Electronics > Projects, Designs, and Technical Stuff
How safe is it to use a SSR to control power to a spa? Or use a relay?
DougSpindler:
--- Quote from: james_s on July 22, 2020, 05:34:44 am ---
--- Quote from: DougSpindler on July 22, 2020, 05:20:25 am ---What size hot tub do you have? That thing is drawing 8,800 watts. If it is like most high end hot tubs it would have 2 - 1.5 hp pumps. That would be 2237 watts. That would leave 6,563 watts for the heater and the electronics. Can't imagine a hot tub having over a 6,000 watt heater. I think the heater in my tub it at most 1,500 watts.
Imagine if you were a PG&E customer having to pay $0.54 kWhr. any idea what it would cost to power your hot tub?
--- End quote ---
It's about 6' square, made by Apollo Spas, I believe it's a 1997 model. There are two 2.5HP jet pumps that the labels say each draw 12A on high speed, a 1.5HP air pump and a 5.5kW heater. I haven't actually measured what the pumps draw but I suspect it may be less than labeled, otherwise we're already up to 46A before you even add the air pump, and the controls and light draw something too.
I pay around 8.2c/kWh from PSE, at least that's what it was last I checked. If I have the tub going it doubles my utility bill, adding $30-$40/mo depending on how much I use it.
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I'm going to have to dig out my amp meter tomorrow to see what the draw is. I could probably do it from my solar panel monitoring system I looked at hot tub heaters and it turns out they can be in the 6 kW range. So with 2.5 hp motors 40 - 50 amp draw is not that out of line.
Be lucky you are paying 8.2c/kWh. PG&E's TOU rate has us paying $0.14 to $0.54.
james_s:
I thought 5.5kW was pretty standard for spa heaters, at least some models of the little 120V tubs use the same heater but it's only around 1.4kW on 120V. It's a lot of power, but on the plus side, most of the time when the pump runs it's on low speed and the heater only comes on when it needs to. It's rare for everything to be going all at once for more than 15-20 minutes. Normally when I use it I go for a dip in the evening for 10-15 minutes and then shower and go to bed.
If I were paying a lot more for power I'd either get a gas fired heater or just get rid of the thing.
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