Hi, hope anyone can help before I take the plunge and buy/arrange
plumber!

I have a largish room (14 x 13ft, high ceilings) with a single 700mm
x1400mm Stelrad double convector...

The rad gets very hot - although not as hot at the very bottom than
the top (we have a newish Greenstart 28 boiler and thats OK) but as
the house has 3 outside walls (solid walls, no cavity) and a large
window (the rad is opposite the wall to the window also as its a low
curved bay) - the room takes AGES to warm up to 21-22m, our desired
temp.

Ive looked on the BTU calc sites, and due to the high ceiling, walls,
window etc, the different cals reckon anywhere between 9,500 and 12000
BTu's for the room!

The Stelrad rad at the moment is a double convector but 10+ years old
(again, gets hot and isnt leaking, but Im sure they have got more
efficient over the years!)

I could actually fit a 700mm x 1800mm rad (double convector) for about
£150 + fitting which would then cover more of the room (it would sit
more central with only minor pipe extension I think)

Am I right in thinking that this would help/resolve my problem??

Anyone have an idea on how long a plumber would need to replace??

If I way off the mark and may ber wasting my money, please let me
know! - I realise that the rad may need a 'flush' but as its 10+ years
old and seemingly under 'BTU'd for the room, I was wondering if
replacement was the best course?

Many thanks

wrote

Hi, hope anyone can help before I take the plunge and buy/arrange
plumber!

I have a largish room (14 x 13ft, high ceilings) with a single 700mm
x1400mm Stelrad double convector...

snip..................

Fitting one larger rad in a cold room may well achieve the desired
temperature quicker - but you will still suffer thermal gradients
across/around the room.
For greater comfort I would consider adding a radiator as far from the
existing as possible and also located to warm "drafts".
If you have suspended wooden floors, this is achievable without too much
hassle - concrete floors like ours is another ball game.

Phil

In an earlier contribution to this discussion,
wrote:

Hi, hope anyone can help before I take the plunge and buy/arrange
plumber!

I have a largish room (14 x 13ft, high ceilings) with a single 700mm
x1400mm Stelrad double convector...

The rad gets very hot - although not as hot at the very bottom than
the top (we have a newish Greenstart 28 boiler and thats OK) but as
the house has 3 outside walls (solid walls, no cavity) and a large
window (the rad is opposite the wall to the window also as its a low
curved bay) - the room takes AGES to warm up to 21-22m, our desired
temp.

Ive looked on the BTU calc sites, and due to the high ceiling, walls,
window etc, the different cals reckon anywhere between 9,500 and 12000
BTu's for the room!

The Stelrad rad at the moment is a double convector but 10+ years old
(again, gets hot and isnt leaking, but Im sure they have got more
efficient over the years!)

I could actually fit a 700mm x 1800mm rad (double convector) for about
£150 + fitting which would then cover more of the room (it would sit
more central with only minor pipe extension I think)

Am I right in thinking that this would help/resolve my problem??

Anyone have an idea on how long a plumber would need to replace??

If I way off the mark and may ber wasting my money, please let me
know! - I realise that the rad may need a 'flush' but as its 10+ years
old and seemingly under 'BTU'd for the room, I was wondering if
replacement was the best course?

Many thanks

As always, you need to start by reviewing the insulation and draft proofing,
and doing all you can to reduce the heat losses. When do have done that you
need to re-calculate the heat losses and find a suitable radiator to match
them.

Looking at ny Stelrad brochure, a 700x1800 P+ has a rated capacity of 11,993
BTU/Hr (3.5kW). That is for a Delta T of 60 degC so, if your Delta T
(difference between room temperature and mean rad temperature) is 55 degC
(more likely than 60), you'll need to downgrade the rated value by about
10% - bringing it down to about 10,800 BTU/Hr.

[The P+ is a double radiator with one lot of fins between the sections. If
you need even more heat, a K2 of the same size (which has double fins) has a
rated capacity of 15,373 BTU/Hr - or about 13,800 when downrated]

If you do increase the radiator capacity, you'll need to make sure that the
pipework is adequate. It generally reckoned that 15mm pipe will support 6kW
of heating capacity. The above mentioned K2 is 4.5kW - so you wouldn't want
much else sharing the same pipes.

If you fit a larger radiator in essentially the same position as the
existing one, it probably wouldn't take a plumber all that long to fit. He
*may* be able to do it without draining down if he freezes, shortens and
caps off the existing pipes and then extends them again when the new rad is
in place.
--
Cheers,
Roger
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Thanks for that, we do have 15mm pipes and this rad (downstairs
frontmost room, furthest away from boiler) doesnt have any other
radiator after it.

Hopefully it wont involve the complete draining of the system....but I
will expect the worse

Any idea how long it *should* take if a drain, refill (and additive
readded) would take?

Ive been warned of a £200 plumbing for this as its a days work????

Thanks


Looking at ny Stelrad brochure, a 700x1800 P+ has a rated capacity of 11,993
BTU/Hr (3.5kW). That is for a Delta T of 60 degC so, if your Delta T
(difference between room temperature and mean rad temperature) is 55 degC
(more likely than 60), you'll need to downgrade the rated value by about
10% - bringing it down to about 10,800 BTU/Hr.

[The P+ is a double radiator with one lot of fins between the sections. If
you need even more heat, a K2 of the same size (which has double fins) has a
rated capacity of 15,373 BTU/Hr - or about 13,800 when downrated]

If you do increase the radiator capacity, you'll need to make sure that the
pipework is adequate. It generally reckoned that 15mm pipe will support 6kW
of heating capacity. The above mentioned K2 is 4.5kW - so you wouldn't want
much else sharing the same pipes.

If you fit a larger radiator in essentially the same position as the
existing one, it probably wouldn't take a plumber all that long to fit. He
*may* be able to do it without draining down if he freezes, shortens and
caps off the existing pipes and then extends them again when the new rad is
in place.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!- Hide quoted text -

- Show quoted text -

In an earlier contribution to this discussion,
wrote:

Thanks for that, we do have 15mm pipes and this rad (downstairs
frontmost room, furthest away from boiler) doesnt have any other
radiator after it.


But does it have any others *before* it, after it splits off from the 22mm
main flow and return pipes?


Hopefully it wont involve the complete draining of the system....but I
will expect the worse

Any idea how long it *should* take if a drain, refill (and additive
readded) would take?

Ive been warned of a £200 plumbing for this as its a days work????


I'm sure that many plumbers could make it last a day if they have to do a
drain-down.

When I partially drain my system, I aways collect the water and put it back
into the F&E tank so as not to lose the inhibitor or introduce a load of new
air.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
wrote:

If you do increase the radiator capacity, you'll need to make sure that
the pipework is adequate. It generally reckoned that 15mm pipe will
support 6kW of heating capacity. The above mentioned K2 is 4.5kW - so you
wouldn't want much else sharing the same pipes.

My understanding was that a 15mm pipe supplying 6Kw is only recomended for
offices, factories and workshops, it requires a water velocity of approx 1
M/sec which would generate water flow noise in the pipes to be at an
unnaceptable high level in a domestic situation.
You should design for a max velocity of 0.75M/sec, a 15 mm pipe will only
supply just over 3Kw for a 11deg C drop across the rad, or am I just too old
fashioned and out of touch these days.
Regards
Don

"Donwill" wrote

You should design for a max velocity of 0.75M/sec, a 15 mm pipe will only
supply just over 3Kw for a 11deg C drop across the rad, or am I just too
old fashioned and out of touch these days.

If old fashioned leads to better (in this case quieter) system design, I'm
with you every step of the way.

Phil