Suprima Boiler refuses to fire up for central heating (ok for hot water). Thermostat?

[JamEnergy]

Boiler: Suprima
Thermostat: Drayton
Programming thing: Siemens

Ok, so symptom:
Central heating does not work at all (no radiators are warm - not even their 'feet', and they've been bled for air)
1) Manual "extra hour" CH set on Siemens pad
2) Drayton dial turned up/down and nothing happens on the boiler (usually it clicks I think)
3) Boiler has a little O-shaped window where I (think...) could in the past see a blue flame (but not anymore)

If I put "extra hour" for HW on the Siemens pad, a blue flame appears.

 

[picasso]

What valve/s you got ? should look something like this...

honeywell 3 port

• picasso
• 18 Oct 2010
• 26

or

honeywell 2 port

• picasso
• 18 Oct 2010
• 31

 

[JamEnergy]

Hi, thanks for your response.

I believe it's the 1st variant.

I'm not quite sure where to look, but here's a thing I found near the Sieman's pad:
(3 pics of the same thing)

If this isn't what we're looking for then I can look again...

 

[TCCHeating]

Second time I've posted this today. Best fault finding guide available. You need to determine whether it is a fault with your programmer, thermostat or motorised valve. (The latter being the most probable)

You will need a multimeter.

If you're not confident working with electrics then you should call an engineer.

 

[JamEnergy]

Are there any simpler diagnostics I can do myself to narrow down the problem (if only so I can best communicate the situation to tradesmen)?

 

[TCCHeating]

Are there any simpler diagnostics I can do myself to narrow down the problem (if only so I can best communicate the situation to tradesmen)?

Not really. The best way to communicate the situation to the tradesman is to tell him you have hot water but no heating. The tradesman will then perform the checks I posted. If he's worth his salt anyways!

 

[JamEnergy]

Ok, thanks, fair enough.

Just out of curiosity now...
What makes the boiler fail to fire in the case that the valve has malfunctioned?

 

[TCCHeating]

Valve supplies live to boiler. When the boiler gets this, it turns on. In your case the valve is supplying live to boiler for hot water, but not for heating. Doesn't necessarily mean the valves at fault though. The valve might not be getting the signal to open on heating from your programmer or room thermostat. That's why it needs fault finding step by step

 

[stem]

First some theory. At rest, the motorised valve is kept at the 'hot water only' position by a spring. When heating is required, the room thermostat makes the white wire to the valve live and winds the valve across to open up the central heating port.

The easiest first test, which will most likely reveal the problem, is to see if there is power getting to the motorised valve's white wire when the room thermostat is calling for heat. Only if you are capable of doing this test safely, and can use a multimeter follow the steps below.

1. Remove the valve head cover so that you can see the mechanism inside.

2. Set the controls to hot water only. (This is to ensure the valve sits at the hot water only position to start with)

3. Get an assistant to turn on the central heating at the programmer and turn up the room thermostat so that it is calling for heat, whilst you watch the valve mechanism. Does it move?

4. Without changing the settings of the controls, use a multimeter to measure between the blue (N) and white (L) wires at the motorised valve. If you see 230vac and the valve still remains in the hot water only position, the valve is faulty.

If you don't see the 230vac or the valve does moves away from the hot water only position, post back what happens.

 

[Dan Robinson]

(if only so I can best communicate the situation to tradesmen)?

I think they should be able to cope without your input

 

[JamEnergy]

This is really interesting actually, good to learn more about how the place I live in works.

Is the "no click" at thermostat information irrelevant?

We replaced the thermostat and the central heating seems to work now. Turning it down gives a click and controls the boiler properly.

Though there is an issue (I think it happened before all this) with the hot water system making clicking noises... but I shall make a new thread for that.

 

[TCCHeating]

Is the "no click" at thermostat information irrelevant?

We replaced the thermostat and the central heating seems to work now.

Some thermostats click, some don't. Even if it doesn't click, but it used to click. It still doesn't mean it's definitely the thermostat. That's why I posted the fault finding guide.

It negates the need to throw parts at a system that don't need replacing.

It seams you were lucky on this occasion rather than methodical.

 

[Agile]

Some are purely mechanical and always click.

Others are electronic and need a supply to make them click. If that kind don't click they can be faulty or just don't have the supply!

Tony

 

[TCCHeating]

Some are purely mechanical and always click.

Others are electronic and need a supply to make them click. If that kind don't click they can be faulty or just don't have the supply!

Tony

Some don't click at all. I think they use something called triac switching.

They are not common but I have definitely come across a few of these. I think some salus stats don't click but there are others out there too