Pump always on !

[bcollet]

Hi There,

I have a programer that is controlling HW or HW+CH. It was working fine until one day: the pump stays on all the time and I have to switch off the main to turn it off (switching the programer on OFF position is not switching off the pump as it used to do).

I tried to follow the wire going into the pump to see what is directly controlling it but it goes far into a place difficult to access (under floor board in the attic).

What is the usual wiring system ? Does the programer remotely control another switch somewhere that is controlling the pump ?

Thanks for your help,

Bertrand

 

[ChrisR]

Often the pump is connected to the boiler, so it can be held ON while the boiler cools, dissipating heat through the rads. That mechanism can go wrong of course.

What's the boiler? If you find the boiler wiring connection point you'll see if there's a Pump connection.

 

[joe-90]

I'm not a plumber, but it occurs to me that if the pump continues to run - then the pump must have a power supply to it regardless of what the controller is telling you. It just has to be contacts in the controller that are sticking (I think!).


joe

 

[ChrisR]

if the pump continues to run - then the pump must have a power supply to it regardless of what the controller is telling you. It just has to be contacts in the controller that are sticking (I think!).

Fink harder, joe. as I've said the pump may well be connected to the boiler, in which case the responsible part(s) in there could be faulty.

If it were the programmer controlling the pump, it would be the same connection as the one controlling the boiler so that would stay on too

 

[bcollet]

Thanks for your fast replies. The boiler is called "Ideal Mexico".

I know that has been a reccurent problem with the motorised valve stuck and the CH system not switching on - I feel that the problem is now reversed !

The system is old and I don't think it has ever been cleaned before and it is what I am doing now (drain - restorer - drain x2 - inhibitor). Otherwise CH and HW is working quite well if only I could have my programer controlling it ...

Bertrand

 

[joe-90]

if the pump continues to run - then the pump must have a power supply to it regardless of what the controller is telling you. It just has to be contacts in the controller that are sticking (I think!).

Fink harder, joe. as I've said the pump may well be connected to the boiler, in which case the responsible part(s) in there could be faulty.

If it were the programmer controlling the pump, it would be the same connection as the one controlling the boiler so that would stay on too

Sorry. I didn't read the part where he said the boiler turned off but left the pump running.

So I suppose he can now call out an engineer and say "There's nothing wrong with the programmer or the pump but I've got a problem with the phased shut-down in the boiler".

At least the engineer won't be able to rip him off now he knows where the fault lies and it should actually work out cheaper without the diagnostic to pay for, so that's a good thing.



joe

 

[ChrisR]

motorised valve stuck

You could indeed have the sort-of opposite; if the valve shuts as it should when demand stops, but leaves the switch in the motorised valve shut, it could be that the boiler is cycling on-off with nowhere to send the water.

Need to know where the pump's connected - I think there are Mexico's of both types.

Without all the info I can't think of a way to diagnose definitely, from here! Probably the switch in the valve stuck though.

 

[stanrog]

I had this problem in March this year. The boiler (baxi solo 3) would switch off, the motorised values closed but the pump kept on running past its 8 minutes timed pump overrun. Switching the wall mounted programmer off at the mains and leaving off for a little while sometimes had the desired effect that when switching back on again, the pump did not run again, but then sometimes it did.
After a fault finding exercise checking wiring etc I called in my C/H engineer who diagnosed that the PCB in the boiler was faulty. This was replaced (just under £200) and all is now ok.

stanrog

 

[bcollet]

Hello,

After some acrobatic exercises, I managed to follow the pump and boiler wires: The pump is not connected directly to the boiler but to a white box well hidden (not accessible unless I cut another bit of floorboard).

It looks like the wire from programmer is going to this white box; coming from it the wire to the pump, the wire to the boiler and the wire to the motorised valve.

I don't know if this setup is common but it looks like I will have to access this white box and check its components. Any idea of what this could be ?

Thanks to all for your helpful replies - thanks to these I understand better how this GCH is working in my house ...

All the best,

Bertrand

PS Stanrog, it looks like I have the same problem that you had but probably my boiler is different - it does not seem to control the pump or at least not directly.

 

[joe-90]

Hi Bertrand. No doubt there will be a post following this one calling me a dimwit - but they aren't offering any help so I'll have a go.

The box you are talking about is probably a white box with a blanking plate on the top. Inside will be big connector block linking everything together.

What I would do if I were you is to try to iscolate where the problem is.

If you get one of those mains testing screwdrivers you should be able to do the following:

Undo the programmer during the time the pump is operating and test to see if you have a voltage from the prog to the pump. If you do, then click the prog to off. If the voltage stays on then the fault is likely to be in the contacts of the prog. If the voltage goes off when you switch to off then the fault is like to be (as others have said) in the run-on mechanism.

It's unlikely there will be anything to infuence the problem in the big white junction box.



joe

 

[oilman]

...........If you get one of those mains testing screwdrivers you should be able to do the following:

Undo the programmer during the time the pump is operating and test to see if you have a voltage from the prog to the pump. ...........joe

What type of programmer is it? Most programmers plug into a backplate, so when you get to the terminals to see voltages, they've gone.

 

[joe-90]

Well use a voltage sensor that you just lay across the wire. It'll tell you if you have a live wire or not.

joe

 

[Gasman1015]

For you joe

http://content.honeywell.com/uk/homes/systems.htm#Y Plan

 

[meldrew's_mate]

I'm not a plumber, but it occurs to me that if the pump continues to run - then the pump must have a power supply to it regardless of what the controller is telling you. It just has to be contacts in the controller that are sticking (I think!).

Much as it pains me to admit it, Joe may have a point here.
We don't know exactly what system bcollet has here. If it is semi-pumped then the "welding-in" of the heating contacts will cause the pump to continue running, because the DHW contacts give the boiler demand signal and they are usually mechanically arranged so that CH ON gives DHW ON as well.

But Joe, it still doesn't have to be these contacts, as there has been mention of a "stuck valve". If the valve (and it must be a 2-port for this to hold true) is stuck OPEN then on a std S-plan the call for heat (and pump) would remain live, so...

Question bcollet, when you say the pump stays on, do you mean the pump AND boiler stay on?

 

[bcollet]

Hi meldrew's_mate,

No the boiler is behaving normally it's only the pump. When the programmer is on off position, the pump circulate cold water ...

The motorised valve is a 2 port one.

Thanks

Bertrand