Central heating radiators going cold downstairs when hot water put on.. Help!!

keystone

mikeluxy wrote: »

Hi There...I can see the place you are talking about on my system but alas no magnetic attraction there...I suspect you are maybe suspecting a build of of gunge at that point which would attract a magnet....?

Yes you are absolutely spot on - its a classic place for magnetite collection. I'll read the thread in some detail now.

Cheers

keystone

This may sound like a really stupid question but you did put the new circulator on the correct way round didn't you?

Which model is it?

Cheers

Edit:

1. Have you tried Andrews suggestion above?

2. What happens to downstairs rads if HW ONLY is on?

mikeluxy

Yes new pump is on right way...I made sure arrow was facing right way etc...im trying a few suggestions now...

If the Hot water only on is on the downstairs radiators stay cold

keystone

mikeluxy wrote: »

Yes new pump is on right way...I made sure arrow was facing right way etc...im trying a few suggestions now...

OK - hope you weren't offended as twas unlikely but it has been known!

If the Hot water only on is on the downstairs radiators stay cold

OK - just wanted to check what the 3 port valve was doing in the "HW only" state.

Are your radiator pipes of the microbore (10mm) variety? You might have a manifold blockage which isn't sufficient to prevent flow when CH only is selected but is when HW is on at the same time. Did you say what the circulator model is?

Cheers

mikeluxy

keystone wrote: »

OK - hope you weren't offended as twas unlikely but it has been known!

OK - just wanted to check what the 3 port valve was doing in the "HW only" state.

Are your radiator pipes of the microbore (10mm) variety? You might have a manifold blockage which isn't sufficient to prevent flow when CH only is selected but is when HW is on at the same time. Did you say what the circulator model is?

Cheers

Cheers...No offence taken at all my friend...im only happy that I am getting so many responses...as you say its often the most obvious points that sometimes get overlooked

No we dont have microbore pipework...its the standard type copper pipe.

The circulator is a Wilo RS50 pump.

I am begining to wonder if its just a case that the downstairs rads (which are getting on for 20 years old) are just knackered with internal rust and the like and its forming a partial blockage of some kind...what do you think...?

keystone

Well I am concerned about the flush you had when the boiler was fitted thats for sure. If all the carp wasn't cleared out then it will have settled somewhere and that will be low down but as I can't see how it is piped (does the CH return come back to the boiler directly and tee in to upstairs return?) and I'm thinking possibly in the return. So we are sort of back to square one as others have suggested earlier - theres an obstruction to flow somewhere.

Unfortunately the bleeding obvious isn't always that obvious sitting remotely from the scene of the accident and I rather think its getting to the time when you have to get someone in to look at it seeing is how the weather is turning. Beware the guy who, on walking through the door, the first thing he says is "you need a powerflush mate" because that might not be the case. Get someone local and recommended by friends, family too.

Cheers

closed

Photo's might help diagnosis?

frank.hopper

Backfill it!

Drain the system completely, (not the HW cylinder) open the motorised valve manually, refill with mains water at the drain off. You'll need someone in the loft at the f&e tank as it fills. If that is successful...

Cleanser
Inhibitor
Magnaclean.

mikeluxy

Hey this backfilling idea has got me thinking....the water in the system seems clean (when bleeding) and not a gungy brown or black so how about if I were to connect a hose to the lowest point and feed in water that way...?...as mentioned surely this would blow out any airlock back up the system to the expansion tank....what are others views on this....?

keystone

Backfilling will not remove an airlock with the system full of water - there is too much weight of water above it. You'll need to drain right down first and the let the system refill from the bottom. Clean water from the rad tops doesn't necessarily mean you still don't have a magnetite obstruction somewhere in the pipework and backfilling won't cure that either. As a matter of interest whats the colour like if you let some out either from a valve union at the bottom of a rad or your draincock?

Cheers