Central Heating Boiler vent Pipe

[walt4545]

Hi,
I am in the process of fitting a Stratford Tf50 Boiler replacing my old open fire and back boiler. There are a couple of things I need help with.
The old pipes from the back boiler to the hot water cylinder are 22mm and the Stratford shows 28mm pipes on its technical information going tfrom the boiler to the hot water cylinder.
Will it be okay to use the existing 22mm as they are all in good condition.
Or is the 28mm critical.
The other thing I wanted to check is does a vent/gravity feed pipe always have to be higher than the gravity return pipe at all points on its way to the hot water cylinder and does it matter if the vent pipe/gravity feed ppe is longer than the gravity return pipe. I will be fitting a new hot water cylinder which has indirect hot water heating fittings and may have to alter the exixting pipework around the cylinder.
Many thanks for your time and advice.
All the bey best
Walt

 

[LUNAT]

HI

it is hard to tell with out looking at the job but 22mm should be adequate
and vent pipe does not have to be higher.

 

[walt4545]

Hi,

Many thanks for the advice. You were absolutely right it worked perfectly.
One other thing I wanted to check is do I need to fit a gravity radiator as I do not want to upset the balance in the system or do I have to have a gravity radiator.
Once again many thanks as I really would not have been able to get this sorted without your help.
All the very best
Walt