I want to change a radiator on my combi based central heating system WITHOUT having to drain dowm the system. I propose to use a freezing mixture on the inlet and outlet pipes and then put the radiator in place. (The old radiator has already been removed and the pipes temporarily closed off.)
My problem is will the pressure of the combi system blow the ice plugs before I can attach the new radiator? Any comments gratefully received. Thanks

"chopsaw" wrote in message
...

I want to change a radiator on my combi based central heating system
WITHOUT having to drain dowm the system. I propose to use a freezing
mixture on the inlet and outlet pipes and then put the radiator in
place. (The old radiator has already been removed and the pipes
temporarily closed off.)
My problem is will the pressure of the combi system blow the ice plugs
before I can attach the new radiator? Any comments gratefully received.
Thanks


--
chopsaw

Why not relieve the pressure during the operation. I suppose there are
various ways to do it, the most obvious being to press the overpressure
relief valve button and shoot a few litres of CH water out of the overflow
pipe.
You can always repressurise it from the filling loop afterwards.

Andy.

Andy wrote:

Why not relieve the pressure during the operation. I suppose there are

Yup good plan...

various ways to do it, the most obvious being to press the overpressure
relief valve button and shoot a few litres of CH water out of the overflow
pipe.

I would not be so keen on that however. It only takes a small bit of
crud to get lodged in the overpressure valve and you will have a leaking
system. Better to save the overpressure valve for what it is supposed to
do.

Draining a litre or two out of a drain point, a radiator tail
connection, or even a bleeding valve will do the same trick.

You can always repressurise it from the filling loop afterwards.

Indeed.


--
Cheers,

John.

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"Andy" wrote in message
...

"chopsaw" wrote in message
...

I want to change a radiator on my combi based central heating system
WITHOUT having to drain dowm the system. I propose to use a freezing
mixture on the inlet and outlet pipes and then put the radiator in
place. (The old radiator has already been removed and the pipes
temporarily closed off.)
My problem is will the pressure of the combi system blow the ice plugs
before I can attach the new radiator? Any comments gratefully received.
Thanks


--
chopsaw

Why not relieve the pressure during the operation. I suppose there are
various ways to do it, the most obvious being to press the overpressure
relief valve button and shoot a few litres of CH water out of the overflow
pipe.
You can always repressurise it from the filling loop afterwards.

Andy.

NEVER open the relief valve unneccessarily. You have a major chance of it
failing to reseat correctly with an ensuing slow pressure loss problem. The
drain valve is the way to go.
To the OP most oil combis have isolating valves between boiler and heating
pipework. Shut these and open the air vent on the rad you are working on,
catching the small amount of water released. this will have effectively
depressurised the rads without affecting the boiler. If the old valves are
good and the rad is the same size there may not be a need to do this. Only
if you wish to change the valves or alter the pipes. Do one at a time or you
may find the system empties itself around you.