?

Thanks,
Bob

 

[MossRoad]

Doesn't your generator have circuit breakers built in?

 

[Trev]

<font color=blue>Doesn't your generator have circuit breakers built in?</font color=blue>

Yes, but the 240 receptacle is rated at 50 amps, so I could melt that 30 amp wire without tripping the generator breaker, right? But the current is still passing through the house breaker, which, hopefully, is rated correctly for the ciruit.

I just wasn't sure if backfeeding power would allow the circuit I'm backfeeding to function normally regarding the breaker?

 

[MossRoad]

<font color=blue>Yes, but the 240 receptacle is rated at 50 amps, so I could melt that 30 amp wire without tripping the generator breaker, right? But the current is still passing through the house breaker, which, hopefully, is rated correctly for the ciruit.

I just wasn't sure if backfeeding power would allow the circuit I'm backfeeding to function normally regarding the breaker? </font color=blue>

That makes sense.

Just my opinion, but I would never backfeed a neighbor's house, just because of the liability involved. Death, fire, destruction have all been covered before. And you have expressed your own concerns about your knowledge of elecricity, hookups, code, etc...

In an emergency at your neighbor's house, get some extension cords to run their major appliances like refrigerator and freezer, or invite the neighbors over to keep warm at your place if you have power.

Hey, I have an associates degree in industrial electronics, covering motors and motor controllers and I don't feel comfortable doing this stuff(maybe that's a good thing /w3tcompact/icons/smile.gif )

I think you are on the right track talking to your electrician about installing a permanent transfer switch. It is the safest, smartest thing you could do. /w3tcompact/icons/smile.gif

Did you get any quotes yet?

 

[Trev]

<font color=blue>In an emergency at your neighbor's house, get some extension cords to run their major appliances like refrigerator and freezer...</font color=blue>

You know, I've heard this suggestion.. but it isn't entirely clear to me how that would work. The generator has one 50 amp 220 outlet, two 10 amp 110 outlets, and one weird square plug that I believe gives you the full 70 amps (and which our electrcian will use for the transfer box.)

Given that, it seems like to be able to run things with extension cords, I would have to limit what I do to just powering two 110 circuits at a time, or I'd have to wire up some system to tap into the higher output sockets and then provide a bunch of outlets to plug the extension cords into (somehow stepped down to 110v, and protected with proper circuit breakers.) Would I just buy the kind of extension cords like we use with computers.. one line that breaks into 5 or 10 distinct 110 outlets? Would my two 10 amp outlets have enough power to run a fridge, freezer, and furnace, for example, without exceeding the amperage?

Maybe it's easiest and safest to just power two circuits at a time? Am I making this a lot more complicated than it has to be? /w3tcompact/icons/blush.gif

<font color=blue>Did you get any quotes yet? </font color=blue>

No.. he's looking into it.. along with getting ready for X-mas, etc. He'll get back to me soon, he said.

Thanks,
Bob

 

[MossRoad]

You could get a small box that would hold 6 or 8 110v 15 or 20 amp circuit breakers made up. Mount it on a board with several duplex outlet boxes. EDIT. Then run that off of the 220v circuit.

 

[Trev]

Thanks Moss.. I'll run it by our electrician.. I wouldn't want to make this up myself.. but it sounds like a great idea.

Bob