Advice on replacing an external expansion vessel

[Nocomp]

Hello

I need to change the external expansion vessel connected to Baxi 105HE Combi boiler.

Is the procedure

Turn off power to bolier
Turn off cold water at mains supply
Empty hot water via lowest hot water tap until boiler pressure is zero
Unscrew old vessel and replace with new one
Turn cold water back on
Turn power on
Re pressure boiler system using fill loop
Turn on boiler and ensure its pressure set to 1.25 bar
Run hot water then central heating, check pressure stays the same
Turn ch and hw off, pressure should stay at 1.25 bar when boiler cold

Many thanks
Nocomp

 

[pallen5000]

It's not related to the hot water in the hot tap. You need to drain the radiators, then remove vessel, then fit new and repressive.

 

[Nocomp]

Thanks for that, I was trying to avoid draining the system via the rads, as non of them have a drain point on!

Nocomp

 

[Whitespirit66]

Yes, afraid your method will result in you getting very wet.

If you drop system pressure to zero through a rad bleed valve, you can do it by creating a vacuum in the system. Close the bleed valve, then carefully undo fitting to vessel with towels/ bucket underneath. If you're lucky, you will get a small amount of water then nothing. If not, will need to drain.

Sounds like a great opportunity to drain system and add a drain point or two. You should be able to remove a rad and attach a hose to one of the rad valves and drain that way.