Tap into existing furnace wiring

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Old 01-22-19, 11:57 AM
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Tap into existing furnace wiring

Hello,

I am new to the forum. I would like to tap into the 110v line going into the furnace. I want to have some kind of a switch where if I flip it off the furnace line goes down. But on the other end of the switch I need a male receptacle so I can attach a live line from a generator. Is this possible? Sounds easy enough.

PS. I don't want to use a transfer station because I have a portable generator and all my other lines are taken care of with extension cords. This allows me to have heat in the winter in case I lose power.

Thanks for any advice.
 
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Old 01-22-19, 12:45 PM
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They make small transfer panels for this. You could use one with an inlet to plug the female end of an extension cord into. A 3-way switch would work too if the load is less than 15a.

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https://www.amazon.com/Midlite-MDT46.../dp/B002XDQAA6

If 3-way switch use a double gang box. On the switch furnace hot to common. House hot to one traveler and inlet hot to other traveler.
 

Last edited by ray2047; 01-22-19 at 01:10 PM.
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Old 01-22-19, 12:58 PM
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If I understand you correctly, here is an idea that might not break the bank.....and mitigates two common dangers...backfeed and suicide cables, but be sure this will pass code and inspection. I have not used these so I can't vouch for them, just suggesting it over a homemade device.
https://www.amazon.com/EZ-GENERATOR-...SIN=B00FADDE0A
 
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Old 01-22-19, 01:59 PM
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That 4" box is quite expensive for what it is. A Reliance single circuit transfer switch runs about $20 less.
 
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Old 01-22-19, 02:46 PM
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Three way switch. Hook furnace to the common. Hook grid to one traveller and inlet to other traveller.
 
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Old 01-22-19, 04:45 PM
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Joed, ECHO-ECHO-Echo-echo
 
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Old 01-22-19, 07:50 PM
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An easy way to connect generator with no obvious code issues:

Between emergency burner off/on switch and burner have wired a duplex 3 prong 120 volt receptacle.



Always keep LED night light plugged into second receptacle to indicate when power is on.
 

Last edited by pcboss; 01-22-19 at 08:12 PM. Reason: Removed suicide cord recommendation
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Old 01-22-19, 09:13 PM
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have wired a duplex 3 prong 120 volt receptacle.
He wants to use an extension cord. There is no safe way to connect an extension cord to a receptacle. How do you provide isolation of line from generator.
 
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Old 01-23-19, 05:41 AM
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Hummmm, is a 3 way switch rated for this application,although it is technically a DP/SP switch.
Geo
 
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Old 01-23-19, 06:38 AM
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He wants to use an extension cord. There is no safe way to connect an extension cord to a receptacle. How do you provide isolation of line from generator.
He is saying install a receptacle on the line side between the service switch and the furnace. Then install a plug on the furnace. In a power outage unplug furnace from line receptacle and plug into extension cord.
 
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Old 01-23-19, 06:58 AM
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install a plug on the furnace
That method has been discussed in previous posts. the question then is if it is code to have the furnace other than hard wired,
 
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Old 01-23-19, 08:14 AM
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Several Points:

Burner is hard wired to electric panel. Inspector would see no reason to think otherwise.

Burner is powered either by utility or generator, not both. Isolation is not used to interconnect two power sources. It is used to isolate a unit from power source.

If by some chance sources were interconnected, circuit breakers on either or both electric panel and generator would open.

Overnight, shut down generator and use this setup to run burner off UPS. For two weeks after Hurricane Sandy worked well.

Generator is on wheels, portable with line cord plug so not covered by code.

House had major damage from Sandy. During reconstruction Town inspectors were here number of times and found no issues.
 

Last edited by doughess; 01-23-19 at 09:37 AM.
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Old 01-23-19, 10:06 AM
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"If by some chance sources were interconnected."

There must be no chance sources can be interconnected otherwise your wiring is improper and dangerous. Circuit breakers on either or both will not necessarily open and persons working on power lines can be electrocuted.

In some cities the homemade solution using the 3 way switch, even though equivalent to the green transfer switch unit shown in the link, may be illegal because of the chance of a wiring mistake. Even the preassembled green transfer switch shown might not be legal in all cities.
 
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Old 01-23-19, 10:30 AM
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In some cities the homemade solution using the 3 way switch, even though equivalent to the green transfer switch unit shown in the link, may be illegal because of the chance of a wiring mistake. Even the preassembled green transfer switch shown might not be legal in all cities.

That's why like the Reliance single circuit transfer switch.

https://www.homedepot.com/p/Reliance...B&gclsrc=aw.ds
 
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Old 01-24-19, 06:31 AM
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(I think of the green EZ transfer switch as being the same thing as the gray furnace transfer switch, links to the pictures provided in preceding replies.)
 
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Old 01-24-19, 01:21 PM
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Thanks All. This very well answers my question. I will contact electrician for code satisfaction. Sounds real easy with that furnace transfer switch. It is exactly what I was looking for. It will isolate the AC between panel and generator. Perfect.
 
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