Hacking a heat pump to increase heating range over 38C
Hi Everyone,
This is a bit out of the ordinary but I am looking to "hack" my heat pump's controller - let me explain.
I have bought a heat pump to heat my hot tub, it came from liquidated stock so it's unlikely I can return it. I read the instruction manual online before I bought it and it states that the operating range of the water temperature is 9-40 deg C which I took to mean it can heat the water to up to 40 deg C. However, when I received the heat pump there was a sticker on the box saying "Temperature Range Heating 9-35 deg C" which isn't quite hot enough, a hot tub should be 38 deg C or so.
I'm wondering if there's a way to "hack" the controller to make it go the extra 3 degrees. Is there a button combination to put it into a special mode for configuration etc.
I know there's a hundred reasons not to tamper with this stuff but from my perspective there's one really good reason to do it, my wife - she'll kill me if I can get this thing to work!
The heat pump is a Hydro-Pro P8/32.
Any help would be hugely appreciated 🙂
Percy P.
Welcome to the forums @percypenguin - this is indeed an odd (but intriguing) question. I’ll put some feelers out and see what the feedback from the pros is.
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Many thanks @mars I'd really appreciate that. I've been looking at the controller and it's a touch screen device made by Topband and based around a STM32F103 microcontroller if that's of any additional help.
@percypenguin have you already installed and tried it to see if it’ll get to 38C?
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Most hot tub heatpump controllers allow you to offset the flow temperature sensor by a fixed value…
failing that you can just fudge the resistance.
disassembling the code and reflashing would be a faff.
Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.
My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.
This sounds like it could be a workable solution. I must admit I wasn’t relishing the idea of poking around with code etc.
Is it only possible to fudge the sensor with a resistor if it’s an analogue sensor? I imagine a digital sensor would not play?
I’ll have a look at the settings on the controller to see if there’s an offset setting. I have noticed anything in the manual but then it doesn’t seem to go into great detail.
many thanks 👍
@HughF, I've been looking at the heat pump and the manual. I can't see any way of inputting a temperature offset so I've been investigating fudging the sensor.
It looks like the output temperature is monitored by a thermistor near the outlet pipe connection. The thermistor is a 5k ohm by the looks of it but I'm not sure if it's a positive or negative temperature coefficient type so I don't know if I need to increase or decrease the resistance in order to offset the temperature by say +3 degrees C and I also don't know if the thermistor's output is linear.
Do you have any suggestions about what sort of value resistor I should try first? Would it be a good idea to use a variable resistor so that I can trim it or should I just put in a fixed value and set the temperature accordingly?
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