Installing Nest thermostat in zoned system

[Kemik]

Hi all,
I have two Nest thermostats that need to be installed on a zoned system (Honeywell ST9500C with . The thermostats run off 12V DC so they come with a converter called a Heat Link. This also communicates wirelessly with the thermostat to call for/stop the hot water heating.

My problem is Nest say the Heat Link should go between the thermostat and the zone valve in their installation instructions. However, according to the wire diagram in this system - www.honeywelluk.com/Documents/Installation-Guide/pdf/837.pdf, the thermostat receives the power from the programmer before it would reach the Heat Link.

Not really sure if Nest is going to be compatible with the system in this case. They say it is compatible with most UK systems, including zones, but I'm not sure how it would work.

Thanks,
Sean

 

[Worcester]

Go back to Nest support with the exact same question. (It works)

What is Heat Link?

The Heat link is effectively a remotely controlled AC contactor that replaces the existing 240V Thermostat.

If you don't understand either the link above or my answer then you need to call in a specialist heating engineer or electrician else you are likely to cause yourself serious harm - 240V KILLS . :shocked:

 

[chris watkins]

Hi all,
I have two Nest thermostats that need to be installed on a zoned system (Honeywell ST9500C with . The thermostats run off 12V DC so they come with a converter called a Heat Link. This also communicates wirelessly with the thermostat to call for/stop the hot water heating.

My problem is Nest say the Heat Link should go between the thermostat and the zone valve in their installation instructions. However, according to the wire diagram in this system - www.honeywelluk.com/Documents/Installation-Guide/pdf/837.pdf, the thermostat receives the power from the programmer before it would reach the Heat Link.

Not really sure if Nest is going to be compatible with the system in this case. They say it is compatible with most UK systems, including zones, but I'm not sure how it would work.

Thanks,
Sean

Hi Sean & welcome to the forum.

It almost certainly can be be made to work but as above you really do need to understand what you are doing if the 230Volts don't kill you it will kill the Nest thermostats.

Please get it installed correctly it is not just a case of plug & play there are things like Building Regulations that need to be adhered you.
PS They look very pretty.

 

[Kemik]

Hi guys, thanks for your comments. I think using an external professional may be the only way to do it. However, getting anyone to confirm whether or not it will fit my system is turning into an uphill battle.

Nest support said they had checked the documents I sent them (wire diagrams, photos, etc) and that "Nest works with 95% of combi boilers". Not the most useful reply.

The concern I have is that one of the Heat Link's functions is to convert the 230V to 12V DC but Nest installation instructions put the Heat Link between the thermostat between the zone valve. In my system wire diagram, power is provided to the thermostats from the programmer rather than the valves.

 

[chris watkins]

By the sounds of it, yours is a system that is common in this country & so should work.
You seem to be asking for a cast iron guarantee that it will work with your system, that seems to me to be a bit unreasonable when both Nest & ourselves do not know your system & you can not describe it accurately.
Let a qualified engineer attend site & confirm what you have got.

 

[Kemik]

I suppose I am being a bit cheeky in not wanting to pay for an engineer to come out just for him to tell me no. I did provide Nest with the wiring guide provided with the programmer to be fair.

I think with zoned systems they assume the systems have two individual programmers or the thermostat performs both functions, whereas on mine I only have one call to heat wire which goes to the single programmer.

 

[chris watkins]

I suppose I am being a bit cheeky in not wanting to pay for an engineer to come out just for him to tell me no. I did provide Nest with the wiring guide provided with the programmer to be fair.

I think with zoned systems they assume the systems have two individual programmers or the thermostat performs both functions, whereas on mine I only have one call to heat wire which goes to the single programmer.

I am missing something here guys & girls?
Can anyone make head nor tail of what the control system Kemik has ????????

 

[Whyme]

I thought they only one thing ie call for heat..

 

[Kemik]

I am missing something here guys & girls?
Can anyone make head nor tail of what the control system Kemik has ????????

Sorry Chris, its:
- Boiler: Ideal Logic Combi 38 with a basic on/off for HW and CH, connected to;
- Controller/Programmer: Honeywell ST9500C, a dual zone timer;
- 2x Thermostats: Honeywell T6360B. Simple temp thermostat.
- 2x Zone valves

Mt understanding of the tech diagrams are the controller sends live power to the stats when scheduled. If the temp it low, they will then send power to the valves to open them up and allow hot water through.

Nest states for each thermostat, one Heat Link is required. I don't see how that would fit seen as I only have one programmer rather than two. I'd imagine normal zone systems have individual controllers rather than one controller and simple stats

 

[lame plumber]

me thinks bg have renamed a wireless room stat and its as per normal but costs more.

 

[Worcester]

Sorry Chris, its:
- Boiler: Ideal Logic Combi 38 with a basic on/off for HW and CH, connected to;
- Controller/Programmer: Honeywell ST9500C, a dual zone timer;
- 2x Thermostats: Honeywell T6360B. Simple temp thermostat.
- 2x Zone valves

Mt understanding of the tech diagrams are the controller sends live power to the stats when scheduled. If the temp it low, they will then send power to the valves to open them up and allow hot water through.

Nest states for each thermostat, one Heat Link is required. I don't see how that would fit seen as I only have one programmer rather than two. I'd imagine normal zone systems have individual controllers rather than one controller and simple stats

From your comments it looks like you have two heating zones, in which case you should already really have two thermostats.

Without a visit and from your description, It should work - you will discard the Honeywell controller and discard the Honeywell thermostats (you'll still need a wiring centre) Sounds like about a 3 - 4 hour job to install and get correctly set up (about 1 hour of physical work, 1 hour thinking before hand, I hour testing and 1 hour debugging )


According to the webiste 2 Nest Thermostats would have cost you £500 including installation. - what did you pay?

I'd suggest the installation for the above based on would be about £150 plus any parts plus extra time over 4 hours if needed. Plus you'll need to do the making good where the old stats are/were.

 

[chris watkins]

If in London the labour cost will be more.
Just make sure you talk to the engineer & make sure he understands controls, You have two heating zones on a combi.

As previously state by many in the thread it will work & please don't try d.i.y as it will end in tears.

Good luck.