What is the electrical requirements for a commercial furnace

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anderson100

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I am going to bid on the electrical install for a commercial furnace and just needed to know if I need to install a standard switch and a gen purpose outlet? Not sure what size the unit is yet but im gessing it will be small.
 
Andy, welcome to the forum! :)


Whether residential or commercial, you must see the nameplates on each piece of equipment. You should end up with two numbers for each piece: Mimimum Circuit Ampacity and Maximum Overcurrent Protection.

Your circuit should be sized for the former, and the breaker or fuse (fuse only if it says so) for the latter. For example, if it says MCA = 24a and MOP = 40a, you can use #12 wire and a 40a breaker or fuses.
 
Take a gander at 422.12. It may be helpful also.

422.12 Central Heating Equipment.
Central heating equipment other than fixed electric space-heating equipment shall be supplied by an individual branch circuit.
Exception No. 1: Auxiliary equipment, such as a pump, valve, humidifier, or electrostatic air cleaner directly associated with the heating equipment, shall be permitted to be connected to the same branch circuit.
Exception No. 2: Permanently connected air-conditioning equipment shall be permitted to be connected to the same branch circuit.
Click to expand...
 
furnace or boiler?

furnace or boiler?

If it's a furnace, I'll reserve comment. I usually see hot water boilers in the large sizes. The question is how much is factory wired and ships in one piece. Just bringing a feed to it may not work. You will have to know sequence of operation and wire in the external limits, accessory equipment, and zone controls.

If it's a boiler it's likely a cast iron sectional type and ships in pieces. Nothing except the burner will be prewired ... and there's no wiring digram that shows how every limit and pump control gets wired. I've done a ton of them. The limits will be hanging on the boiler, operating control, lwco, high limit, hot water reset - heat timer, gas train, combustion air. Each boiler is pretty much a custom wiring diagram depending on the trim and accessory equipment.

I've bid boilers very competitively for $3000 and the prime would find someone who has not done them before to wire for $800. caveat.

It's very easy to break boilers with thermal shock. I get called all the time to look at boilers wired by others. If it's a boiler you should know what thermal shock and flue gas condensation is ... before you cause it. Steam boilers have a condensate pump feedwater control.
 
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