Boiling Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Anita1]

Hello , we have a problem with our central heating , in the fact that sometimes the room thermostat will not switch off.It clicks but the led stays on , so does the boiler. Its about 7 years old , have changed thermostat.

boiler
3 way valve
cylinder and stat
room stat
pump and programmer

oh if we switch off the mains it works fine again.HELP PLEASE.

[plumbbob]

The first thing to do is to discount a frost stat that may be overriding the room stat. If you don't have one or it is set correctly, then the three port valve may be faulty. The room stat does not control the heating, it just closes the 3PV which in turn switches the pump and boiler off.

[Anita1]

Thanks , but what we cannot understand is why the neon light on the room stat stays on , even when you hear it click off.
How would a live feed from the 3pv get back , since the live should come from the programmer if you see what I mean. , No frost stat.
We are convinced it must be the 3pv but cannot see how.
It's a Tower model , can we just change the motor and mechanism ?

[plumbbob]

The 3PV contains various electrical components so if it has failed, anything may be happening. IF we assume the wiring is not at fault, then the problem must be with either the stat or valve. You could download the wiring diagram of the Sundial plan from the Honeywell website, and try to figure out what is happening, but I have done this in a thread before, and the topic ran to many posts from various contributors which caused my head to really hurt, and in the end, we never worked out why other than the change fixed his fault.

When the heating is stuck on, unscrew the stat and remove it from the wall. If the heating remains on, then only one possibility remains.

I think the Tower valve head can be replaced with one from Honeywell as Tower is a cheaper clone of Honeywell. Thing is it may be cheaper to purchase a complete new Tower valve than it is to just buy a Honeywell head. With a complete valve, just fit the part you need and keep the body as a spare.

[Anita1]

Thanks, just got a new 3pv Tower off ebay for 32 quid, will change the top half first to see if it cures it.
See , us gals are not all useless..............

[Anita1]

Hmmmmmm. looks like the new top is slightly different from the old one .

[Anita1]

maybe we are ......