problem heating

[sherren]

i have just moved into a house which is about 40 years old, it has

back boiler and from what i can work out a gravity fed central heatin system, we have no header tank, and the feed comes off the emersio tank in the airing cupboard. The rads worked when we moved in but whilst decorating we took a coupl off after putting them back on all the rads are now playing up. we have drained the system, the water wasnt too dirty just weak te colour. we have taken off each rad and run water through, it was filth and black and some of them had long charcol looking solid peices comin out. this hasnt made any difference to the operation of the rads. we have replaced the pump as this was leaking around the joints problems are not limited to upstairs/downstairs but aparantly random. some of the rads are cold, they are full of cold water the taps ar completely open, when you blead these sometimes water comes ou sometimes no air and no water? i bleed a rad and can feel it heating up but within 10 mins it is col again and i bleed it again and again and again? i have put into the bathroom towel rail, the only constantly hot ra Wicks Radiator desludge treatment. I have balanced the rads and thi makes no difference, i have turned off all better performing rad (there is only one!) in the hope that a cold one will get hot - bu no. I am getting despirate now, and wish it were summer !!!! please ca anyone offer any advise. If i am going to need a power flush doe anyone have experiance of how much it will cost

-- sherren

[Roger Mills (aka Set Square)]

From your description, it sounds as if you have a primatic cylinder - in which a single header tank attempts (often not very successfully!) to do the same job as separate cold header and F&E (feed and expansion) tanks. If I am right, putting any sort of chemical into the system is a *bad* thing - because it will find its way into the domestic hot water. Whatever you do, don't drink the water from the hot tap!

Assuming that your back boiler is gas fired (and not solid fuel) the only decent solution is to throw away the primatic cylinder and replace it with a normal indirect cylinder (preferably fast recovery) and separate tanks so as to completely separate the primary and secondary circuits. If the hot water relies on gravity circulation, convert that to fully pumped at the same time.

[Sponix]

Doesn't a primatic cylinder have a bubble of air separating the DHW from the heating circuits?

If it's a primatic cylinder it'll have "Primatic" stamped on it somewhere.

sponix

[Roger Mills (aka Set Square)]

In theory - but you ain't supposed to use inhibitor in such systems - so the separation can't be that reliable.