Replacement Thermostat & Pump Issues Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[phill123]

I have recently replaced an old Honeywell 3 wire thermostat with a SunvicTLX4101. Having looked at other postings I haven't connected a neutral cable. Everything appears to work okay however the pump is running all the time even when the heating/hot water is off. Any ideas?

[plumbbob]

You do not need the neutral.

If the problem occurs when the timer for the heating is off, the problem is not with the stat.

What type of system have you?

[phill123]

Thanks for your interest.

Gravity feed, boiler is quite old, but regularly serviced Ideal Mexico. Timer is a British Gas UP2, (I believe this is a Drayton Lifestyle Dual Channel) which was installed about 2 years ago. Pump is a Superflow 500 plus set at speed2.

When I first replaced the stat and got the wiring wrong, I did blow a fuse a couple of times?

Thanks

[plumbbob]

My first step would be to remove the thermostat and turn the boiler power back on and see if the pump runs unexpectedly. Most likely though, the fault will remain.

Unfortunately, although you have detailed what boiler etc you have, what is important is what type of SYSTEM it is and consequently how it will be wired.

Google Honeywell.com for system plans and sort out which you have.

My guess is (assuming all was well before the change of stat) that you may have damaged the two or three port valve which controls the on/off of the pump.