Hive Wont Stop Heating

[microkid21]

Hi All - I have just installed a Hive Dual Channel Thermostat for heating and hot water. It is replacing an old Honeywell ST9400C and a Potterton mechanical type room stat.

First up In a previous life I was an electrician and as such consider myself able to understand and perform this work.

First off I traced back the old room stat connections to the wiring centre (12 way choc block in a double gang back box with blanking plate over it) in the airing cupboard. I disconnected it here (double checking with a meter that it was indeed the thermostat by testing continuity while rotating temp dial around) and linked out the terminals.

Only 4 connections were used in the Honeywell L+N (each with 3 wires on each terminal) - H/W On (3) and C/H on on 4. This matched the Hive so I replicated this arrangement.

Everything appeared to work ok - except when the Hive reaches temperature and the C/H green LED on the Hive receiver goes off the boiler stays on and will not switch off until I reset the power. I have checked all connections but I am stumped on this. Hive says CH & HW is off - both green leds off on receiver - yet boiler keeps running! Any pointers of suggestion of where to look. Thanks,

 

[Deleted member 267285]

Might be best posting a photo of the wiring, something must have changed.

 

[microkid21]

I will take some pics tomorrow - im not sure you will get much from them. It doesn't seem to follow any of the typical plans. I have noticed that the boiler will randomly start even when the hive is not demanding heat.

 

[Deleted member 267285]

I have noticed that the boiler will randomly start even when the hive is not demanding heat.

Could be stuck motorised valve and/link left in the boiler side.

 

[microkid21]

After spending hours today trying figure this out I finally discovered that somewhere between the kitchen (boiler, controller and isolator) and upstairs airing cupboard (valves, pump and wiring centre) someone has joined the controller C/H ON output and the boiler heat demand wires together. I know this because I have disconnected everything at both ends and have measured 0 Ohms between them! This results in the circuit energising and then self latching until the power is removed - or the old mechanical thermostat physically breaks the circuit. I have no idea where this 'adjustment' has been made but as I am not going to rip up floors to find it / replace it have decided to relocate the hive receiver to the airing cupboard, as I have enough cable cores coming back down to make this work without using the 'commoned' pair.

 

[MeldrewsMate]

Good. You have fixed it yourself.
I would have suggested getting out your multimeter and checking the SL feed to the boiler.
With the Hive receiver local to the connection box all should be much simpler.
If it helps, the Hive call for heat will switch to its relevant zone valve's brown wire.
Each zone valve's grey should be at L.
The orange wires are connected to boiler SL, and maybe to the pump, unless the pump is driven from the boiler (with pump overrun).
Here's your chance to tidy up that rat's 'nest' of wiring (pun absolutely intended).

 

[microkid21]

Good. You have fixed it yourself.
I would have suggested getting out your multimeter and checking the SL feed to the boiler.
With the Hive receiver local to the connection box all should be much simpler.
If it helps, the Hive call for heat will switch to its relevant zone valve's brown wire.
Each zone valve's grey should be at L.
The orange wires are connected to boiler SL, and maybe to the pump, unless the pump is driven from the boiler (with pump overrun).
Here's your chance to tidy up that rat's 'nest' of wiring (pun absolutely intended).

Yes I pulled out all the old wiring from the wiring centre and started again. I bought a new wiring centre box and remade all of the connections so nice and neat. My boiler has a pump run on so pump is controlled by boiler. Fortunately I had two runs of 3 core running up from from the boiler so had just a enough for power, call for heat and pump as with two cores linked together somewhere I couldn't use them. I tested it all with the meter after completely and everything is working perfectly now.