In an earlier contribution to this discussion,
Dark Angel wrote:

My father, DIY "genius" that he is, was having some trouble with his
central heating system and was told by the service engineer that the
problem was the head on one of the 2-port valves.

Anyway, turned out the next door neighbour had a spare motorised
valve head from when he had his sytem altered and it happened to be
the same make (Danfoss). However, when I examined what my father had
done it turned out the head he was given was for a 3-port valve
sytem, which he's fitted onto the 2-port valve body.

Apparently the cable colours are all the same so he's just wired it
up the same way. The valve is on the hot-water side of things, so has
anybody got any ideas what i liable to happen when he goes to turn
the heating back on?

Assuming that it will fit physically, the electrics are totally different. A
2 port-valve is either open or closed. A 3-port valve can be half-way open
(mid position). But probably the biggest difference is that a 2-port
actuator has 2 wires for the motor, and 3 totally separate wires connected
to a switch which toggles when the valve is open - and which is used in an
S-Plan system to switch on the boiler and pump. A 3-port actuator *doesn't*
have separate circuits - they're all mixed in together. So you'll get very
peculiar results. When I get time, I may look in more detail as to actually
what will happen. But you're likely either to end up with the boiler not on
when it should be - or on when it shouldn't be. It may not actually do
anything dangerous - just undesirable!
--
Cheers,
Set Square
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