Drayton MiTime Programmer Issues

12 Jan 2010
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United Kingdom

Recently had a new central heating system installed - something is not quite right with it though. I've had a heating engineer out to look at it twice but still not resolved.

I have a Drayton MiTime T740R programmer with two MiStat N1 10R thermostats - one for upstairs and one for downstairs heating.

When I turn the downstairs heating on, the valve opens but the pump and boiler doesn't activate. It's only when I then turn on the upstairs heating or the hot water, does the pump and boiler activate and heat flows to my downstairs heating as the valve is already open.

On the programmer, the upstairs heating zone states the current temperature and the thermostat temperature, as it should. But this information is not displayed for the downstairs heating zone. Instead, this information is stated for the hot water zone on the programmer.

This obviously isn't right. I'm wondering if the downstairs thermostat needs to be re-bound to the downstairs heating zone on the programmer? Or is it the wiring that is wrong - could there be two wires from the downstairs heating valve and the hot water valve that need to be switched over?

Any advice gratefully received.

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If the downstairs valve opens but the boiler and pump don't switch on, then either the micro switch in the valve is faulty or the orange and grey wires are not connected correctly in the wiring centre, they connect to the same place as the orange and grey wires of the other 2 valves. The system appears to be programmed or at least has the zone labels wrong. Surely the installer can work out what the issues are?
OK, I've managed to rebind it so the programmer shows the correct temperatures for each zone. However, still got the problem of the boiler and pump only activating when the hot water is on.

Having looked at the wiring diagram for the MiTime T740R and compared it to the actual wiring, there does seem to be a couple of wires out of place. I am going to try and switch these around so it corresponds to the wiring diagram. However, the one thing that is puzzling me is the diagram only shows 4 cores for the boiler wiring but I actually have 5 cores - L, N, E and a black and a grey core. Which one is the switched live? And what do I do with the 5th wire? Do I just put it in a spare terminal in the wiring box?
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The grey and black wires might be volt free connections to switch on the boiler, none could be live. If that is the case, connecting 240V to there will not do the boiler any good...

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