Different Levels of heat from Radiators

[pekae]

I'm in a new (3-bed 2 bath) house (less than a year). It has radiators in all rooms, fed by boiler (which is in the kitchen). All radiators (except the hall & downstairs wc) have thermostatic valves.

The boiler temp is set to it's highest setting.

My problem is that some of the rads are OK, some are just warm - irrespective of what the thermostat is set to. The dining room, however (which is right next to the kitchen) is ALWAYS scalding hot, irrespective of the thermostat setting - even when it's turned almost off !

I've had the builder's plumber in several times and he is adamant that there is nothing wrong with the system.

Having read some of the posts here, I suspect that the dining room thermostat is on the wrong end of the rad and that the whole system is either clogged with muck and/or air.

Anyone any thoughts ?

All help very gratefully received!

Paul.

 

[IanDB]

It sounds as though your system needs balancing. As it's a new installation I wouldn't have thought that the thermostatic valves were sticking although it's worth checking.

What you're meant to do when you commission the system is to open up all the valves (including the lockshield valve at the opposite end to the TRV) and then adjust the lockshields until you get an even temperature rise in each radiator. This involves letting the heating system come on from cold and then rushing round each radiator to see how quickly it warms up. You have to do this several times as normally the heating system gets hotter quicker than you can check the rads. The one nearest the boiler always gets the full blast of hot water as it's nearest the source so you have to wind that lockshield down quite a bit. That then puts more pressure into the rest of the system to feed the other radiators. After your system is balanced you then use the TRVs to control the temperature in each room.

I think that most TRVs can fit at either end of the radiator these days so it's unlikely to be that.

I assume your plumber will have bled the rads? You can check by loosening the square peg at the top of each rad and checking for air - only water should come out.

You shouldn't have any muck in your system as it's too new BUT it should have had inhibitor put in to prevent this from happening - another question for your plumber.

The reason you don't have a TRV on one or two of the rads is to prevent overpressure in the system if all the TRVs decided to close at once - it maintains a flow.

There is a post on this site somewhere about this but I don't know where it is.

 

[pekae]

Many thanks Ian.
I asked the plumber at the time of his last visit whether it was balanced and he asssured me it was - I've had two different of the builders plumbers out three times in total and all they have done is whack all the rads up high and then said "it's ok - just needs to settle down" ! - Needless to say, when I then turn all the stats back down to a tolerable level, I get the same symptoms.

I'll try bleeding them tonight when I get home and see if that makes a difference (although they told me they'd done that too!)

Paul

 

[IanDB]

Found a link but I've never tried this before so here goes

here

Eureka!

 

[IanDB]

"Just needs to settle down" - my backside!!!!

If it doesn't work now it never will - I've never come across a self healing central heating system. Neither has anyone else as you can judge from the 38 pages of related posts on this site!!

Good luck - if all else fails do it yourself!

 

[pekae]

Thanks Ian. I'll maybe give that a try - though I suspect that I just might call the builders back in and insist that they get it right - or else !

 

[pekae]

Well - I did bleed the rads last night when I got home. Hardly any air at all from any of them & the water coming out was fairly warm (the system was off). When turned back on, after an hour it didn't seem to have made any difference.

However - I then went round and turned all the rads up to just over 4 (of a max of 5) on the TRV's and miraculously they all then got really hot !

Does this mean that they do need balancing to cure the problem and to allow me to control them properly with the TRV's ?

 

[boilerbeasty]

Unrelate, but just a nasty thought: did the builders lag your pipes? We bought our house 'renovated' and they hadn't bothered. Imagine a) the waste of energy and b) the burst pipe opportunities in weather like this. The ground floor is peppered with airbricks so the CH pipes were near as dammit 'outside' !!

 

[IanDB]

Right, so they don't need bleeding any more. You can go round bleeding them every now an then initially until all the air is out of the system as you always get little bits left.

You say that you turned your TRVs up to 4 and the radiators got hot. What do you normally have them set to? If you turn them all up full do all the radiators heat up? If so do they heat up evenly (i.e. do they heat up at the same rate?).

 

[pekae]

Generally, I have them set around 3 (the bathrooms are 2-3, the bedrooms, 3 and the lounge 3-4) The dining room is still on 1(in fact almost 0 ) and is still scalding though !

They do seem to heat fairly evenly at a setting of 4-ish, but any lower and they are all over the place - i.e. some warm, some scalding and some not hot at all!)

Paul

 

[IanDB]

The dining room is still on 1(in fact almost 0 ) and is still scalding though !

The way that a TRV works is that as it heats up a valve expands and shuts down the water flow depending on what you've set the control to. A rad set to 0/1 should hardly get hot at all and this now sounds as though the TRV is stuck open. Which sounds a bit strange as in my (limited) experience they normally fail shut. Anyway, if you unscrew the TRV you should see a small metal post which should be able to manipulated up and down with a twisting motion (gently). I have used a small pair of pliers to do this in the past. If it moves OK then it is the TRV. You could check this by swapping it with a known working one. If the post is stiff then this gently movement may be sufficient to free it off.

The TRVs take a little while to work so initially your radiators might get quite hot but should then "settle down" to quote a well known phrase! I don't know how consistent TRVs are in operation (i.e. one to another) so you just set the control to what you are comfortable with.

Worth a try. (Don't worry, removing the TRV head does not involve losing water!!)

 

[pekae]

Thanks Ian. That sounds like a plan for this weekend then!
Failing that, I'll kick up enough fuss with the builders (they've still got one or two "snags" still to fix anyway. Thanks for all your help.

 

[robert99d]

are you sure he room is not colder than the valve is set to
if it is the rad should be hot