Central Heating Suddenly Stopped Working

[thorpelea]

Hi all - my first post on here.

We've just developed a bit of a major problem with out heating system.

It's a conventional system consisting of boiler, rads, hot water tank and header tank in the loft.
We've always had a minor issue with the 3-way valve not functioning properly - you have to have the HW on to get CH - but this has never been a problem (ironically, I bought a new 3 -way valve a few days ago ready to fit this weekend)

However it all went a bit wrong today. When we woke up, everything was fine, radiators all hot and no problems.
But when we got home, the house was freezing, no radiators were on. Basically the boiler isn't firing up.

The controls on the programmer are set correctly, and switching both HW and CH to On makes no difference.

Turned HW thermostat right up, and CH but no difference.

I did find that after turning the whole system off for a while, then the boiler would fire up when you first turn it back on, but only for about 4 minutes - during which time all radiators remained stone cold, so I'm thinking the boiler is ok and it's likely to be a problem elsewhere in the system? - maybe the valve completely seizing up, or the pump, which does seem to be running.

Any help/advice would be greatly appreciated.......

 

[cross thread]

i would start with checking the pump

 

[thorpelea]

Ok, it seems to be running - if I turn the dial between i and iii then you can hear it get louder, and it sounds like water is running through. Is there a proper check I can do?


A bit of additional info. I've left the whole system switched on for the last hour or so, and the boiler fired up again a few minutes ago, but only for about 4 minutes again though......

 

[clearhead]

if you undo front of the pump, put some old rags below to soak up any water, you should be able to gently put the end of a biro on the spinning gland and see what resistance you have- this is normally a good indication of weather pump is doing its job
also when you turn on your boiler for all four minutes-feel pipework close to pump- be careful might get really hot and try and see whats going on

have you tried to manually open your 3-port vale

is their a cold feed (15mm pipe before the pump & 22mm open vent pipe)
sometimes these get blocked

 

[thorpelea]

This is a picture of the piping around the pump:-

Untitled

• thorpelea
• 17 Nov 2010
• 1

The pump is this one - a BG Multihead II

I can undo the big black screw in the middle, but it doesn't seem to come all the way out. Not sure what to do to try and free it up.

 

[spraggo]

This is a picture of the piping around the pump:-



The black screw is to enable you to free the impeller by unscrewing it, pulling it out a little to engage with the impeller and then turning it either way. However, before you do this I would suggest, after looking at your photo, that you check that there is water in the small expansion vessel in the loft.

 

[thorpelea]

Ok, checked the expansion tank and there is water in there. I pulled the black screw out and then turned it each way a few times. It turned fairly easily.

I've just noticed though, that one of the pipes coming from the 3-way valve is cold after the 90 degree bend - the one going to the radiators. I've marked it on this picture:-

Untitled

• thorpelea
• 17 Nov 2010
• 1

I'm wondering now if the valve is jammed up. I've taken the cover off the motor and tried to move it manually (with electrics off of course!), and the lever doesn't seem to lock into any position - it just hangs loosely.

Is it possible to remove the motor mechanism from the valve altogether or would this cause a leak?

 

[spraggo]

Is it possible to remove the motor mechanism from the valve altogether or would this cause a leak?[/quote]


It depends on what make and model number of 3 port valve you have, although with most you can get replacement actuator heads.

 

[thorpelea]

I've managed to take apart most of the head, just leaving the valve sticking through. If I try and turn this with a pair of pliers - it barely moves, maybe an eighth of a turn in total.

 

[spraggo]

I've managed to take apart most of the head, just leaving the valve sticking through. If I try and turn this with a pair of pliers - it barely moves, maybe an eighth of a turn in total.

It does seem then that the actual valve has seized, therefore I would suggest a complete new valve replacement.

 

[clearhead]

ok you are changing your valve anyway as you said earlier
when you drain heating-check how quick your expansion tank drains down
and your system empties

does hot water enter the cylinder pipework(have you vented the bleed screw on pipe

try your new valve and see how much you can turn that manually(don't force it)
lots of valves only move a few degrees to open and close them

you could always try turning lower pump valve off undoing nut on 3-way valve if its seized closed you should not get any water or very minimal amount(put old towels and container to catch water)

 

[expertgasman]

This is a picture of the piping around the pump:-



The black screw is to enable you to free the impeller by unscrewing it, pulling it out a little to engage with the impeller and then turning it either way. However, before you do this I would suggest, after looking at your photo, that you check that there is water in the small expansion vessel in the loft.

OP: as above, but when you engage the impellor, if the pump is running, the nut will spin. If everything is caaling, and the nut does not spin, the pump is seized. Grasp your nut and spin! Does it move freely?

 

[gavinda]

to be honest its worth just changing that pump any way. we fitted them for a few years as part of a cost drive. they were f'ing dreadfull. we usually fitted it and then removed a couple of weeks later and put i a proper pump(grunfdoss).

 

[thorpelea]

Thanks for all the advice everyone. Fitted a new mid position valve this morning, and everything is now nice and warm!!