Circ pump running continuously

[thematelot]

Good morning all

My wife and I returned home after a couple of days away to find the CH running continuously. The boiler is a c. 25 year old Glow Worm 65-80 which is situated in an outhouse with the circulation pump upstairs in the airing cupboard.

I searched the forum and noted common problems appeared to be the programmer or a frost stat. I removed the programmer (Landis and Gyr) and reconnected the electricity and the boiler immediately started, despite the room thermostat being turned right down. As it was late I disconnected the electricity again, turned the boiler thermostat right down and went to bed.

This morning as soon as I connected the electricity again I heard the cirulation pump start up immediately, however the boiler didn't start until I manually switched it on. I thought it might be something to do with the programmer but no matter what I do with the programmer controls the pump keeps going. Turning the boiler thermostat off has no effect either. Is this consistent with a frost stat problem - even though the temperature outside is around 5 degrees this morning?

Any advice would be most appreciated.

Alan

 

[ChrisR]

Check your motorised valve . If it stuck open it would cause your symptoms.

 

[meldrew's_mate]

Suggest you take the cover off the froststat and turn it down until you hear it click. Now it's off see if the pump stops. Lots of froststats are set to about 5 degrees, not suggesting they're anywhere near accurate so they may be showing 2 degrees and operate around 5. You may wish to turn yours down by a couple of degrees to avoid this nuisance, though be mindful of the need to protect the boiler and pipework from freezing.

If this has no effect then ChrisR has suggested a possible solution.

 

[thematelot]

ChrisR and Meldrews Mate

Thanks for your prompt response to my question. As ever, a reply poses further questions!

Worryingly I cannot find any evidence of a Froststat in or around the boiler. I have checked the original manual and that makes no mention of one and I cannot see one anywhere around the boiler (attached to pipes etc). Is it conceivable that it coud have been fitted without one originally, bearing in mind its age?

Also, I have 2 MVs on the system. They have little levers, one of which slides freely but the other won't go past the detent. Is this one stuck do you think?

Again, many thanks for your help.

Alan

 

[thematelot]

Well, I am glad to say the problem has been solved! Good old WD40! I gave both MVs a liberal dose at lunchtime and this evening everything is back to normal. It seems to have been that one MV which didn't move completely across its slot. Many thanks to ChrisR and Webster's Mate for putting me on the right lines.

Still a bit worried about the froststat though (mind you, it has gone through some pretty severe weather without problems thus far. Maybe it is concealed somehow within the boiler body).

Again VMT

Alan