difference between 3 port & mid position valves

[angelf]

what is the difference between a 3 port valve & a mid position motorised valve?

Can one be replaced with the other?

If not why not?
Cheers

[Mr Smyth]

A 3-Port valve lets you select HW or Htg whereas a mid position valve lets you select HW, Htg or both HW and Htg.

Yes you can change a 3-Port to a mid position valve but there will be some simple changes to your wiring.

Hope this helps

[45yearsagasman]

Both of these have "3 Ports" ie inlet port and hw and heating outlet ports.
A mid position valve is able to allow water to flow to HW only,CH only and to both at once by holding the valve in the Mid Position,These valves normally have 5 wires. A 3 port diverter normally has 3 wires and can only supply CH on its own or HW on its own but not both together.These valves as such are interchangeable with some wiring alterations.

[angelf]

thanks Mr Smyth & 45 year gas man