pipe size and motorised valve

[jjj]

I have a fully pumped system that was previously converted from a gravity system - so the feed and return to the hw cylinder coil are still in 28mm pipe.

There's no control of water temp, so I want to add a 2-port valve into flow and put in a cylinder stat.

I've noticed a big difference in the price of motorised valves in 28mm compared to 22mm ones e.g. screwfix sell a danfoss 22mm valve for £35, whilst a honeywell 28mm valve from discount heating costs £59.

Would it be ok to reduce the 28mm flow to 22mm over a metre or so, to fit a

22mm valve?

thanks,

Jim

[Ed Sirett]

Yes since the system is fully pumped (on both CH and HW primaries). Not otherwise. Make sure that the valve won't block the vent pipe!

[JJJ]

Great. pump duly ordered..

it's also been converted to a pressurised system with an add-on pressure vessel, and the vent pipe's been removed from the top of the flow pipe (only an automatic bleed valve on it now), so I'm assuming I'm ok with putting the valve in downstairs on the feed going up.