3 port valve

I've discovered my valve works as follows:

heating only on - no problem.
hot water only on - no problem.

heating AND hot water on: heating works but hot water does not heat up.

Is this normal?

Nice pics but they don't really tell us anything.
I suspect it has always been like this and therefore, as a guess, I'd say there is not a connection from the "HW off" connection in the timer to the cyl 'stat satisfied and grey from valve.

No, you should be able to have hot water and heating at the same time. Assuming that both the room and cylinder thermostats are calling for heat of course.

Anything been changed recently?

Is there a manual regulating valve in the hot water circuit to the cylinder? has it been closed down too much, so that the resistance is too high preventing the water circulating when the radiators are on as it offers a lower resistance?

If you have a manual by-pass, has it been opened too much, so that there is insufficient flow left for the hot water and radiators at the same time?

Is the pump set at the correct speed for the size of the system?

If the system used to work correctly and nothing has changed, you can check the motorised valve by observing how it operates. If you are able to safely take the top off and see what happens to the mechanism, you can check its operation as follows.

1. Make sure that both the cylinder & room thermostats are calling for heat (on)

2. Switch on the hot water only at the programmer. The valve mechanism should sit at one side fully pulled across by the spring. (hot water only position)

3. Leave the hot water on, and get someone to switch the central heating on at the programmer, whilst you watch the valve. it should slowly start to wind its self across, but not fully. You should hear from one of the microswitches inside click. The valve should now be in the mid position. (hot water & heating)

4. Whilst the heating is still on, switch the hot water off, the valve should continue to travel in the same direction as before, and after a click from the second microswitch stop at the opposite side from where it started. (heating only)

5. With the heating still on, switch on the hot water and check the valve returns to the mid position

6. Finally switch off the heating, leaving the hot water on, and the valve should be pulled by the spring back to its original rest position

twgas said:

I'd say there is not a connection from the "HW off" connection in the timer to the cyl 'stat satisfied and grey from valve.

Click to expand...

But the op said the hot water is on.

Mike_e said:

heating AND hot water on: heating works but hot water does not heat up.

Click to expand...

There shouldn't be a live from the "HW off" at the programmer because the hot water is on. It might be the supply from the cylinder thermostat to the grey wire though, or possibly failure of the cylinder thermostat changeover contact. having said that they grey would only be energised if the hot water was up to temperature and the OP says that its not heating up.

Difficult to tell from the pics, but is the valve a three or two port - see pics?

View media item 5946 View media item 11762

Just to confuse it a bit more.....It might be a 3 port diverter (3 wire) and not a Mid Position (5 wire) valve.

So the question is.... how many ports does it have and how many wires does it have?

you can check the motorised valve by observing how it operates. If you are able to safely take the top off and see what happens to the mechanism, you can check its operation as follows.

Click to expand...

Thanks. Will try this tomorrow. (I'm assuming I CAN safely take the top off - will let you know if I flood the airing cupboard)

But the op said the hot water is on.

Click to expand...

Just to be clear, I meant the timer was set to 'on' and the cylinder stat calling for heat.

Difficult to tell from the pics, but is the valve a three or two port - see pics?

Click to expand...

Must be being dumb but.... the two pics look the same! How to differentiate 3 port from 2 port? Both pics seem to show a pipe with a joining spar (supply?) with a control box sitting on top.

.....It might be a 3 port diverter (3 wire) and not a Mid Position (5 wire) valve.

Click to expand...

Hmm. Yes, if you say so. How the h*ll would I know?!!

.....It might be a 3 port diverter (3 wire) and not a Mid Position (5 wire) valve.

Hmm. Yes, if you say so. How the h*ll would I know?!!

Click to expand...

post the number on the actuator could help.

Mike_e said:

How to differentiate 3 port from 2 port? Both pics seem to show a pipe with a joining spar (supply?) with a control box sitting on top.

Click to expand...

Easy. 3 port has 3 pipes going to it, 2 port has 2 pipes.

Am I the only on that can see 3 pipes going to the valve in the photographs?

Mike_e said:

.....It might be a 3 port diverter (3 wire) and not a Mid Position (5 wire) valve.

Click to expand...

Hmm. Yes, if you say so. How the h*ll would I know?!!

Click to expand...

Hint, count the number of wires?

stem said:

twgas said:

I'd say there is not a connection from the "HW off" connection in the timer to the cyl 'stat satisfied and grey from valve.

Click to expand...

But the op said the hot water is on.

Mike_e said:

heating AND hot water on: heating works but hot water does not heat up.

Click to expand...

There shouldn't be a live from the "HW off" at the programmer because the hot water is on. It might be the supply from the cylinder thermostat to the grey wire though, or possibly failure of the cylinder thermostat changeover contact. having said that they grey would only be energised if the hot water was up to temperature and the OP says that its not heating up.

Click to expand...

sorry!!!!!!!!!!!!