Problem

A radiator attached to a pressurized, combi-fed, central heating system
doesn't get hot (it gets just slightly warm).

- I've bled it but this makes no difference.

- The radiator is fed from what is essentially a spur off the same pipes as
a second radiator, which does get very hot. Turning this "hot rad" off, in
the hope that all the water will go to the cold radiator, doesn't achieve
the desired result.

- I've checked and now both the radiator tap, and the valve at the other
end, are full open (assuming they're working - perhaps they're not?).

- Finally, this radiator is on the ground floor, but fed from the first
floor so crap could easily be coming down the pipes, blocking them and never
getting away again.

So, what next? "Reinstall the entire pipework" is not an option so I intend
to "flush" the pipework. Before I start, any tips? I'm planning to (after
turning off the heating)...

1. Close of the pipes to the radiator (there are values which allow this -
no idea why they were originally installed!)

2. Close off the radiator taps

3. Remove the radiator

4. Flush the radiator with a hose

5. Connect a hose to the radiator taps

6. Get the wife to open the radiator taps whilst I maintain pressure using
the "fill" loop from the boiler. I'm hoping this will provide enough
pressure to flush crap out along the hose and clear the taps.

7. Replace the radiator.

Clearly I'm no heating expert, but any suggestions for making this as
painless an exercise as possible would be appreciated.

Thanks,
Paul DS

In article , Paul D Smith
writes

So, what next? "Reinstall the entire pipework" is not an option so I intend
to "flush" the pipework. Before I start, any tips? I'm planning to (after
turning off the heating)...

1. Close of the pipes to the radiator (there are values which allow this -
no idea why they were originally installed!)

2. Close off the radiator taps

3. Remove the radiator

4. Flush the radiator with a hose

5. Connect a hose to the radiator taps

6. Get the wife to open the radiator taps whilst I maintain pressure using
the "fill" loop from the boiler. I'm hoping this will provide enough
pressure to flush crap out along the hose and clear the taps.

7. Replace the radiator.

Sounds fine but why not try it with the radiator still in place to start
with?

Points to note:

1. You'll need to find (or fit) a drain point to get rid of the flushing
water.

2. You'll need to isolate the boiler in order to stop the flow going
through it instead of flushing the rad and to stop it filling up with
crap. Some boilers have isolation valves but I just fitted a 22mm full
bore ball valve in the return of mine to do this.

3. Close off the rad valves to all the rads you don't want to flush then
open up the filling loop to flush through the rad in question, being
careful to watch the pressure and ease off before the system pressure
relief valve pops off at 3 bar (avoid this as any crud in the system may
affect the sealing of this later).

4. Repeat for each rad in turn if you want.

5. You may wish to run the system with some flushing fluid in it for a
day or so before you do this as it will loosen up any crud.
Alternatively, try this first to get some flow going, then use the
flushing chemical as the chemical wont reach the blocked area until you
get some flow going.

6. If this fails then take off the rad but protect the room like a scene
from Dexter, plastic ever and old blankets to mop any spills (they will
inevitably be black (iron oxide) and will stain anything they touch).
Invert the rad before moving (open ports to the top to avoid the risk of
spills).
--
fred
it's a ba-na-na . . . .

On 12/12/2012 11:38, Paul D Smith wrote:
Problem

A radiator attached to a pressurized, combi-fed, central heating system
doesn't get hot (it gets just slightly warm).

- I've bled it but this makes no difference.

- The radiator is fed from what is essentially a spur off the same pipes
as a second radiator, which does get very hot. Turning this "hot rad"
off, in the hope that all the water will go to the cold radiator,
doesn't achieve the desired result.

- I've checked and now both the radiator tap, and the valve at the other
end, are full open (assuming they're working - perhaps they're not?).

If they are conventional taps then its rare for them to fail stuck -
especially if they feel like they are working and wind from closed to
open with a definite stop at each end. (if the handle twiddles endlessly
then that is a different matter).

With thermostatic valves however, its not uncommon for the pin to get
stuck down in the closed position. Taking the head off the valve to
check will usually tell you. Sometimes the pin is of a design you can
grab with pliers and work free. With some a sharp tap from a small
hammer will do it.

- Finally, this radiator is on the ground floor, but fed from the first
floor so crap could easily be coming down the pipes, blocking them and
never getting away again.

So, what next? "Reinstall the entire pipework" is not an option so I
intend to "flush" the pipework. Before I start, any tips? I'm planning
to (after turning off the heating)...

1. Close of the pipes to the radiator (there are values which allow this
- no idea why they were originally installed!)

Valves perhaps? What sort of valves? and are you sure those are working?

2. Close off the radiator taps
3. Remove the radiator
4. Flush the radiator with a hose
5. Connect a hose to the radiator taps
6. Get the wife to open the radiator taps whilst I maintain pressure
using the "fill" loop from the boiler. I'm hoping this will provide
enough pressure to flush crap out along the hose and clear the taps.
7. Replace the radiator.

Yup if you make up an adaptor to connect the hose to a valve, then you
can flush from the filling loop and out the hose. To concentrate efforts
on just that rad you will need to close the valves to all the other rads
- then you can have full mains flow through that pipe. Do the same for
the other rad tail.

Clearly I'm no heating expert, but any suggestions for making this as
painless an exercise as possible would be appreciated.

It sounds like you are on the right track.

An alternative slightly less complicated method to try first might be to
connect a hose to the normal drain point, open it and then turn on the
filling loop. If you have shut off all the rads except the one in
question, you should force through any blockages and give it a fairly
decent flush into the process. (wait until the water runs clear - which
may take several minutes)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
John Rumm writes:
On 12/12/2012 11:38, Paul D Smith wrote:

1. Close of the pipes to the radiator (there are values which allow this
- no idea why they were originally installed!)

Valves perhaps? What sort of valves? and are you sure those are working?

I've had a couple of cases of gate valves which could be screwed
closed, but not opened anymore as the gate was no longer attached
to the shaft. You can't directly tell this without removing them
for a post mortem, although you might infer it from other indications
of a lack of flow.

Now all replaced with full bore ball valves (although you have to
remember to operate these periodically, or they seize up).

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

On 13/12/2012 10:41, Andrew Gabriel wrote:
In article ,
John Rumm writes:
On 12/12/2012 11:38, Paul D Smith wrote:

1. Close of the pipes to the radiator (there are values which allow this
- no idea why they were originally installed!)

Valves perhaps? What sort of valves? and are you sure those are working?

I've had a couple of cases of gate valves which could be screwed
closed, but not opened anymore as the gate was no longer attached
to the shaft. You can't directly tell this without removing them
for a post mortem, although you might infer it from other indications
of a lack of flow.

Yup, been caught by that a few times!

Now all replaced with full bore ball valves (although you have to
remember to operate these periodically, or they seize up).

I think on this last fiddle I managed to eliminate most of the gate
valves... IIRC there is only one left now, and only after I had the
system all up and running did it dawn on me that its actually pointless
anyway as its after the zone valve on the cylinder heating loop -
presumable installed in the original system to allow the cylinder
circuit to be balanced with the rads. Since the new system never runs
the rads and cylinder at the same time, its more decorative than
anything else!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

....snip...

OK, this might help someone! Tried to sort this out and discovered...

1. Neither gate valve seals, so they're a complete waste of time.

2. I cannot get the water out of the pipework without totally draining the
heating (see #1)

3. I did managed to get a drain cock which fits into the radiator where a
bleed valve would sit. I managed to fit this buy turning off both radiator
valves, checking the bleed valve to confirm the radiator valves had sealed,
and then fitting the drain cock (needing some of that sealing goo around the
threads).

That was the good news - the bad news was that on turning on the radiator
valves (independently) with the drain cock open and my wife working the
filling loop to maintain pressure, one site of pipes flushed nicely (black
crud all round) but the other flowed slowly for a while and then blocked
completely.

So, off to get the nice plumber out. Emptying and sorting this is within my
skill range, but a professional will do it quicker, better and will know how
to sort nay more gotchas (I hope!).

Paul DS.

On Wednesday, 12 December 2012 12:37:07 UTC, fred wrote:



6. If this fails then take off the rad but protect the room like a scene

from Dexter, plastic ever and old blankets to mop any spills (they will

inevitably be black (iron oxide) and will stain anything they touch).

Invert the rad before moving (open ports to the top to avoid the risk of

spills).

--



An Aqua Vac or similar is very handy for capturing the water to be drained from a radiator. Close the inlet/outlet valves and, with vac running and held near the TRV, gradually undo the TRV-to-rad coupling. The water will start to trickle out and most will be caught by the vac. If you are feeling brave you can increase the flow by opening the bleed valve.

Richard