Cord connected furnace

[geochurchi]

Hi All, can a furnace be connected by cap and plug, I think this was brought up before at some point, also would a 3Way switch qualify as a SP/DT switch?
Geo

 

[kwired]

Hi All, can a furnace be connected by cap and plug, I think this was brought up before at some point, also would a 3Way switch qualify as a SP/DT switch?
Geo

Only if the furnace were designed/listed with the cap and plug. Some stand alone and portable type units this is maybe likely. Most (maybe all) permanent central furnace systems are intended to be "hard wired".

By design a 3 way switch is a SPDT switch. If using the switch as a disconnecting means for whatever reason, one issue with three ways is the switch isn't marked with "on/off" and therefore creates code issues if used for that purpose.

 

[hbiss]

Sounds like the intent here to allow connection to an extension cord from a generator. I don't see anything wrong with using a 3-way as a transfer switch as long as you use a red plate marked on and off. If that doesn't fly, put the 3-way in a separate box nippled to the service switch or disconnect. Either way, provide a SO cord pigtail out of the box with a plug on it for connection to the extension cord.

-Hal

 

[qcroanoke]

Sounds like the intent here to allow connection to an extension cord from a generator. I don't see anything wrong with using a 3-way as a transfer switch as long as you use a red plate marked on and off. If that doesn't fly, put the 3-way in a separate box nippled to the service switch or disconnect. Either way, provide a SO cord pigtail out of the box with a plug on it for connection to the extension cord.

-Hal

It cost more but I would use single pole, double throw, with a center off of good quality.
The bottom shelf switches at big box aren't gonna last very long.

 

[jap]

Sounds like the intent here to allow connection to an extension cord from a generator. I don't see anything wrong with using a 3-way as a transfer switch as long as you use a red plate marked on and off. If that doesn't fly, put the 3-way in a separate box nippled to the service switch or disconnect. Either way, provide a SO cord pigtail out of the box with a plug on it for connection to the extension cord.

-Hal

If your going to allow for connection to an extension cord from a generator, where does the 3 way switch nippled into the service disconnect come into play?

This all sounds like very poor advice.

JAP>

 

[texie]

It cost more but I would use single pole, double throw, with a center off of good quality.
The bottom shelf switches at big box aren't gonna last very long.

Gee, I hate to rain on the parade again, but snap switches-even spec grade are not list for use with one load from 2 sources.
I know of a growing number of AHJs that allow cord connection of furnaces because of the generator issue. Seems harmless to me.

 

[al hildenbrand]

Not all threeway switches keep the two traveler terminals electrically isolated from each other.

It happens less, now-a-days, but, I will, from time to time, get a trouble shooting request from someone who has attempted to replace a threeway switch on a polarity reversing "Carter" stairway lighting wiring setup. The "someone" will usually call after they've blown the fuse, or the switch, once or twice.

When toggled, for a brief instant, both travelers are shorted together.

As a generator / PoCo transfer switch such switch behavior could be disastrous for a PoCo lineman.

 

[hbiss]

If your going to allow for connection to an extension cord from a generator, where does the 3 way switch nippled into the service disconnect come into play?

This all sounds like very poor advice.

JAP>

Service switch on the furnace or boiler, not the service disconnect for the building! :happysad:

Gee, I hate to rain on the parade again, but snap switches-even spec grade are not list for use with one load from 2 sources.

You sure about that?

Just how would you connect what really is a whole heating system these days and not just a boiler or furnace with a cord and plug and make it look like it wasn't done by some hack?

At some point you are beginning to tread into the area of interlock on the panel and power inlet. Makes more sense because the HO is going to be running more extension cords than the one to the furnace, guaranteed.

-Hal

 

[texie]

Service switch on the furnace or boiler, not the service disconnect for the building! :happysad:



You sure about that?

-Hal

Yes. See UL Product Category WJQR: "Snap switches have not been investigated for switching a load between two alternate sources of supply. Double-throw enclosed switches (see Switches, Enclosed (WIAX))or switches certified as transfer switches (see Transfer Switches[WPTZ] and Emergency Lighting and Power Equipment(FTBR)) should be used for this purpose."

 

[hbiss]

OK, then I defer to @gcroanoke

It cost more but I would use single pole, double throw, with a center off of good quality.
The bottom shelf switches at big box aren't gonna last very long.

and recommend this-

https://www.hubbell.com/hubbell/en/.../Industrial-Series-Switches/HBL1381/p/1546122

It is shown switching loads between two alternate sources. I think the key words in your UL quote is "Snap switches have not been investigated for switching a load between two alternate sources of supply." It doesn't say "Snap switches have been investigated and found not suitable for switching a load between two alternate sources of supply". So really what they are saying is they don't know but recommend better options.

-Hal

 

[MAC702]

Only if the furnace were designed/listed with the cap and plug. Some stand alone and portable type units this is maybe likely. Most (maybe all) permanent central furnace systems are intended to be "hard wired".

By design a 3 way switch is a SPDT switch. If using the switch as a disconnecting means for whatever reason, one issue with three ways is the switch isn't marked with "on/off" and therefore creates code issues if used for that purpose.

Most 120V permanent gas furnaces I deal with on a daily basis are cord and plug connected. This includes up to 5-ton split systems. I even prefer this to the other common method of having them wired through a standard 15A switch, which is a weak link failure point, and I prefer to set the cord in sight of me when working on a machine instead of just remembering that I turned the switch off. And I was only picturing machines in attics just now. When the air handler is in the garage or closet, every one of them is cord-and-plug connected.

To me, a SPDT switch includes a center OFF position, which a 3-way does not. I would have thought this means it is NOT a SPDT switch. But I've not confirmed that from any research yet.

 

[jap]

Most 120V permanent gas furnaces I deal with on a daily basis are cord and plug connected

Yes,most are,but, are they actually listed for that type of connection,or, are guys just installing cords because that's what they've seen others do?


Jap>

 

[hbiss]

Most 120V permanent gas furnaces I deal with on a daily basis are cord and plug connected. This includes up to 5-ton split systems. I even prefer this to the other common method of having them wired through a standard 15A switch, which is a weak link failure point, and I prefer to set the cord in sight of me when working on a machine instead of just remembering that I turned the switch off. And I was only picturing machines in attics just now. When the air handler is in the garage or closet, every one of them is cord-and-plug connected.

To me, a SPDT switch includes a center OFF position, which a 3-way does not. I would have thought this means it is NOT a SPDT switch. But I've not confirmed that from any research yet.

Maybe this is another left coast thing? That's just nuts. I can't even comprehend a qualified electrician putting a line cord on a furnace! Sounds like something an HVAC guy would do. Betcha if I dig around it's a violation to do that with a permanently installed piece of equipment. You are using flexible cord as building wire.

A SPDT toggle switch can have two positions or three positions, one being a center off. That would be called a SPDT center off switch.

Not all threeway switches keep the two traveler terminals electrically isolated from each other... When toggled, for a brief instant, both travelers are shorted together... As a generator / PoCo transfer switch such switch behavior could be disastrous for a PoCo lineman.
​

Thank you for that information. Though I never noticed it, it certainly makes sense that it could happen considering how cheaply switches are made today and the fact that there is no real necessity (since it's intended for use as a 3-way switch) to make certain the travelers aren't shorted together when the switch is operated. So I take back my recommendation to use a 3-way switch as a transfer switch. You can use the switch I showed you in my post #10 above.

-Hal

​

 

[busman]

I have never seen a furnace that complies with any of these reasons:

400.7 Uses Permitted
(A) Uses . Flexible cords and cables shall be used only for the
following:
(1) Pendants.
(2) Wiring of luminaires.
(3) Connection of portable luminaires, portable and mobile
signs, or appliances.
(4) Elevator cables.
(5) Wiring of cranes and hoists.
(6) Connection of utilization equipment to facilitate frequent
interchange.
(7) Prevention of the transmission of noise or vibration.
(8) Appliances where the fastening means and mechanical
connections are specifically designed to permit ready
removal for maintenance and repair, and the appliance is
intended or identified for flexible cord connection.
(9) Connection of moving parts.
(10) Where specifically permitted elsewhere in this Code.
(11) Between an existing receptacle outlet and an inlet, where
the inlet provides power to an additional single receptacle
outlet. The wiring interconnecting the inlet to the single
receptacle outlet shall be a Chapter 3 wiring method. The
inlet, receptacle outlet, and Chapter 3 wiring method,
including the flexible cord and fittings, shall be a listed
assembly specific for this application.

The only other applicable article that would apply would be Art. 422 which basically says the same thing.

Just my 2 cents.

Mark

 

[kwired]

Most 120V permanent gas furnaces I deal with on a daily basis are cord and plug connected. This includes up to 5-ton split systems. I even prefer this to the other common method of having them wired through a standard 15A switch, which is a weak link failure point, and I prefer to set the cord in sight of me when working on a machine instead of just remembering that I turned the switch off. And I was only picturing machines in attics just now. When the air handler is in the garage or closet, every one of them is cord-and-plug connected.

To me, a SPDT switch includes a center OFF position, which a 3-way does not. I would have thought this means it is NOT a SPDT switch. But I've not confirmed that from any research yet.

You prefer cord and plug on about anything else as well or just furnaces?

You know that if furnace is located in unfinished basement, garage, crawlspace at/below grade, outdoors (roof top unit), etc. it will need GFCI protection if supplied by 15/20 amp 120 volt receptacle right?

Three way switch is SPDT, (ON/ON).
Standard single pole wall switch is SPST (ON/OFF)

Get into AC/DC snap switches or others of that style and you come up with a lot of combinations that are rare or non existent for the typical wall switch including two and three position switches as well as multi-pole switches.

I'd guess none of them are rated for use in switching between two sources, unless they cost at least 5-10x the others - then they probably are listed.

Wall switch style I have seen that is listed to switch between two sources are pricey, have a center off position and you can't switch from one source to the other without first stopping at the center position. I don't believe they make it in a single pole version either, that won't isolate both conductors of the two sources.

Yes,most are,but, are they actually listed for that type of connection,or, are guys just installing cords because that's what they've seen others do?


Jap>

I almost never see one permanently connected with a cord and plug, if I do see one it was either some temp setup or a DIY connection.

 

[jap]

I almost never see one permanently connected with a cord and plug, if I do see one it was either some temp setup or a DIY connection.

Well that's a contradiction in terms, but, most all new residential furnaces units in our area that I've seen are connected by the cheapo 6 ft appliance cord plugged into a duplex receptacle.

I don't do much residential at all so not sure how they get by with it.

JAP>

 

[kwired]

Well that's a contradiction in terms, but, most all new residential furnaces units in our area that I've seen are connected by the cheapo 6 ft appliance cord plugged into a duplex receptacle.

I don't do much residential at all so not sure how they get by with it.

JAP>

Ok, fixed in place appliances is what I really meant, doesn't comply with NEC probably 99+% of the time.

Are those you mentioned on new construction or are they replacement units in existing buildings and are connected by the HVAC guy replacing them?

Here you may find some HVAC guys put them on a cord and tell owner to get an electrician to hook it up, and it never ever goes any further than that - but even that is somewhat rare unless maybe the old furnace supply didn't have an EGC and they did it just to get by until an electrician could wire it up properly. Some won't hook them up without an EGC as it is needed to help make the flame sensor work correctly.

 

[MAC702]

Come to think of it, every 120V tank or tankless water heater I've seen has been plugged in to a dedicated receptacle, too.
Same with permanently mounted dishwashers and garbage disposals.
Those are all things that are permanently fixed. And I've never seen one that wasn't connected with cord-and-plug, and I fix them on a regular basis.

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.

Now, washers, dryers, and refrigerators I'm guessing are not normally considered to be permanent? What conditions would make them so? I've seen large refrigerators that are built-in as part of the cabinetry. They are still plugged in. I've seen Jacuzzi tubs that are, *shudders* plugged in.

Now, I'm no home builder, but I work in 10K ghetto houses and 5M mansions. They are all the same, whether built 70 years ago or last year.

I don't know what to tell you except that's how it is here. And this is a county with more HVAC contractors than you can shake a stick at.

 

[kwired]

Come to think of it, every 120V tank or tankless water heater I've seen has been plugged in to a dedicated receptacle, too.
Same with permanently mounted dishwashers and garbage disposals.
Those are all things that are permanently fixed. And I've never seen one that wasn't connected with cord-and-plug, and I fix them on a regular basis.

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.

Now, washers, dryers, and refrigerators I'm guessing are not normally considered to be permanent? What conditions would make them so? I've seen large refrigerators that are built-in as part of the cabinetry. They are still plugged in. I've seen Jacuzzi tubs that are, *shudders* plugged in.

Now, I'm no home builder, but I work in 10K ghetto houses and 5M mansions. They are all the same, whether built 70 years ago or last year.

I don't know what to tell you except that's how it is here. And this is a county with more HVAC contractors than you can shake a stick at.

Dishwashers and disposers are commonly listed for cord and plug connection. Central furnaces are not. I have seen limited number of hot tubs that are marketed as portable (though not very portable at all while filled with water) that have a factory installed cord and plug - usually a 5-15 plug and only a 1000 watt heater, which does not run at same time jets are running or would be too many amps for the circuit.

 

[busman]

Dishwashers and disposers are commonly listed for cord and plug connection. Central furnaces are not. I have seen limited number of hot tubs that are marketed as portable (though not very portable at all while filled with water) that have a factory installed cord and plug - usually a 5-15 plug and only a 1000 watt heater, which does not run at same time jets are running or would be too many amps for the circuit.

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