cold rads


Postby bazza » Tue May 05, 2009 4:00 pm

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
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Postby htg engineer » Wed May 06, 2009 8:02 pm

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.

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Postby bazza » Thu May 07, 2009 2:37 pm

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
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Postby htg engineer » Thu May 07, 2009 7:30 pm

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.

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Postby bazza » Fri May 08, 2009 3:09 pm

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
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Postby htg engineer » Fri May 08, 2009 6:38 pm

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 ?


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Postby bazza » Sat May 09, 2009 3:43 pm

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.
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Postby willie gas » Sat May 09, 2009 6:29 pm

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...
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Postby willie gas » Sun May 10, 2009 2:51 pm

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.
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Postby bazza » Sun May 10, 2009 3:39 pm

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
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Postby htg engineer » Sun May 10, 2009 3:57 pm

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.


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Postby bazza » Sun May 10, 2009 6:10 pm

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!
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Postby bazza » Sat May 16, 2009 11:24 am

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 .
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Postby htg engineer » Sat May 16, 2009 6:56 pm

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.


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Postby bazza » Sun May 17, 2009 10:19 am

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
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