I have a sauna heater from Harvia that had limited information about the controller prior to receiving it from Ireland after a 4 week wait. The stove itself seems to be compatible with 220v US wiring, but the controller does not immediately seem to be workable without some serious help from the internet. I unfortunately took the 230V 1N~ in the stove documents to mean that I could do 1 phase 230V only to find out that the controller does not contain an option in the documentation for that.

I really could use a general solution (or even wild ideas) along with the size of breakers and wire needed for a 70 ft run from the breaker box.

I am posting the board connections, heater connections and charts from both manuals in desperate hopes that someone smarter than me will have a solution as this is not returnable.

I do have a 3-phase rotary converter in the garage that could probably power it as a last resort, but firing that thing up in the garage every time we want a sauna does not sound remotely enjoyable.

My house has 1 phase 120V/240V service.

If anyone sees a way that this can be installed without 3 phase service and without using the rotary converter, PLEASE HELP!

Stove Controller: Stove Controller

Controller Spec Table (9kw): Controller Spec Table

Controller Wiring Diagram (9kw): Controller Wiring Diagram

Stove Connections: Stove Connections

Stove Spec Table (9kw): Stove Spec Table

Stove Wiring Diagram (9kw): Stove Wiring Diagram


The solution I was hoping would work below (and which worked great for 2 weeks) wound up burning out the controller board (transformer and some of the relays). I am amending this question to try to discover a better board for this set-up:

Is there anyone out there who can tell me how this circuit would in any way regulate the kW that make it to the stove, or is that all just a function of the heating elements in the stove? It is a WX361 controller board from Harvia and uses contactors (ZSL-940) to open and close the power to the stove. I think there are two contactors there simply to allow the overheat protection (A1 and A2) to cut power on overheat. If I use this board, it will now be hooked up 240v 1Ph with a neutral.

Harvia WX361 Diagram Harvia  WX361 Diagram

Harvia WX361 Board Harvia WX361 Board

Harvia ZSL-940 Contactor Harvia ZSL-940 Contactor

  • Will need an expert to answer before connecting, but if the sauna does not require neutral, then possible you will use N for one hot and L1 for the second hot to get 240v. Ground is ground. It is always iffy trying to use electrical devices from other countries not made for your electrical system.
    – crip659
    Feb 17, 2023 at 22:18
  • Thank you, I’m hopeful there will be some trick like that, but totally waiting and praying for a professional to bump into this question. The Harvia support so far has been completely dismissive and did not even try to help.
    – Scott M.
    Feb 18, 2023 at 1:11
  • @ScottM. -- does your AHJ even approve of this equipment being installed? Feb 18, 2023 at 5:00
  • That is a bridge I will have to cross after I can prove it will work, but generally they are reasonable people. Do you have any ideas? Does hooking a 2-pole breaker 2 phase, one side to a bridged neutral set (1,2 in the controller diagram) and the other side to a bridged 3phase L1,L2,L3 (3,4,5 in the controller diagram), while still using ground, sound sane? I’d be upping the gauge and breaker size. Skipping neutral.
    – Scott M.
    Feb 18, 2023 at 13:50
  • @ThreePhaseEel tag for above comment… thx!
    – Scott M.
    Feb 18, 2023 at 14:00

1 Answer 1


L1 to N, L2 to the phases should work

Since your unit supports 240V 3Φ delta wiring as per the manual, it shouldn't have any difficulty with a split-phase setup either. Wire L1 to the neutral terminals and L2 to the phase terminals, and use 6AWG copper for the wiring with a 50A breaker, to accommodate the case where this is treated as a continuous load.

  • thank you for helping validate what I am hoping for. I am going to test this today. Could you comment on the connection between the stove and the controller. It shows jumping the same way on its diagram for the stove, but there are 6 wires on the controller connector and 6 in the stove (5 terminals, one paired N set). Should I just jump them together into N and L groups before exiting the controller and run the 3 wire 8AWG (2+Ground) between and jump them in the stove as shown? I think the photo makes what I’m saying clear, but let me know.
    – Scott M.
    Feb 18, 2023 at 16:45
  • Of course using appropriate wiring for the heat and humidity…
    – Scott M.
    Feb 18, 2023 at 18:31
  • This worked! Long term, finger's crossed. I will likely just do the same 6AWG to the heater as is going into the controller even though it calls for 10mm (8AWG) between.
    – Scott M.
    Feb 18, 2023 at 22:53
  • The final solution: Harvia Spirit HSP904MXW Wired the line in to the controller as 2Phase 230V from a 50Amp 2 Pole Breaker. Service lines go to the green terminals. I jumped the two neutrals together (left two terminals). Jumped terminal 3,4 and 5 (3 phase terminals) together. Ran one phase to the Neutrals and 1 to the 3 phase terminals. Between Controller and Stove, I combined the purple neutrals together & the black lines / phases together and ran a single wire from each to the stove. Stove is jumped like the 230V 1N~ diagram (same as the lines into the controller green terminals).
    – Scott M.
    Feb 20, 2023 at 3:38
  • I unfortunately need to amend the comment above to state that this is not a long term solution. It ended up working great for about 2 weeks then an electronic overheat smell started presenting. After that I could hear some of the relays clicking, but no power came out. Follow Up question to come in a second...
    – Scott M.
    May 17, 2023 at 21:09

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