Heater control for hot tub

Posted on
Tue Jun 18, 2019 9:11 am
mwoodage offline
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Posts: 90
Joined: Dec 19, 2014
Location: Devon UK

Heater control for hot tub

Hello,
I've recently re-wired my hot tub to have full control over the heater and pumps. :) It was getting old (10+years) and the programmer was failing so it was a good time to upgrade.
All has been working perfectly, however I had a problem recently with heating the water and need to put a safeguard in place so it dosen't happen again.

I'm using a Fibaro Universal sensor to monitor the temperature of the water which works perfectly - until for unknown reasons it stops sending updates and sticks at one temperature until i execute Define / Sync which starts everything working again.
This happened a few nights ago and the pump / heater were on all night resulting in the hot tub being heated to 52 degrees and taking 3 days to cool down! The set temperature is 38 degrees.

The sensor updates about every 2 mins, so what i'd like to put in place is something to monitor the temperature (that sits in a variable) and if it doesn't change after a given time (15mins) then the heater and pump switches off and sends me an email alert.
Or is there someway of activating Define / Sync once a day to keep the sensor active?

What would be the best way to achieve this, or can anyone think of other ideas to stop the heater overheating.

Current Setup
Fibaro Universal sensor with 2 probes (one in the water, one fixed to the heater element)
The water temperature probe updates a variable (hottubtempact)
Unistat Plug-in to monitor the temperature and turn on the heater / pump as required via action groups.
2 x Fibaro switches through contractors to control the pumps.

Thanks in advance
Martin

Posted on
Tue Jun 18, 2019 2:16 pm
johnpolasek offline
Posts: 874
Joined: Aug 05, 2011
Location: Aggieland, Texas

Re: Heater control for hot tub

One way to do it would be to create a trigger on variable "hottubtempact" has any change with a condition of "heater on" and a 15 minute delayed action of Send alarm (whatever you want to load into that action) and Override previous delay option set. Set a second trigger when the heater system is turned off to removed the delayed actions on the first trigger. That way, the first time the temperature changes when you turn the heaters on, a 15 minute countdown starts and every time the temperature variable changes, the countdown restarts and when the heater turns off, the countdown gets aborted... About the only way it can fail is if the temperature transmitter is in a failed state when the heaters kick in and I suppose you could tweak the "hottubtempact" variable down to 10 when you kick the heaters in which would cause a change in a couple of minutes.

Posted on
Tue Jun 18, 2019 3:27 pm
mwoodage offline
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Posts: 90
Joined: Dec 19, 2014
Location: Devon UK

Re: Heater control for hot tub

Perfect, thank you Johnpolasek, i've set everything up as described and its currently working well :D
I didn't think of using conditions with the action group.

I'll keep an eye on it in the next few days and will report back any errors

Thanks for the suggestion,
Martin

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