Can I put 3 electric wall heaters on same ciruit?

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Old 09-30-19, 08:43 PM
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Can I put 3 electric wall heaters on same ciruit?

I have 3 electric wall heaters that I need to run power to. Here's the amps for each heater 8.3, 9.0, and 6.3. I have a 30 amp breaker available with #10 wire already wired to the 8.3 amp breaker. Can i add the 9.0 and 6.3 amp heaters to the circuit? I would have to add approximately 20 feet more of #10 wire.

Any help or recommendations is appreciated.

Bob
 
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Old 09-30-19, 08:46 PM
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Here's the problem..... those heaters cannot be connected to a circuit over 20A. The internal wiring is sized to be safe up to 20A. If you protect at 30A..... you run the risk of a fire within the heater due to undersized wiring if the element shorted.
 
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Old 09-30-19, 08:48 PM
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You have enough capacity on the 30 amp circuit for all three heaters. However what is the max breaker stated in the heater specs for those units? It is probably less than 30 amps.
 
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Old 09-30-19, 08:56 PM
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That was one of my concerns. I didn't see anything on the heaters about the circuit size. So, can I put the 9.0 amp and 8.3 amp on a 20 amp breaker or will the startup amps of both be too much for the 20 amp breaker.

Bob
 
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Old 09-30-19, 09:20 PM
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An electric heater is considered a continuous duty device. That means you can only connect loads up to 80% of the circuit ampacity. In this case it would be 16A maximum on a 20A breaker.
 
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Old 09-30-19, 09:42 PM
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Thanks PjMax.

I forgot about the 80% rule. I'm going to have figure out another way to do this.

Bob
 
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Old 10-01-19, 07:03 AM
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You can install a small subpanel close to where the wiring you originally planned would branch off to the second and third heaters. The existing #10 gauge branch circuit from the main panel would end there. Now you continue separate 20 amp (or 15 amp) "sub branch" circuits to the individual heaters.

If the "maximum circuit amperage" is not specified for the heaters then you will have to use the "suggested" or "minimum" circuit amperage as the maximum. For cord and plug equipped appliances or devices, the plug implies the maximum amperage rating.
 
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Old 10-01-19, 08:17 AM
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Sub panel with existing cable will only work if your existing cable is a 10/3.
 
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Old 10-01-19, 10:15 AM
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Joed,

Whay would I need 10/3 wire?

I thought about using the 30 amp cirucuit and then a sub panel with 15 amp breakers for the 9.0 and 8.3 amp heaters. And then adding the 6.3 amp heat onto a 20 amp breaker that has another 6.3 amp heater already on it.

Bob
 
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Old 10-01-19, 10:41 AM
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Two other possible solutions:

1) If these are 120v heaters, look into 240v heaters, the wattage and heat output will be the same, but the amperage (and resulting wire size) is cut in half.

2) Use a thermostat connected to a relay. The relay then can control 2 (or more) separate circuits. One thermostat, multiple circuits of heat. You can also use a low-voltage thermostat which gives you more options than standard 120/240v thermostats.
 
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Old 10-01-19, 10:49 AM
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Zorfdt,

These are 240 volt heaters. I'm unfamiliar with using a relay on the thermostat to control two heaters. Can you explain this more or a link that I can look at?

Thanks,
Bob
 
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Old 10-02-19, 05:56 AM
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A 10-2 Will go fine into a (120/240 volt panel wired up as a 240 volt only subpanel.

All of the breaker sets would be two pole with 12-2 (or 14-2) for the branch circuits going to the individual heaters.

No 120 volt branch circuits may be installed in that subpanel. But you probably already have enough 12 and 14 gauge 120 volt circuits around the room.
 
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Old 10-02-19, 07:35 AM
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You can use something like this:
https://www.supplyhouse.com/Honeywel...-o-Transformer


This allows you to connect your 240v heaters to a 24v thermostat. Or you get 2/3 relays and connect them to the same low-voltage thermostat

There's also a similar model R840-T that has a 24v transformer built in.
There's a post here from a while back about using one R840 and one R840-T together to control 2 circuits worth of heaters.
 
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Old 10-02-19, 08:06 AM
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AllanJ,

That's the way I'm going to wire them. I think I have a box and breakers at home even. The 6.3 amp heater can be wired to another heater circuit.

Zorfdt,

I'll have to check the relays out. That may be an option for me down the road.

Bob
 
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Old 10-02-19, 09:16 AM
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All three heaters together draw a smidgen under 80% (23.5 amps) of the 30 amp circuit.

You will probably need a box with at least 8 slots. You may not use separate breakers on the left and right sides respectively for one 240 branch circuit; the breaker handles need to be tied together.
 
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Old 10-02-19, 10:23 AM
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Allanj,

I had not thought about putting all three on the 30 amp breaker that way, but it will work. The 9.0 amp heater is in a porch and we only keep it at 60 degrees and it doesn't run a lot anyway.

Thanks again.

Bob
 
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