EXPANSION VESSEL SIZING - TO BE PRECISE?

[jacobball]

how can i precisely calculate the correct sizing for an expansion vessel for my heating system. - is there any rule of thumb? i know it is better to get a larger one, and an undersized one is dangerous.

 

[GPlumb]

Undersized ones are not dangerous they just won't do the job. For the average domestic system a 12l one does the job.

 

[jacobball]

thanks i'll get a 12l one then.

i thought if i put an undersized one in and the water expanded then there may be an explosion as not enough room for it to expand and no where for it to go to...

 

[GPlumb]

The PRV (pressure release valve) will stop anything dangerous happening. If you have the space an 18l vessel is a good buy too, this would allow adding more rads or bigger ones without any problems.

 

[jacobball]

yes of course, the PRV would kick in. Is it not a bad idea to badly oversize the vessel though, as it may not work properley? I'll take into account your advice about an 18L one but I am not really looking to add any extra radiators in the near future, so maybe well really oversizing it will make it not work properley?

 

[GPlumb]

Over sizing will have no ill effects. 12L should be fine in your case tbh.