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Old 06-14-2017, 02:36 AM   #1
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Default Heating and Cooling Equipment Question

In regards to the furnace in the attic, specifically, what is required by code when you have 2 furnaces? Does it have to be (2) dedicated 120v, 20a ckts? Is it ok to run a MWBC to the furnaces?
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Old 06-14-2017, 04:38 AM   #2
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Why wouldn't it be okay? An attic seems to be a strange place for a furnace. Let alone two. Are these oil burners, or natural gas, or...........?
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Old 06-14-2017, 06:36 AM   #3
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Fairly common here, nat gas or propane.
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Old 06-14-2017, 06:48 AM   #4
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Forced hot air furnaces are common in attics.

Many of them are 120V, however they can also be 240V. Code requires them to be on a dedicated circuit. I don't know of any code that would stop those circuits from being a MWBC. Typically 15A is fine, but you need to check out the units to see the voltage and amperage.
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Old 06-14-2017, 11:02 AM   #5
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Attic furnaces and or air handlers are common in many areas, especially flood zones.

I've done an MWBC many times for dual furnaces with no problems.

Just don't forget you need emergency switches at the attic entrance and a service receptacle.
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Old 06-14-2017, 11:13 AM   #6
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Quote:
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Attic furnaces and or air handlers are common in many areas, especially flood zones.

I've done an MWBC many times for dual furnaces with no problems.

Just don't forget you need emergency switches at the attic entrance and a service receptacle.
I believe that is only for oil. I have asked this question before and from what we all found, there is no requirement for a shut-off near the basement or attic entrance for natural gas fired furnaces, only by the furnace.

I definitely could be wrong.
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Old 06-14-2017, 11:16 AM   #7
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I believe that is only for oil. I have asked this question before and from what we all found, there is no requirement for a shut-off near the basement or attic entrance for natural gas fired furnaces, only by the furnace.

I definitely could be wrong.
Not sure if it was just a local requirement but I know it is required in many locations for gas or oil fired units .
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Old 06-14-2017, 11:18 AM   #8
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Not sure if it was just a local requirement but I know it is required in many locations for gas or oil fired units .
Yeah, it could definitely be a local thing.

I noticed around here it was never done so I looked into it once before feeding a furnace and found the only thing was an old building code talking about oil.
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Old 06-14-2017, 11:28 AM   #9
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Yeah, it could definitely be a local thing.

I noticed around here it was never done so I looked into it once before feeding a furnace and found the only thing was an old building code talking about oil.
I know in Deal and Allenhurst they required one at each basement entrance.

Plainsboro it was required for the attic furnaces but they have some other bizarre things they require.
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Old 06-15-2017, 12:53 AM   #10
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Forced hot air furnaces are common in attics.

Many of them are 120V, however they can also be 240V. Code requires them to be on a dedicated circuit. I don't know of any code that would stop those circuits from being a MWBC. Typically 15A is fine, but you need to check out the units to see the voltage and amperage.
The reason I posed the question is I had an HVAC guy call me who is having a temper tantrum with his electrician. The HVAC guy and I are friends. They ran a MWBC to the 2 furnaces in the attic. When they spliced the neutral to run to the 2 units, they did a poor job. He was looking for a code reference to make him fix it. He said his equipment only asked for a 15a ckt.
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Old 06-15-2017, 06:02 AM   #11
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The reason I posed the question is I had an HVAC guy call me who is having a temper tantrum with his electrician. The HVAC guy and I are friends. They ran a MWBC to the 2 furnaces in the attic. When they spliced the neutral to run to the 2 units, they did a poor job. He was looking for a code reference to make him fix it. He said his equipment only asked for a 15a ckt.
Code wise it is fine. But if that neutral comes unspliced it could be disastrous.
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Old 06-15-2017, 06:10 AM   #12
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done quite frequently here

just did an attic addition here and the electrical contractor that originally wired the house was so kind as to run a 14/3 to the original gas furnace installed. I was thankful because it would have been a pita to go through 3 floors, a crawl space and fish the panel.
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