Can anyone help please. My neighbours radiator in the bedroom is getting
hot at top, but not the bottom. It is a puzzle to me why. Any suggestions?
Thanks
Neil

In article ,
"Neil" writes:
Can anyone help please. My neighbours radiator in the bedroom is getting
hot at top, but not the bottom. It is a puzzle to me why. Any suggestions?

If the outlet is cold, then the flow is too small.
If the outlet is hot, then the radiator is silted up.

--
Andrew Gabriel

On Fri, 13 Jan 2006 21:02:33 -0000, "Neil"
wrote:

Can anyone help please. My neighbours radiator in the bedroom is getting
hot at top, but not the bottom. It is a puzzle to me why. Any suggestions?
Thanks
Neil



This one is a classic.

Basically the system has accumulated sludge consisting of iron
compounds from corrosion of metal components - principally the
radiators.

Inside the radiators, the flow speed past any given point is fairly
slow, whereas in the pipes it is faster. Hence, the sludge is
circulated and deposited typically in a triangular pile at the bottom
of some or all radiators. Thus, heating water doesn't reach these
areas and they feel cool. You can easily feel the shape and size of
the pile in each.

All of this comes about through a combination of

- possible poor system design where the pump causes water to be pumped
over the header tank vent into the tank or it is sucked down instead,
thus introducing fresh oxygen and promoting corrosion
- lack of a corrosion inhibitor added to the system normally annually.

Eventually, the radiators will deteriorate to the point of developing
holes and leaking.


The fix is to thoroughly drain and clean the system.

This can be done by draining completely and then taking the radiators
off and outside one by one. Containers to catch the water and sludge
and plastic bags rubber banded onto the disconnected radiator tails
are important since sludge is an indellible stain on furnishings.
Once outside, they should be thoroughly flushed with a pressure washer
ot mains water hose.

The system should be flushed at each radiator position such that
anything in pipes is delivered out as well.

After this, the system can be reassembled and at that point it is a
good idea to add a flushing agent. THis is a chemioal additive which
is run hot in the system normally for a week. It will pick up and
dissolve a lot of remaining material. After this, the system should
be drained and thoroughly flushed again and finally a corrosion
inhibitor added.

An alternative approach is to do powerflushing. This can be bought
as a service - BG love to do this and relieve customers of £500-800
for the privilege. One can rent the equipment and buy the
chemicals from tool and equipment rental places for considerably less.
This technique works by pumping a chemical solution around under
pressure and forcing the sludge through. Efficacy may vary.




--

..andy

inhibitor added.

An alternative approach is to do powerflushing. This can be bought
as a service - BG love to do this and relieve customers of £500-800
for the privilege. One can rent the equipment and buy the
chemicals from tool and equipment rental places for considerably less.
This technique works by pumping a chemical solution around under
pressure and forcing the sludge through. Efficacy may vary.




--

.andy

Thanks for the advice. With it been one radiator do you think taking that
one of and flushing it out may solve the problem? I am a bit reluctant to
attempt the whole system for them.
Neil

"Neil" wrote in message...
Can anyone help please. My neighbours radiator in the bedroom is getting
hot at top, but not the bottom. It is a puzzle to me why. Any
suggestions?

An accumulation of sludge at the bottom of the radiator. Remove the
radiator, take it outside and flush it through with a hosepipe. That should
do the trick.

You may wish to consider adding extra inhibitor to the expansion tank before
refilling though.


--
Best Wishes
Simon (aka Dark Angel)
"Dark Angel's Realm of Horror" - http://www.realmofhorror.co.uk

On Fri, 13 Jan 2006 22:30:45 -0000, "Neil"
wrote:


inhibitor added.

An alternative approach is to do powerflushing. This can be bought
as a service - BG love to do this and relieve customers of £500-800
for the privilege. One can rent the equipment and buy the
chemicals from tool and equipment rental places for considerably less.
This technique works by pumping a chemical solution around under
pressure and forcing the sludge through. Efficacy may vary.




--

.andy

Thanks for the advice. With it been one radiator do you think taking that
one of and flushing it out may solve the problem? I am a bit reluctant to
attempt the whole system for them.
Neil



Do note Andrew Gabriel's point as well though. One radiator *can" be
cold at the bottom due to very low flow because the lockshield or
radiator valve (or both) are set too low in comparison with others.
This would manifest itself as warmth up the end of the radiator where
the flow enters, warm across the top and then cool towards the bottom
and return side.

If it turns out to be this, then try adjusting open the radiator
valves on that radiator. If that doesn't work, then you can try the
balancing procedure in the FAQ, which will involve reducing the flow
through other radiators to divert more water through the misbehaving
one. I'll warn you that this is a time consuming procedure, though.

However..... If it turns out to be sludge (telltale "pile" in the
bottom), then I suspect that you will find two things.

1) If you feel all the radiators shortly after the system comes on,
you will probably find sludge to some degree in all in the form of a
cool area. If there isn't too much, the radiator warms eventually by
conduction through the steel.

2) When you drain the system, the water will be filthy black.

If you have the first scenario, then just flushing the bad one will
eventually mean that there will be some further build up and you have
to do it again.

So really it is better to do it properly if possible.


Another short cut is to just do the one radiator and then use the
flushing agent in an attempt to deal with the rest. A bit
unpredictable, though.

One thing that is important is to make sure that there is no pumping
over or sucking down in the feed tank. Go up into the loft and ask
the neighbour to start and stop the pump on the heating by turning the
CH off and on. You are lookig for dribbling out of the vent pipe or
listening for a gurgling sound. Make sure that there is about 75-100
mm of water in the bottom of the tank. It should comfortably cover
the feed pipe exit when the system is cold and not approach the
overflow when hot. If water overflows then it gets replaced by fresh
and this becomes another cause of corrosion. Adjust the float valve
if you need to do so.

If pumping over or sucking down is suspected, try to trace where the
feed pipe from the tank and the vent pipe join the main circuit. They
should connect no more than 150mm apart and should definitely not be
on opposite sides of the pump. If this bit is wrong it becomes a
plumbing job. You can cheat by reducing the pump setting sometimes
but often that results in inadequate flow to the radiators.

However, it is very important to fix this problem if present or the
corrosion will continue.

The other essential part at the end is to add corrosion inhibitor, but
there is no point unless the system is already pretty clean.

Above all, so make sure that you protect the neighbour's decorations
and furnishings by having copious amounts of plastic sheet, old
newspapers and towels etc. THe water will stain and it will not come
out. For containers under the ends of the radiator, new cat litter
trays from the supermarket work well.

Good luck.


--

..andy

"Neil" wrote in message
...
Can anyone help please. My neighbours radiator in the bedroom is getting
hot at top, but not the bottom. It is a puzzle to me why. Any
suggestions?
Thanks
Neil


Thanks to Andrew, Andy and Dark angel for help and advice. I am going to
give it a go this morning.
Neil

On Sat, 14 Jan 2006 08:30:36 -0000, "Neil"
wrote:


"Neil" wrote in message
...
Can anyone help please. My neighbours radiator in the bedroom is getting
hot at top, but not the bottom. It is a puzzle to me why. Any
suggestions?
Thanks
Neil


Thanks to Andrew, Andy and Dark angel for help and advice. I am going to
give it a go this morning.
Neil



Great. Do please come back with the outcome.


--

..andy