How to wire Hive single channel

[T4ken]

I’m trying to replace Honeywell ST9420c controller with hive single channel for a combi boiler .
I’m thrown by there being two sets of wires , one has an additional black wire and grey wire , the other twin and earth.
I only need Neutral, Live, Live looped to 1 , and 3 connected but which wire do I disregard ? Black or grey ?
The fact it was a time clock to also control hot water threw me as it’s a combi boiler and oddly when I tried running a timed programme the water went on and off even though it’s a combi

 

[stem]

Sometimes combi's have a pre-heat function that allows them to have hot water ready to go. In this case, the HW channel of a dual channel programmer is used to select the 'on' times for the pre-heat.

If that is the case with yours, then you need a dual channel Hive if you want to retain that function.

What did the HW channel of the ST9420C do?

You can see the Hive Dual Channel and Honeywell ST94000 series have exactly the same connections.

Don't worry about the 2 sets of N&L, some installers wire to the programmer from the fused spur (1 cable) and then another cable goes to the boiler (second cable)

 

[T4ken]

Thank you
The boiler has a reservoir not a tank in the house we left the time clock to continuous for water , when we turned it to timed the water went cold and didn’t heat on demand .
I’m hoping that means I’m correct in getting the single channel as advised by Hive as no hot water tank present.
So the question is , which wire do I use for heating , black or grey ? (Both have brown sleeving at the end just to confuse things further (or is that because both need to be connected as per your installers using 1 cable to controller then second to boiler ?

 

[stem]

If you look at the diagrams I posted above:

Terminal 3 = Hot Water on
Terminal 4 = Central heating on

Both wires have brown sleeves on to indicate that they are being used as live wires.

If you use the Hive single channel, the wiring is completely different.

Both sets of N&L stay as they are in N&L
Link Hive L to Hive 1 Common
The CH wire now in 4 goes to Hive 3 Heating On

But you wont be able to heat the water in the reservoir using a Single Channel Hive.

The idea of the reservoir using the HW channel is that it is set to be on during the daytime when you're using hot water and off over night when you don't need hot water to save fuel keeping it hot overnight. It wouldn't work if it was only on for an hour our two during the day.

 

[T4ken]

Thank you , I wish I’d asked you first before I spoke to Hive and on their advice , bought the single channel!
Will wire for single channel and give it a try and if it’s no use I’ll need to get a dual channel I guess

 

[stem]

Yes, sadly Hive failed to realise the reservoir is a form of hot water cylinder, albeit a small one.

There is a distinct possibility that without the hot water on wire connected, you won't get any hot water whatsoever. Although you could get around it by putting the hot water on wire (Now in the Honeywell 3) in the Hive 1. Common. That way it would be 'on' permanently, but it's not really a good idea to do that, and personally I wouldn't recommend it.

As Hive have incorrectly advised you, they should let you exchange it for a dual channel and then you could set it up properly to switch the reservoir heating off overnight and save energy.

 

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Thanks I bought from tool station and as the box is open I can’t return
I’ve found someone with a dual channel who wants a single channel - result! So will wait for the dual channel
Thanks very much for your help