Nest thermostat e

[John Anderson]

Hi I've just connected my thermostat e up. Swapping from a Honeywell t40. It has 4 cables in brown (live) n black (sw live), blue (neutral) and earth. Now my nest only has connections labeled as C, NO, FP, OS1 and OS2. Just wondering is anyone can help with the right layout?

 

[ericmark]

Look at this post no one seems to know what the FP terminal is for.

 

[bernardgreen]

These devices vary from country to country ( and possibly from year to year ).

If you buy a Nest E ( USA version ) and then try to get support for it on the Nest website you will be told that because you are in the UK you cannot ( easily ) access the information about the Nest E ( USA version ).

Do the ( so called ) benefits of Nest outweigh the potential problems of replacing a defective unit in a years time ?

 

[ericmark]

There is a video as far as I can see the FP terminal is the N/C contact through a diode 100 mA maximum which is marked on the terminal box cover not a clue what it's for, I would expect never used.

So it will have just two wires connected so Line feed in to Com and Line feed out to NO or normally open unless your using Opentherm. There is no neutral or earth connected. It is powered by set of batteries in top compartment.

I had not realised this cut down version existed, would like to hear how you get on with it?

 

[Taylortwocities]

As far as I can see, if you connect those up as in your photo, you stand a very good chance of blowing a fuse, a programmer, the stat or something else.
You say the grey is neutral, and you will not need that for the stat-e. It only needs a permanent live and a call for heat (switched live). So brown in C, black in NO. terminate the grey in an insulated bit of choc block.

And PS, if you already have a programmer, you need to set that to ALWAYS ON. Or electrically bypass it.

 

[John Anderson]

Thanks for replies, I've tried the brown into the C and black into the NO terminals. Isolated the grey/blue. Hearings comes on and stays on. Not sure if that's an issue with the heat link. Really confused now.

 

[Taylortwocities]

If you have a continuity tester, remove all cables and check that the connection between C and NO goes on and off properly.
If it doesnt, the stat is (now) faulty.

Its just a switch, so the heating should go on and off if you connect/disconnect brown and black. (Remember, there's 230volts on there).

 

[John Anderson]

Cheers got a friend coming on Tuesday to test that for me. Luckily don't need heating at the moment lol.

 

[Simon Tompkins]

Hi. I can confirm that you want live/brown wire from your T40 to connect to C on the Nest Heatlink and the black switched live into the NO on the Heatlink. NO meaning Normally Open. Cap off your earth and neutral.

I spent ages scratching my head coz I connected the way I have said and the boiler fired constantly, regardless of thermostat setting on the nest e. I looked at every possibility and even got the metre out to check voltages and ohms. I could hear the device click off but not on when I moved the thermostat. In the end I rechaed the conclusion the Heatlink was faulty and the relay was jammed open. Google Nest helpline were very good and agreed with me and sent a replacement. Pleased to say it works fine now

 

[Taylortwocities]

Hopefully the OP has sorted it out. His post was from nearly a year ago!