rad not heating up

[Reggaeman]

Hello.
Another new problem with radiators that you might find interesting.
I have had this problem for a long time. My rad in the hallway never did heat up properly’ so just this week I decided to replace it with a new one. I drained the system. Fitted the new rad and refilled the system. I then turned on the heating and bled the system from the top and did the new rad last. Hot water started to come into it but it did not last long. It only got warm on one side near the bottom were the hot water came in.

The rad has inlet and outlet valves. And small refill tank in attic.

Thanks for any help

 

[Steve]

1. refill and bleed the system, THEN turn on the heating to circulate and remove trapped air.

2. This radiator - is it supplied by pipes that are maybe the lowest on the system?

If so, then a cure I used was to close the valves on every other radiator while the heating is running (obviously make sure this one is left open). This forces any crud out of the pipes to this radiator - being the lowest end and having little flow over summer can mean dirt/rust settles here.

I have a radiator I did this on. Worked a treat.

 

[cantaloup63]

Search the wiki on how to balance the system

 

[Steve]

Or you could balance the system

 

[cantaloup63]

Or you could balance the system

After you've followed Steve's advice and forced crud through

 

[MANDATE]

Could be blockage as suggested 'air' or 'Crud'
Before new radiator was fitted, system should have been filled and each of the radiators valve opened to run off bucket or two of water.
This would remove any air locks and loose 'crud'.
Of course it may be another reason, the radiator may be the furthest away from pump with high resistance in pipe work. So the system may need balancing if the problem radiator is get its share of water flowing through it.
There could be a by pass valve open too much allowing water to return to boiler rather than go through pipe work.
Also the pump although working may be full of 'crud' and restricted in its output.

 

[Steve]

How many systems are actually properly balanced?

If you install a new system, turn it on, and all the radiators heat up, do you balance it? It strikes me that most DIYers are unaware of the technique of balancing, and wouldnt know of such a practise. My Dad certainly used to turn off radiators for decorating and then turn them back on, opening the valves fully (or a random amount).

So in many cases, balancing the system is not a worthwhile activity in my eyes, unless you inform the homeowner of the fact you've balanced it.

I'm not slagging off plumbers or anything, its a genuine enquiry.

 

[Reggaeman]

Thanks.
This is what is happening now.
Well the new rad is the nearest to the boiler and its at the lowest point. I turned off all the upstairs rads and left the rads downstairs on. Turned on heating for 60min. My other two rads got hot in no time. The new one started well' the fitting to the right got very hot and heat was all over the rad.
The bottom of the rad was lukewarm' the rest was warm. The fitting to the left and entry pipe was only lukewarm.

 

[MANDATE]

That suggests no flow through radiator due to (a) air lock (b) blockage or (c) lockshield valve closed and preventing flow.
Check (c) first
suggest close both radiator valves and remove radiator. Then try to run off bucket or two of water from both sides.
If an 'air lock' this will be an easy escape route.
If blockage or partial blockage the water flow will be either none or just a trickle.
You could try closing the flow valve to radiator, then try bleeding radiator.
A blockage will prevent water being bled.
A 'air lock' will still allow water to be bled, but it would take forever to remove the air lock via a bleed valve.