Fitting additional expansion vessel

[MtM]

I am replacing an open vented oil boiler with a Worcester Bosch 25/32 system boiler with an integrated 10 litre expansion vessel fitted within the casing connected to the flow side of the integrated circulating pump. The house has 21 radiators and research indicates a system of this capacity needs an expansion vessel of 21-24 litres. I am about to buy and fit an additional 12 litre vessel next to the boiler but would be grateful for advice before doing so:

- Is the advice to fit an additional vessel correct or should I risk relying on the smaller integrated vessel alone?

- The integrated vessel connects on the flow side of the integrated circulating pump and yet advice suggests expansion vessels are best fitted on the return line. Should I connect it to the flow side just along from the existing one or connect to the return line? Would it then matter that the 2 vessels were fitted each side of the pump?

- what are the downsides of having 2 separate vessels on the same system, ie would they compete/conflict. Should I accept the higher cost and do away with the integrated vessel to fit a single 24 litre one external to the boiler - best on the return line as suggested?

MikeM

 

[AWheating]

the vessel size is calculated on system volume, so you need to fit whats required.

the boiler manufacture is the best place to ask about the position and preesure of the external vessel, phone there technical help line or read the boilers instructions. Do not remove the one in the boiler it will probably void the warrantee.

 

[MtM]

Thanks for the good advice, particularly about the warranty. The manufacturer and installation instruction are both vague about how you achieve the right expansion vessel volume. I'll go back and press.

Cheers

MikeM

 

[chris watkins]

Hope this help's, MtM

[DLMURL]http://www.rwc.co.uk/ABOUT_EXPVESS.html[/DLMURL]

 

[AWheating]

you need to calculate the total system volume........so the amount of water in the boiler,rads,pipework etc..... added together. The boiler manufacture will tell you what its expansion vessel's max system volume is. any extra needs to be taken up by the additional vessel.