Cold downstairs radiators mystery??

The cylinder is a very short, wide route for the water to go through, so if it can get past the 3-port valve, it will take the path of least resistance, and go through the cylinder instead of the long, tight route through the downstairs rads.

I am thinking about your motorised valve not tightly closing off the cylinder coil.

See if you can manually operate the valve, and see if there is a possibility you fitted or connected it in such a way that it does not close off the DHW circuit.
 
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But i had the same problem before i changed the Motorised valve.

The reason i changed the MV was because the Hot Water Cyclinder was getting hot even when the Hot Water was switched off on the programmer. The old MV appeared to be working when i took the top of it but i think the valve was physically failing.

When i installed the new one last week, i just turned the CH on to test it and the Hot Water Cylinder side of the valve did not get hot so it closes effectivly.

Besides, the downstairs rads don't work when the Hot water is Off and the upstairs rads are on.
 
OK. If you are sure that there is no heat being provided to the hot cyl, then the flow isn't going there and stealing from the downstairs rads.

However, if the cyl is excessively hot, that suggests to me that the cyl is receiving excess heat, for example because the cyl stat is not turning off the valve, or the valve is not making a tight seal, or it is bypassing through the bathroom rad.

Can you manage to have the cylinder cold, and check that there is no supply going to it (not just setting the controller to HW=Off, but feeling the pipes)?
 
When i fitted the MV, i set the heating to ON and the water to OFF and then felt the pipe on the cylinder side of the MV.

It didn't get hot which is correct.

I think the hot water is a bit red herring as we never have the HotWater on constant anyway so the water we used to feel was probably no where near 60 degress anyway. It's just that because the CH circuit is restricted, the Hot Water cylinder is now getting the majority of the flow and is getting upto 60 degrees.

We normally have the CH and Water on for a couple of hours in the morning then a couple of hours in the evening when we get home. When it switches off at 6.30pm we just turn the CH on until midnight. Probably not the most effiecent use of the system but whats the point in keeping a tank full of water hot when we aren't going to use it.

Could it be a red herring??
 
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It's only a red herring when you've checked again that excess circulation is not getting to the cylinder and starving the rads. The cyl shouldn't be overheating because the motorised valve should close when the cylinder reaches temperature and the cyl stat commands it to shut.

If, as you say, the cylinder is getting too hot, then it seems to me that the cylinder is getting too much heat when it isn't (shouldn't be) calling for it. And if excess heat is going to the cylinder, then the low resistance of this circuit would tend to starve the downstairs rads.

The reason the cylinder is getting too hot we don't know yet. It might be the cylinder stat, or the 3-way valve, or the bathroom rad short-bypassing, or some other bypass pipe hidden away, or something else.
 
Ok thanks.
I'll do some more investigation.

For info, the Cylinder Stat is new. I fitted it last night and set it to 60.

Thanks for your help.
 
Hi,

Did you ever manage to solve your downstairs radiator issue? We seem to be experiencing the same problem and have tried the same things to fix it

Thanks
 
In case the link above doesn't work or is removed in the future, the cure that finally resolved my cold downstairs radiator problems was to use Fernox DS40.
This stuff is magic but should be used with caution as it can eat your boiler and/or pipework. You can buy it in B+Q and comes in a large tub.

I tried about 3 different sludge removers, DIY powerflushing with a hosepipe, drained the system about half a dozen times, banging the radiators, even changing a radiator but nothing fixed it until i used DS40.
After about 10 minutes in the system, the rads downstairs started to work. hooray! They are still red hot now some 2-3 years later.
 
Hello there. Richard, we have been having a gradual problem with just one radiator downstairs for the past couple of years. The other rads downstairs don't get as hot as the upstairs, but they are sufficiently warm, however the main lounge rad has good heat in the in pipe, warm rad and a cold out pipe. We've been told and quoted for a powerflush by British Gas (robbers) at £695, which i begrudge paying as they cannot guarantee it will work. We've been looking into Fernox, but I can't seem to find the one you mention. Has it been given another name/code, or is it maybe delisted? We've been looking at the Fernox F3 cleaner and wonder if that will be as effective. I just dont want to be cold this Christmas. The rad was changed this weekend and its made no difference, so the problem must be in the pipework.

Thanks.
 
Hi,
I didn't go down the powerflushing route for the same reason. (i.e there was no guarantee it would work)

I would try a standard sludge remover first to see it that helps as these are normally easier to add to your system.
http://www.uk-plumbing.com/fernox-restorer-heavy-duty-universal-cleanser-1-litre-p-2303.html

Failing that, I tried DS40 which worked wonders.
http://www.uk-plumbing.com/fernox-ds40-system-cleaner-2kg-p-2295.html
Don't forget to follow the instructions to the letter as i believe it is acidic.
Also, don't forgot to add inhibitor to the system after treatment.

Maybe some of the heating engineer members can add additional words of wisdom.
 
loved reading through all the postings .It was like a real agatha christie whodunnit.Glad your sorted.....!
 
richardhill84 said:
In case the link above doesn't work or is removed in the future, the cure that finally resolved my cold downstairs radiator problems was to use Fernox DS40.
This stuff is magic but should be used with caution as it can eat your boiler and/or pipework. You can buy it in B+Q and comes in a large tub.

I tried about 3 different sludge removers, DIY powerflushing with a hosepipe, drained the system about half a dozen times, banging the radiators, even changing a radiator but nothing fixed it until i used DS40.
After about 10 minutes in the system, the rads downstairs started to work. hooray! They are still red hot now some 2-3 years later.
Click to expand...

I know this is not so relevant but do you still have your Baxi WM?

If so is it the one with the brown line in front?

I was just wondering if it was the same model as my old Baxi that lasted approximately 22 years and was still working when taken out.
 
D

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