Upstairs rads cold - pump at fault?

[marchesini]

I have a Vailiant Combi boiler which has had so many parts replaced over the years, it's unreal but that's another story.

It was last serviced in April this year where it had a powerflush, a magntec magnetic filter and all the relevant inhibitors installed. It has been working pretty well up (heating had not been needed) until we had the cold spell where I noticed some of the rads were not working.

I have bled all of the rads (some big air pockets there), and then tried balancing the system. It seems that the radiators at the end of the chain only get hot if I turn all of the radiators downstairs completely off. In one bedroom, it only gets hot if I turn half of the upstairs rads off aswell!! However, once I have the end rads upstairs get really hot, I turn on the downstairs rads (some by only a quarter turn - or less) and then it seems to mess up the upstairs rads.

Onto my question - is this then likely to be the pump (again) or is there anything else I can try? All of the hot water and downstairs rads work fine - get nice and hot but it is very strange on the upstairs rads. In one bedroom they will be boiling and then the next door - not more than 4 metres away will be freezing cold? I would have thought they would at least be slightly warm hence my confusion.

Thanks in advance for any replies.

 

[Bahco]

Try this checklist

Balancing looks the first one.

 

[marchesini]

Balancing looks the first one.

I think that's what I've done- unless I'm misunderstanding something. The first rads are completely off until the upstairs cold rads get hot. Then I open the valves slightly (quarter turn only in most cases) - starting from the ones that get hot first and working my way upstairs.

This doesn't seem to make any difference and the upstairs rad get cold again? The only way to make the upstairs rads to be hot consistently is to completely turn off most, if not all of the downstairs rads.

Am I doing something wrong? By the way, all of the rads (bar one) used to work perfectly.

Cheers

 

[marchesini]

8 )Check the bypass which should only be open just a little.

An open bypass valve will provide an easy route for the water back to the boiler without going along the full length of the flow and return pipes. This means radiators furthest away either stay cold or just warm.

This sounds like it might be the cause? Probably a really stupid question - is the bypass valve the TRV valve? So even though I may have the downstairs rads open only a 1/4 turn, the TRV's need to be only open a little as well? Or is the bypass valve something completely different?

Cheers

 

[Bahco]

is the bypass valve the TRV valve?

No.
You probably will have an internal bypass on your combi. Maybe your pump needs bleeding or have a blockage.

 

[marchesini]

is the bypass valve the TRV valve?

No.
You probably will have an internal bypass on your combi. Maybe your pump needs bleeding or have a blockage.

That's what I was thinking - the pump. I have again got the end rads working by shutting off all the downstairs rads so doesn't that eliminate a blockage as the water does get to them but only if the others are not on?

How do I bleed the pump - any instructions (preferably with pictures). BTW, its a TurboMax 282.

Cheers

 

[Bahco]

FAQS