I've an old house and therefore all radiators that I've fitted are double. My bathroom one is furthest from my large Alpha combi boiler. Its about 13m in 15mm pipe length....would this affect it getting hot? Seems to take ages to heat up, and not at all as hot as others. Bathroom is downstairs, boiler upstairs. Help !!
SYSTEM MAY JUST NEED BALANCING!!!
SPEED UP FLOW THROUGH RADS CLOSE TO BOILER AND SLOW FLOW THROUGH RADS FURTHEST FROM BOILER.
IF NO JOY, BOILER MIGHT NOT BE ABLE TO HANDLE LOTS OF DOUBLE RADS AND ASSOCIATED PIPE WORK!!!
IF YOU HAVE OR CAN GET BOILER INSTALLATION INSTRUCTIONS/MANUEL, THEN THIS WILL TELL YOU THE BOILER RATING AND FROM THAT YOU CAN ADD UP THE BTU VALUE OF EACH RAD TO SEE IF YOUR OVER THE MAX FOR THAT BOILER.
First question. Is it a single pipe system or a dual pipe flow and return. If you've piped as single pipe then the rad furthest away from the boiler will always be coldest. If a single pipe you perhaps need to do some balancing.
Assuming it is dual pipe does it have a TRV? If so take the head off and see if the centre pin operates properly. If it's sticking that could be the problem. If it's an ordinary valve is it open enough? Is the lockshield valve at the other end of the rad closed?
If that doesn't work try turning off ALL other rads and see if it then gets hot.
If it doesn't then you probably have a blockage of some description or an airlock.
Yes it should be 22mm with 15mm branches tee'd in for each radiator. This will be why it takes a while for the bathroom radiator to heat, if you're wanting to improve the performance - upgrade the pipe to 22mm as far as possible with 15mm branches.