Horstmann 425 to Hive

[David Horne]

Hello,

I’ve just moved house and found myself with a Ideal Mexico Super ideal C125 boiler, Horstmann 425 control and Sunvic thermostat. I’d like to replace the control for a hive but need some assistance with the wiring please.
I’ve attached a couple of pictures.
Thanks in advance!
David

 

[stem]

This has been asked before, you can find an example that should help you here.

There should be a diagram on your Sunvic thermostat somewhere; maybe the lid, that shows where the L, N and Switched L wires are terminated. The L and SL need to be bridged / connected and the N isolated safely.

EDIT
As you don't describe the type of plumbing the controls are connected to, I forgot to add: If you have a fully pumped system with motorised valves then the Hive is already set for that. Much less common now, but if you have an older system with just pumped central heating & natural (gravity) circulation of hot water, the Hive should be changed to gravity mode. The Hive instructions will tell you how to do this

 

[David Horne]

Hi,

thanks for your reply. I did see that post but I wasn’t too sure what to do within my own thermostat. Linking out L and SL makes perfect sense.
Thanks again.

David

 

[stem]

Ideally it's best done at the origin of the cable if you know where it is. Note where the individual wires are connected, disconnect the cable, then insert a link between the terminals where the L and SL to the thermostat have just been removed from.

The old thermostat and its cable can then be removed completely.

 

[David Horne]

Hi looking into this further, there is only a live and neutral on the thermostat with a resistor.

 

[bernardgreen]

there is only a live and neutral on the thermostat with a resistor

 

[ianmcd]

As above you dont have a neutral , you have a live and a swtched live

 

[stem]

As it is switching a load well under 13A it should have had a neutral connected to terminal 4 as shown in the diagram, so its working accuracy wouldn't have been very good. However as has been said, it's only the L and SL you are interested in. If there was a neutral wire it wouldn't be required anyway .....

the N isolated safely.