Problems with system after replacing radiator

[DeltaCity]

Hi all,
Please excuse me - very new to all this. Today i drained the system to put in a new heated towel rail. Beforehand everything was working fine. I turned the water back on, bled all the rads ok, but the boiler now turns itself off after about 30sec and i guess must be tripping the overheat stat because it wont ignite again for a few mins. I think the problem may be with the Honeywell motorized valve which is just above the pump. When the boiler stops, the pump keeps going and gets very hot - presumably this is what happens to pumps when they are trying to force water through a closed valve. A closed valve would also explain the boiler's overheat stat kicking in. Am i on the right track?

System is:
Potterton Profile gas boiler
Honeywell ST7100 controller
Honeywell V4043 motorised valve
Grundfos Selectric UPS 15-50 pump

All seems like too much of a coincidence, but i can't see how draining the system has knackered one of the components. Please advise!

thanks
Pete

 

[kevplumb]

if you look at the actuator on the valve there is a lever
man or auto move it to man with system running
should do the trick

 

[oilman]

aaaaaarrrrrrrrrrrgggggggggghhhhhhhhh!!!!!! 04:08am? don't you ever sleep?

 

[DP]

Kevin is a boy scout. Ever ready to help.

elsandalos, I would suggest the pump and valve are OK. The saying 'little knowledge is a...............' comes to mind. What is more likely is that you have drained the system without prior knowledge or knowhow and now the system will not fill. TV make diy tasks look easy. By all means get a new motorised valve and a new pump. Then it will be a new pcb and a new gas valve. In the end it will be air locked pipes or sediment movemment movement that has caused the problem.

 

[DeltaCity]

In the end it will be air locked pipes or sediment movemment movement that has caused the problem.

Thanks for the quick replies

The system seemed to fill fine, in that all the rads are full (including the new one i installed). I thought that any air in the system would move around until it found the top of a rad to get trapped in, and could then be bled off. Is it possible that air is trapped inside the boiler?

cheers

Pete

 

[kevplumb]

did you open the threee port valve when filling

 

[DeltaCity]

did you open the threee port valve when filling

no, i didn't touch the valve when i filled. By opening it, do you mean flicking the switch from auto > manual as you described above?

Pete

 

[kevplumb]

yup

 

[DeltaCity]

Flicking that switch seems to have no effect. As it's motorised i would expect to hear the motor briefly when i flick the switch - but nothing happens.

I read somewhere else on the forum about a guy who got his system clogged up with gunk when he refilled it (header tank contained years of gunk, which was then introduced to the system on refilling). I was careful to avoid this (mine was filthy too), and i manually emptied and cleaned the header tank before draining the system. Unless it's a big coincidence that a component has failed on the same day that i drain/refill the system, it must be a trapped air issue.

Quick question - presumably the big screw at the centre of the pump is for bleeding it? If so, then should i get water squirting through when i open it up (like when you bleed a radiator)? I opened it up and some air came out, followed by a slight drip - not the squirt i was expecting.

Pete

 

[kevplumb]

thats normal
try turning the pump speed up
still think its air

 

[DeltaCity]

WORKING AGAIN!

Thanks for the advice folks (quickest forum i've ever used!). I bled the pump, which i hadn't done before, for ages and suddenly the boiler kicked back in. Everything seems to be ok now.

Didn't realise that air was such an issue - i'll know better next time.

cheers
Pete