Honeywell Smartfit to Nest installation

[Graeme Souter]

Hi,

Just looking for a little help and guidance on installation of a nest heating system. I currently have a conventional boiler system with hot water tank. I have a Honeywell Smartfit thermostat system; the wiring is basically specialised so not able to “plug and play” the nest system as it were. I’ve included some photos of the wiring on the current system below.

I think I need to replace the cylinder sensor and actuator on the valve with proper wired versions. Then re-wire all in a junction box. I can then connect the hive heat link into the junction box too. I think the existing low voltage wires (twin) can be used to connect a wired hive thermostat.

Am I on the right tracks here? Or are there any glaring mistakes?

Thanks in advance!

 

[Dan Robinson]

Hi,

Just looking for a little help and guidance on installation of a nest heating system. I currently have a conventional boiler system with hot water tank. I have a Honeywell Smartfit thermostat system; the wiring is basically specialised so not able to “plug and play” the nest system as it were. I’ve included some photos of the wiring on the current system below.

I think I need to replace the cylinder sensor and actuator on the valve with proper wired versions. Then re-wire all in a junction box. I can then connect the hive heat link into the junction box too. I think the existing low voltage wires (twin) can be used to connect a wired hive thermostat.

Am I on the right tracks here? Or are there any glaring mistakes?

Thanks in advance!

The smart fit peaked my interest in car crash projects... But you start off with a Nest, then change to a hive. Which is it? And why do you think be wire can take 230vac?

 

[Graeme Souter]

Sorry I meant nest heat link. Been looking a both but decided on the nest. The smartfit is a right pain!

Which wire do you mean for 230vac? The mains in the picture are connected to a switched fused spur. Do you mean the wire that connected to the old thermostat?

 

[Dan Robinson]

The wire to the thermostat.

 

[Graeme Souter]

I don’t think it can. The nest thermostat says it has to be 12v which this connection also was from the smartfit system. Says on nest website that the thermostat can’t take 230.

 

[Dan Robinson]

Ah, I see for some reason I thought you were talking about the cylinder thermostat. It's been a long day.

You'll need to use the Center Brand heads from plumbcenter on your valve bodies; or replace the whole valves.

 

[Graeme Souter]

Thanks Dan. I’ll get replacement head then do a wire diagram to put on here just to double check!

 

[Neil E]

Graeme, Did you have any success with this? I have just bought 2 of these (which I thought were the correct item):

https://www.wolseley.co.uk/product/center-replacement-head-for-2-port-valve/

...but on getting home and comparing them with the smartfit valve head, there is a difference in the interface to the valve spindle: the smartfit valve has a circular spindle with a slot down the centre (and corresponding shape to the head actuator spindle) whereas the new head looks like it works with a solid spindle with a flat on each side.

Whilst I could attempt to file the 'flats' into the brass spindle, I'm not sure this is a good idea!

Am I missing something?

 

[picasso]

The smartfit system works on thermistors so its fairly straight forward to fool the heating using a relay and a couple of different value resistors, the hot water also works using a thermistor but that is better left alone.

 

[Graeme Souter]

Hi Neil,
Yes I have it all up and running now!
I replaced both the tank thermostat and the actual valve with traditional ones which weren’t smart fit. As you point out the fitting for the head on the valve is different.

Good luck!
Graeme

 

[Neil E]

Hi Graeme,

OK thanks for confirming. So it seems the Center Brand heads aren't a direct swap after all

New valves it is!

Neil

 

[allyks]

Hi

Do you happen to have the wiring diagram you used to swap between smartfit and the nest

Thanks