Revisiting the PTO-generator question

Jim_W · Dec 21, 2002

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 · Dec 22, 2002

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 · Dec 22, 2002

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 · Dec 22, 2002

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 · Dec 22, 2002

Doesn't your generator have circuit breakers built in?

Trev · Dec 23, 2002

Doesn't your generator have circuit breakers built in?

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 · Dec 23, 2002

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? 

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 · Dec 23, 2002

In an emergency at your neighbor's house, get some extension cords to run their major appliances like refrigerator and freezer...

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

Did you get any quotes yet? 

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 · Dec 23, 2002

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 · Dec 23, 2002

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

Spencer · Dec 23, 2002

Trev, Carol brand (division of General Cable) makes what they call "Gen-Cords". Their 220 volt version has a twist lock on one end to plug into your generator and then they have a box on the other end that has both 110 volt and 220 volt outlets in it. Grainger sells them but at a high price. I have attached a picture from Graingers website to show you what I am talking about.

Spencer · Dec 23, 2002

Here are the specs for the various Gen-Cords that Grainger sells.

Anonymous Poster · Dec 23, 2002

Point 1, magnetic circuit breakers will work equally well for cvercurrent protection regardless of feed dorection.
Point 2, the $3.00 computer cord with 6 outlets will work well for generator distribution. You are better served using the more expensive version with it's own circuit breaker.
Point 3, the number of things you truly need to run from a genset in an emergency is small, and other than yout furnace, most of them can be run off an extension cord.
Point 4, Most furnaces require about 5 amps. You can easily set your furnace up with a plug and receptacle for normal operation so you can just pull the plug and run the furnace from a cord in an emergency situation.
This stuff ain't rocket science.
A generator will tolerate a lot of current imbalance, but runs far better & cooler with a balanced load. You can spend lots of money on fancy controls & meters, OR, you can buy an Amprobe type meter on Ebay for about $30, and employ it to balance your load.
Load balance is rarely proper or equal in a residential service because the people installing services rarely consider load balance.
The most difficult starting loads will be sump pumps and furnace blowers because of the type motor used in those applications. Well pumps and other motors that are capacitor start put far less load on the generator when starting than sump pumps do.

Anonymous Poster · Dec 23, 2002

HUH...? Are you sure about #1. ??

MossRoad · Dec 23, 2002

I agree with all of your points except for Load balance is rarely proper or equal in a residential service because the people installing services rarely consider load balance I think most electricians try to balance the loads. Most installations that I have seen seem to have the heavy 110 appliances split almost evenly between sides. Aren't all 220v appliances automatically load balanced since they pull 110 from each leg?

Also, I got the impression that Bob wanted to accomplish two things:

1. Install a transfer switch in his house, so all he would have to do is plug in the generator, fire it up and flip one switch to get it going. That requires two things; a transfer switch and a power cord.

2. Be able to help out the neighbors without re-wiring their houses. That's where I think a power distribution panel would be better than a couple of computer-type power strips.

The generator has one 50 amp 220 outlet, two 10 amp 110 outlets

Would my two 10 amp outlets have enough power to run a fridge, freezer, and furnace, for example, without exceeding the amperage?

That might be pushing it. My freezer and fridge each pull 8 amps at start up and my furnace pulls 5 or 6. That's 21 amps. Add the sump pump you mentioned, and it'll pop the breaker.

By using a panel box with multiple breakers fed from the 50amp circuit on his generator, he could run more circuits than he could from the two 10 amp 110 outlets. A panel of this type could have several 110 and 220 breakers. It wouldn't cost that much to put together and would be very handy.

But you are right. This ain't rocket science and he could get by in an emergency with two power strips and extension cords for a while.

And I like your idea of wiring your furnace with an electrical cord into an outlet instead of directly into the breaker panel. Then it would be just a matter of unplugging from the outlet and plugging into the generator. That is good advice to anyone that doesn't want to go with a transfer switch. You could do that with any appliance, I suppose? I'd probably use twist locks, just to make sure the cords didn't get knocked out accidentally.

Anonymous Poster · Dec 24, 2002

Am I sure? Well, let me think, I been to the other side of the world and back installing gensets and making them work. I been connecting wires to make things work for the best part of 48 years. My License says Mine Safety & Health Administration Electrician.
YUP, I'M SURE!
NOTE, Magnetic breakers, not all breakers.
By the way, I own 13 gensets and service about a hundred more. So far, I have yet to blow one up. Now, would you like to discuss how we run a Cat genset in a trailer outputting 480 volts 3 phase into a distribution grid art 113kv? Or, would you like to discuss dead field paralelling gensets?
I dam sure ain't wearin an orange apron at Home Depot, and I do know what I'm talking about.

Anonymous Poster · Dec 24, 2002

Geez.......take it easy. It was only a question? Like are you sure? Some things that were done 48 years ago are done differently today. Have you in all your years of experience ever tried or watch someone try to backfeed a 200 amp magnetic breaker with enough current to force it to trip?
If so did it work?....How many times did it work?...How many times can it be reset before it fails the next time..and it will fail....or was it the (other kind of breaker)?

Do I want to dicuss 480 volt 3 phase gensets to a 110kv grid with you? Yes I would, but the key word here is dicuss, not fight with you.! I don't believe the poster (trev) is trying to hook this type of genset?
Yes, I am one of those guy,s that works on 113kv feeders, 33kvfeeds, 4160v, 2300v, 440v, all the way down to low voltage, 24v, fiber optics, and plc's. When working on high voltage, and have the convience to deenergize the feeder, the feeder conductors are bled to ground and the grounds are left on till the job is complete so someone who might have been given the wrong info from ....(who ever) doesn't back feed me.
Home genny's are nice for who ever wants them, but please for my safety, do it the right way and use a properly wired transfer switch..!! How you want to wire up the rest in your own home, I don't really care as long as you and your family are safe.
Franz....I truly hope that you do have a Great Holiday.!
Byeeeeeeeee George.

Trev · Dec 24, 2002

The generator has one 50 amp 220 outlet, two 10 amp 110 outlets
Would my two 10 amp outlets have enough power to run a fridge, freezer, and furnace, for example, without exceeding the amperage?

That might be pushing it. My freezer and fridge each pull 8 amps at start up and my furnace pulls 5 or 6. That's 21 amps. Add the sump pump you mentioned, and it'll pop the breaker.

After looking more closely last night, I see that I mis-spoke slightly. There are two 110 receptacles, and underneath them is a single label that says "20 Amps." I guess I was thinking 10 each, but I suppose maybe it's 20 amps collectively.. i.e., one could perhaps put out the 20 amps if the other wasn't doing anything. Either way, it seems a shame to waste the potential of putting out the full 70 amps the genset is capable of.. so something else would probably work better.

One thing puzzles me. I would think, given the risk to the power company linemen if someone miswires something like this, that the power company would bend over backwards to help folks out when it comes to installing gensets. It might even pay them in the long run, in terms of both safety and customer relations, to provide the switches needed and whatnot. After all, we'll only need these setups if they fail to provide the power we pay them for. So it would be a win/win situation if they did something like this for the tiny percentage of customers who actually have generators. Just thinking out loud here.. but maybe I should call the power company and see what stance they take about these things?

Thanks again for all the advice, folks, and sorry to have created the record monster thread! /w3tcompact/icons/smile.gif

Bob

MossRoad · Dec 24, 2002

Some power companies will install a device in the meter base that when you plug in your generator, it de-energizes the power from the line and when you pull the plug, it puts you back on the grid. Mine doesn't, but I've seen them on the internet somewhere?

As far as bending over backwards to help someone install a generator, if you owned a utility company would you help someone run their house on someone else's product? If you did it too well, they might not need you. Remember, most utilities are "for profit" companies. They will come out and disconnect your power for your electrician to install the transfer switch.

Trev · Dec 24, 2002

Some power companies will install a device in the meter base that when you plug in your generator, it de-energizes the power from the line and when you pull the plug, it puts you back on the grid. Mine doesn't, but I've seen them on the internet somewhere?

Might this conceivably be more cost-effective than having the electrician wire up a transfer box?

As far as bending over backwards to help someone install a generator, if you owned a utility company would you help someone run their house on someone else's product? If you did it too well, they might not need you. Remember, most utilities are "for profit" companies. They will come out and disconnect your power for your electrician to install the transfer switch.

I see your point, but even if we have a generator we are still paying customers. It's not like they give us a break on our bill whenever they fail to provide power (at least, not to my knowledge.) They could buy devices in bulk, cheap, provide an instruction sheet for the electrician, protect their people, protect their customers (from freezing, etc.) Seems like a good deal all around. I dunno, it was just an idea. Now you know why I'm not the CEO of some company! /w3tcompact/icons/laugh.gif