last 400mm to the boiler reduced in size?

[mike42]

I want to fit a crossover to the return next to the boiler. 28mm copper crossovers are seemingly very difficult/expensive to obtain as is a 28mm pipe bender.

Currently flow and return are both 28mm and have a long run (15M ?) before they get to the airing cupboard where the cylinder and MVs are.

The boiler flow/return terminals are 22mm and currently the 28 is reduced about 100mm away.

My question is could I have about the last 500mm in 22mm of the returns instead of the 100mm there is today? The flow would remain at 28mm for its entire length except the last 100mm.

 

[fixitflav]

Unlikely that would be a problem. Most systems have 22mm boiler flow and return, with 22mm headers, dropping to 15mm (or less) at the rads. But why is it 28mm, is it a conversion from a gravity HW?

 

[mike42]

It probably was a gravity 30-50 years ago but about 25 years ago someone added a pump and moved the boiler into the garage and ran a pair of 28mm back to the house where the pump is. Possibly 20M long so presumably they thought it would maintain flow/pressure that way. Not sure.

 

[fixitflav]

It probably was a gravity 30-50 years ago but about 25 years ago someone added a pump and moved the boiler into the garage and ran a pair of 28mm back to the house where the pump is. Possibly 20M long so presumably they thought it would maintain flow/pressure that way. Not sure.

Thought so. I still think you'll be OK