Disconnect Temp Sensor

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C

ckeyes888

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Dec 1, 2011
4
Hi,

I would like to be able to control my hot tub, Dimension One, temperature using my home automation system. The one thing I haven't worked out yet is how to defeat the heat control to
to cause the heater to stay on regardless of its temp setting.

Ideally what I'd like to have happen is to have the heat control on the tub set to a cool setting,
just enough to keep things from freezing, that I can override with a relay to force
the heater to stay at maximum heat. I have a temp sensor attached to the tub
that my automation system will monitor the water temp and when it reaches our desired temp
will shut off the relay, hopefully putting the tubs heat control back on and shut off
the heater.

I would think the easiest thing to do would be to interrupt the connection to the temp sensor
to force the heater to stay on?

Any ideas greatly appreciated!

Thanks,

Carl
 
Carl,

The simplest solution would be to do it the opposite of the way you've laid out. I'd put a contactor in between the heater terminals and the circuit board, powering the coil with your automation. You would then leave the spa temp set to 104 and control the actual temp with automation. The only trouble would be that you'd probably wind up with 24hr circulation as the tub will always see a demand for heat, but most of the D1's I've seen have a small 100w circ pump which is ideal for 24hr circulation so hopefully that's not an issue in your case.

The problem with doing it the other way around is that in order to keep the spa's safety circuit and logic involved you'd have to be able to interface with the programming between the topside and the circuit board, so unless actually programming home automation software is your cup of tea it wouldn't be feasible.

Sounds like a fun project!

Tim
 
Thanks for the great info!

I have a 60 amp relay, controlled by my HA system, that turns the tub on when the outside temp drops below 33 degrees.
Seems to be working very well. I've just been leaving the temp control on the tub set to "cool". So I guess what you're
suggesting is to leave the temp control set to our desired temp and switch it on or off with a relay depending
on what temp the HA system needs it to be?

I assume the heater is always full on or off, not variable as to what the control is set to?

Many thanks,

Carl
 
Correct. The heater resistance is constant. You could change the incoming power. All 230v heater elements are convertible to 115v, for instance, by wiring them Line + Neutral rather than Line + Line, so it's possible to vary it but your pack isn't made to do it on the fly. Some are convertible to match the incoming power but not all.

What you currently have in place is pretty much what I'm describing, except interrupting just the heater instead of the whole tub would allow you to run regular filter cycles without necessarily heating the water. If you didn't use yours for a month in your current setup and there was no freezing weather then the water could get pretty funky. Do you have the automation set to turn the tub on daily for a set amount of time regardless of temperature? If you did that then we'd basically be talking about the same thing depending on how your tub is programmed to filter, except that anytime the water is below 60F or so the tub will heat constantly when you turn it on to filter.
 
Hmm...well still leaning toward disconnecting the temp sensor, if that would force the heater to stay on, as I'd rather only have to use the
automation control when the tub is actually in use. If I control the tub heater entirely with my automation system it would have to be turning the heater
on and off throughout the winter as opposed to only when we want to heat it up for use.

Do you think disconnecting the temp sensor would force the heater to stay on?

Thanks,

Carl
 
You'd need to keep it plugged into the circuit board but leaving the temp sensor exposed to the air and setting the tub to 104 would basically force the heater to stay on until either the high limit tripped or your home automation shut it off.

You'd still need to turn it on and off daily to filter though, and since the hot tub's controls already do that automatically it would make some sense to allow the hot tub to control filtration 24/7 and just use the home automation to control the heat. That would also essentially give you automatic freeze protection should the water get too cold. Although this may become an issue where all the pumps come on once the water gets below 50 or 60 rather than waiting for it to get to 35-40.

I think the thing to do would be to try it both ways and see which you prefer. You can use the same relay for either application and the wiring wouldn't be much different.
 
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