DIY Doctor UK DIY Forums

hi guys got 2 rads that wont heat up . the flow pipe on the entry to the rads get hot but the return pipe stays cold , tried turning off all other rads, and leaving them 2 open and they did get hot ,but as soon as i openened other rads on curcuit they went cold again.? ive tried rebalancing the system, and av also removed the 2 rads flushed them out but still nothing . it seems as tho the water is not flowing thru those rads 4 sum reason ,just dont kno why ? ps both rads are on the first floor second floor rads all work fine .thanx 4 any advise bazza

What size pipe ?
Possibly a partial blockage in the pipework or manifold.

Both downstairs radiators ? check the pump, pump could be on it's way out.

htg

thanx 4 reply htg engineer the pipework is 10mm. and ive checked pump and there is power going to the pump ok, ive also bled the pump to check 4 air but again ok, is there anything else i can check on the pump ? also if it is a blockage; wud the best way to get rid of that be to flush out the system ? or wat wud your advise be on upgrading the pipework to 15mm, both rads are on drop feeds. thanx bazza

I would definately try to rule out a pump problem first - change it if you can.

How many radiators are downstairs ? if you have more than the 2 - turn off 2 of the others and see if these two work - if they do - then i would definately be looking at the pump. Upstairs will heat naturally, it's only downstairs that required the pump really - if the pump is on it's way out - it may just not be working well enough to heat these two rads.

How is the system piped ? manifolds or each rad tee'd into flow and return ?

I suspect manifolds, so if the pump is ok and you suspect a blockage,
try to back fill ? or cut the pipes at the manifold and check for blockages and clear where possible - or re-pipe the two rads.

There's no reason you need to change to a 15mm system, it's up to you though. I'd rather have 10mm coated than 15mm uncoated - reduces heat loss.

htg

hi htg engineer. cheers mate 4 advise i av 3 rads downstairs, so i turned off the one that works' 2 c if it heated up one of the others that dont' but it didnt work the 2 rads stayed cold ? so do u think it cud still be pump or more likely a blockage. also the boiler is still under warranty so cud it be worth getting them out 2 investigate the problem' or will they charge 4 sending out an engineer ? cheers bazza

You will be charged if there's nothing wrong with the boiler.

It's more than likely a blockage, if you're happy with the pump. Do you not have a spare pump lying around ? change the head - see what happens ?


htg

hi htg engineer. when i switched boiler on 2day the error code f22 flashed once for a second, then the boiler continued to run ok ( no error codes )so i checked manual and the code means a blocked or defective pump. so i thought id undo the bleed vent again and turn the shaft a couple of times, but wen i undun the vent screw water just kept pouring out, and the water was black' but the boiler is only a few months old. so why was the water black ? maybe it wasnt flushed out properley on installation.? so if i was to flush out the system now. do u think it cud solve the problem.or will it need a new pump ? cause with being new u wouldnt think the pump wud fail so quick ? thanx 4 your help bazza.

hi take one of the rads off again,make sure c/heating is off. open one rad valve at atime & let it flow into a container. if both flow at same rate good chance no blockage. chk rad valves. GOOD LUCK...

hi bazza did you have new boiler conn to old system? black water is a sign of lots of sludge. can u discribe the way your system is piped up, follow flow pipe. is there just 2 water pipes coming from boiler. is there a 3 port valve. for more ref check hydn 98 for checking systems. GOOD LUCK.

hi willie thanx 4 advise.. av already tried that wen i removed rads first time' and the water flowed ok from both valves cheers bazza

Probably hasn't been flushed properly, I would drain and flush and add inhibitor - continuing to run a new boiler like this - the heat-ex will become full of crap.

The pump uses the system water for lubrication - remove anfd clean the pump housing, but again - possibly require a new pump/head.


htg

cheers htg engineer. i will drain and flush wen i finish work on friday, i will let you kno how i get on. thanx 4 all your help bazza!

hi mate. i drained system 2day and flushed it out a couple of times' but still no joy with the two downstairs rads. ( still wont heat up ) after filling system up i tried to bleed pump. but again asoon as i unscrew the plug in the front it just pours out with water, i was always told just a few drops shud seep out ? also the pump gets red hot. again shud it be getting that hot so u cant touch it ? and wen refilling the system my bedroom radiator took ages 2 fill,i ad 2 play about with the bleed valve pin 2 get it 2 fill up.and altho it gets hot at top it stays cold at bottom (i think valves are knackered they r well old )so if the valves are knackered. cud that possibly stop the two rads downstairs heating up (maybe stoppin the water from flowing round sysem properley )? thanx 4 all your help so far mate cheers bazza .

I really would consider changing the pump - it shouldn't get that hot.

CHANGE THE PUMP - lol.

If the two problem radiators have the same type old radiator valves on them - then yes it could also be the cause, but again the pump shouldn't get excessively hot.


htg

hi htg engineer guess your right i'l change the pump lol. but with the boiler being under warranty do u think i shud just get them 2 send a engineer out .or just change it myself (just thinking of the cost im being tight in the reccession lol) thanx 4 all your help mate nice one cheers bazza