New radiator & the valves on a micro bore C/heatng system yet in will not heat up bled & balanced system stil

Question

old rad had a stuck valve & the rad hasnt heated up for nearly 18 months so I decided to replace entire rad/vlaves and expanded onto 15mm pipe from the 8mm - rad will get warm after nearly 3 hours, have flushed system thru and blanced rads to the best of my ability - will onlt get fairly hot when all rads closed off - help please - boiler is only 2 years old and serviced every year and I have increased the pump speed to the fastest setting

Answer 1

Based on your description, I would guess that the microbore pipe to that rad is twisted or flattened somewhere on its route, you will need to follow both flow and return from rad. to the manifold and inspect EVERY inch. If its not damaged then it must be blocked with dirt or solder or whatever, you will then have to unblock it or replace the length of pipe.

Answer 2

It seems that there is a bad air lock in the pipework to this radiator.Bleeding air through the little air vent will never shift it. You will have to turn both radiator valves off and drain out this radiator. If there is no drain off point on the radiator, you will have to loosen the radiator valve until the water trickles out and catch the water in a bowl or something similar. Open the air vent as you do this to ensure all the water runs out. When the radiator is drained out, you then loosenthe radiator valve at one end completely. and try to pull it away from the radiator as much as you can. Then open the valve a little and let the water run into a bowl or bucket until you find that the pipe to the valve is getting hot. if you hear the water hissing as it comes out, that is the air in the pipes coming out with the water. Wait until the pipe is very hot, and turn off thre valve and connect it back to the radiator. you will then have to do this again with the other radiator valve. When both valves are reconnected, then turn them on and see how that is.

Answer 3

Sounds like there is a restriction in the pipe somewhere, try turning all other rads off & open valves full on the problem one. The trouble with microbore pipe is that it dont take a lot to cause a blockage

Answer 4

Jayktee96 gave a good answer.
Personally I would try to replace the microbore from the rad to a more central point in the system with plastic pipe of 15mm, its surprising how fluff, old solder and magnetite, which is black rust etc can block microbore pipe.
It should never have been allowed in the first instance., when you get it working properly, insert FERNOX or similar in the system to prevent internal rusting.

Answer 5

Try flushing the system before you spend any money, it might work.