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I'm converting an existing sauna room to infrared. It currently has one 240/30A circuit. I have two heaters and one power supply/controller. Before purchasing I believed the power supply would handle powering both heaters from one on input side, but now I know two circuits are needed (PS has 4 inputs/4 outputs)

Each heater is 13A. Rather than run a 2nd circuit from the subpanel (would be difficult), I am hoping to add a small sub panel to split the 30A into two 15A circuits. The 30A is already coming from a subpanel but I wouldn't be making any changes there.

Is this approach ok or do I need to run a 2nd circuit? power supply

Control panel

heatersoutlets for heaters

heater nameplate Wire diagram back of door

So L1/N1 - L4/N4 on input side, L10/N10 - L40/N40 on output side 240v/30A coming in. I'm getting from this conversation that I'll need to replace the feed side 30A breaker with a 40A or 50A?

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    Does the existing circuit have a neutral wire? Also,13a is over limit - should be 12a max for a continuous load on a 15a circuit.
    – manassehkatz-Moving 2 Codidact
    Commented Mar 4, 2021 at 14:33
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    Where on earth are you?
    – NoSparksPlease
    Commented Mar 4, 2021 at 15:14
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    When you say power supply could you explain? Running a small sub to break down into individual circuits could be done but the supply/controller if it uses additional power would be questionable. If there are no motors and you use a sub the field wiring could be 20 amp & breakers but the supply can be 30 amp to the sub your controller cycles the heat control? But if any motors in the system it needs to be rated at 125% as this would be considered fixed heating equipment. This is covered in article 424 of the NEC
    – Ed Beal
    Commented Mar 4, 2021 at 15:15
  • Are the new heaters 13A @ 120V or 13A @ 240V? Makes a big difference in both power available and (unless the controller needs it) need for a neutral.
    – manassehkatz-Moving 2 Codidact
    Commented Mar 4, 2021 at 15:21
  • @Bob Could you please give the model & specs for the new power supply/control and the two heaters?
    – ScienceGeyser
    Commented Mar 4, 2021 at 16:58

3 Answers 3

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The posted pictures help a lot. Your heating elements are only 10.4 A each, so you don't need to change the breaker. The 13A in the part number is not the ampere rating.

You need to wire L1 and L2 together and N1 and N2 together in the control box. Each Ln is not indicating a phase but an input to the relays which are all isolated from each other so you have the option to run all the heaters on seperate breakers.

It looks like the equipment is only rated for 20A per circuit. This means that if you draw enough current through one heater to trip the breaker (say during a malfunction) then you may start the controller on fire before the breaker trips. In this case, I would recommend going with the subpanel and two 15 A two pole breakers feeding each of the two inputs you need to power. The only way it would work by pig-tailing is if all components are rated at the breaker capacity up to the point of additional circuit protection.

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  • You can't simply throw a 15A-rated device on a 30A circuit without down-breakering. There is some leeway, depending on the device - e.g., motor loads often will allow a higher breaker in order to account for startup, but 13A on 30A? Not generally a good idea.
    – manassehkatz-Moving 2 Codidact
    Commented Mar 4, 2021 at 15:00
  • @manassehkatz-Moving2Codidact Wouldn't he be "down-breakering" in the new sub-panel? But there is another issue derating the 30 amp circuit for continuous use yields a capacity of 24 amps and with 2 13 amp heaters he'd be drawing 26 amps.
    – George Anderson
    Commented Mar 4, 2021 at 15:09
  • @manassehkatz-Moving2Codidact Thanks for pointing out that I implied adding a receptacle by using the word "device". I edited the post to be more clear.
    – ScienceGeyser
    Commented Mar 4, 2021 at 15:11
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    @GeorgeAnderson But the load is only 13A on each circuit and he should be able to use a subpanel with two 20A circuits. I edited to add that too.
    – ScienceGeyser
    Commented Mar 4, 2021 at 15:14
  • The way this is worded is not best and there needs to be clarification of what the actual load is, a “non continuous load” can add up to 30 amps but put 1 fan Motor and everything is considered continuous so the max load would be 24 amps. I started this comment and was called away and there are edits and comments not there when I started but more info is still needed see article 424 fixed heating. This will be the basis on the derate if needed.
    – Ed Beal
    Commented Mar 4, 2021 at 15:20
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Besides the question of the maximal current matching the existing installation, those IR heaters are most likely not specified for the high temperature and/or high humidity/condensing air inside saunas. Also the IP class for electric installations inside saunas should/must be IP65 or better, at least if a water outlet/shower/faucet is inside the sauna. And of course, GFCIs are mandatory.

If the sauna was made of glass walls, the 2 IR heaters could be installed at 2 neighbouring sides outside with 2 mirrors at the 2 other sides.

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If the owners manual/installation instructions say two 240v 15A circuits are required then you are good to go if you mount a new subpanel with two 240v 15A breakers. Those instructions are part of the NRTL Listing and override general NEC provisions.

If the instructions don't specify then IR saunas are normally considered "fixed electric space heating" which NEC 424.3 designates as continuous load, so circuits are calculated at 125% of nameplate. So the branch circuit from a new subpanel would need to be 20A.

For the feeder calculation there is a little, but very little, wiggle room, for the feeder for the new subpanel. Then general rule in 220.51 says the feeder is to be calculated at 100%, but then there is an exception that allows an authority having jurisdiction to allow reduction under cycling conditions. I doubt many local inspector would grant this permission.

Edit: Now seeing the nameplate says 10.4A, not 13A. Then 10.4 x 125% = 13A. It appears the 13A is the circuit requirement, not the actual heater draw. So two 15A receptacles on separate 15A breakers being fed by a 30 feeder should be fine.

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  • Assuming you are in the US, and 220/30A means 240v 30A three wire (two hots/ground) and when you say the new requires 13A you mean 240v 13A (two hots and a ground), not 120/240v (two hots, neutral, ground) and not two 120v 13A circuits.
    – NoSparksPlease
    Commented Mar 4, 2021 at 16:15
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    Yes two hots, no neutral. In US. Heater manual says 13A, good to know about the 125%, so I'll plan on swapping the 30A breaker for a 40A. Feed wire is 8 gauge. Thanks for awesome answer, references to the code will help me learn more about this.
    – Bob
    Commented Mar 4, 2021 at 16:48

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