Central Heating - Return Blocked?

[RzB]

The system has a one year old condensing boiler, and is a conventional 3 port valve job for CH and hot water cylinder. There is a roomstat and all except one of the radiators have a thermostatic valve. The original system was installed in the late sixties.

Some weeks ago I removed some radiators as part of a kitchen/diner refurbishment. Today I drained the system down, added a couple of pipes in preparation for new radiators to be fitted after the plasterer comes next week. After refilling I am unable to get any heat from the radiators.

It's as if there is a blockage on the return side. The flow side gets hot but the radiators stay cold. The only things that get hot are the bathroom towel rails - they are connected between the pump and the 3 port valve. All the radiators have been bled. What can possibly be wrong? An air lock? Wouldn't the pump just pump it round? Or perhaps a real blockage in the return somewhere?

Whilst fitting the pipes today I noticed quite a bit of crud in the 22mm return pipe. Not enough to block it though...

surprised me. When the boiler was fitted 12 months ago the plumbers spent many hours flushing the system. I'll definitely flush the system myself in a few weeks when I have some time spare.

Any thoughts, cos it's a bit nippy :-)

Thanks, Roy

[marcusb3495]

[marcusb3495]

if you heating enginner did it properly it would have flushed it then put in a inhebitor

do i understand your a diy er with a =A3800 flushing maching kicking around

it sounds like you may have an air lock--which is not just a matter of bleeding rads

any yes the boiler may have been fitted 12 months ago--to old pipework/rads?? and then you messed with it

is your hot water working ? the best way to get rid of air lock if first concentrate getting hot water going--the lock all rads down bar the nearest one,,get that going then move on to the next turn off the one you got going

some times there is a bypass valve--turn it off as you are doing this and make sure hot water is off

RzB wrote:

[RzB]

Yes - they did that. It's been without inhibitor for about a month.. since I removed radiators..

I am a DIY'er - the local plumbing shop have a rental flushing machine.

hmm.. I imagined the pump would push the air into the rads..

Yep - correct. Old pipework, new boiler and I messed with it:-)

Hot water just fine.

Ok - that makes sense - I'll do that.

Don't think I have a bypass valve. Are the towel rails performing a sort of bypass function? Or is that summat different?

I put the original post up at 19:44 and then had to go out. I left the system running while I was out. On my return a few minutes ago (22:45) all the upstairs radiators are hot (with one exception). The downstairs rads are still cold. So it looks like summat has shifted. I'll do as you suggest and see if I can get the downstairs rads running as well.

Many thanks for your help, Roy

[RzB]

OK - just to close this thread neatly..

My problems were down to a dicky pump. It finally failed completely over the weekend.

I have installed a new pump and all my problems are fixed!

One thing might be of help to others searching... When the pump failed the boiler stopped with an F5 Overheat Fault error code. (Glo-Worm hxi). The overheat thermostat needs to be reset before the system will run again. I should have realised this but didn't think it through. I was a bit dismayed when the system didn't run having changed the pump!

On the Glo-Worm hxi the overheat thermostat is behind two covers.

All OK now though - yipee!

Thanks, Roy