Ideal Classic system, hot water working, heating not Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[PaulXX]

I have an Ideal Classic conventional boiler. The boiler itself is working fine for hot water but it simply isn't switching on for heating.

When you turn the thermostat (Drayton) up, it 'clicks' as normal but nothing happens at the boiler. I had thought the thermostat may be faulty but having read a little more widely, it seems that this problem is more usually a faulty three-way valve.

The three-way valve is an acl Lifestyle, with the model number 679H340-30L0.

First off, how do I determine whether it's the thermostat, three-way valve or something else that's causing the problem?

If the three-way valve is at fault, is this something that's repairable or will I need to replace it? And if so, how do I go about doing that? I will have to drain down the system, obviously, but is there anything else I need to do before attempting to replace it?

[Steve the gas]

Paul,
If it is the 3 way valve, it's easy to check, by removing the head to see if the vavle will operate manually. If it has a slider on the side set this to manual b4 removing head to see if heating works. Hope this helps

Steve

[PaulXX]

[quote="Steve the gas"]Paul,
If it is the 3 way valve, it's easy to check, by removing the head to see if the vavle will operate manually. If it has a slider on the side set this to manual b4 removing head to see if heating works. Hope this helps[/quote]
Interesting. I had tried moving the slider before and never being able to get it to move over far enough (it's fairly flimsy and felt like it would snap if I pushed it any harder).

But I hadn't noticed until now that there's a black plastic tab at the back of the unit too (it's in a very awkward position to see round the back, I just looked with a mirror right now). Now when you move this tab, the switch on the side moves to the heating position - but will not stay there. It keeps moving back to the W position.

I've now tried this with the heating set to constant and the thermostat up. When I flick the switch now, the boiler does start to fire up but then stops because the switch just won't stay there.

So it's definitely looking like the 3-way valve. My valve says "Warning: Disconnect supply before removing cover" on the top. Is it referring to teh mains supply or the water supply or both here? Do I need to drain down the system before removing this cover?

If the valve is unserviceable and I need to replace it, I've done a quick google and a company called Heating Controls Online says the Drayton MA1/679-3 is a direct replacement (apparently my valve is obsolete). I presume this is correct info?

[Steve the gas]

Paul,
Yes it means disconnect the electricity to valve head NOT water. The slider can be bent over into its manual position as a temporary measure. If you have to replace the valve body then you will have to isolate the water!!