Hive 2 Wiring

8 Dec 2015
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United Kingdom
I have a warm air heating system (Johnson and Starley Hi Spec J50) with a hot water tank. This has a built in single timer control for both hot water and heating with a wired room thermostat. My current set up is the hot water controlled by the built in timer with the switch in the ‘timed position’. The heating switched to ‘on all the time’ with the room thermostat being a programmable type. This allows the heating to be fully controlled and timed by the thermostat making programming independent from the hot water.

I have bought a Hive 2 heating and hot water controller, but the wiring does not seem to be directly compatible with my current set up. The question is, is there a work around?

The existing timer has live & neutral but the diagram does not show live linked to any of the other connections like a conventional timer. Not really sure if this is possible but would this work?

Wire 9 to Hive N
Wire 7 to Hive L
Wire 2 to Hive 1 & 2
Wire 1 to Hive 3
Wire 5 to Hive 4

Wire 3 redundant (fan only for summer never used)
Wire 4 redundant (timer replaced)

Hive 2 wiring.jpg
Wiring Diagram (On=left side, Timer=right side).jpg

The existing 2 thermostat wires on the main block I assume would be bridged as the Hive would take over this.

Any help would be really appreciated as I'm determined to sort this out.
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I would say you you'd have been better off with a single channel timer just doing the heating. I hope your heater isn't a modair variant as it won't work properly with hive
Thanks for the quick reply. Yes it is a modair variant. Could you explain what the problem is with a modair variant?
It's very likely your existing room thermostat isn't just a bog standard temperature sensitive switch but instead contains a thermistor which allows a current to flow representing the actual room temperature. Can you post some pictures of the room stat?

If so, the boiler won't take kindly to having 240V from the Hive receiver connected to the same terminals.

I'm not sure how easily an ordinary thermostat could be attached to a modairflow boiler.
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The original 'thermista-stat' was just a dial with no temperature markings. This has been replaced by the newer one shown below to allow the heating to be programmed independently. I think this just clicks on or off to maintain the temperature but maybe this is not how it is meant to work with the modairflow. It looks like the modairflow has 3 different on conditions but I may have lost this function with the newer thermostat / timer.

The thermista-stat connects to the main board rather than the programmer as shown in the bottom of the diagram. I assumed if this connection was bridged it would pass control to the Hive if it could be wired in to replace the built in timer. This was when I thought it was simply an on or off signal to the boiler. I was not intending wiring the Hive to the thermista-stat connections.

Can you identify the boiler terminals where the BG thermostat is connected?

Hopefully it is switching a 230V signal to fire up the boiler but you need to be certain of this before connecting up the Hive in it's place. Do you have a multimeter?
The BG thermostat is just wired to the existing wiring in the front room which connects to the main board as circled in red.

I can check with a multimeter at the weekend. It looks like this connection Is intended for the thermista stat to allow the boiler to run the 3 different on conditions depending on the room temperature: -

1. Gas Continuous + fan high speed.
2. Gas at regular intervals + fan low speed.
3. Gas at short periods + fan intermittent low speed.

I'm guessing my BG thermostat is simply an on or off signal (it clicks) so maybe I just have no.1 on condition, although the gas does cut out with the fan being continuous when it is first warming up. I will try and figure this out.

I was thinking the connection circled in red could be bridged to effectively give a constant on signal but then wire the Hive in place of the built in timer. The problem is understanding the difference in the way they are wired. My initial suggestion for the wiring would mean sharing the old wire number 2 between the water and heating. My thinking was that the Hive would control the return signals for these via old wire number 1 (HW) & 5 (CH). Could this work?
So the BG thermostat is effectively simply shorting out the thermistastat connections when demanding heat and that works OK.
I would want to check at the boiler end that this is definitely where the present thermostat is connected then measure the voltages present at terminals 5 & 4 (both measured with respect to Earth) when heating is ON & OFF.
That will determine whether you have any chance of using those same terminals with the Hive receiver for Heating.

If that turns out to be a non starter you'll have to use the multimeter to measure both the Heating ON and HW ON voltages supplied by the timer.
Hopefully they will be mains voltages and you can check which wires become Live when Heating / Hot Water are selected in turn.
I decided against using my budget multimeter for mains testing and ordered a mid range one last week but still waiting for this to arrive. I did however do a rough check using a neon screwdriver.

The main board thermista stat terminals 4 & 5 showed nothing for on & off.

The built in timer showed wire 4 & 7 live when heating & hot water are off. Wire 5 goes live with heating on and wire 1 goes live when hot water is on. Not sure what wire 2 is doing?

I will go round this again when I get the multimeter.
I decided against using my budget multimeter for mains testing and ordered a mid range one last week but still waiting for this to arrive. I did however do a rough check using a neon screwdriver.

Even a budget multimeter is better than a neon screwdriver. Smash the neon screwdriver into tiny peices and incinerate them so there is no chance of anyone putting them back together again
True. One of the leads has broken though. I could have bodged it but decided it was a good time to replace it with a better one that would be safe. Curiosity got the better of me while waiting for the delivery!
If you put a conventional stat in place of a J&S thermistastat the fan/gas valve (gas valve pulses under the J&S stat) will not module correctly and over and under shoot the target temp.

So I'm afraid all you have done is mess it up. When working correctly the modairflow can keep temps to 0.1C accuracy. Not a great J&S fan myself (we fit Lennox units) but Modairflow does work well. When someone hasn't taken the stat off it.
Even if you can bypass the mod air flow stat with a Hive (which clearly you can if the PT Plus is working), you needed a single channel receiver, not dual channel. That's so you can use the terminal 1 (common) and switch it across terminal 3 (demand). If you try put 240v down it you will blow the PCB on your WAU and that's the only thing you can do with a dual channel receiver without using additional external relays etc. Timing your hot water would just have to be done with the existing timer unless you pay even more and use 2x receivers and set it up as a multi-zone install (excessive if you ask me).
You can't bypass Modairflow with a PT2 stat without messing up the whole temperature regulation of the heating. The gas valve pulses and the fan varispeeds, but with a straight short across the contacts instead of the J&S thermister (like has been done here) none of this works properly.

I thought we were meant to give proper advice on here? Would you short out an eBus on a Vaillant?
Thanks for the feedback. I understand the modairflow is not currently working as designed but the current set up has been running for years now (before I was educated). I guess it won't maintain the temperature within 0.1 degree as has been suggested and may be up and down a little around the target temperature but if this range has been acceptable then the Hive won't change things. Perhaps the hive may switch the boiler on and off closer to the target room temperature than the current stat. I guess if I can get the Hive working and I'm not happy with the temperature it maintains then I suppose I could add a thermista stat back in to the main board to regulate temperature and the Hive would become a dual timer and controller.

Ok so my new multimeter has finally arrived and it has confirmed what the much hated neon screwdriver suggested.

Main board thermista stat connections 4 & 5 are not mains voltage: -
Off signal for both = 0v
On signal for both = 0.003v

Built in timer does use mains voltage: -
Wire 4 = 240v
Wire 7 = 240v

Wire 5 = 240v

Wire 1 = 240v

I have been trying to understand what wires 2 & 4 are doing but I think the diagram was initially a bit dusty! I thought wire 2 had a vertical line up to CH & HW but I think it in fact only goes to the summer air as does wire 3 which makes sense and eliminates these two.
Boiler diagram.jpg

So would this work?
Wire 4 to Hive 1 & 2
Wire 1 to Hive 3 HW
Wire 5 to Hive 4 CH
Wire 7 to Hive L
Wire 9 to Hive N
Hive 2 wiring.jpg
Hive 2 Diagram.jpg

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