Cord connected furnace

[drcampbell]

It cost more but I would use single pole, double throw, with a center off of good quality. ...

Regardless of "quality", you're still talking about a device that's not guaranteed to break-before-make, which is one of the buzzwords that labels a switch as suitable for two sources.

 

[jap]

The cords for 120V furnaces are sold with the furnace at the wholesale house. It's not like hacks are having to go to Home Depot to do it.

But, are the cords actually already terminated to the furnace when you buy it? or Are the cords being provided seperately simply because the Heat and Air Wholesale house don't know any better?

I can see these units being installed with the defense of "That's what the supply house gave me to hook it up", without ever even stopping to think whether it's an NEC violation or not.

That may be the reason the new homes around here have so many cord and plug connected Furnace units, right or wrong.

JAP>

 

[MAC702]

That's a fair question. I don't know. I rarely install in new construction. But that means not only has every contractor done it, but every inspector has allowed it, for a century, in every jurisdiction in the county (at least 4). Now here is where you say: "That doesn't make it right."

It is perfectly normal for me, everyday, to unplug a central furnace to work on it. I'm on my way to go do one right now.

 

[hbiss]

Regardless of "quality", you're still talking about a device that's not guaranteed to break-before-make...

Precisely. I was going to get into break-before-make and make-before-break but I didn't want to add unnecessary information. I think the design of a 3-way switch was described adequately.

-Hal

 

[jap]

Now here is where you say: "That doesn't make it right."

I also get a warm fuzzy feeling knowing a garbage disposal,dishwasher, or, even a furnace for that matter,is unplugged rather than wondering if a switch someone may have installed for a disconnect will accidently be flipped on when I'm working on it.

I guess if I were doing residential for a living, I'd probably use a cheap AC Pullout and hard wire it instead of using the cord and plug scenario,
but that's just me.


JAP>

 

[jim dungar]

Regardless of "quality", you're still talking about a device that's not guaranteed to break-before-make, which is one of the buzzwords that labels a switch as suitable for two sources.

It also is not guaranteed to have barriers to prevent arcing across the two sources, which is an important feature when the sources are not synced.

 

[hbiss]

Another aspect comes to mind. Around here, there has to be an EMO switch located on the wall outside the area where the furnace or boiler is. It has to have the usual red plate that says gas furnace or oil burner emergency off. How would you deal with that with a plug and cord connected heating system?

-Hal

 

[jap]

Another aspect comes to mind. Around here, there has to be an EMO switch located on the wall outside the area where the furnace or boiler is. It has to have the usual red plate that says gas furnace or oil burner emergency off. How would you deal with that with a plug and cord connected heating system?

-Hal

With a Shunt Trip feeder breaker controlled by the Emergency Power Off Button.


JAP>

 

[winnie]

Another aspect comes to mind. Around here, there has to be an EMO switch located on the wall outside the area where the furnace or boiler is. It has to have the usual red plate that says gas furnace or oil burner emergency off. How would you deal with that with a plug and cord connected heating system?

-Hal

If, instead of having a _cord_ feed the furnace, the furnace is hard wired to an _inlet_, then the fixed wiring of the structure would be compliant. You could then have a 1 foot extension cord connected between a receptacle and the inlet to power the furnace circuit, and this extension cord is not part of the fixed wiring of the structure, so doesn't violate article 400.

With this setup, the furnace switch can be wired as a standard switch loop between the inlet and the furnace.

This gives you a furnace that can be plugged into a generator, which still has its power off switch on generator power, and doesn't have a cord as a fixed part of its installation.

-Jon

 

[jap]

If, instead of having a _cord_ feed the furnace, the furnace is hard wired to an _inlet_, then the fixed wiring of the structure would be compliant. You could then have a 1 foot extension cord connected between a receptacle and the inlet to power the furnace circuit, and this extension cord is not part of the fixed wiring of the structure, so doesn't violate article 400.

With this setup, the furnace switch can be wired as a standard switch loop between the inlet and the furnace.

This gives you a furnace that can be plugged into a generator, which still has its power off switch on generator power, and doesn't have a cord as a fixed part of its installation.

-Jon

I don't see where you gain any more compliance by having a short extension cord between an outlet on the wall and an inlet installed on a furnace, vs. a cord and plug installed directly on the unit.

JAP>

 

[petersonra]

There seems to be a fair number of practices in certain areas that are not quite up to code requirements, but are safe and have few if any disadvantages. It seems like it would make sense for the NEC to catch up with reality, especially with respect to the use of cord for connecting things up. It is a perfectly safe practice in most cases, and common in the rest of the world, but usually not allowed here, and for no real good reasons.

 

[hbiss]

With a Shunt Trip feeder breaker controlled by the Emergency Power Off Button.


JAP>

-Hal

 

[LarryFine]

You could also use a single-circuit transfer switch:

 

[MAC702]

...It seems like it would make sense for the NEC to catch up with reality....

Very good way to put that. Thank you.

 

[kwired]

Dishwashers and disposers are specifically mentioned in Art. 422 which gives explicit permission to use C&P.

That too.

That's a fair question. I don't know. I rarely install in new construction. But that means not only has every contractor done it, but every inspector has allowed it, for a century, in every jurisdiction in the county (at least 4). Now here is where you say: "That doesn't make it right."

It is perfectly normal for me, everyday, to unplug a central furnace to work on it. I'm on my way to go do one right now.

OK, I have to say it "That doesn't make it right"

I also get a warm fuzzy feeling knowing a garbage disposal,dishwasher, or, even a furnace for that matter,is unplugged rather than wondering if a switch someone may have installed for a disconnect will accidently be flipped on when I'm working on it.

I guess if I were doing residential for a living, I'd probably use a cheap AC Pullout and hard wire it instead of using the cord and plug scenario,
but that's just me.


JAP>

NEC says that the disconnecting means must be within sight of the appliance.

I don't know what 70E says regarding this, but pretty certain many LOTO procedures will still want you to lock that disconnecting means even if within sight. If a cord/plug is the disconnecting means LOTO procedures often say you need a lockable cover and lock to put over the cord end so it can't be plugged in while "locked out".

Another aspect comes to mind. Around here, there has to be an EMO switch located on the wall outside the area where the furnace or boiler is. It has to have the usual red plate that says gas furnace or oil burner emergency off. How would you deal with that with a plug and cord connected heating system?

-Hal

If outside the area where the furnace or boiler is, NEC will still require a disconnecting means within sight of the appliance.This EMO switch is for other than electric related issues, like if the boiler is about to blow up because of malfunctioning burner control, you don't want to have to go up to it to turn off power. The higher pressure the boiler operates the more critical this EPO usually is, it doesn't necessarily have to remove all power either but must at least disable the burner control power. I have one industrial client where the EPO kills all control power but not the 480 volt three phase feed to the boiler. Don't know what actual boiler codes say, but boiler inspector is fine with it.

I don't see where you gain any more compliance by having a short extension cord between an outlet on the wall and an inlet installed on a furnace, vs. a cord and plug installed directly on the unit.

JAP>

I think his comment maybe was about how you make a remote EPO switch work whether on normal power or on the generator.

There seems to be a fair number of practices in certain areas that are not quite up to code requirements, but are safe and have few if any disadvantages. It seems like it would make sense for the NEC to catch up with reality, especially with respect to the use of cord for connecting things up. It is a perfectly safe practice in most cases, and common in the rest of the world, but usually not allowed here, and for no real good reasons.

You are certainly welcome to submit PI's for changes, I'd guess some have but never gave enough substantiation for their proposed change. Type of cord typically used here vs elsewhere in the world could maybe have some impact on why it may or may not be allowed.

 

[augie47]

It's not just the NEC
Here's an article from UL a few years ago. I don;'t think it's changed.

[FONT=&quot]Question:[/FONT]
[FONT=&quot]Has UL Listed any cord-and-plug connected central air-conditioning units, central heating furnaces or storage tank water heaters?[/FONT]
[FONT=&quot]Answer[/FONT]
[FONT=&quot]No, UL has not Listed cord-and-plug connected central air-conditioning equipment or central heating furnaces.[/FONT]
[FONT=&quot]These types of equipment have been Listed for permanent wiring installations only. They are Listed under UL product category Heating and Cooling Equipment (LZFE), located on page 223 in the 2010 UL White Book or may be found on UL’s Online Certification Directory at [FONT=&quot]www.ul.com/database[/FONT] by entering the category code at the category code search field.[/FONT]
[FONT=&quot]Only small capacity (5 gallons or less) electric household storage tank water heaters or electric commercial water heaters that are designed to permit removal for maintenance and repair have been Listed for cord-and-plug connection. These products are Listed under the product categories Household Water Heaters (KSDT) and Commercial Storage Tank and Booster Water Heaters (KSBZ), both located on page 220 in the 2010 UL White Book, or may be found on UL’s Online Certification Directory at [FONT=&quot]www.ul.com/database[/FONT] and entering the category code at the category code search field.[/FONT]
[FONT=&quot]The requirements used to investigate these products are detailed in the Standard for Safety for Household Electric Storage Tank Water Heaters, UL 174 and in the Standard for Safety for Electric Booster and Commercial Storage Tank Water Heaters, UL 1453.[/FONT]

 

[hbiss]

You could also use a single-circuit transfer switch:

View attachment 22130

Perfect! I was looking for that to suggest but I couldn't find anything that small. :thumbsup: Looks like it's even made exactly for the application.

-Hal

 

[peter d]

There seems to be a fair number of practices in certain areas that are not quite up to code requirements, but are safe and have few if any disadvantages. It seems like it would make sense for the NEC to catch up with reality, especially with respect to the use of cord for connecting things up. It is a perfectly safe practice in most cases, and common in the rest of the world, but usually not allowed here, and for no real good reasons.

This is exactly why I follow the code of common sense rather than following the NEC to the letter. :thumbsup:

 

[augie47]

This is exactly why I follow the code of common sense rather than following the NEC to the letter. :thumbsup:

but the you run across an inspector like me

 

[LarryFine]

but the you run across an inspector like me

You mean one that makes Yoda sound like a scholar?