Hot water OK but no C/H

[butwhy]

Hi all
I wonder if you can help? I have just had a new bathroom fitted and whilst all the water was off I thought it would be a good idea to change the C/H pump and both M/V's. I re wired the controller wrong( two cables both brown and black but nothing to indicate which was L and N) the h/w came on and I could not shut it off and I could not get the C/H to work at all. This rung alarm bells so I shut the system off spent a few hours on the internet and found how to take the controller apart this is when I found I had re-wired it wrong. I then re-wired it and problems so bought a a new controller. H/W works great but when I turn the C/H on it works for about 20 min's rad's get warm but then light on the Baxi boiler goes to amber it ties to fire up approx 3 times then goes to red (Boiler tripped out) I re-set it and it works for approx 20 min's and trips out again. I have done voltage checks and everything seems OK. So everything points to the boiler but why does it work OK with the H/W but not the C/H?

 

[ianmcd]

you are not getting circulation when CH only is selected and boiler overheat stat is clicking in

 

[butwhy]

you are not getting circulation when CH only is selected and boiler overheat stat is clicking in

H/W works 24/7 C/H trips boiler weather H/W is on or off. I did drain off about 4 buckets full of water from the C/H system this seemed to prolong the trip of time to 1.5 hours also shutting of the first two rads seems to prolong the time before it trips out? But it is a brand new pump and I can feel it working??? But I think you maybe right as when only the H/W is on the boiler light stays on green but when the C/H is on it goes from green to amber to green every 5-10 minutes then it stays on amber and I can hear it trying to fire up after about 3 tries it goes red.

 

[butwhy]

So next question is if the pump is ok then I must have some sort of blockage is there any way I can pump water under pressure through the system to hopefully clear it?

 

[CBF]

have you made sure you put the pump the right way round ?

 

[butwhy]

Yes I did check but I will double check again when I get home from work

 

[butwhy]

OK just to let people know. It was not a circulation proplem my boiler had not been serviced for over 5 years. I thought I would solve this proplem and then have it serviced, but it turned out that the service was the proplem once done everything worked fine. The moral of the storey is make sure you have your boiler serviced regulary