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, 03:51:15 am ---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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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?
DougSpindler:
--- Quote from: themadhippy on July 22, 2020, 02:47:23 am ---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.
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Thanks - Is there a difference between a contractor and a relay? Isn't a contactor just a high current relay? Or is there more to it?
james_s:
--- 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?
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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.
james_s:
--- Quote from: DougSpindler on July 22, 2020, 05:25:18 am ---Thanks - Is there a difference between a contractor and a relay? Isn't a contactor just a high current relay? Or is there more to it?
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A contactor is just a relay. Usually the term refers specifically to an open frame relay with a mounting base and screw terminals to attach wires, as opposed to a relay which is usually enclosed and solders to a PCB or plugs into a socket.
DougSpindler:
--- Quote from: james_s on July 22, 2020, 05:36:12 am ---
--- Quote from: DougSpindler on July 22, 2020, 05:25:18 am ---Thanks - Is there a difference between a contractor and a relay? Isn't a contactor just a high current relay? Or is there more to it?
--- End quote ---
A contactor is just a relay. Usually the term refers specifically to an open frame relay with a mounting base and screw terminals to attach wires, as opposed to a relay which is usually enclosed and solders to a PCB or plugs into a socket.
--- End quote ---
Thanks
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