Horstmann 425 Diadem To Hive Dual Channel

[Will2007]

Hi
I am new to forums although have read them previously, including the following link and I have copied it but my Hive hearing does t seem to work.
https://www.diynot.com/diy/threads/changing-horstmann-425-diadem-to-hive-dual-channel.491978/

I have attached the pics of my HOrstmann wiring and the wall thermostat.

Your help would very much be appreciated.
Thanks
Will

 

[stem]

There are two main steps. The Hive dual channel will replace the Horstmann 425 and the existing thermostat will need decommissioning.

Your Horstmann wiring is as below. terminals 3 or 6 are not used.

The existing wires should be disconnected from the Horstmann and reconnected to the Hive as follows:

INSTALL THE HIVE
Earth is a straightforward transfer to the Hive earth tether
N is a straightforward transfer to the Hive (N)
The red wire currently in the Horstmann terminal 2 goes to the Hive (L) terminal. Discard the two existing red links
The Horstmann 1 green wire is 'Hot water on' = Goes to Hive terminal (3)
The Horstmann 4 yellow wire is 'Heating on' = Goes to Hive terminal (4)

DECOMMISSION THE EXISTING THERMOSTAT
Trace the existing thermostat cable from the thermostat back to its origin. Make a note where the 'red' and 'yellow' wires are connected, then disconnect and remove the entire cable. Next, insert a wire link between the terminals where the 'red' and 'yellow' wires have just been removed from. Finally make sure any other wires remain as they were and that terminals are tight.

 

[Will2007]

That’s great thank you.
How do I trace the wires from the imd thermostat as they in the wall, where are they likely to go?
Thanks

 

[stem]

Unfortunately, over a forum it's difficult to advise. The cable would have been installed the way that whoever installed it found the easiest. So, it's usually a matter of following it to see where it goes, generally straight up the wall and into the void between the ceiling and floor above, to a wiring centre in the airing cupboard.

Having said that, the yellow wire is the 'switched live'. So, assuming that your system is an S-Plan with two motorised valves (You haven't given any info about your system) it will be connected to the brown wire of the motorised valve controlling the central heating. So you might be able to trace it like that.

As an alternative, if you don't mind leaving the existing thermostat in place, simply moving the yellow wire from the thermostat terminal (3) and putting it in with the red wire in terminal (L) will achieve the same thing. The existing thermostat will then have no control of the heating and will have just become a junction box.

 

[Will2007]

I have done the 2nd option to see if it all works as it should, before ripping it all out.
I have a floor standing old boiler, an ideal Mexico in the garage with a hot water tank on the airing cupboard.
I’ll let you know if it all works ok.

 

[Will2007]

The heating doesnt come on when request, the radiator nearest get boiler makes a slight noise, as does the boiler bit there is no heat from them.
Could this be due to the s plan you spoke about?
Thanks

 

[stem]

The S-Plan is a type of plumbing system. The wiring suggests this is what you may have. If you do, you will have two of these (or something similar) motorised valves. One controlling the heating and the other for the hot water. Whatever you have, the wiring won't change. If it worked with the Horstmann it will work with the Hive. Electrically speaking, you are just swapping wires over functionally like for like.

Untitled

• stem
• 26 Mar 2010
• 6

But, having said that, you may not have an S-Plan. The wiring would also apply to a 'gravity fed hot water system with pumped central heating' In which case you won't have any motorised valves. If you have this second type of system you need to set the Hive to 'gravity fed mode' to get it to work. See the Hive instructions "Important Information Gravity Fed Part Pumped" for further details. In this case you will not be able to have the central heating 'on' without the hot water being on also.

Only you can tell us what sort of system you have installed in your home.

 

[Will2007]

Ho
Ive changed the settings to gravity fed and it works spot on now.
Thank you very much for this.