Electronics > Projects, Designs, and Technical Stuff
How safe is it to use a SSR to control power to a spa? Or use a relay?
sokoloff:
For once or twice daily cycling and no need for anything more than bang-bang control, I’d use a relay.
DougSpindler:
That's what I'm going to do.
For educational purposes.. Could I use an SSR? Can you explain the advantages and disadvantages?
Thanks
themadhippy:
ssr's tend to have a bleed current,if theirs something that can sink that current its going to cost you money,even 5ma comes in at about 4kw over a year.Another issue is some ssr's dont like inductive loads.stick a proper contactor in,not an elcheapo relay.
floobydust:
What is the spa load? Assuming it's two-phase and there's a circ pump, heater and jets?
An SSR does not wear out like a contactor or relay, but they make a lot of heat. About 1W per amp in a one-pole SSR. So you need a heatsink and good cooling for two SSR's. A decent manufacturer of SSRs like Crydom is expensive then add on the heatsink costs and a place to put them. Cheapola Fotek SSR's and the knock offs are just a hassle as they fail easily, due to the fake specs and bad thermal design.
The highest cost is switching high current. If you can instead find a way to cause the spa controller to shut off the spa, it would be much easier. Like tapping into the run/stop switch or falsely trip a safety limit switch such as low water. The spa should already have some control logic.
james_s:
1W per amp is pretty substantial at the currents involved here. My hot tub is on a 50A 240V circuit and with everything going on high it draws more than 40A.
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