Replacing Truma thermostat with a better one - wiring doagram

[RobbieBobby]

I'm looking to replace the Truma heating thermostat with a better, digital, one so I can set an actual temperature rather than just a number on a dial. The existing unit A. senses at the wrong position in the van and B. has too much hysteresis i.e. by the time it turns the heating off, we are sweating, and by the time it switches on, we are chilly. I have a suitable controller but I need a wiring diagram for the interconnections between the heater unit and the remote thermostat/kW selector. I'm thinking of leaving the original off/500W/1000W/2000W selector where it is above the habitation door but placing a new thermostat elsewhere.

 

[mitzimad]

the dial on the wall isnt a thermostat as such you cant wire a domestic one to it theres a small black dome somewhere in your motor home that is a thermistor its that that sense the temperature that interacts with the pcb in the heater as the resistance changes with temperature

 

[tonyidle]

As mitzimad says but you can switch the heating on/off using those same wires. The little domed thing changes resistance with temperature. As the temp rises its resistance falls and vice versa. So with it disconnected the heating will come on and stay on. If you connect the two wires together the heating will go off and stay off (actually useful info for anyone if it fails). Your thermostat will need to make that connection as the temperature rises and break it as the temperature falls which is the opposite to its normal function. If the device you want to use has both NO and NC contacts you can use the NC ones. If not you'll need a relay.

 

[dipsie]

I moved our heat sensor a couple of years ago in our V Line. We had the same unpredictable heating.
I realised that the sensor was four or five inches from the top of my wife’s head when she sat back with her feet up on the lounge settee, I lifted the bottom panels that were the base of the roof locker, disconnected the two wires, making sure which one went where. I had to find some wire the same so as not to alter the signal, soldered on about 35cms, drilled another hole and ‘ transplanted’ the sensor and reconnected the wiring. Luckily Auto Trail left a sheet of stick on screw covers of different wood grain patterns so that allowed me to cover the old hole.
It was’nt until months later until we had some cold weather again that the mod was tested, I am pleased to say it had cut the “ moaning “ about the inconsistent heat by half. You can’t win all time but I think it was worth the effort.

 

[Scotch mist]

my New pilote is the same , the sensor is above the hab door in a ducted area , unfortunately when the heating was not on it picked up the cold from outside , then when the heating (Alde) is on the heat rises through the duct & it cuts out , it was -4 to +4 deg out of target temperatures, the cable was long enough so l moved it to behind my tv , it is spot on now

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[Lenny HB]

The other alternative is to fit the CP-Plus controller. They do a really good job of controlling temperature and fan speed and also have an offset adjustment to compensate for the position of the sensor.

 

[RobbieBobby]

Thank you everybody. Does anybody know the colours of the two wires so I can identify them at the pcb end of the wiring loom. It's easier to make the modification at that end I think. If I can identify the wires I can splice my new wiring at that point and run it to the new thermostat. I'm happy to leave the off/500W/1000W/2000W selection where it is. I might even do it in such a way that I could revert to the old stat in case of a failure.

 

[Sapper520]

The other alternative is to fit the CP-Plus controller. They do a really good job of controlling temperature and fan speed and also have an offset adjustment to compensate for the position of the sensor.

Lenny, is it just a straight swap replacing the Classic Controller for the CP-Plus controller? No extra wiring etc?

 

[Lenny HB]

Lenny, is it just a straight swap replacing the Classic Controller for the CP-Plus controller? No extra wiring etc?

I did it on my last van just a straight swap it was a gas only C6.
Boiler needs to be CP-Plus ready or it means a new PCB at 300 quid.