Furnace plugged in to wall outlet? - Contractor Talk - Professional Construction and Remodeling Forum

rhinoguy · 02-19-2007, 11:25 PM

I keep seeing furnaces that are connected to the power by plugging in to an outlet. The outlet is always on it's own circuit and is controlled by a (kill) switch. The object is to make it easy to run off a generator in a power failure. We have two to three day failures in NC because of ice storms. Ice brings down wires like nobodies' business. Is this acceptable? One inspector said "no', another said "yes" and the third said "damfino". I can't find it in the (2000) NEC book I have.

thom · 02-19-2007, 11:34 PM

In my area a dedicated receptacle and plug is standard. No switch though. What would that accomplish. It's not like you would be switching off your furnace with any regularity.

I guess I don't understand the point of hard-wiring. The codes don't require it. If you need to use a generator, just add an extension cord and you're in business.

rhinoguy · 02-19-2007, 11:41 PM

I plan to hook up my furnace that way. My dishwasher and garbage disposall are already on plugs for easier servicing.

terrynistler · 02-20-2007, 01:24 AM

Check ansi z21.47, Nec 422.31 , 32, 424.19 & 430.102. Personally, go with your local code. There are a ton of factors that contribute to these codes. With all of that said mine are cord and plugged but allowed here for now. I have used them on a generator 3 times in the last 4 years. Natural gas two small units and only run one to stay warm. Really only running the blower and electronics no load to speak of. Would hate to have this misinterpretated as someone wanting to run an electric furnace though. Have seen some pretty intelligent people try some stupid things.

JamesNLA · 02-20-2007, 02:04 AM

As far as I know, the furnace needs its own recept (pigtailed) on its own circuit AND there must be a light (candescent will do) on a switch in the general area. THat light can be on the same power circuit as the furnace. Your area wants it hard wired? What for?

hf05 · 02-20-2007, 06:31 AM

hi its probably of no use to you ,i'm a little north of Toronto;but up here the furnace must have its own circuit as well as a customer switch[shut off switch] in the same room as the unit.Having said that it sounds like a great idea if you experience a lot of power outage.Sorry but can't help with regulations south of the 49 th.

mdshunk · 02-20-2007, 05:21 PM

Installing a cord on most furnaces is a technical violation of the NEC, that many inspectors will overlook.

thom · 02-20-2007, 05:56 PM

MD, how is a cord on a furnace a violation? That is the standard way we do it here. The receptacle must be a single, not a duplex, and dedicated. We also pigtail our diswashers and disposals. I don't understand why you would want to hard wire appliances.

mdshunk · 02-20-2007, 09:29 PM

Quote:

Originally Posted by thom

That is the standard way we do it here.

That's the standard answer when a person is informed about a violation, but it doesn't make it right. The NEC 422.16(A) is clear about the conditions that need to be met for flexible cords with attachment plugs to be used as a means of wiring.

422.16 Flexible Cords.
(A) General. Flexible cord shall be permitted (1) for the
connection of appliances to facilitate their frequent interchange
or to prevent the transmission of noise or vibration
or (2) to facilitate the removal or disconnection of appliances
that are fastened in place, where the fastening means
and mechanical connections are specifically designed to
permit ready removal for maintenance or repair and the
appliance is intended or identified for flexible cord connection.

The furnace does not qualify under (1) or (2). The flexible cord is not required to prevent transmission of noise or vibration. The flexible cord is not used to permit quick changeout of the furnace, because there'd need to be some sort of quick couple device on the pipework and/or ductwork also to qualify. The cord, as installed to permit easy connection to a portable generator, is not on that list.

The next part of 422.16 lists some appliances that are more or less exceptions from the general rule:

422.16 Flexible Cords.
(B) Specific Appliances.
(1) Electrically Operated Kitchen Waste Disposers.
Electrically operated kitchen waste disposers shall be permitted
to be cord-and-plug connected with a flexible cord
identified as suitable for the purpose in the installation instructions
of the appliance manufacturer, where all of the
following conditions are met.
(1) The flexible cord shall be terminated with a grounding
type attachment plug.
Exception: A listed kitchen waste disposer distinctly
marked to identify it as protected by a system of double
insulation, or its equivalent, shall not be required to be
terminated with a grounding-type attachment plug.
(2) The length of the cord shall not be less than 450 mm
(18 in.) and not over 900 mm (36 in.).
(3) Receptacles shall be located to avoid physical damage
to the flexible cord.
(4) The receptacle shall be accessible.
(2) Built-in Dishwashers and Trash Compactors.
Built-in dishwashers and trash compactors shall be permitted
to be cord-and-plug connected with a flexible cord identified
as suitable for the purpose in the installation instructions
of the appliance manufacturer where all of the
following conditions are met.
(1) The flexible cord shall be terminated with a groundingtype
attachment plug.
Exception: A listed dishwasher or trash compactor distinctly
marked to identify it as protected by a system of
double insulation, or its equivalent, shall not be required to
be terminated with a grounding-type attachment plug.
(2) The length of the cord shall be 0.9 m to 1.2 m (3 ft to
4 ft) measured from the face of the attachment plug to
the plane of the rear of the appliance.
(3) Receptacles shall be located to avoid physical damage
to the flexible cord.
(4) The receptacle shall be located in the space occupied
by the appliance or adjacent thereto.
(5) The receptacle shall be accessible.
(3) Wall-Mounted Ovens and Counter-Mounted Cooking
Units. Wall-mounted ovens and counter-mounted cooking
units complete with provisions for mounting and for
making electrical connections shall be permitted to be permanently
connected or, only for ease in servicing or for
installation, cord-and-plug connected.
A separable connector or a plug and receptacle combination
in the supply line to an oven or cooking unit shall be
approved for the temperature of the space in which it is
located.
(4) Cord-and-Plug-Connected Vending Machines. Cordand-
plug connected vending machines shall be one of the
following:
(1) For new and remanufactured machines ground-fault
circuit-interrupter protection for personnel shall be
factory-installed, and shall be an integral part of the
attachment plug or be located in the power supply cord
within 300 mm (12 in.) of the attachment plug.
(2) Listed vending machines identified as incorporating a
system of double insulation.
(3) Vending machines shall be connected to a circuit protected
by a ground-fault circuit-interrupter.
(5) Range Hoods. Range hoods shall be permitted to be
cord-and-plug connected with a flexible cord identified as
suitable for the use on range hoods in the installation instructions
of the appliance manufacturer, where all of the
following conditions are met.
(1) The flexible cord shall be terminated with a grounding
type attachment plug.
Exception: A listed range hood distinctly marked to identify
it as protected by a system of double insulation, or its
equivalent, shall not be required to be terminated with a
grounding-type attachment plug.
(2) The length of the cord shall not be less than 450 mm
(18 in.) and not over 900 mm (36 in.).
(3) Receptacles shall be located to avoid physical damage
to the flexible cord.
(4) The receptacle shall be accessible.
(5) The receptacle shall be supplied by an individual
branch circuit.

The furnace isn't on this list either.

mdshunk · 02-20-2007, 09:32 PM

I'm not trying to be a jerk, because it's already well known in my trade that this occurs with great regularity all over the country. It is also well known in my trade that this is a violation. A violation that is regularly overlooked, for some reason.

ozmy6 · 02-21-2007, 03:55 PM

For some reason I thought this was a fire code [switch] you know like window egress. but who checks these things never had a fireman show up at a job well at least not before i cashed the check

thom · 02-21-2007, 05:11 PM

Well MD obviously you're correct. I salute you.

mdshunk · 02-21-2007, 07:01 PM

Quote:

Originally Posted by ozmy6

For some reason I thought this was a fire code [switch] you know like window egress. but who checks these things never had a fireman show up at a job well at least not before i cashed the check

Yes, you're right. The NEC requires that any permanently wired appliance needs some form of disconnect within sight of the appliance. Many model mechanical codes are even stricter. They normally require a switch that is operational while the flame is being observed. That pretty much means right on the side of the furnace or really close by.