IMIT CONTACT THERMOSTAT

[dave176]

Has anyone else been having issues with the IMIT pipe stats recently? using contact 1 and 3 to regulate temperature on solid fuel boiler but I've had several of them turn on and just stay on even after the fire has gone out. Getting very frustrated at this stage

 

[John.g]

Have you just tried turning it up and down around whatever the pipe temperature is, the stat should make when you turn up the SP and break with a hysteresis of ~ 6/10C when you turn it down.

 

[dave176]

Have you just tried turning it up and down around whatever the pipe temperature is, the stat should make when you turn up the SP and break with a hysteresis of ~ 6/10C when you turn it down.

hi John, yea tried from 40° up to 90° and it just stays on. I'll set at 40° just as a test and light the fire, allow the pipe to reach the 40° then turn the thermostat up as far as 90° but it makes no difference. I think the only thing to do is try a different brand. it seems really hit and miss coming off the shelf. others I've fitted are fine. it's really puzzling

 

[John.g]

Just to make sure we are on the same wavelength, On solid fuel, you require that stat to supply power to a pump when the temperature rises and when the fire dies down you want the stat to open. First thing I would do is just remove it from the pipe and let it cool down to ambient temperature, turn the setting knob to minimum, then very slowly turn it up until you hear a click and note the setting, turn it very slowly anticlickwise until you hear another click, if it doesn't click on/off in the range of say 6C/10C then you have a faulty stat, if it does switch between those limits then its either wired wrongly or the stove isn't moving the hot water through the pipe via convection, if it is wired correctly and the stat is OK then turning it up should stop the pump and turning it down should start the pump.
I have a spare EPH stat and it has three terminals a common C and a 1 & 2.
C&2 make on rising temperature and open on falling temp, correct terminals if used on solid fuel where you want the pump to start on rising temperature and stop on falling temperature. C&1 make on falling temperature, correct terminals if used say on a oil fired boiler where you want the burner to fire up on falling temperature and cut out on rising temperature

 

[dave176]

Just to make sure we are on the same wavelength, On solid fuel, you require that stat to supply power to a pump when the temperature rises and when the fire dies down you want the stat to open. First thing I would do is just remove it from the pipe and let it cool down to ambient temperature, turn the setting knob to minimum, then very slowly turn it up until you hear a click and note the setting, turn it very slowly anticlickwise until you hear another click, if it doesn't click on/off in the range of say 6C/10C then you have a faulty stat, if it does switch between those limits then its either wired wrongly or the stove isn't moving the hot water through the pipe via convection, if it is wired correctly and the stat is OK then turning it up should stop the pump and turning it down should start the pump.
I have a spare EPH stat and it has three terminals a common C and a 1 & 2.
C&2 make on rising temperature and open on falling temp, correct terminals if used on solid fuel where you want the pump to start on rising temperature and stop on falling temperature. C&1 make on falling temperature, correct terminals if used say on a oil fired boiler where you want the burner to fire up on falling temperature and cut out on rising temperature

I think I'm going to get an EPH and put that one on. The ones I'm using and have been for a few years now are wired 1 and 3 to turn on the pump when.the pipe reaches required temperature and turn the pump off when it gets cooler but the last 3 I have used will turn on at required temperature but just keep the pump running for hours even when the fire has gone out the pump is still running 8 to 12 hours later

 

[John.g]

Wonder has it got anything to do with the contacts rating or the pump itself, there was a batch of Grundfos circ pumps a few years ago that caused a lot of issues because of high inrush current, solved I think with a new cable.
The EPH stat states it can switch 16(4)A 250VAC which I take to mean it can switch up to 4A inductive.

 

[dave176]

Wonder has it got anything to do with the contacts rating or the pump itself, there was a batch of Grundfos circ pumps a few years ago that caused a lot of issues because of high inrush current, solved I think with a new cable.
The EPH stat states it can switch 16(4)A 250VAC which I take to mean it can switch up to 4A inductive.

I'm wondering myself if it's something to do with the pump. I know it sounds crazy but it's like the microswitch in the stat sticks when it has power going through it. it's causing flow issues as there is also a kerosene boiler on the system and when the pump on the solid fuel boiler stays on even when the fire has been out for hours and the kerosene system is turned on the pumps fight each other

 

[dave176]

I'm wondering myself if it's something to do with the pump. I know it sounds crazy but it's like the microswitch in the stat sticks when it has power going through it. it's causing flow issues as there is also a kerosene boiler on the system and when the pump on the solid fuel boiler stays on even when the fire has been out for hours and the kerosene system is turned on the pumps fight each other

I have another system that also acting extremely strange. open vented that's very very slowly filling the expansion tank via the filling loop, my only guess on this on is a restriction in the pipe work somewhere, the tank is absolutely full of something very strange looking. I'm going give the system a powerflush and clean out the tank.