Replacing a room thermostat

[doitall]

Two possible faults.

No power on the grey.

The micro switch is duff.

Check the wires are making a good connection, redo the grey if necessary.

Also open the MV manually, and see if it makes any difference.

 

[SamNotSpam]

Right, checked and rechecked, rewired, but no power on grey. Which surprises me as I had one of the valve actuators replaced about 8 weeks ago (by a proper heating engineer) and I'd have thought that any problems would have shown up then.

EDIT forgot to do the manual MV check, doing that now.

 

[doitall]

If you check the wiring strip you'll see the grey is common to both valves, and the hot water one works, so could be a broken wire.

Does the mv open when the htg is calling.

The brown drives the mv open, and the grey puts power on the orange, via the micro switch.

 

[SamNotSpam]

Hold on, new info - I realised I was checking the wrong grey (bloody tangle of wires!) and the CH one is showing about 120v.

 

[doitall]

All the browns and greys in the same connector should have 230vac.

 

[SamNotSpam]

Only getting 1-2 volts off the brown coming from the Honeywell programmer, so I guess tomorrow morning's job will be to replace the cable!

 

[doitall]

Only getting 1-2 volts off the brown coming from the Honeywell programmer, so I guess tomorrow morning's job will be to replace the cable!

Explain the above.

Does the hot water work as it should.

Is the browns and greys in the wiring center connected in some way to a brown in the programmer.

 

[SamNotSpam]

Yes, HW is working. On the block that has two browns and a grey at the bottom, and a brown and a grey at the top - one of the browns at the bottom connects to the Live terminal on the programmer.

 

[doitall]

Does the heating valve open when the htg is calling, check the slider for any resistance.

Back to the block, one of the browns should be from a fused spur, or is the brown supplying 230vac from the programmer to the wiring center.

 

[SamNotSpam]

One brown from the fused spur, one from the programmer.

No resistance on the valve, so no it's not open - no whirring when I turn off either, so definitely staying shut.

 

[doitall]

No resistance on the slider means the valve is open.

Is there resistance when you power the system down.

Are the actuators inter changeable, if so can you swap them over, (remember where the wires go)

 

[SamNotSpam]

Yes, there's resistance when the power's off.

Swapped them over, the one that was originally on the CH system still had no resistance.

I don't understand, everything was working fine with the old room stat. I was only changing over to get more control of day/night temps.

Thanks for all your help so far, I'm going to return the system to its original state with the original room stat, hopefully it'll work. Then I think I'd better have some dinner and return to this fresh tomorrow morning.

 

[doitall]

You have missed something obvious otherwise the hot water wouldn't work.

Check all the connections for broken wires etc,

You have a switch live from the room stat.

 

[SamNotSpam]

Sod's law applies, the old room stat died so I can either have heating that's on or off with no temperature control, or no heating at all. Last night was cold, and I think my family hates me!

Right, the new stat is on. I have live, the red wire, connected to LX. I have switched live, the yellow wire, connected to L1. When there's demand on the CH, the yellow wire is live. When I turn down the room stat to below the current temperature (I hear the click of it 'turning off') the yellow is still live and the CH continues running. Same when I turn the room stat off completely.

 

[doitall]

what happens when you take the yellow wire out of L1, remember it could be live, but does the heating stop.