Is there a rule of thumb for calculating the vertical distance between the boiler and the expansion/feed tank in a vented twin pipe central heating system?
All boilers have a have a maximum working pressure so as long as the head pressure created by the height of the F & E tank does not exceed this I do not see why it would matter.
Most even specify the max working head in meters
10 M gives you 1 bar so you would have to go some to create something bad
As long as all system components working pressures are not exceeded then this would be fine
Many thanks to Carl83 for the reply. However, my concern was focussed on the extent to which expansion of the water in the system when hot would cause an overflow into the header tank with the potential for siphonage rather than the pressure as such. The pressure is a factor which I had not considered so thanks for that.
Any overflow and siphonage problems are caused by poor system design specifically in relation to the positioning of the pump and its proximity to the expansion and feed pipe. Any such issues have no connection to the height of the header tank.
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by Edpaterson » Mon Aug 31, 2009 8:01 am 
