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Heater Thermostat Wiring

by bilyo
posted 09-27-2018 08:11 PM


17 replies so far

View waho6o9's profile

waho6o9

8803 posts in 3142 days


#1 posted 09-27-2018 08:15 PM

Where are the instructions?

View bilyo's profile

bilyo

910 posts in 1667 days


#2 posted 09-27-2018 08:56 PM

The instructions are in the box and are not informative regarding wire size. Mostly have to do with thermostat operation.

View Scap's profile

Scap

88 posts in 492 days


#3 posted 09-27-2018 10:58 PM

Assuming you have an electric unit heater like the Markel HF1B5103N or similar, the 5kw 240/1 heaters pull roughly 21 amps.

Even though your breaker is 30A, the stat being rated at 22A line voltage is appropriate for that type of heater.

Odd that the tstat is a 4 wire setup. Is it digital/electronic or old school mechanical?

View Craftsman on the lake's profile

Craftsman on the lake

3069 posts in 4002 days


#4 posted 09-27-2018 11:25 PM

Hmm…. 240 volts should mean that the 30 amps breaker is a split 15 amp right? 15 amps for each 110 wire on the heater. If so then a #12 wire is plenty fine for this setup.

And if it’s like my electric baseboard heaters 12/2 (three wires, white, black, and ground) are all that should be needed. Or am I missing something.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View TheFridge's profile

TheFridge

10859 posts in 2051 days


#5 posted 09-27-2018 11:30 PM

It isn’t split.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View bilyo's profile

bilyo

910 posts in 1667 days


#6 posted 09-27-2018 11:58 PM

It is this heater. It requires a 240 volt 4 wire circuit with 30 amp breakers (30 amps each leg). Thermostat is this one. It has two red and two black 12 ga connection pigtails.

View Scap's profile

Scap

88 posts in 492 days


#7 posted 09-28-2018 12:05 AM



It is this heater. It requires a 240 volt 4 wire circuit with 30 amp breakers (30 amps each leg). Thermostat is this one. It has two red and two black 12 ga connection pigtails.

- bilyo

That’s pretty much the same heater…just different mfg.

Now the 4 wires makes total sense. Red and black from breaker to stat, then red and black to heater with green passing straight through from panel to heater.

Sorry, been a few years since I’ve played with an actual tstat instead of just selling heaters with them. :)

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bilyo

910 posts in 1667 days


#8 posted 09-28-2018 01:03 AM

Thanks. What about the question regarding 10 ga to 12 ga pigtails?

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Scap

88 posts in 492 days


#9 posted 09-28-2018 01:10 AM



Thanks. What about the question regarding 10 ga to 12 ga pigtails?

- bilyo

Heater only pulls 21A, tstat rated for 22A. You’re good to go

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bilyo

910 posts in 1667 days


#10 posted 09-28-2018 02:29 AM

Are you saying that I can go with 12 ga all the way with 20 amp breakers?

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Scap

88 posts in 492 days


#11 posted 09-28-2018 02:40 AM


Are you saying that I can go with 12 ga all the way with 20 amp breakers?

- bilyo

Stick with 10 for your feed. But 12 is ok on the stat.
Also, stay with the 30a breaker since heater pulls 21a

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bilyo

910 posts in 1667 days


#12 posted 09-28-2018 02:53 AM

Just for my education, why is it OK to connect the 10 ga to the 12 ga? Does it have to do with the short length of the 12 ga? Isn’t that putting a restriction midway between the source panel and the heater?

View ArtMann's profile

ArtMann

1447 posts in 1381 days


#13 posted 09-28-2018 04:31 AM

You are making an erroneous assumption that a 12 gauge wire is incapable of carrying more than 20A. That simply isn’t true. It depends on the situation. The whole issue is about heat. If a wire is in an environment where it can dissipate enough heat, it can safely carry considerably more current than what the reference tables you have seen show. The people making the switch know what they are doing. Most consumers do not and need to rely on the accepted guidelines.

You need a 4 wire device because both hot legs of the 240VAC feed need to be switched in order for the switch to be safe under all circumstances. If one side is left hot then the device being controlled can still shock or kill someone even if the device isn’t running.

View TheFridge's profile

TheFridge

10859 posts in 2051 days


#14 posted 09-28-2018 04:48 AM

If the device is rated for don’t worry about it. Undersized wire in a device or piece of equipment is common. I usually chalk it up to wire with a higher thermal rating. Even if it isn’t, as long as the specs say it’ll handle it just roll with it.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View bilyo's profile

bilyo

910 posts in 1667 days


#15 posted 09-28-2018 01:29 PM

Thanks for the info. I’d never given much thought to the fact that a lot of internal wiring in devices is actually smaller thnt the wire that feeds the device from the panel. I do understand about both legs of the 4 wire circuit needing to be switched.
Thanks again

View Fresch's profile

Fresch

455 posts in 2485 days


#16 posted 09-28-2018 02:58 PM

Take a look in your electric oven or dryer.

View bilyo's profile

bilyo

910 posts in 1667 days


#17 posted 10-05-2018 09:49 PM

All wired up and working fine. Thanks to all for the help.

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