Expansion/feeder tank height

[Tinkler]

looking to change boiler...manufacturer says the minimum head of pressure between header tank and boiler heat exchanger is 2m - Would this be to the header tank bottom or to the water level inside?

Have only got 1.71m presently to header tank bottom and have had no problems with present boiler. Is this critical as I will struggle to move the tank higher - maybe 150mm at most. Moving the new boiler to a lower level is not an option either.

 

[corgiman]

why not install a sealed system boiler no tank no bother

 

[Tinkler]

why not install a sealed system boiler no tank no bother

A conversion to a sealed system has been mentioned...may have to consider it if nothing works out! Reluctant to go with a sealed system as rads are old...fear a pressurised system could force leaks...nowhere down below to situate a fill loop, would have to keep going into loft to check/top-up..and that can mean regular trips according to some folk I know!...plus an open vent system is very easy to fix yourself unlike a pressurised one - would save on calling the likes of yourself!

 

[corgiman]

nope a sealed system is easier to drain and refill by miles

no airlocks etc

but if you think you can then good luck to you

 

[Tinkler]

C'mon guys...a qualified guess will suffice.

 

[corgiman]

the water level is where the MI's are taking their measurements

 

[chrishutt]

I expect 2 metres is an approximate figure, so I wouldn't worry too much if you can only achieve 1.7 metres. I think the minimum pressure is needed to avoid negative pressures occurring upstream of the pump, although it might also relate to avoiding localised boiling in heat exchanger. Probably best to check with the manufacturer's technical dept.