power flush then no heating??

[christrax66]

Hi All,
I did a job recently where I power flushed the system using a kamco via the 15/50 pump. After the flush was complete i got the 1st floor rads to work but had trouble getting the ground floor to work. Some rads that were cold in the middle before the flush worked fine afterwards & some that worked were just warm.There was a lot of sludge coming through the flush throughout the day & the pump took a while to go quiet. A few days later the customer called me to say that everytime they switch on the hot water the ground floor rads go cold? Any ideas as im stumped on this, probably overlooking something simple?

 

[ChrisR]

Balancing problem?
Was the pump OK?

 

[christrax66]

I balanced all the rads after the flush, the pump, grundfos 15/50 was a bit noisy but settled down after a while

 

[ChrisR]

I think it could be that the pump's old/worn/slow. Why else would you have trouble balancing it if the systems fairly clean?
I meant is there a balancing valve on the hw?

These callback jobs are such a pain it's worth sticking in a new 6m head pump!

 

[christrax66]

Yea know what you mean about callbacks, its a pain, think I'll just stick a new pump on like you suggest, wont do any harm, thanks for the advice Chris!!

 

[superdupergasman]

If the pump dont work then there must be a restriction some place...... sounds like some sludge has moved maybe?

Get a magnet and check the neutral point where the cold feed joins in, if cold feed is into cylinder connections check where the cylinder return connects back into system..... also is there a balancing valve on the return from the hot water cylinder to restrict your flow a bit.

 

[gas4you]

You don't say what system it is.

Any chance that there is an old dumb ball valve in the flow/return to downstairs that is now sticking or slighty blocked?