Honeywell St699 to Hive

17 Aug 2010
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United Kingdom
well Hive is on offer and the st699 sometimes shows as being on but the pump is not running, I slide the switch to off and back on and it starts pumping so assume it's on it's way out.

I have a boiler in the garage, hot water tank with cylinder thermostat, room thermostat in living room and 3 port valve plus central heating pump all in the airing cupboard.

Should it be a simple swap. I've got plenty of wires in the St699
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Whilst it may be the ST699 that is the problem, there could be other causes of your fault. Some boilers control the pump, so in that case you boiler may be at fault. Check to see if your boiler manual says that your boiler requires a pump overrun. If so, then the boiler will be controlling the pump.

With other systems that don't have a pump overrun, the pump may be controlled via an integral microswitch inside the the 3 port valve, that may be faulty and only operate intermittently. So whilst it maybe the ST699 that is the problem, it also may not be. Only electrical testing by someone that has a knowledge of the wiring of heating systems and the equipment to test it safely will be able to confirm for certain.

Regarding the swap, the wires required for the Hive are all present at the Honeywell, but you will need to look at the wiring diagram for the ST699 to see what each wiring terminal does and then find the corresponding terminal at the Hive that has the same function. [For example terminal 3 at the Honeywell is 'Central Heating On' at the Hive dual channel version terminal 4 is 'Heating On'.]

The ST699 will also have links between terminals L, 5 & 8. These are not needed with the Hive as it has these links made internally.

Finally the existing room thermostat must be decommissioned to prevent it interfering with the operation of the Hive. It cannot simply be disconnected otherwise the heating wiring will be 'open circuit' and the heating will never come on. This means that the existing thermostat switching wires will need to be bridged out by connecting them together at the wiring centre or other convenient point.
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Thanks Stem for the info I'll check out the wiring diagrams. Looks like I can get fitting for not a lot more might be worth the extra in the long run.

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