Room Thermostat overriding controller.

[dcb0]

Hello,

I've moved a four wire room thermostat and it now seems to override the controller for the system. That is to say that if the room thermostat is calling for heat then the heat comes on regardless of whether the Central Heating is on at the controller or not.

The Thermostat is a four wire version with Red, Blue, Yellow and Earth wires with ACL marked on it. There is an 'LWC1 Wiring Centre Wiring Guide' available.

It includes guides for various systems, but I don't know which type of system we have. The options on the wiring guide are as follows:
'C-Plan Type Systems, Valve on Gravity HW Return.
'Mid-Position Spring Return Valve Systems (Biflo, Y-Plan, etc.)'
'Spring Return 2-Valve Systems 22mm. (Twinzone, S-Plan, etc.)'

All of these three plans call for the Room Thermostat to be wired as follows:
Wire 1 (Com) in Thermostat -> 3 in Wiring Centre
Wire 2 (Call) in Thermostat -> 2 in Wiring Centre
Earth -> Earth
Wire 4 (Neutral) in Thermostat -> Neutral in Wiring Centre

View media item 78188
The image appears upside down, I'm not sure how to reverse it for here.

Can you help me wire this in correctly?
Many Thanks,
David

 

[St0rmer66]

You have a mid-position/Y-plan for starters. It's too late for my weary eyes to be looking at it in detail upside down though, sorry! . Will have another go tomorrow if nobody else has helped by then!

 

[picasso]

View media item 78194

 

[D_Hailsham]

The Thermostat is a four wire version with Red, Blue, Yellow and Earth wires with ACL marked on it. There is an 'LWC1 Wiring Centre Wiring Guide' available.

I assume you are running a new cable from the LWC1 to the stat.

Did you make a note of which colour wire went to which terminal at the stat and at the wiring centre?


Which motorized valve do you have?


PS If the stat is made by ACL it is very old. Might be a good idea to relace it with a modern digital stat which will be more accurate and give better control over the cental heating. The Honeywell DT90E is good.

 

[St0rmer66]

You need to check that: Number 9, black wire, is the "CH On" (switch heating on timer, should go live). Number 8, blue wrapped wire is "HW Off". Number 16, yellow, is the satisfied from the cylinder start (turn it down and it should go live).

 

[dcb0]

The Thermostat is a four wire version with Red, Blue, Yellow and Earth wires with ACL marked on it. There is an 'LWC1 Wiring Centre Wiring Guide' available.

I assume you are running a new cable from the LWC1 to the stat.

Did you make a note of which colour wire went to which terminal at the stat and at the wiring centre?


Which motorized valve do you have?


PS If the stat is made by ACL it is very old. Might be a good idea to replace it with a modern digital stat which will be more accurate and give better control over the cental heating. The Honeywell DT90E is good.

I made only a mental note of the order of the wires in the Stat (which certainly wasn't good enough). I would be happy to replace both the wire and the Stat. Thanks for the recommendation, I'll have a look for that.

Is there a standard or convention for the colour of the wires?

The motorized valve is labelled Drayton, Mid Position Actuator.
Actuator code MA1.

 

[St0rmer66]

If the thermostat is bringing the heating on and off when you turn it up and down then it's definitely not faulty. It's a wiring issue or... As we haven't even discussed yet, a faulty timer! Could be sending live down the CH ON permanently. If terminal 9 is permanently live then that would be it.

 

[dcb0]

You need to check that: Number 9, black wire, is the "CH On" (switch heating on timer, should go live). Number 8, blue wrapped wire is "HW Off". Number 16, yellow, is the satisfied from the cylinder start (turn it down and it should go live).

Thank you, I've checked these with a volt meter between the connection and the neutral. Here's what I found:

Number 9, black wire is at 230v whether or not the CH is on at the controller.

I guess that might mean that the Stat is wired in correctly and the problem is elsewhere. I didn't think that I had changed the stat wiring. However we've just moved into the property and it is perfectly possible that it wasn't working correctly beforehand.

Number 8, Blue wrapped wire is at 230v when there's no HW call from the controller, it drops to 106v when the controller is calling for HW.

Number 16 Yellow wire, with the tank at 65 degrees and the HW off at the controller this was live. It remained live when the cylinder stat was turned down to 50 or turned up to 80 degrees. With the HW on at the controller the voltage was 108v regardless of whether the cylinder stat was at 50 or 80 degrees.

Perhaps this indicates that the controller is faulty? I haven't done anything with the controller except take it off to look at the faceplate behind and put it back. However there was an electrical fault in the circuit supplying the controller which meant that it was supplied with a low voltage of about 120v for a while. While the low voltage was supplied to it it just flickered and didn't operate. However it appears to be operating correctly as far as the screen, programming options and clock are concerned.

 

[dcb0]

If the thermostat is bringing the heating on and off when you turn it up and down then it's definitely not faulty. It's a wiring issue or... As we haven't even discussed yet, a faulty timer! Could be sending live down the CH ON permanently. If terminal 9 is permanently live then that would be it.

Thanks St0rmer66. I was just wondering that too. I'd begun my previous post before measuring, and I hadn't seen what you'd written here. Even though the controller appears to be working fine (on the outside as it were), it looks like that's where the problem is.

So it might be a case of replacing all the controls. It would bring the system up to date, since the boiler itself is pretty new.