How to add the generator power input to the switch

[NW-Bound]

When I had my furnace replaced, the techs said they had to convert it back to being hardwired. As soon as it passed inspection, I wired it back to a plug in.

So, it is really against code.

Now, what is the rationale? I can't think of a safety reason. Look on the Web, and found this.

According to NEC’s section 400.7 code requirement, you shouldn’t use flexible cords and cables for furnaces. That’s why these appliances usually leave the factory hardwired without a flex cord or an attachment plug.

The NEC is against plugged-in furnaces for a good reason: they consume so much electricity that they need a dedicated circuit. When you have a plug-in furnace, you’re likely to plug it into a shared outlet with other appliances. As a result, the circuit gets overloaded, damaging the furnace and the other plugged-in electrical devices or even resulting in a fire.

But there's always a risk of overloading a circuit with plug-in appliances. The place this most likely happens is in the kitchen, when people plug in too many appliances at a time. That's what the circuit breaker is for.

And in this case, you are plugging the furnace into its own dedicated circuit that it is not sharing with anything.

 

[travelover]

And in this case, you are plugging the furnace into its own dedicated circuit that it is not sharing with anything.

Exactly, and the outlet can be single, so no possibility of plugging in another device and tripping the breaker. Seems a bit excessive.

 

[ncbill]

Just powering the furnace?

Have an electrician add an outlet after the switch, disconnect the hard wires and wire them to a standard 3-wire plug for that outlet.

in normal use the furnace is plugged into the outlet controlled by the switch, but can be unplugged to run from an extension cord plugged into the generator.

When power fails, use a long outdoor-rated extension cord to run the furnace.

 

[travelover]

Just powering the furnace?

Have an electrician add an outlet after the switch, disconnect the hard wires and wire them to a standard 3-wire plug for that outlet.

in normal use the furnace is plugged into the outlet controlled by the switch, but can be unplugged to run from an extension cord plugged into the generator.

When power fails, use a long outdoor-rated extension cord to run the furnace.

This is what I and others are suggesting but I mentioned that the furnace techs said it was not code to have it plug in. I think it is a good low cost solution, though.

 

[youbet]

Exactly, and the outlet can be single, so no possibility of plugging in another device and tripping the breaker. Seems a bit excessive.

When you can do a transfer switch for $85, and you'd spend at least a few bux converting the furnace to a plug in, why fight it?

 

[ncbill]

This is what I and others are suggesting but I mentioned that the furnace techs said it was not code to have it plug in. I think it is a good low cost solution, though.

I plan on paying an electrician to do so...can have him hook it back up hardwired to the switch when I sell.

 

[Walt34]

But there's always a risk of overloading a circuit with plug-in appliances. The place this most likely happens is in the kitchen, when people plug in too many appliances at a time. That's what the circuit breaker is for.

And in this case, you are plugging the furnace into its own dedicated circuit that it is not sharing with anything.

Maybe YOU wouldn't plug anything else into that plug. But everyone else and their brother will "because if it wasn't safe they wouldn't put it there". And then Aunt Matilda plugs in her space heater when she comes to visit, starts a fire from the overload, and then everyone blames the installer for the unsafe installation.

And that's why the code says the furnace has to be hardwired on it's own circuit.

 

[freedomatlast]

Maybe YOU wouldn't plug anything else into that plug. But everyone else and their brother will "because if it wasn't safe they wouldn't put it there". And then Aunt Matilda plugs in her space heater when she comes to visit, starts a fire from the overload, and then everyone blames the installer for the unsafe installation.

And that's why the code says the furnace has to be hardwired on it's own circuit.

Another option is to use a typical duplex outlet and just clip the jumper between the two outlets so only one side is active. I wouldn't do this but for those that are concerned, it's an option.

I don't understand the scenario above being exclusive to the furnace circuit since "Aunt Matilda could plug her space heater" into any other outlet in the house and possibly overload it as well.

Most gas fired hot air furnaces use less than 600 watts of electricity, or less than half of a typical 15 amp electrical circuit. The one at my new house is actually on a 20 AMP circuit.

My gas fired water heater actually came from the factory with a plug and uses about 500 watts of electricity.

I've read the NEC (NFPA70) and maybe I missed it, but can't find where it states furnaces have to be hardwired.

 

[Walt34]

I don't understand the scenario above being exclusive to the furnace circuit since "Aunt Matilda could plug her space heater" into any other outlet in the house and possibly overload it as well.

Sigh. You're missing the point, which is that it is KNOWN that the furnace draws enough power that it needs to be on it's own circuit and that enabling people to add additional loads to that circuit is just asking for an overload. So for safety's sake, keep it on it's own circuit.

Why do people insist on jumping through all the mental hoops to justify doing something foolish?

 

[Sunset]

Weirdly, our furnace has the wires come down, go into a junction box mounted to the side of the furnace, then wires from that junction box go to the furnace AND to a 2 outlet box with an outlet and an on/off switch.

Thinking about this, I suspect the previous owner (who died in a plane crash) added this to back-feed the furnace via a suicide cord in case of power failures, which were common here until the power company re-laid some lines.

I haven't looked at it and wouldn't bother to use it as I don't trust the wiring that might have been done. No idea what the on/off switch for the outlet actually does

 

[homestead]

Here is an outlet that will prevent overloading of the furnace circuit.

 

[freedomatlast]

Sigh. You're missing the point, which is that it is KNOWN that the furnace draws enough power that it needs to be on it's own circuit and that enabling people to add additional loads to that circuit is just asking for an overload. So for safety's sake, keep it on it's own circuit.

Why do people insist on jumping through all the mental hoops to justify doing something foolish?

Most gas fired hot air furnaces use less than 600 watts of electricity, or less than half of a typical 15 amp electrical circuit.

How does that justify a dedicated circuit?

If we were talking about a dedicated circuit for a space heater, I would totally agree.

 

[gauss]

Exactly, and the outlet can be single, so no possibility of plugging in another device and tripping the breaker. Seems a bit excessive.

Maybe it is against code to have a non-hardwired furnace to guard against scenarios such as when a practical joker or a wayward pet knocks out the plug and then the pipes freeze and then bad things happen.

I suspect that the insurance industry is in favor of hardwired furnaces.

-gauss

 

[youbet]

Here is an outlet that will prevent overloading of the furnace circuit.

Couldn't you just defeat that with a multiple outlet strip?

 

[homestead]

Couldn't you just defeat that with a multiple outlet strip?

Not if the furnace is plugged in.
Only time you will unplug it is when you are running the furnace from the generator. And then
the outlet will be dead as power is out.

Same as any other outlet in your house, protected by breaker in panel.

 

[youbet]

Most gas fired hot air furnaces use less than 600 watts of electricity, or less than half of a typical 15 amp electrical circuit.

How does that justify a dedicated circuit?

If we were talking about a dedicated circuit for a space heater, I would totally agree.

It's not just what the furnace draws...... It's what everything else that might get plugged into a non-dedicated circuit might draw. Here in the chilly north, we don't like the breaker opening on the furnace circuit when it's below zero!

Say you're out for the evening. The babysitter plugs her hair dryer into the outlet sharing the furnace circuit. The breaker blows. By the time you and DW get home several hours later, she and the kids are sitting huddled up in their parkas!

I'm leaving my furnace circuit dedicated.

Why not just use the $85 manual transfer switch brought to our attention earlier in this thread? It's a one time install that meets code and will not have to be removed if you sell the house. There is no plug to get accidentally knocked out. There are no cords, everything is still in conduit. It just looks too inexpensive and easy to not be a better choice than trying to homebrew another solution.

What am I missing?

 

[youbet]

Not if the furnace is plugged in.
Only time you will unplug it is when you are running the furnace from the generator. And then
the outlet will be dead as power is out.

Same as any other outlet in your house, protected by breaker in panel.

Not what I was thinking. Say I'm in the basement by my furnace and want to have another appliance plugged in. I unplug the furnace from the outlet. I plug in the multiple outlet strip. I plug the furnace and the additional appliance into the multiple outlet strip.

Wouldn't that do it? I now have the furnace and an additional appliance on the same circuit.

 

[teetee]

It's not just what the furnace draws...... It's what everything else that might get plugged into a non-dedicated circuit might draw. Here in the chilly north, we don't like the breaker opening on the furnace circuit when it's below zero!

Say you're out for the evening. The babysitter plugs her hair dryer into the outlet sharing the furnace circuit. The breaker blows. By the time you and DW get home several hours later, she and the kids are sitting huddled up in their parkas!

I'm leaving my furnace circuit dedicated.

Why not just use the $85 manual transfer switch brought to our attention earlier in this thread? It's a one time install that meets code and will not have to be removed if you sell the house. There is no plug to get accidentally knocked out. There are no cords, everything is still in conduit. It just looks too inexpensive and easy to not be a better choice than trying to homebrew another solution.

What am I missing?

You are good. I think we just like to share our life experiences and get a sense of contribution. It is easier to tell good suggestions from the not-so-good ones only if the later are present.

I am going to go with ez generator manual switch (it is the only one in stock right now) that is compliant to code but I will DIY the installation.

 

[teetee]

, how would your single outlet prevent the generator from back-feeding power onto the grid?.

It is a non issue because only the load side (the plug from the furnace) will be connected to the generator during the outage.

 

[homestead]

Not what I was thinking. Say I'm in the basement by my furnace and want to have another appliance plugged in. I unplug the furnace from the outlet. I plug in the multiple outlet strip. I plug the furnace and the additional appliance into the multiple outlet strip.

Wouldn't that do it? I now have the furnace and an additional appliance on the same circuit.

That wouldn't hurt anything as long as the furnace circuit wasn't exceeded.
But to fix that ... Lets put a non-standard outlet in the there and then no one can plug a power strip or anything else in there only the furnace. But you would have to make a custom extension cord for the generator with the same connector on one end.

 

[teetee]

That wouldn't hurt anything as long as the furnace circuit wasn't exceeded.

But to fix that ... Lets put a non-standard outlet in the there and then no one can plug a power strip or anything else in there only the furnace. But you would have to make a custom extension cord for the generator with the same connector on one end.

I would just put a label that says "the house will explode if you unplug this except during power outage". And make sure the socket is well hidden from kids.

But yeah it is not a 100% to code unless you can lock it.

 

[homestead]

I would just put a label that says "the house will explode if you unplug this except during power outage". And make sure the socket is well hidden from kids.

But yeah it is not a 100% to code unless you can lock it.

I guess you could also lock the plug so it couldn't be unplugged. But I'd be surprised if that met code.

 

[NW-Bound]

Sigh. You're missing the point, which is that it is KNOWN that the furnace draws enough power that it needs to be on it's own circuit and that enabling people to add additional loads to that circuit is just asking for an overload. So for safety's sake, keep it on it's own circuit.

Why do people insist on jumping through all the mental hoops to justify doing something foolish?

If the furnace has a dedicated circuit that is only wired to a single outlet in a closet, and the furnace is the only thing plugged into that outlet, how do people plug any additional load to it?

I saw that a poster suggested that someone may still plug an extension strip to that single outlet and manage to overload it. But, but, but can't they overload any outlet with an extension outlet strip? Why pick on the furnace outlet? What is so special about it? Maybe the circuit breaker will trip, the furnace does not run, and people freeze to death?

Youse guys forget that the utilities have no problem with power turning off to millions of people, and they froze to death all the time. Or they have their plumbing all frozen up, and their house all flooded and ruined when it warms up. Silly furnace wiring code does not do anything for them there.

 

[freedomatlast]

It's not just what the furnace draws...... It's what everything else that might get plugged into a non-dedicated circuit might draw. Here in the chilly north, we don't like the breaker opening on the furnace circuit when it's below zero!

Say you're out for the evening. The babysitter plugs her hair dryer into the outlet sharing the furnace circuit. The breaker blows. By the time you and DW get home several hours later, she and the kids are sitting huddled up in their parkas!

I'm leaving my furnace circuit dedicated.

Why not just use the $85 manual transfer switch brought to our attention earlier in this thread? It's a one time install that meets code and will not have to be removed if you sell the house. There is no plug to get accidentally knocked out. There are no cords, everything is still in conduit. It just looks too inexpensive and easy to not be a better choice than trying to homebrew another solution.

What am I missing?

I really liked the idea of the $85 manual transfer switch mentioned earlier in the thread and was considering ordering one. So, I did some further investigating.

It's a Reliance Controls Easy Tran TF, model number TF151W. They are readily available on ebay. I was going to order one until I was able to find and read the instruction manual online. It's really designed to mount next to the service panel and it leaves the neutrals (white wires) tied together whether using the power from the service panel or from the generator.

I was hoping to find it to be a 3 pole double throw switch that actually completely switches the hot, neutral and ground from the panel input to the generator input when the switch is activated, but it's not and it doesn't. After reading that, I feel safer with a plug and receptacle mounted on a joist above the furnace. It will still be a dedicated circuit to the furnace using a single rather than a duplex outlet. That way the furnace would have to be unplugged before anything else could be plugged in, and thus no worries or fear about an overloaded circuit.

If I was going the transfer switch route, the only switch I was able to find that would do what I want it to do is called a "100 AMP Disconnect Knife Switch 3 Pole Circuit Breaker for back up generators" that I found on ebay. This is truly a 3 pole double throw switch for a mere $23.00 if anyone is interested.

 

[homestead]

It's really designed to mount next to the service panel and it leaves the neutrals (white wires) tied together whether using the power from the service panel or from the generator.

Why is that an issue for you?