Creating a vacuum (?!) on a sealed CH system

[stu550]

Evening all

Excuse the terminology to start with...

I have a sealed/ pressurised (is that the same thing?) heating system where i'd like to cut into the pipes at ground floor and put stop ends on as a temporary measure until the plumber comes and installs some new rads after some alterations have been made by a builder starting on Monday. I'll then be draining down 3 rads and removing the existing pipework.

Do I need to release the pressure in the expansion vessel to start with?

One pipe (the flow) has a zone valve in near where its being cut which should make it slightly easier.

I assume I should shut all other rad valves as well as this valve.

Should I drain the radiators i'm removing first or will this not make a difference/ make it worse?! Some are at the same level, some are at first floor.

Any other tips?!

thanks.

Stuart

 

[Burnerman]

Just depressurise the system by bleeding water out of a radiator valve, and when the gauge reads zero no more water will come out. When you cut the pipe there will be a little water there but not much and you can pop on a stop end quickly. The system can be repressurised later via the filling loop to get the rest of the rads working.
Check the air pressure in the expansion vessel when the pressure is zero too - in fact its better to disconnect it completely.
John

 

[stu550]

Thanks John, very helpful. When you say bleeding water, do you mean out one of the top normal bleed valves on a rad as opposed to a drain valve?

Assume this should be on one of the ones i'm removing?

 

[Burnerman]

A radiator bleed valve is probably the safest (but slowest) method of letting water out....no rubber washer to fail and so on. Any radiator will do! If you have a drain down cock on the system then that will be much quicker but fingers crossed that it seals off again!
Personally I wouldn't go near the pressure relief valve on the boiler itself - asking for problems with those!
John

 

[45yearsagasman]

You will also have to close off any auto air vents.