Loft extension - radiator not getting very hot

leroyJ

We had our loft extension done in the summer, a bedroom and a bathroom was added.

The radiator in the bedroom doesn't get very hot.  It gets warm, but it's noticeably less-hot than all of our other radiators. 
The plumber from the loft extension company has been round a couple of times to balance the system.  This has involved turning down the loft bathroom radiator (which does get very hot) letting the bedroom radiator get some heat, then turning back on the bathroom radiator.
For a while the bedroom radiator wasn't getting any heat at all.  Now it does, but it's still not "piping hot" (and not enough to heat the room).  However the plumber seems to think that as it is getting some heat, his job is done.
He also claims that it's not "piping hot" due to new materials used by radiators manufactures, which for health and safety reasons are not as hot to touch.  I'm sceptical about this, I called the company we bought the radiators from and they had never heard of this before.

I'm trying to work out what to say to the plumber, and I'm also wondering if whether the radiator is not specced correctly.  We were told all we needed was 5000 BTU to heat the room, even though online calculators say almost double this.  When I initially questioned their calculations, they said that not a lot of heat was required for a loft room, as heat rises etc etc.

Also, our boiler is in the kitchen on the ground floor, so the loft bedroom radiator is the last one to get heat.  
The boiler is possibly slightly under-powered, it's a 24kw heat-only, and it was installed before the loft extension.  However we've tried turning off other radiators but it hasn't made a noticeable difference.

Ebe_Scrooge

leroyJ said:

The plumber from the loft extension company has been round a couple of times to balance the system.  This has involved turning down the loft bathroom radiator (which does get very hot) letting the bedroom radiator get some heat, then turning back on the bathroom radiator.

That's not balancing a heating system.  My first thought was that the system would need re-balancing if you've added extra rads, but that's not how you do it.  The whole system needs to be done, and whilst not particularly difficult, it does take a fair amount of time.

It's true that the boiler may be struggling to supply enough oomph to cope with the extra rads - but my first thought would be to get a plumber in who actually knows what he's doing to balance the system, then take it from there.  The guy who fitted it sounds somewhat less than proficient from what you've said.

housebuyer143

As above, you need to correctly balance the entire system. My rads were like this and balancing it correctly has solved the problem.
He's not interested because it's a tedious and annoying job. 

leroyJ

Thanks, I'll get on his case.

I had assumed that the rest of the house was already "balanced", and it was just the new ones that need adjusting.  But now I know otherwise  

FreeBear

leroyJ said:  He also claims that it's not "piping hot" due to new materials used by radiators manufactures, which for health and safety reasons are not as hot to touch.  I'm sceptical about this, I called the company we bought the radiators from and they had never heard of this before.

If the other radiators in the house are getting piping hot, then the new one should also be the same. The materials used in the manufacture of radiators has not changed - It is still steel (aluminium or copper for expensive ones).

One possibility is that the circulation pump can't deliver sufficient water to the loft. But most pumps have a "head" rating of 8m - Worth checking the label on the pump.

Ebe_Scrooge

leroyJ said:

I had assumed that the rest of the house was already "balanced", and it was just the new ones that need adjusting.  But now I know otherwise  

Yep - if you add or remove rads, the whole system needs to be re-balanced.  Actually, you can do it yourself, if you're so inclined - there are tons of guides and videos you'll find online.  And you don't need much in the way of specialised equipment.  But it really is a tedious and time-consuming job.  Not difficult, just tedious.

Far simpler if you can get the folk who did the extension to actually come back and finish the job properly!!

Although, I guess they could picky, and you'd need to start going through the contract to see what actually was and was not included in the price ......

plumb1_2

There are radiators that don’t gets hot to touch, LST.  Surprised your rad supplier never heard of them.
I used to fit them years ago, in schools, offices and pubs etc.

Anyway it could be a number of issues, unbalanced system, undersized pipe work, and as FB says worth checking the pump rating.

leroyJ

plumb1_2 said:

There are radiators that don’t gets hot to touch, LST.  Surprised your rad supplier never heard of them.

I only asked about the specific radiator we had purchased. We used the same company for all our other radiators a while back, so they would have had to have changed to somekind of new material since then. Obviously it’s just an excuse our plumber made up.

FreeBear said:

One possibility is that the circulation pump can't deliver sufficient water to the loft. But most pumps have a "head" rating of 8m - Worth checking the label on the pump.

Thanks. Our pump has a “max head” of 6m. Possibly that’s not enough to reach the loft? Not quite sure how I’d measure. 

Like I said the bathroom radiator (in the loft) gets hot. But the bedroom one is probably about 6 metres away from that (horizontally). So maybe it’s just a bit too far.

Anyway, thanks for all the advice. I’ll feed this back to the plumber tomorrow.

macman

Have you tried increasing the pump speed to cope with the extra head required?
Is it more than 6m from the pump to the highest rad?

leroyJ

macman said:

Is it more than 6m from the pump to the highest rad?

Is the measurement the direct line between the pump and the rad?  I.e. as the bird flies, straight up?  
As I've measured the rad to be about 4 metres above the pump.  But in terms of the pipework going up to the loft, it will be a lot more than that.

leroyJ

Just thought I'd update this as we found one of the main issues causing the radiator not to heat up.
It was installed the wrong way round!

After contacting the shop we bought the radiator from, they said:
"Also due to the unique flow diverter built within all Revive column radiators the flow MUST to be on the same side as the permanent blank which is the opposite side to the air vent bleed valve."

We got the plumber back to switch the rad over, and it now heats up much better.  (Although still some balancing was required on the other rads).