Downstairs heating not working

[TheShak]

Hi,
I've just joined this forum hopefuly to get some inspiration... as i am out of ideas.
We had a new boiler + megaflow put in earlier this year. everthing worked great, we also had the system flushed out twice before the new boiler was put in.
The system was working great this year as well. It is dual zone system with a separate feed for hot water, i.e. three zone valves.
About two weeks ago I heard some noise from the boiler, sort of rattleing noise. So, I called valliant and the chap came and cleaned the pump, apparently there was some solder in it. He then tested the whole system and everthing was fine.
A few days later the downstairs zone stopped getting warm , with the exception of one rad which is nearest to the boiler. when checking the boiler it seems to get to operating temp 75 deg really quick and the goes into anti-cycling mode really quickly.
The upstairs heating is fine, all rads excellent. The H/W is great. Just the downstrairs. We've had two plumbers in and they've done the TRV sticking bit but to no avail. So are all the TRV in 7 rads got stuck all at the same time?
Finally the pipe leading to the TRV is very hot, but somehow not getting past TRV into RAD....

Any ideas, clues, what to do ...

Thanks in adavance

TS

 

[TheShak]

Also the TRV are Temtrol TM M15, is there a direct replacement for these?
I'm told these fittings are not the "normal" ones?

thanks

 

[moliver34]

zone valve or central heating pump fault

 

[TheShak]

Thanks for your reply.

We checked the heating pump and it fine, if it wasn't the upstairs heating would also fail.
Also the zone valve - the plumber left this permanently open (also these are new only put in earlier this year) but it made no difference.
So out 8 rads downstairs we have;
1 working fully, also this is the one nearest to boiler
5 rads working about 40% of the 1st rad
1 rad at about 20% of the first one, this one funnily happens to be the one after the hottest rad
1 ice cold, last rad in the system...

Go figure?

Thanks