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Discussion Starter · #1 ·
- Had a thread - got some answers (TY) - learned some things (thermostats/24v relay etc.) - taking awhile to get this last one answered:
I have a 4500w (18.8amp)and a 2000w (8.3amp) heater on a 10awg 30a circuit (open studs right now). I was told in my thread that NEC says wall heaters should be wired at 125% of capacity...
- I have two questions:
I'm curious how long that has been code?
and
In my situation I'd assume that means I would either need to switch to 8awg wire and a 40a breaker OR wire each heater to separate breakers (one 30a and one 20a)?
are my assumptions correct?

answers/thoughts/advice appreciated - TY
 

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Discussion Starter · #3 ·
I would wire each separately. Having the 2000 watt heater on even a 30 amp breaker is way over 125 percent.
Yes - I suppose I could get a 2-pole 15a for the smaller.... (Obviously) I'm a complete novice, tell me, is there any real "drawback" to something that's "over-protected?" If I were to wire a 1500amp heater alone to a 2-pole 60a breaker, as long as the wire awg is correct, it's ok - right?
 

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Red Seal Electrician
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The elephant in the room here is an approved heater has a thermal cut-out. It's impossible to overload a heater. You may want to check if NEC has a maximum size circuit when aggregating smaller heaters. Oversizing to that degree it going to make for a frustrating splice in a tiny space.
 

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Remodel and New Build GC
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The elephant in the room here is an approved heater has a thermal cut-out. It's impossible to overload a heater. You may want to check if NEC has a maximum size circuit when aggregating smaller heaters. Oversizing to that degree it going to make for a frustrating splice in a tiny space.
Boy U2SLOW......I'll say....OP....U2 is being nice....by "frustrating" he really means $^&%#@$^&^%$##$ dang.

(I replaced a Tstat for some baseboard that had been wired in #10 120V 30A....and that was a %^^$%^b1tch.

Have no idea why it had not been done in 240 #12.)
 

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Discussion Starter · #9 ·
I've read (in a couple of places) that many jurisdictions (and I'm going to guess Minnesota is one of them) that 10 awg is minimun size for a 240v circuit. Are you guys talking about the connection directly to the thermostat? I'm not really understanding why that would be hard? If I wire each heater on its own 30A breaker with 10 awg and use bigger boxes where I install wall thermostats, I should be good - right? - other than maybe (?) where is put a 24v relay in the 4500w heater?
 

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Don't let "wire size bump" mentality push you into ever larger and more costly copper wires. Before you even go to #10, jump ship and go to #2 aluminum and a subpanel.

It's a bit of an undertaking but the wire is actually cheaper by the foot than #8. It also satisfies the Code requirements for local disconnects for hardwired heaters. And you will be pleased as punch to support just about anything the future brings. You could do full-bore EV charging or an RV concurrently with the heaters.

I've read (in a couple of places) that many jurisdictions (and I'm going to guess Minnesota is one of them) that 10 awg is minimun size for a 240v circuit.
That doesn't make any sense. The USA is a 240V country in the full meaning of the words. You can have dozens of 240v outlets if you want it. And 15/20A 240V circuits follow the same rules as 120V circuits, right down to 15A receptacles being allowed on 20A circuits if there are 2 or more sockets.

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