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Question DetailsAsked on 5/22/2016

I'm having a exterior steam sauna installed it needs 220 v with 40 amps and no slots are open in panel, what now

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In addition to 220/240V service to it, new electrical code provisions require (or at least many inspectors are interpreting it that way - not totally clear in code if applies to enclosed saunas or just to hot tubs and non-bathtub jacuzzis) that there be a power emergency disconnect switch close to the sauna - I don't remember the exact distance allowed (at least 5 feet from water/steam but max something like 15-20 feet and has to be in sight of it and clearly marked as emergency shutoff) but commonly located right on the outside by the door. Some code areas require the emergency shutoff switch be INSIDE the sauna - which means a rather expensive totally waerproof and steam-rated switch, though some saunas come with this already. This would be in addition to any switch on the unit itself - theory is you need an emergency disconnect close by which can be turned off if something goes haywire with the unit (like shorting and sparking or fire) so you are not trying to turn off the defective unit itself, especially when wet.

GFCI protection and bonding of all metal parts other than barrel stave bands to ground is also required.

Electrical is the Search the List category for this type of work to find a well-rated and reviewed vendor.

He can assess the total load on your panel, and advise you on which one of three possible solutions would be best in your case:

1) run a new tap off the main incoming feed to the house (assuming it has the power capacity - generally does if you existing main house breaker is 125A or more - if 100A probably real iffy if mostly electric house but commonly OK if gas-fired water heater and furnace/boiler, range and clothes dryer. If under 100A main breaker you will likely need a total service upgrade first, depending on the meter/meter base and incoming feed capacity, which can be much higher than the main breaker rating. This would be a dedicated line from the main connection panel (at or right next to/below the meter) to a breaker box dedicated to that use then on to the sauna, or might tap the incoming line from the meter to the existing panel if it has the capacity, though not likely - normally sized only for the installed main breaker capacity.

2) put in a secondary panel fed by your existing breaker panel, providing additional circuit slots - using 2 existing breaker slots in the existing main panel to protect it, but providing additional breaker positions for one or two of the existing main panel circuits (which would be displaced by the breakers for the auxiliary panel) plus the new double breaker needed for the sauna, and if the incoming main feed has the capacity, possibly additional spare slots for future circuits. Whether you can do this or not depends on the existing load demand at the main panel - there is a calculation which depends on number and types of appliances, lighting, outlet circuits, etc. to determine how much power the panel is being asked to provide. This "simultaneous load estimation" calculation is what the breaker panel rated capacity and main panel is generally sized for - because if you add up all the amperages of the individual breakers the total will typically be 2-3 times the main breaker capacity, but as they are not all in use at one time the main breaker and panel rated capacity is based on the maximum surge and/or sustained (depending on types of demand and breaker type) estimated load at any one time.

3) simplest, but likely only workable if 125-150A or larger current capacity panel, is to take several of the smaller load circuits (120V circuits, typically lighting) and reconnect them to half-thickness breakers - which fit into half the width of the existing breakers - or with some makes and models twin or "siamese" breakers - the same width breaker housing, but provides 2 separate breakers and breaker switches for 2 separate circuits in the same space as one existing one. Subject to same load calculation as in #2 above, and works only if your panel has significant (50A in this case because this is a sustained load) available load capacity. Some locales do not allow half-thickness or siamese breakers.


Probable cost - depends of course on how long a run to the sauna because the wiring and conduit run several $/LF just for materials, but typically around $500-800 range if slim/twinned breakers can be used to free up space for a new breaker pair and simple wiring run. [220/240V circuits take paired breakers which are connected together with a bar so they trip together]. If you need an auxiliary or secondary panel - either tapped off the existing box or of the meter base, or difficult access to get there from here (like length of house) typically more like $800-1500 range. In rare cases where the incoming service drop (the power company line) does not have the capacity for the added load, so it needs to be upgraded too (sometimes meaning the meter base and meter also need replacement to higher capacity unit), then cost can go up by several thousand $ in some areas, depending on how expensive the utility company prices its upgrade andon whether they have to upgrade the transformer too. Some do it real cheap or even free figuring they will get the $ back in added usage fees - others want the $ up front to pay for it when installed and then get the usage fees too. A few (mostly co-ops) will cre4dit back part of the upgrade cost if you prove so many years of increased electricity usage.

Add several hundred $ more typically if going with an underground run to the sauna, assuming no utility conflicts en route that require it go deep or into bedrock.

I would contact several contractors to give bids, because this sort of job can be pretty variable on cost between bidders. It is possible the bidders will want to charge you $100-200 (depending on local costs) to figure the existing loads on the main panel to determine if it can handle it or not - if so, fair to pay that to one but have him provide the calculation to you, signed by him with his electrical contractor license number on it, so you can show it to the other bidders so you don't have to pay them to figure the load too.

Other alternative, especially if sauna is near the meter, is to use a separate run from the meter base (if it is configured for it - some are not) through a new separate panel to the sauna - not going through the main breaker panel at all (so case #1 above), totally avoiding the issue of whether the existing main breaker panel can handle the load. This would actually be my preference - for a large load like this, I don't like running it through the main panel if not needed, because I have seen too many fried panels because the estimated demand calculation was not conservative enough, and during a party or holiday family get-together too many appliances and lights and such were in use at one time and overloaded the panel, sometimes by as much as 50-100% over rated capacity. Technically, the breakers should prevent this - but as they get older their reliability decreases, plus there have been quite a number of breaker recalls for failure to trip when they should.

BTW - if in an area where it can get below freezing be sure to check out the draining procedure to prevent damage to the unit, and if having an external water supply line put in make sure it is frostproof. Also consider WHERE the drained water will go to - so it does not ice up and frost heave the sauna or the deck or porch it is sitting on.

Answered 4 years ago by LCD

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