Isolating DHW and CH in a combi boiler

Chunks

I have a Greenstar 440 combi boiler and was hoping to be able to work on my radiators (replace a couple and drain, remove, clean, refit the others) while still having the boiler ‘on’. Idea is to be able to supply only hot water as normal, while temporarily isolating the CH part ( so it can be drained). Can it be done?

Many thanks in advance.

vw100

Some boilers will not work if the system has been drained down. My old boiler carried on supplying hot water if the CH was drained. My new boiler does not do DHW if the CH has been drained.

southcoastrgi

The simple answer is no, your boiler needs to be pressurised, turn off the rad valves to remove the rads, or drain the system then turn the valves off & repressurise the boiler

Chunks

southcoastrgi wrote: »

.......or drain the system then turn the valves off & repressurise the boiler

Many thanks to both of you.

So, just to check, if I drain down the whole system and start work on the rads, so long as l turn off all the valves, l can re-pressurise the boiler and use it for DHW? There will be pressurised air in the flow and return ‘loop’ to the rads and pressurised water in that part of the boiler that handles the DHW side of things?

The boiler is on the ground floor and the way the pipework runs it seems to supply the upstairs first. If I drain the rads but not the boiler, there should be water in the boiler even with all the rads off.

What do you think?

vw100

Slight confusion. What you can do is turn of the rad valves on the pipework. This isolates the radiator. Then you can remove the radiator and drain the water into a bucket from the radiator. This will mean your system is still pressurised and the boiler continues to work. If you are working on the pipework then you need to drain the system down totally.

Chunks

vw100 wrote: »

....If you are working on the pipework then you need to drain the system down totally.

I am doing both. However, in my previous post l was referring to the fact that flow (pipework runs to the first floor) and return (pipework returns from the first floor) means that some water will remain in the boiler after draining the rads. The routing of the pipework gives me the opportunity to repressurise the boiler as l described in my last post.

What do you think?

vw100

If you drain the system, it empty's most of the water from the system. It is a closed loop system. If you want to work on the pipework and remove radiators and also have DHW say at the end of the day you need to re-fill the system, have the rad valves closed and use push fit pipe end stops where continuation of the pipes has been severed.

southcoastrgi

What vw said