Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.

Running on a Worcester Junior 28i combi, pressurised system, if it makes
any difference.

--
(\__/) Bunny says NO to Windows Vista!
(='.'=) http://www.cs.auckland.ac.nz/~pgut00...ista_cost.html
(")_(")

"Mike Tomlinson" wrote in message
...

Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.


Hot water tends to rise. If your entry and exit pipes are both at the top
you'll get a shallow flow of hot water across the top and most of the
radiator will be full of cold water.

You would probably be able to get away with letting the hot water in at the
top and having the exit valve at the bottom, but I doubt you'd find a
suitable radiator anywhere off the shelf.

Suggest that as far as poss you bring your pipes down in a corner of the
room, along to the Rad, through the Rad, back to the same corner and back up
beside the in-pipe. Personally I'd insulate both pipes - it's the radiator's
job to release heat in the right places, not the pipes. And any pipes in the
roof space should be double and triple insulated with an extra layer of
insulation on top. Then buried in more insulation.

"Mike Tomlinson" wrote in message
...

Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.

The best way to do it, but a bit involved, is to run soft copper pipe from
the tapping to the bottom of the rad. Don't use a lockshield valve, use
chrome 15mm joints. Use a 15mm to 8mm reducer and file the pipe stop out.
Run the 8mm soft copper through and solder up. The 8mm pipe should be on
the flow. Hot in the bottom and cold out the top, then better heat transfer
thropugh tall rad. You don't want hot water at the top all the time as all
it will do is heat the air near the ceiling.

In article ,
Mike Tomlinson writes:

Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.

It doesn't matter if the hot enters top or bottom,
but the return must be from the bottom or most of
the radiator will remain cold.

Radiators are available with connectors top and bottom,
unless you have a particular designer one in mind.
You can run the pipes down the wall behind the radiator
to hide them.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sun, 03 Feb 2008 00:37:33 +0000, OG wrote:

You would probably be able to get away with letting the hot water in at
the top and having the exit valve at the bottom, but I doubt you'd find
a suitable radiator anywhere off the shelf.

Nonsense, most compact rads have tappings at all four corners.

--
John Stumbles

87.5% of statistics are made up

"John Stumbles" wrote in message
...
On Sun, 03 Feb 2008 00:37:33 +0000, OG wrote:

You would probably be able to get away with letting the hot water in at
the top and having the exit valve at the bottom, but I doubt you'd find
a suitable radiator anywhere off the shelf.

Nonsense, most compact rads have tappings at all four corners.

Fair enough .

Doctor Drivel wrote:

"Mike Tomlinson" wrote in message
...

Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.

The best way to do it, but a bit involved, is to run soft copper pipe
from the tapping to the bottom of the rad. Don't use a lockshield
valve, use chrome 15mm joints. Use a 15mm to 8mm reducer and file the
pipe stop out. Run the 8mm soft copper through and solder up. The 8mm
pipe should be on the flow. Hot in the bottom and cold out the top, then
better heat transfer thropugh tall rad. You don't want hot water at the
top all the time as all it will do is heat the air near the ceiling.



That's a good idea. Actually sounds a bit like some of those rads with
a single feed at one corner. My mother-in-law has them; one failure
mode is for the internal pipe to drop off...

However, as for the efficiency - if the rad is hottest at the bottom,
the hot air from there will rise up and the warmish water at the top
will be in warmish air, and there will be very little heat transfer. If
OTOH the hot is pushed downwards, the warmish bit will meet cold air and
work reasonably well, while the hot bit will meet warmish air and also
work reasonably well. This is counter-current heat transfer.

I wrote the above before looking up

http://en.wikipedia.org/wiki/Countercurrent_exchange

Andy

On Sat, 2 Feb 2008 23:44:43 +0000, Mike Tomlinson
wrote:


Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.

You must have the Return from the bottom UNLESS the rad has a baffle
inside it that forces the water down and then up the other side.
Unlikely but it might be worth a look.

The message
from Andy Champ contains these words:

However, as for the efficiency - if the rad is hottest at the bottom,

Radiators don't work quite like that. With a bottom feed the general
temperature drop is still from the top to the bottom. Even at the bottom
feed end you are unlikely to get a significant drop from bottom to top
as the ascending column is much narrower than the descending column.

--
Roger Chapman

In message , Mike Tomlinson
writes

Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.
Can't you run the pipes down the back of the rad and bring them out to
the sides? It'd probably look neater as well.

Running on a Worcester Junior 28i combi, pressurised system, if it makes
any difference.


--
Clint Sharp

"Andy Champ" wrote in message
...
Doctor Drivel wrote:

"Mike Tomlinson" wrote in message
...

Must radiators be bottom fed? I want to fit a tall, slim radiator in my
bathroom, almost the full height of the wall, and the only way to get
the pipes to it is through the ceiling, so it would be mounted upside-
down.

The best way to do it, but a bit involved, is to run soft copper pipe
from the tapping to the bottom of the rad. Don't use a lockshield valve,
use chrome 15mm joints. Use a 15mm to 8mm reducer and file the pipe stop
out. Run the 8mm soft copper through and solder up. The 8mm pipe should
be on the flow. Hot in the bottom and cold out the top, then better heat
transfer thropugh tall rad. You don't want hot water at the top all the
time as all it will do is heat the air near the ceiling.

That's a good idea. Actually sounds a bit like some of those rads with a
single feed at one corner. My mother-in-law has them; one failure mode
is for the internal pipe to drop off...

Because they were a type of rubber instead of soft copper. The one end
valves were great and if copper inserts are far better and one on each end.

"John Stumbles" wrote in message
...
On Sun, 03 Feb 2008 00:37:33 +0000, OG wrote:

You would probably be able to get away with letting the hot water in at
the top and having the exit valve at the bottom, but I doubt you'd find
a suitable radiator anywhere off the shelf.

Nonsense, most compact rads have tappings at all four corners.

The modern roll top rads do not.