Pump on-heating & water off - help please!

simonhgreen

Hi Guys

I am after some advice.

I have a Baxi bBrmuda 675 that works well (just been serviced & new stat). I know it has motorised valves and it works of a 24hr manual programmer.

I turned it off before I went to work this morning.

When I came back from work I noticed the pump is still going, although the heating went off as it should.

Any advice anyone can offer would be most appreciated, particularly on how to fix it!

Thanks in advance!

moneysavingplumber

If the programmer is off and the pump is running (and assuming the boiler and pump haven't fired because of a frost stat, highly unlikely for a back boiler) I'd be inclined to think there was a wiring fault. This is a common fault that occurs when the Potterton Profile boiler is used in gravity hot water/pumped heating mode. If it was a faulty stat, programmer or zone valve i would usually expect the boiler to fire as well. I'm assuming the boiler hadn't been on before you got home and had switched itself off on stat?

However if it has only started recently then it would tend to suggest one of the controls was at fault, as a feed is being sent to the pump when it shouldn't be, and there is no pump over-run on the Baxi Bermuda.

If you have a reputable local electrician someone has recommended to you it might be worth getting them round to diagnose it before you spend any money otherwise, it shouldn't take a good spark long to determine where the feed to the pump is coming from, and it should be worth paying for if it stops you throwing money at random parts.

simonhgreen

Thanks for the update.

I switched the programmer off at the mains this morning & when I got home I turned the switch on & the pump didn't start as I imagined it would!

I wonder if one of the motorised valves isn't closing properly, as I assume when it shuts it sends a signal to turn the pump off?

I'm going to try & run water & heating separately & see if the pump keeps running when I then turn either off.

Hopefully I may be able to isolate which of the valves is not working properly-I am of course assuming/hoping that I am on the right lines.....I'll let you know!!

Thanks again

simonhgreen

The problem seems to be that the water is ok i.e. the pump turned off when I turned the hot water on and off after 15 mins.

However, when I did the same with the heating the pump kept running.

Am I right in thinking that the electrical signal from the heating motorised valve is at fault, or are there other possibilities??

Thanks in advance for any help.

plumb1_2

simonhgreen wrote:

The problem seems to be that the water is ok i.e. the pump turned off when I turned the hot water on and off after 15 mins.

However, when I did the same with the heating the pump kept running.

Am I right in thinking that the electrical signal from the heating motorised valve is at fault, or are there other possibilities??

Thanks in advance for any help.

imo, it is the MV,

simonhgreen

Hmm, I would tend to agree but when I leave the electric off to the programmer for a few hours, when I turn it on again the pump doesn't start & it appears to be OK!!

Could this be due to anything obvious, or could it be the MV may have an intermittent problem that somehow cures itself after a few hours (what about the falling temperature in the pipe running up the mv as it cools over a few hours).

As you may guess I'm clutching at straws here - have you/anyone come across this before?