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Hi,We have just replaced the very old boiler with a Vailliant boiler,its not brand new but taken out of other property its only 3 years old and was working 100% before
The central heating was working fine with OLD BOILER all the rads were roasting hot
But now ith new boiler(use vailliant)only few of the boilers are hot at max and rest are just warm at best,the hot ones are on one side of the house and cold ones are at the other side of the house(both upstairs and downstairs)
Tried with bleeding ,balancing,even totally shutting the hot ones to force through cold ones ,but still no good they are warm at the best
The plumber did bleed the whole system and refilled it again,just wonder whats wrong with radiators and how to cure it,the feed and returns pipes are roasting hot,and the feed and return to most radiators is very hot but rads are only worm
The plumber is on holidays and i need to get this sorted asap
any help please?
1 Answer from a MyBuilder Heating Engineer
An individual radiator not working is often just air within that radiator and can be solve by bleeding that particular radiator. A series of radiators not working is likely to be air trapped in sections of pipework.
The only solution that I have found is to do the following (preferably on the furthest 'cold' radiator from the boiler) -
1. Close valves on both sides of the radiator
2. Drain the radiator through the bleed screw at the top till water stops coming through - if the water does not stop then the valves are not properly closed
3. Remove the plug from the top of the radiator at the opposite end to the bleed screw.
WARNING - there will still be some water left that will come out when you remove the plug, be sure to put a drip tray under the radiator and protect carpets etc. with old towels/plastic sheet etc.
4. A compression elbow (http://www.homebase.co.uk/webapp/wcs/stores/servlet/ProductDisplay?langId=110&storeId=10151&partNumber=105364) with some thread tape on should thread into the plug hole.
5. Having screwed the elbow in fit a short piece of copper pipe to the free end and use this as a drain off point.
6. You can either attach a hose to the piece of copper pipe and lead it to a drain, or similar, or you can drain direct into a bucket. The idea is to open one side of the radiator and drain a couple of bucket fulls of water through, close the valve again and then open the valve on the opposite side and repeat the procedure.
WARNING - do not let the water in the system run out as you will simply draw more air in and will not solve your problem
7. Disconnect the compression elbow, refit the plug and refill the radiator by opening a valve and bleeding through the bleed screw.
This procedure may need to be repeated on more than one radiator.
Of course there is no guarantee that this will work but it does sound as if the is air trapped in the system so you have a pretty good chance of getting things working again with the above.
Answered 20th Sep 2012
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