Is it the flow?

[macap]

We have a Chaffatuex and Maury Britony 100 combi boiler, and a total of 5 rads downstairs and 4 rads upstairs.

The main problem with this system is that the rad in the front room has never had uniform heat, it's usually cold to warm at the bottom and hot at the top half. In the past i have shut down other rads in order to get it running correctly but when i open these back up the problem returns.

It was fed by 10mm pipe until i had a brainwave and repiped it in 15mm by teeing off the hall rad, but this has made no improvement at all, i also flushed it with a hosepipe before reconnecting it, so i dont think it's sludge. Any other ideas? the manual for the boiler says something about adjusting the by-pass but i'm unsure where that is, would an extra expansion vessel help?
Thanks
Mark

 

[bengasman]

Was it okay when they installed the boiler?

 

[macap]

I did miss out the fact that the boiler is about 10 years old, i'm sure the problem was present after it was installed, but i've really noticed the problem over the last couple of years..maybe because i'm getting older.

Since changing to 15mm i think it's got worse, the rad goes lukewarm when someone is using the shower (which is fed off the boiler)and i hadnt noticed that before

 

[bengasman]

Ch stops whilst the dhw is used on a combi, that is normal.

 

[macap]

Yes i am aware of that, but like i said i have never noticed the rad to go lukewarm before. Are there any suggestions on what to do about getting the rad to run correctly?

 

[bengasman]

As it is normal that the ch stops when somebody is running a shower, I'd say the rads is running correctly.

 

[picasso]

if your radiator is hot at the top and cold at the bottom then you have got sludge in the system, try flushing the whole system with mains water and then balancing the rads.

 

[JohnD]

and if you can afford £100 and do basic DIY plumbing, fit a Magnaclean as well as using a sludge-removing chemical cleaner, I guarantee you will be amazed and delighted to see how much black sediment it traps from the water.

The chemical will cost you about £15. I use Sentinel X400 which is very mild and non-aggressive, you leave it circulating for 4 weeks before draining and rinsing. I am not a pro.

As one of the guys said on another thread, trying to clean the system with plain water is like trying to do the washing-up without Fairy liquid.

 

[bengasman]

...As one of the guys said on another thread, trying to clean the system with plain water is like trying to do the washing-up without Fairy liquid.

Just for clarity, flushing the system using mains pressure it quite different from filling and draining.
If you care to do a mainsflush, I would do this before the cleaner goes in as it removes some of the loose gunk.

 

[bengasman]

Does anyone know where ChrisR's explanation of mainsflushing went? It used to be on faq, but seems to have disappeared.

 

[macap]

Thanks for the replies, i have managed to improve the situation a little today by cleaning out the inline filter in the boiler CH return pipe, it was quite badly blocked, now i've got all rads open and the front room rad is a lot better than it was but still not perfect.

I will try a mains flush if someone could give me some guidance on it, that would be good, i did try the no nonsense system cleaner from screwfix last year but guess i will look for something a bit better and try that also
Thanks again

 

[bengasman]

You might want to read through the entire wiki and faq section, various bits on flushing there.