downstairs rads cold

fta

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Upstairs rads are hot, downstairs rads are cold. Pump replaced today. Right way round, working fine, good pump (Grundfos 15-60), middle speed (though problem occurs at any speed). Pump and Rads bled. Water in heating cistern. All valves open etc.

If I shut off the upstairs rads, downstairs warms up fine. If i open the upstairs rads, downstairs is cold.

Any ideas ?
 
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Try balancing the system first by reducing the flow through the upstairs rads lockshield valves.
If that doesnt work you will probably find that the downstairs rads are full of sludge so it's time for a flush or better still a powerflush.
Another less likely possibility depending on your system layout is that the manifold to your downstairs radiators is blocked either by sludge or other debris.
Turning your pump to full speed should help
 

fta

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thanks slugs. seems odd that it suddenlty started happenning. i'll try balancing, failing that a powerflush
 
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fta said:
thanks slugs. seems odd that it suddenlty started happenning. i'll try balancing, failing that a powerflush
An airlock is a possibilty then.
Between your diverter valve and the cylinder flow connection you should find an air vent. Bleed the air out from there.
Remember whenever you bleed a system you should do it with the system turned off.
Another last resort before lashing out on a powerflush is to close all the radiators barring one and work your way around the system making sure that at least one rad has water flowing through it all the time.
Is the pump noisy? ... If so it could have air in it!
I know this sounds a bit obvious but have you opened the pump valves fully. It's amazing how often I get called to 'silly' mistakes. I recently had to drive 30 odd miles just to open a stoptap!
 
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Posted: Sun Oct 09, 2005 9:27 pm Post Subject: downstairs rads cold

Hi I have a similar problem to that mentioned in another post (copied below).

I have a single pipe (or even single feed - not sure which one) system . I moved in 1 yr ago and the ssystem is probably the original one ffitted in th 60's. there is a back boiler and gravity fed HW which is wkg fine. Before we moved in the 6m head pump was changed to a Grundfos 15 50 and it looks new and shiny and seems to be working. The 2 downstairs rads only get hot 2 inched around the sides and top and no where else. The 3 upstairs ones get hot on the sides and the top half . But they do not get hot along the bottom or the middle lower section. I think the rads are only getting hot due to convection. All 3 rads upstairs have the same areas being heated up . Have removed the pump cap and it is spinning and have set the pump to full spedd (and tried min speed too). Nothing has helped. The HW gets very hot after an hour or two as i guess there is a flow issue on the CH loop. The pump is mounted horiwontally as the pipework is horizontal and the pump shaft is vertical (not recommeded in the installation noted for the pump), however the manula says that this simply reduces the life of the pump due to extra wear. Could this be a reason for my flow restriction?
My pump seems to be on the return just before th boiler. If i bleed the rads i get clean water straight away ,even with the pump running (air should be sucked in if the water was flowing well i have been told, but it doesn't).
Any help/advice would be much appreciated.
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Upstairs rads are hot, downstairs rads are cold. Pump replaced today. Right way round, working fine, good pump (Grundfos 15-60), middle speed (though problem occurs at any speed). Pump and Rads bled. Water in heating cistern. All valves open etc.

If I shut off the upstairs rads, downstairs warms up fine. If i open the upstairs rads, downstairs is cold.

Any ideas ?
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This was my problem. It turned out it was sludge in my system. When I got the rads flushed it cleared up - then I had boiler probems but that is another saga.

Usignuolo
 
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fazal said:
The 2 downstairs rads only get hot 2 inches around the sides and top and no where else

You should have started a new topic for this! However to save you the trouble what you have told me points to a bad case of sludge. At least take the downstairs rads off and flush them out with a hosepipe. This should be followed with a chemical flush and treatment with an inhibitor.
A powerflush may prove to be the best option. If you do go for the powerflush expect to pay £300 - £350. This could be more or less depending on where you live the size of your system and who does it for you
 
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thanks for the advice, i 'l try to flush out the downstairs rads.
If i close the upstairs rads, the downstairs still dont heat up, hot water seems to go up into the rad s but goes straight up and across the top and down to the return valve. could it be convection ? The boiler is on the return just before the boiler and hence i thought it could be the same problem as suggetsed in this post (anti gravity switch) . A couple of the rad valves have started leaking upstairs and there is brown rusty liquid coming out of the radiator valve downstairs . This implies corrosion and sludging i guess?
 
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Brown rusty liquid is worse than black gunge as it implies air ingress. Normally theres not enough oxygen in the water to produce rust hence the normal black gunge.
Look out for causes of aeration after you have flushed the system and renewed the valves
1 Pumping over through the vent
2 Air drawn in through vent
3 Air drawn in through leaks/ microleaks due to the pump sucking air in. You say that valves are leaking, so that is most likely cause here.

I could go on a bit about it but fitting a de-aerator is the best cure for 1 & 2.

hot water seems to go up into the rad s but goes straight up and across the top and down to the return valve.could it be convection ?
No, thats the only place left for the water to go!

Take a look at THIS
 
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Slugbabydotcom said:
...If you do go for the powerflush expect to pay £300 - £350.
Or just buy yourself 6 or 7 new rads with the same money!
 

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