Remove Honeywell stat from heating system wiring

[Harburt]

Hi folks. I'm a rank amateur here at best, however with a bit of work I have successfully installed a Nest Thermostat and Heatlink to run my heating and hot water.

However there is an old Honeywell thermostat which is still wired through the junction box which is still active in the system so I'd like to remove this. I've attached pictures of the Honeywell stat and the wiring diagram contained within it. I've also drawn some very rudimentary circuit diagrams to show how it is currently wired into the system and how I believe I cam rewire to bypass it.

So what I want to know is, do my crude wiring diagrams look correct and if they are then can I rewire the junction box as per picture B to bypass the old thermostat? The thermostat diagram shows some resistors in the thermostat, am I risking causing damage to the system if theae are bypassed?

Any help would be greatly appreciated

20171213_111346

• Harburt
• 13 Dec 2017

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• Harburt
• 13 Dec 2017

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• Harburt
• 13 Dec 2017

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• Harburt
• 13 Dec 2017

 

[Taylortwocities]

No pictures!
To do this, simply drag the JPG file to the reply pane.

 

[Harburt]

Apologies, pressed the wrong button on my phone and it posted too early, pictures are all there now. Thanks

 

[Taylortwocities]

The resistor in the stat is just there to improve the accuracy of the stat itself, it’s not required.
You should be disconnecting the thermostat wiring at the heating wiring centre. I assume that is where the NEST receiver is located?

Your wiring diagram is wrong. If you connect the neutral to the call for heat there will be a bang, and you’ll be buying a new Nest.
Just remove the stat wiring at the wiring centre. Nothing else needs doing b

 

[Harburt]

Yes exactly, the main junction box is upstairs in the airing cupboard which is where the Nest receiver is. I am assuming then I can just patch the relevant cables on the junction box as per picture B and that would cut out the thermostat then? Does that sound right?

Thanks

 

[Taylortwocities]

I just edited my post. Do not follow your diagram B’!!!!

 

[ericmark]

The old heating system is similar to shown above, you will note the thermostat is feed from the programmer which Nest replaces, and feeds the motorised valve, which once open then fires up boiler and pump, so on diagram above the pink wire needs connecting to the brown call for heat wire, looks easy in that diagram but what you have is a wiring centre and what you have to do is work out which cable is which in the wiring centre to remove the thermostat.

If everyone followed Honeywell's wiring centre diagram it would be great, however in the main I find a socket back box with a blanking plate and a strip of connector block inside. The diagram I show is Y plan there is also C, S and W plan. Until you understand what you have, it is hard to work out how to modify.

 

[Taylortwocities]

I rather think that doesn't help someone who admitted that

I'm a rank amateur here at best

 

[Harburt]

Haha. I am perhaps a tad above a rank amateur. I do indeed have a panel box with connector block strip and blanking panel acting as the main junction box/wiring centre.

The thermostat wires are easy enough to locate and are currently wired in as per my picture A. The nest heat link has indeed replaced the original programmer. From what I can see it looks like the heat link is feeding the thermostat which in turn feeds the motorised valve.

So currently the call for heat from the nest feeds into the live in the thermostat. So if, as per your instruction to join the pink to brown cables in the picture, I need to join the call to heat from the nest directly to the motorised valve. Currently the live switch cable from the old thermostat is feeding into the motorised valve.

So therfore does it make sense that I feed from the call to heat from the nest into the motorised valve (I.E. where the switched live is currently connected)? As per in my diagram B but without the call to hear also feeding the neutral?

Thanks!

 

[Taylortwocities]

Yes. I see what you seem to have. The call for heat is currently routing through the old stat.
On your diagram B. Install the left hand strap but do NOT connect the neutral up. So no right hand strap.
Capishe?

 

[Harburt]

Success! Thanks folks, the thermostat has been removed at the wiring centre and the system is working fine. Thanks for your help!