could anyone shed some light on this one for me? i need what i thought was a 3 port valve for my heating/dhw, looking in a plumbing catalogue for a similar honeywell valve i was somewhat stumped when i saw both 3 port and mid position. The descriptions read pretty similar so what are the differences. i presume it's probably quite simple. This is on an open vented system. Any help much appreciated.
Both valves are 3 port. But one is simply a diverter. The mid position valve however flows water to both systems simultaneously when CH is turned on. The hot water will usually be satisfied first due to lower flow resistance which then allows the valve to divert fully to the central heating. When central heating is satisfied valve then diverts back fully to hot water. It has a spring return mechanism when de-energised to return to the HW port.Hope this helps .Regards r2d2.