Help. Motorised valve and boiler problem.

[pipfootball]

Hi all. Posted a thread some time ago regarding motorised valve. Please be patient while I explain. Initial problem was I changed valve only to find system was working wrong way round i.e hot water came on when central heating was demanded and vice versa.After checking I found valve was upside down ie A,B etc. Was informed by other member valve would need refitting correct way. Have just got round to doing this and come across problems since doing so. When switching on boiler it fired up for a short time and would then knock off with overheat lit up. I thought this was down to air in system so proceeded to bleed rads.Found upstairs ones had a lot of air in and had to keep bleeding, leaving and then going back. Have been doing this since yesterday afternoon and have eventually got water through to all bleed valves now, problem is when firing up system boiler is doing same, running for a short time and then knocking off with overheat illuminated. Really got me frustrated and other half giving me massive amount of grief. Hope someone can advise and please accept apologies for length of post. Thanks. Phil:banghead:

 

[BLOD]

Have you checked the pump is working ?

 

[pipfootball]

Yes pump is running.

 

[AWheating]

sound like a circulation problem..........is pump running? may need bleeding? are any isolation valves you may have touched closed? does the motorised valve open/move with required?

be careful as some modern boilers you cant remove the case unless your gas safe registerd.

 

[pipfootball]

Pump is running, all rad valves open. Motorised valve seems to be working as when heating is on pipe is hot either side

 

[oz-plumber]

What sort of Motorised valve do you have?
Depending on what make - some open immediately and some may take 3 minutes to open
Some of the slow opening valves can cause the boiler to go to overheat.
If the boiler doesn't have an internal by-pass this will definately cause the boiler to go to overheat with a slow opening valve

 

[pipfootball]

It is a siemens 3way motorised valve if that helps. Whats annoying is system ran ok before swapping valve round apart from obvious hot water coming on when heating switched on and vice versa with heating

 

[BLOD]

Does sound like air still in the system to me, any air release valves in airing cupboard ?

 

[pipfootball]

There is one on pipe from tank but it is soldered (no idea why)

 

[BLOD]

There is one on pipe from tank but it is soldered (no idea why)

can you post a photo of it ?

 

[Dotty]

Probably a manual one.

 

[pipfootball]

hope this helps

 

[BLOD]

where the pipe disappears out of the top of the photo, is there a fitting to bleed air out there ?

 

[pipfootball]

Pipe that sticks up at top near entry to tank is the one i mentioned with bleed valve that as been soldered.

 

[BLOD]

any chance of a photo of the bleed valve ?

 

[pipfootball]

Sorry not much to see really just a knurled top that as been soldered round (not very well either as the bleed valve had a very tiny leak round where it had been soldered so had to do a quick fix with epoxy putty which can just be seen on top of pipe in picture.

 

[BLOD]

Can't see why anyone would solder up a bleed valve - but if you're sure then you have a bit more work on your hands.
Whether it's the problem or not you need to let the air out of the cylinder coil for water to circulate properly.
You might be lucky by keeping the pump running overnight with the boiler turned off - if the system allows this.

Would have saved a bit of time if you'd given all the info first off.
Probably best to call a plumber to fit a new air release valve - he might not need to drain it all down again to do this.
Best of luck

 

[pipfootball]

Thanks BLOD. I've no idea why it was soldered.I only noticed it a while ago whilst looking for something else in cupboard and saw it was weeping so fixed as said before. I assume it's bleed valve as it has knurled edge and slot in top to I assume turn with screwdriver. Again I can only guess that when it was fitted that it wouldn't seal so numpties decided to solder it. Will contact plumber to sort and hope it doesn't cost and arm and leg. Cheers.Phil.

 

[pipfootball]

Update news. Phoned friend who's a plumber and he suggested that I could try leaving pump running on it's own to see if that cleared problem although not guaranteed to work. i did so and left pump running for some time and you could hear air and water noises at cylinder. Have since tried both heating and hot water and boiler as stayed on with no apparent problems. Will monitor to make sure all is well. Hope so (touch wood/head). A big thanks to all who contributed and will not hesitate to come back for any further advice and help. Cheers. Phil.