Vaillant combi store cylinder stat problem

[robd]

Evening all,

A job I am on as an aside the customer asked me to have a look at the heating/hot water system as the hot water is not heating up. It is an unvented system with vaillant boiler and combistore cylinder.

Anyway I tested up to the tank stat/cylinder control and found power up to it (terminal 1) but not going through it out to terminal 2 or terminal 3 if I turned the temperature down. So I've called vaillant to check I'm not being daft (always a good chance) and they say no the stat is faulty you need a new one.

Long story short the customer ordered a new stat, I replaced only to find the same problem, I scatched my head and rang vaillant again and they said that's unlucky you must have a 2nd faulty stat....got another one sent and same problem again.

Anyway I bypassed the stat and had the system running fine. Bit of a head banger, have tested across terminals 1, 2 and 3 but nothing. Any thoughts welcome!

 

[Corbs]

any thermal cut out device on the stat that's tripped? other thank that you have bypassed the stat and the boiler and the motorized valve has opened so the wiring's ok so looks like you have another faulty or wrong stat

 

[Megavolt]

Is there a high limit stat your not seeing that needs resetting

 

[robd]

What a pipe stat? There is one I'll check it again when I go back next but don't think it's that, the cylinder control has 240v coming in but no going across, the pipe stat is above the cylinder and not directly connected so don't see that it could affect that.

 

[Corbs]

maybe a silly one but hay have you set the temp right should be around 60-65 dc

 

[robd]

Yeah had it right round doesn't switch over regardless

 

[davesparks]

What a pipe stat? There is one I'll check it again when I go back next but don't think it's that, the cylinder control has 240v coming in but no going across, the pipe stat is above the cylinder and not directly connected so don't see that it could affect that.

No, the high limit stat in the unvented cylinder controls, also known as a safety cutout.

 

[Meggerman]

Well, if you have the stat in your hand, turned down and no continuity across NC contacts then that's your problem still. You have already proved system by linking out (assuming you linked out at stat position).

 

[robd]

Sorry I see what you mean...possibly, would that be somewhere on the cylinder as opposed to being integral to the part that I've changed then?

 

[robd]

Well, if you have the stat in your hand, turned down and no continuity across NC contacts then that's your problem still. You have already proved system by linking out (assuming you linked out at stat position).

Yes mate linked across terminals.