Building a transfer switch for a furnace

[applescotty]

First off, I am aware that the whole generator/backfeeding/transfer switch subject seems to often lead to hot tempers. I'd like to avoid that discussion in this thread.

I am also very aware of the dangers when backfeeding a breaker box using a generator.

I have purchased a small generator to power my furnace, fridge, and freezer in case of a power outage. The fridge and freezer will be powered using extension cords that I string out when/if the power goes out. Not an option for a hardwired furnace, of course. I am aware that I can purchase a transfer switch for the furnace for around $90, but since I only paid $100 for the generator, and there's pretty low chance that I'll need to use this setup (I wouldn't have needed it in the 7 years I've lived here), I'd of course rather put the money towards something else. However, knowing that when the power goes out at 3 in the morning you might not be thinking straight, I want to utilize a transfer switch to make it foolproof.

So, here is my proposal. Rather than buying the aforementioned transfer switch, I would like to build one using a DPDT toggle switch. For $6 or so I can buy one, rated for 20A 125V AC. My furnace circuit is 15A, so this should be sufficient. I understand this is not the inductive load rating, but since my furnace has a solid state control board, the blower motor will not start up when power is first applied, since the control board goes through some self checks first. The DPDT switch would break before make, and would switch both the live and neutral (the ground would stay connected). I'd mount the DPDT in a box next to the furnace, along with a receptable, something like this:
http://www.4.midlightelectric.com/acatalog/Leviton105066.html

I believe that this should function the same as the purpose built transfer switch. Is there anything that I'm missing here? If your answer is "Just buy the purpose built transfer switch", I'd like to know what function it has (besides the nifty light) that my version does not.

Thanks!

Scott

(oh, and the furnace is in the garage, so that makes it on topic, right? )

 

[nate379]

What I do, (since my gen set is just a pull a crank and fire it up 5000 watt unit) is turn off the main and turn off all the breakers I don't need power to. I have 2 50 amp plugs in my garage for welders, so I just plug into one and plug a pigtail I have into the other end of the cord (8/3 wire about 100ft long).

I know some people feel that this is wrong/illegal/etc but the power company here is fine with it.

I have heard some newer boilers don't like the dirty power gen sets make so be careful with that. Same with fridges.

 

[willf650]

I bought similar components to do the exact same thing. Only real difference is my outlet is a flanged mount with no cover. I'm mounting my stuff in the face of a 6x6 box. It will work fine and cost less than half of a purpose built transfer switch. The only thing I saw on the transfer switch was a circuit breaker but there is no real need for it as the plugs on the generator are protected.

 

[Aceman]

I know some people feel that this is wrong/illegal/etc but the power company here is fine with it.

No. It is wrong. And stupid.

Welders are only 3 prong. Your suicide cord is setup even worse than the idiots who at least know to use a 4 wire dryer recep, so at least they have a proper ground and neutral terminal.

First off, I am aware that the whole generator/backfeeding/transfer switch subject seems to often lead to hot tempers. I'd like to avoid that discussion in this thread.

If folks would do things to code, they're wouldn't be heated discussions. Seems pretty simple....?

I'd disconnect your hardwired furnace and cord and plug it. Then plug it into your generator. Then it'd be perfectly legal and safe.

 

[Stuart in MN]

I'd disconnect your hardwired furnace and cord and plug it. Then plug it into your generator. Then it'd be perfectly legal and safe.

Depending on how you read the Code, a furnace may or may not be supposed to be hard wired, but for practical purposes I agree that putting a cord and plug on it would be the safest (and easiest) way to do it.

 

[mrb]

I would use a DPDT switch with center off (the proper listed units have this, and there is some reason behind it)

 

[nate379]

Uh, top prong is neutral and gen set grounds through separate wire which is tied to house ground rods.

So.. before blowing something out of the water, maybe you should know the whole story huh jackass?

No. It is wrong. And stupid.

Welders are only 3 prong. Your suicide cord is setup even worse than the idiots who at least know to use a 4 wire dryer recep, so at least they have a proper ground and neutral terminal.



If folks would do things to code, they're wouldn't be heated discussions. Seems pretty simple....?

I'd disconnect your hardwired furnace and cord and plug it. Then plug it into your generator. Then it'd be perfectly legal and safe.

 

[Aceman]

You're using the suicide cord and I'm the jackass?

OK.

 

[nate379]

No, I was calling you a jackass for calling me an idiot without knowing how my setup works.

 

[applescotty]

Thanks to those of you that gave input on my question. I'll continue ahead with my plan.
Sorry for everyone else that it's still devolved into the typical generator backfeeding thread.

Scott

 

[nate379]

It's a house backfeeding thread because that is what you are pretty much doing to the boiler, just running through a switch instead of the breaker panel.

At least with backfeeding the panel you have the breaker at the gen set and the breaker in the panel.

Thanks to those of you that gave input on my question. I'll continue ahead with my plan.
Sorry for everyone else that it's still devolved into the typical generator backfeeding thread.

Scott

 

[applescotty]

I'd say that I'm not backfeeding. I thought that backfeeding is sending power back into a panel through a circuit that is normally designed to power something. In my case, I'm disconnecting the furnace from the line, and powering it with my generator, just like a commercially purchased transfer switch would. I therefore don't see how it's considered backfeeding.

I don't see how having the extra breaker in the panel would make any difference.

Thanks for you opinion, though.

Scott

 

[Brandon_K]

It's a house backfeeding thread because that is what you are pretty much doing to the boiler, just running through a switch instead of the breaker panel.

At least with backfeeding the panel you have the breaker at the gen set and the breaker in the panel.

Considering he has asked about building a TRANSFER SWITCH, I would say that it's not a backfeeding thread, not until you made it one at least. And I would be VERY surprised if your poco really says "Sure, go ahead, we would love for someone to mistakenly flip the main back on and kill one of our lineman who thought he was working on a de-engergized line!"

The idea of using a DPDT with center off is spot on, this is exactly what a professionally produced manual transfer switch is afterall. Use a flanged outlet, make one side of the switch the mains side, the other side the generator side, going to a flanged outlet. The center terminals of course going to the furnace. This is far safter than using a suicide cord.

Take a look on Craigslist and eBay for some of the older GenTran switches; http://www.gen-tran.com/eshop/10Browse.asp?Category=VPTS

You could do all of the circuits you want, freezer, fridge, furnace plus still have another 3, so you could do your TV/living room, a bathroom and even a bedroom. For under $200 you really can't go wrong. The first time you have to drag out extension cords in the dark you'll say to yourself "I should have just spent the money and did it right." They're fool proof, even the wife and kids can get it up and running if you aren't around.

Take a look on eBay and Craigslist, I picked up my 5kw for $50. I need to go to a 7.5kw or 10kw model with the new generator now.

 

[nate379]

They told me that their lineman are trained to treat all wires as live, so if there is power going into it or not, it doesn't matter, if they get zapped it is because they didn't follow policy and are usually fired.

Considering he has asked about building a TRANSFER SWITCH, I would say that it's not a backfeeding thread, not until you made it one at least. And I would be VERY surprised if your poco really says "Sure, go ahead, we would love for someone to mistakenly flip the main back on and kill one of our lineman who thought he was working on a de-engergized line!"

Seems to me instead of cobbling together what you are trying to do a ~$200 manual transfer switch would work better and is the "correct" way to do it.

 

[willf650]

How is buying the exact components and assembling one your self cobbling it in an incorrect way. You wind up with a single circuit tranfer switch for less than half the cost of a preassembled one with the exact components but without a manufacturers sticker.

 

[6768rogues]

For what it's worth, our code requires that main heating equipment be hardwired.

 

[mrb]

How is buying the exact components and assembling one your self cobbling it in an incorrect way. You wind up with a single circuit tranfer switch for less than half the cost of a preassembled one with the exact components but without a manufacturers sticker.

because your home made one is not tested and listed by a NRTL.