Help - central heating problem

Posted by: MichaelC on 20 December 2006

Hi Guys

Looking for some help here.

Yesterday morning our central heating system failed to come on. Our builder's plumber was not available so we called in another plumber. He had a look around the system and found that the motorised valve distributing the hot water to the radiators was not working and could not be manually over-ridden. The motorised valve was replaced this morning but for no apparent reason the boiler shut down after half an hour. The plumber returned this evening but could find no faults - the boiler [a Baxi model] was recording no error codes, the thermostat appears to be working [current tested], the programmer appears to be working [current tested], the new motorised valve appears to be working. And yet the boiler switched itself off after half an hour or so. On resetting the boiler it will fire up temporarily but switch off after half an hour or so. Anyone got any bright ideas?

On a separate note our gas supply had to be temporarily switched off on Monday for an old unused gas pipe to be cut back. This may be purely coincidental but then again maybe relevant. The central heating worked fine on Monday evening after this work was carried out though.

Any suggestions will be greatfully received.

Mike
Posted on: 20 December 2006 by joe90
Set fire to your TV - you will have the appliances round to sort it all out in a jiffy, and you will have rid yourself of mankind's greatest curse.
Posted on: 21 December 2006 by cider glider
You say that THE thermostat appears to be working, but there are likely to be two thermostats in the system, the room thermostat and a thermostat in the boiler itself.

What level is the bolier thermostats set to? It may be set too low, causing the boiler to switch off prematurely.

Hope that helps,
Mark S
Posted on: 21 December 2006 by MichaelC
We have just changed the room thermostat to see if there was a fault but that didn't fix it. Both the room thermostat and the boiler thermostat have been set to their highest settings.

An electrician is on the way - two plumbers who have looked over the system believe that there is an electrical fault whereby the signal to the two? port valve is not being relayed to the boiler to fire up for central heating purposes. It has been noticed that the boiler fires up to heat the hot water though as and when needed.

Incidentally the plumber took voltage readings at various points and found readings of up to 390 volts - quick consultation with EDF Energy and they are sending someone around as well because those voltages are not expected.

The saga continues.
Posted on: 21 December 2006 by Steve2701
As it works for a while I'm wondering if the 'limit stat' has failed as well due to the motorised flow valve failing. This would explain it reaching a certain temp then cutting out. It is completeley seperate to the variable thermostat and room stat - at least on my system it is?

390 volts - Yikes - most things will fail at that kind of over voltage!

Good luck - not a good time of year for this to happen. Some idiots went through the water main yesterday in our road - it was repaired, but valves failed in the house today (toilet cistern and hot water cistern) due to the amount of sand / dirt they left in the main. Not everyone has spares like I do...
Posted on: 21 December 2006 by full ahead
Do your'e rads get warm?Do your'e rads need bled?If the boiler only runs for a short time it may be a circulation problem,faulty circ.pump? Have you checked the time clock?Is the boiler on auto ie.on the clock or in the manual mode?
George
Posted on: 21 December 2006 by Rasher
Why did the plumber think that the motorised valve wasn't working? It sounds as if the boiler is giving priority to heating water, but when done switches to heat the rads, finds the temperature reaching its top and turning off. If you are not getting heat to the rads then it is a circulation problem and points to either the valve head (again), the pump to the heating loop, or the room themostat. Seems strange that this happened when the valve head was changed, and therefore if the valve head had actually failed as suspected, it sounds as if the new head has been wired incorrectly, or it's the wrong type. This seems the most likely reason. It may not be turning fully to the heating loop position.
Posted on: 21 December 2006 by MichaelC
Problem solved, possibly. A loose electrical connection between the thermostat and the valve giving rise to an intermitant fault. The system seems to be running properly at the moment. We shall see. BTW it looked like a faulty meter giving rise to the voltage readings.
Posted on: 21 December 2006 by PJT
How about a diet of baked beans and a match...