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We're planning on installing this Harvia Cilindro 10.5kW Electric Sauna Heater (Model HPC11-U1H) when it gets here.

The manual wants us to put a 50amp breaker in the main panel, and then run that to a sub panel with 2 40amp breakers, before finally connecting them to the power unit box for the heater/controls.

My question is, could I skip that 50amp breaker part and just install the 2 40amp breakers directly onto my main panel? My main panel is 200amps and has plenty of room for more breakers, and both the main panel and the sauna are in the garage so there's no benefit to me installing a sub panel there as well (unless this is a dumb idea and I'll burn my house down unless I do it).

Pictures for reference. Thanks!

Manual

Breaker and Wires

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  • What make and model is your breaker panel?
    – ThreePhaseEel
    Commented Jun 14, 2020 at 22:06
  • Generally the manufacturer's instructions take precedence, so you have to do what they require even if it isn't technically necessary. Having said that as long as there is a clear line of sight from the main panel to the heater unit I don't think many inspectors would fault you for just installing the 40 amps in the main panel. I am surprised that they don't require a GFCI breaker.
    – mfarver
    Commented Jun 15, 2020 at 1:44
  • The (UL) Listing is only valid when installed according to the manufacturers installation instructions. I don't have access to their submital standards for sauna, I wouldn't be surprised if somewhere the listing standards requires a single switch capable of being locked off for service. Maybe also consider what the safety, legal and liability implications might be if the sauna suffers some type of failure that results in the two circuits drawing more than 50A.
    – NoSparksPlease
    Commented Jun 15, 2020 at 3:54
  • Thanks for the feedback everyone. Y'all are right, I'd best just put in a sub panel and wire it according to the manufacture to be on the safe side for everything.
    – Yunyidi Han
    Commented Jun 15, 2020 at 23:36
  • @NoSparksPlease -- it's a space heating appliance whose disconnects are governed by 424.22(B)
    – ThreePhaseEel
    Commented Jun 16, 2020 at 4:05

2 Answers 2

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Normally you'd need the sub panel if for no other reason than to have a means to disconnect the sauna for maintenance. Since the sauna is in the same room you can go directly to it from the main panel as long as you have clear line of sight from the panel to the sauna. Your instructions show a sub panel and you shouldn't deviate from them but they also give wire sizes for going from main breaker to power unit (4#8,N & G) so I guess it's OK.

I think going to the sub panel would be cheaper.

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There are two reasons to use a subpanel:

  • As a disconnect in sight of the sauna. If the main panel is in the same room, that is not an issue.
  • To save on wiring costs. A single 50A cable (6 AWG copper cable, 4 AWG copper wires in conduit, or even better, a larger but much cheaper aluminum cable or wires) will cost less to install than to separate circuits. However, if the sauna is in the same room as the main panel then the cost savings (which is based on the length of the cable/wires) is offset by the cost of the subpanel.

So for the typical situation, 50A from main panel to subpanel, 2 x 40A in the subpanel makes sense. Spelling out the difference is important - otherwise you might think you need 80A for the feed circuit. But there isn't anything magical about a subpanel when everything is in the same room.

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