Is it a CH Blockage ?

[Kspencersmith]

please help.
Serious money already paid out to plumber who diagnosed a blockage in central heating. WE had already changed pump and motorised valve.
Pressurised wash carried pout by plumber and blockage cut out of pipe near boiler. The CH system worked ok for a few days and now the boiler is cutting in and out every 20 seconds. All upstairs radiators get hot but even with upstairs radiators all turned off downstairs only gets luke warm. Do you think there is still a blockage. Any ideas? We have tried turning boiler up high and pump speed up to 3 but no improvement. All radiators have been bled.

 

[mickyg]

Has the cold feed been checked??

 

[Kspencersmith]

Header tank checked. Cold water supply fine.

 

[namsag]

What boiler , and is it a microbore system or normal

 

[Kspencersmith]

The boiler is HW/CH Myson Apollo and its mainly microbore with 15mm going to an extension radiator

 

[namsag]

Personally first port of call would be the microbore manifolds to check they are not parially blocked.
Very small possibility the heat exchanger is partially blocked

 

[Kspencersmith]

sorry what do you mean by microbore manifolds

 

[namsag]

Usually on microbore system after your 22mm pipe comes out of the CH motorised valve and under the floor there will be a special fitting(s) that the microbore comes off and goes to all the rads .
There will also be the same on the CH return

 

[Kspencersmith]

Thanks will try to get under floor boards to investigate

 

[Kspencersmith]

Hello, Thanks for your help to date. If the microbore manifolds are blocked; whats the best way of cleaning them ?

 

[namsag]

Cut them out and clear them.
How small are you to fit under the boards