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.
--------------------------------------------------------------------------------
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 ?
__________________________