Central heating pump problem

southcoastrgi

Did they drain the system or just change the head of the zone valve ?

Upzeecreek

Just changed head of zone valve..They didn't drain anything down. 

Jeepers_Creepers

Hard to diagnose further from this side of the screen, Upz.

I suspect (ie - it's most common) the pump is wired 'alongside' the boiler and not from it - ie. when the timer says 'on' and this supplies a signal to the room stat which also says 'on', and this then goes to the valve which opens, then the valve passes this 'on' signal on to both the boiler and pump together. So each item - boiler and pump - fires up independently of the other. (The other method is that the boiler is told to fire up, and then the boiler tells the pump to do so.)

What I'm trying to work out is, is the pump getting a rogue signal from the timer/stat/valve, or one from the boiler?

How much electrical testing can you do, Upz? I mean, if you were to open the wiring centre (where the valves and pump etc go to) would you be able to check for 'lives' without killing yourself? You'll likely find that the three oranges from the zone valves go to a single terminal and that the pump (and boiler signal) is then fed from this. That would be my starting point, I think - see if any of these individual oranges are 'live' when they shouldn't be. If one is, that's the rogue. Or, is there a live coming back from that boiler wire? That's a rogue boiler.

Jeepers_Creepers

Without even touching or testing any wires, if you lift the cover off the wiring centre (with the boiler system's main isolator off), could you check to see what other wires are going to the orange wires from the zone valves? You could take a photo to show us if you like.

If there's just one wire going to these oranges, it'll almost certainly be going to the boiler - its 'control' wire (the one that tells it to go on). That'll then mean that the pump is controlled by the boiler and not the valves. That in turn would lay likely blame on the boiler and not the valves for the pump running when it shouldn't.

If the orange wires have TWO other wires going to them, one will almost certainly be to the pump and the other to the boiler. In this case, the pump will be controlled independently of the boiler, so it could be the valves giving it the rogue signal, so laying the most likely blame on a valve (tho' I guess it's 'possible' for the boiler to send a rogue signal back down its own control wire?!)

Upzeecreek

Thanks for the above advice. I'll try and have a look in the wiring centre. I think I've located it! I'll report back! 

Jeepers_Creepers

If you don't report back, we'll fear the worst...

Rodders53

Boiler manual (probably) https://www.plumbase.co.uk/documents/product/3550111  dated July 2013 so right era?
Pump for that boiler Ideal state MUST be direct from boiler pump connections to provide thermal safety over-run.

That's not to say the original installers did things correctly and BG have failed to see or check it is done properly in visits since?

BUT as the boiler is Calling for heat why is it not firing (apart from briefly) unless there's a very short by-pass loop at the boiler and it's circulating warm-enough water not to fire again for a very long time?  {Boiler flow/return pipes would be hot/warm then?}   Or it's over-running due to a boiler stat/thermistor issue on the pump control side, sensing heat where there is none?  But then removal of the head would not stop it, would it?  Baffling. 

Upzeecreek

Would this be the wiring centre that I need to remove cover from?? 

Jeepers_Creepers

Yupski.

(I had to use an elongated form of 'yup' 'cos the forum wouldn't let me post it otherwise.)

I think that's enough characters now.

Upzeecreek

The weird thing about his fault is that when it first started happening , after the radiator leak and the loss of pressure, the pump was staying on every night after timer clicked off for weeks on end. Now it's only once a month. Faults don't tend to get better over time which is what led me down the path of it possibly being an airlock!