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Original poster

New radiators not getting hot..

44 replies

Marmitelover55 · 09/10/2014 18:30

Our extension was finished in the summer and we have a new boiler, 2 new radiators, a heated towel rail and plinth heater connected to the central heating system. Today is the first day of turning the heating on, although I have vague recollections of the plumber testing it back in July.

Out old radiators are all nice and hot (after bleeding them), but the new ones are only luke warm. I haven't tried the plinth heater yet.

Does anyone have any ideas/suggestions about why and what we can do to get them hotter?

Thanks.

OP posts:

Original poster

Marmitelover55 · 10/10/2014 07:53

Hopeful bump..

OP posts:

PigletJohn · 10/10/2014 09:37

It might need balancing. Turn off all the hot ones. Do the cold ones heat up?

Often, with extensions, new radiators are attached to the pipes for old ones, in a way that means most of the flow carries on round the old circuit snd not much finds its way to the new.

Are the pipes to the radiators the size of your finger or the size of a pencil?

What do the knobs on the radiator valves look like?

digger123 · 10/10/2014 09:41

Are the valves open at the opposite end to the thermostat? I think that it is these are are used to balance the rads and they might be closed??? (self taught DIYer here so hoping I'm right ) See if you open them a bit and feel the pipe feeding to it

digger123 · 10/10/2014 09:42

Oh - and you have turned up any thermostat on the rads???

Original poster

Marmitelover55 · 10/10/2014 11:26

Thanks piglet and digger . Here is a pic of the thermostat and the thing at the other end which might be the valve? The things that might be the valves are closed and I will try opening them when the heating is on as well as trying turning off the hot radiators. The pipes are finger sized rather than pencil sized.

OP posts:

PigletJohn · 10/10/2014 11:38

Similar photos of the old ones please.

How tall are the new rads? Are they hot at the top or the bottom?

PigletJohn · 10/10/2014 11:40

Do not alter the things at the other end (lockshield valves) yet. They take a long time to adjust correctly.

SweetsForMySweet · 10/10/2014 11:45

Air locked or turned off/on halfway maybe? Could you need to heat more of the water in the tank so it circulates to all the rads? I'd ring the plumber and ask.

Original poster

Marmitelover55 · 10/10/2014 12:00

Oops have closed the lock shield valves again. Here are pics of one of the old radiators. We have 2 new rads - one vertical about 4 feet high and one horizontal about 2 feet high and 4feet wide. They were warm all over, top an bottom. Some of the old ones were cold but heated up fine when we bled them.

OP posts:

Original poster

Marmitelover55 · 10/10/2014 12:03

Sweets - not sure what you mean about air lock?? One if the builders did break the thermostat thing off an old radiator in the hall, would that have any effect? Plumber is supposed to be coming back to fix that. I will give him/builder a call if necessary, but didn't want to look silly if its easy to fix myself Thanks

OP posts:

digger123 · 10/10/2014 13:12

Ok so try this...turn off the thermostats on the old rads and turn them on on the new rads and turn on the heating. Are the copper pipes hot that lead into to new rads at either end?

Madmog · 10/10/2014 14:43

If the above advice doesn't help, do phone the plumber who installed the boiler and radiators. My Mum had a similar thing, she had her new boiler installed in the August and two months later only half of her radiators were heating up. One of her radiators was pretty much full of air, but she also ended up having a little tank fitted next to her boiler which solved the entire problem. In fact, the radiators heated up better than they have ever done afterwards.

Original poster

Marmitelover55 · 10/10/2014 17:15

The heating has come on now and the copper pipes to the new rads are very hot but radiators cold. Should I try adjusting the valves now? Thanks

OP posts:

PigletJohn · 10/10/2014 17:16

no.

Turn off all the hot ones.

Original poster

Marmitelover55 · 10/10/2014 17:17

Sorry forgot to add that the copper pipes the other end by the valves are cold.

OP posts:

PigletJohn · 10/10/2014 17:19

as expected.

digger123 · 10/10/2014 17:25

So are the copper pipes to the new rads hot at both ends? And have you turned the thermostats on? I would then try to turn the valve at the other end. I did this on an old radiator where the thermostat wouldn't work and it kept on coming on in summer when the hot water was on. So I closed the valve at the opposite end to the thermostat to make it stay cold. I realise this could be messing about with any balancing that might have been done previously, but if you just turn it slightly, and find it has been turned off in that heat then floods into the rad, then there is your problem

Original poster

Marmitelover55 · 10/10/2014 17:29

I have been around the house and turned the rads off but a couple were a bit unclear so I may have turned them on more. Will check again in a few mins.

OP posts:

Original poster

Marmitelover55 · 10/10/2014 17:29

Copper pipes to new rads only hot on one side. Other side pipes are cold

OP posts:

PigletJohn · 10/10/2014 17:29

if the inlet pipes are hot, then hot water is flowing, therefore the valves ends are not closed at either end.

If the outlet pipes are cold, we only know that the water is flowing very slowly.

When the hot rads have been turned off for half an hour, we will know more.

PigletJohn · 10/10/2014 17:31

have you got a hot water cylinder?

Original poster

Marmitelover55 · 10/10/2014 17:35

Yes we do have a hot water cylinder.

OP posts:

Original poster

Marmitelover55 · 10/10/2014 17:39

I haven't been able to turn off all of the hot rads because 2 have broken thermostats. Heated towel rail still feels hot even though I hoped I had turned it off. Does this matter for our experiment? Thanks

OP posts:

PigletJohn · 10/10/2014 17:43

turn hw to "off" on the programmer.

Run the hot tap and see how hot it feels. In half an hour see if it has got hotter. You can use a thermometer if you have one. Now you have turned most of the radiators off, you should see the boiler firing less often, and/or with a smaller flame.

In half an hour you might find the cold radiators are fully hot. The TRV in your pic was on "5" which is usually fairly warm, you can turn it to a higher number if you want. All the other rads should have cooled down somewhat within half an hour. You can turn them to "0".

PigletJohn · 10/10/2014 17:51

Your old trv's look like Drayton TRV4's. These were until recently the best on the market, they are very widely used. The thermostatic head can be removed by undoing the large nut under it. You can buy replacement heads but it is actually cheaper to buy complete new valves and take the heads off them.

See here

If you have two broken ones and can use a spanner I would buy two new ones. The heads come off without affecting the valve, no water squirts out. Always wind the head fully upwards before trying to remove or refit. Compare your old ones carefully to the photo to make sure they are the same. The colour does not matter.

Before fitting, practice taking the heads off the new valves and putting them back to see how it is done. Instructions will be in the box.

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