Will Draining the central heating mean the water heater wont work?

Joined
14 Dec 2013
Messages
99
Reaction score
3
Location
London
Country
United Kingdom
Hi,

Since we're not currently using the heating at present, I would like to embark on the project of removing and replacing the old radiators within our flat.

In which case, I thought the best way to go about this would be to drain the system and all the radiators.

We have a sabre 25 HE Plus combination boiler fitted.

If I were to drain the combi boiler, would it mean that I would have to turn of the heater and thus we wont have any hot water on demand?

Thank you
 
Sponsored Links
Joined
26 Jun 2004
Messages
64,092
Reaction score
4,620
Location
London
Country
United Kingdom
Yes.

But if you isolate the heating system under the boiler then the boiler will carry on providing hot water. Opinions will differ on if you should do that but I have never had any problems when doing it.

If you choose to do that make sure the system pressure is well topped up before you do that as you will not be able to repressurise with the system isolated.

Tony
 
Joined
14 Dec 2013
Messages
99
Reaction score
3
Location
London
Country
United Kingdom
Yes.

But if you isolate the heating system under the boiler then the boiler will carry on providing hot water. Opinions will differ on if you should do that but I have never had any problems when doing it.

If you choose to do that make sure the system pressure is well topped up before you do that as you will not be able to repressurise with the system isolated.

Tony
Thanks Tony

Is that difficult to do?

I know how to pressurise the system, as indicated in my photo.

but once or if i've drained the system, by releasing the radiator water from the lowest tap in the flat, wont that drop the water pressure to zero.

59309F9B-EC99-4C73-B623-E9D2BB0642D7.JPG 45850C73-1CCE-4CBE-BE4F-3BB231D8B48E.JPG IMG_1942.JPG
 
Joined
3 Nov 2006
Messages
26,587
Reaction score
2,812
Location
Bedfordshire
Country
United Kingdom
Make sure the expansion vessel is NOT isolated from the boiler. When the heating system water in the boiler is heated it will expand and if the expansion vessel is not available then the pressure will increase, possibly beyond the maximum acceptable pressure.

The heating system water inside the boiler transfers heat from the primary heat exchanger ( the flame heated one ) to the secondary heat exchanger that heats the hot water to the taps.
 
Joined
14 Dec 2013
Messages
99
Reaction score
3
Location
London
Country
United Kingdom
Make sure the expansion vessel is NOT isolated from the boiler. When the heating system water in the boiler is heated it will expand and if the expansion vessel is not available then the pressure will increase, possibly beyond the maximum acceptable pressure.

The heating system water inside the boiler transfers heat from the primary heat exchanger ( the flame heated one ) to the secondary heat exchanger that heats the hot water to the taps.
how do ensure the expansion vessel isnt isolated from the boiler?
 
Joined
26 Jun 2004
Messages
64,092
Reaction score
4,620
Location
London
Country
United Kingdom
This is a combi boiler containing its own EXV inside.

So just don't take it out of the boiler!
 
Joined
14 Dec 2013
Messages
99
Reaction score
3
Location
London
Country
United Kingdom
This is a combi boiler containing its own EXV inside.

So just don't take it out of the boiler!

if I release the lowest valve on the Central heating pipes (In the picture), that will drain the central heating and would I be right in thinking that this wont be taking it out of the boiler?
IMG_1942.JPG
 
Sponsored Links
Joined
16 Jan 2012
Messages
9,814
Reaction score
2,034
Location
Uk
Country
United Kingdom
how do ensure the expansion vessel isnt isolated from the boiler?
Unless, of course, the integral EV has not failed and been replaced with an external one. But, Tone, I suppose your Crystals have told you that isn't the case
 
Joined
26 Jun 2004
Messages
64,092
Reaction score
4,620
Location
London
Country
United Kingdom
In spite of the advice I have given him he seems very unclear.

Calling an engineer may be a better option for him.
 
Joined
14 Dec 2013
Messages
99
Reaction score
3
Location
London
Country
United Kingdom
IMG_1976.JPG
You do know which 2 valves under the boiler you need to shut off to isolate the boiler? I take it you are changing the radiator valves too?

Hi Madrab, my intention is to drain the radiator system, and remove existing radiators and replace and refill.

I figure I would need to turn off the values indicated by the yellow arrow, which would be the return. since there is only one value, turning this off will be sufficient?

thank you
 
Joined
8 May 2017
Messages
6,643
Reaction score
1,413
Country
United Kingdom
that is not your boiler old son. here is a simple trial , turn a hot water tap on and feel which pipe gets hot , that's the dhw outlet. think you will find its the one you marked " return ".
 
Sponsored Links
Top