New Tank Stat does not seem to work

[Lizardman]

I have a Potterton Sumprima 30 with the PTT2 tank stat unit which crumbled over time leaving live wiring - so replaced as per above. I also have Hive Heating which has been working fine.

I have replaced the PTT2 with Standard Honeywell L614a tank stat and wired up as per instructions and installed a flat plate where the PTT2 was, terminated the live etc.

All went fine however now my Central Heating will only work with Hot Water on now and not on its own. We think we had done all the wiring correctly and checked and double checked

Could this be a faulty Diverter which is not switching on CH when called but still diverting the water flow when HW is on? Appreciate any advice

The hive boiler side receiver only has HW On/CH On wires - There is no “off” wires present.

Mid Diverter is Myson Power 3-way. Which I have a hunch is knackered and causing this

Appreciate any help!

 

[CBW]

You have a mid position valve but no hot water off, this is your problem.

 

[Lizardman]

Does this mean running a new wire from hive receiver “HW off” up to the new trunk box and hook up to orange wire will fix it? Or which wire