only hot water when central heating on

[andymac147]

3 port fully pumped heating and hot water with an indirect cylinder.i am only getting hot water when central heating is on,have changed the 3 port valve and still same problem,i am now thinking about the timer clock? could that be it?

[Wingedcat]

What else could it be? Not a lot! The best starting point is to test the programmer for correct outputs, i.e.

HW OFF HW ON CH OFF CH ON

For instance when the Hot Water is OFF, you should see +240V at the HW OFF output on the back of the programmer. (You won't need a CH OFF by the way, so don't worry about that one).

And check that the thermostats (both tank and wall, if fitted) are working correctly, and check that there are no other complications (by-pass valves etc) which are confusing matters.

There is quite a good explanation of a 3-way valve and how it works in the FAQ (I've learned a lot from it) but at the end of the day wiring the thermostats, the programmer and the 3-port valve is quite a complicated business so come back here if you get stuck.

Luke

[Roger Mills]

Has it *ever* worked properly? I presume that the 3-port valve hasn't been installed the wrong way round?

How much of the valve was replaced - the whole thing, or just the actuator?

[Lobster]

Just what I was going to say! I was once faced with the same problem; decided it was definitely the 3-port valve which I replaced, taking care to rewire it in exactly the same way, but it didn't help - eventually I had to get an engineer out who diagnosed the problem as incorrect wiring, which it clearly had been all along. They system had evidently 'worked' that way all along, with the radiator TRVs turned right down in summer.

David