Central heating not working

[whydowebother]

Hi there, please can someone help me fathom out what's wrong with my heating:

The hot water works fine, and when the programmer commands the water to be heated, the boiler fires up, the pump starts running, the 2-way valve opens and everything is working OK.

However, the rads never get hot (any of them) when the heating is on at the same time as the hot water (my programmer has a 'twice per day' setting, which I usually use for both water and heating).

If I turn the hot water off (on the programmer), and the heating to 'continuous', then the 2-way valve motor opens and hot water obviously flows through the valve as the pipe downstream of the valve gets hot. If I move the room-stat then when I turn it to a low setting I can hear the valve-motor closing the valve, and when I turn the room-stat up I can hear the boiler firing up. However - in this condition (i.e. with the hot water turned off), the pump never starts operating and downstream pipe is very slow to heat up as if the hot water is just trickling through and not being pumped.

I'm a bit confused, as the pump works OK when the hot water is on, and the room-stat and heating valve seem to be operating. I just can't get the rads to heat up. I checked a few of the rads to see if there was air and there doesn't seem to be any, water came out of the bleed valves straight away.

Please does anybody have a suggestion? Thanks.

 

[Boilerman2]

The Heating 2 port valve actuator is faulty - there is an auxillary switch that powers up the pump etc once the valve has opened - although the valve is opening & Closing, it is not making the electrical switch live to the pump etc NEW ACTUATOR required ... is it a DANFOSS actuator per chance???

 

[whydowebother]

Thanks Boilerman. I've taken the valve actuator off and it is a Honeywell product. From what you've said, do I understand that its not just the round motor in the middle that needs replacing (since this appears to be working) but the whole unit?

I turned the heating on with the actuator in my hand, and I saw the motor operate and the metal contactor move around to operate the microswitch - are you saying its this microswitch that is broken?

Why doesn't the heating work when the hot water is on, as this gets the pump going. With the pump running and both 2-way valves open, wouldn't the rads get hot anyway, even if the microswitch was inoperative?


Cheers

WDWB

 

[Agile]

It would seem that EITHER the microswitch has failed and that can be tested with a meter.

OR the valve is jamming and not allowing the actuator to move far enough to operate the switch.

Test: With the head removed and CH selected then does the boiler/pump start?

Tony


PS However, you said that with both selected, the boiler fires up but still the rads dont get hot. In that case I would have expected that the rads would get hot, possibly after a while if the HW circuit is not balanced against the CH.

 

[whydowebother]

Hi there - I've done a bit more trouble-shooting and this is what I found. I took the actuator off the valve and turned the CH on (with HW turned off). The valve motor operated normally, and when it reached it's full limit the lever hit the microswitch and...the pump turned on. The boiler is fired up OK as well. I then turned the valve with my fingertips to open it, its not stiff at all so the motor should have been able to turn it when the system was intact, but perhaps it didn't.

So now I have hot water in the pipe either side of the CH valve. This hot pipe disappears under the floorboards and presumably splits off to all my rads. After about 30mins, a couple of rads in the house are just getting slightly warm, the rest are stone cold, but this is the first time the heating has worked at all since last winter.

Shall I just wait and see what happens next - I guess the motor in the CH valve will need replacing, how long do you think it will take for more of the rads to show signs of life?

Thanks for your help so far!

 

[whydowebother]

Mmmm...now I've really confused myself. in my last post I said that the pipes had got hot, and a couple of the rads had started to get warm. I left it all alone for a couple of hours and then went back to have a look and I don't understand what I found:

The actuator is still removed from the CH valve, so can't move the valve. It was still in the open position, with the lever still pressed against the microswitch. The room-stat is still set at 30degC. The pipe above the CH valve is really hot (this is just below where it branches to the HW valve, which was open cos the water had come on via the timer). However, the pipe below the CH valve was cold - how can this happen? Surely the valve must be still be open, because I hadn't moved it and the actuator is removed and dangling down on its flex. The pump is still running (presumably because the water has come on?), so how on earth can the pipe below an open valve not be the same temp as the pipe above it. The rads which got lukewarm have gone cold, needless to say, so I'm back to square one.

I think there must be something fundamental I don't understand about this system - I thought I'd worked it out in my head, but clearly not! Please help.