wiring a vaillant ecotec 656 boiler

[jjth]

im an electrician, recently wired an s plan central heating system for a vaillant 656 ecotec system boiler. The central heating works fine and the boiler fires up when the room stat calls for heat, however the hot water is not firing up the boiler even though the two port valve is working as it should and the switchline back to the boiler is bcoming live via the hot water cylinder. the switchline for the boiler is on terminal 4 which fires up the central heating. Is there a seperate terminal for hot water? help

 

[corgiman]

try posting this in plumbing matey

you'll have more luck there I would have said

 

[gas4you]

Can you clarify the model number. I've never heard of a 656 unless it is a small commercial boiler?

The boiler obviously does not know what the demand is for, only that there is a demand, so it should make no difference whether HW or CH is being called for.

Have any othe Vaillant controls been fitted, ie VR65 and/or a unistor cylinder?

 

[jjth]

yeah it is a small commercial boiler. bit of an overkill apparantly.the hot water goes through a timeclock and then through a smartline cylinder, it then opens the valve as it should do and a sw live is going on to the boiler control panel but it just doesn t fire up.

 

[gas4you]

Is there a full 240VAC when the HW is calling?

I can't see how the boiler is fine for CH and not HW as all it is looking for is a call for heat

 

[David937]

Are you sure it's not a Vaillant ecoTEC 46 or 65.

Never heard of a 656 myself.

 

[jjth]

it could well be the 65 actually, sorry not got the number to hand, but im sure thats what it is, a small commercial boiler.