Nest Self Install-Help

[uumai]

Hi There,

I wonder if you can give me some pointers here. I have a Next 3rd gen device replacing a Hive 1st gen.

I have a boiler and hot water tank system. The Hive was controlling hot water and heating.

Hive connections were as follows with descriptions from their wiring diagram:

N - Blue (Permanent Neutral)
L - Brown (Permanent Live)
1 - Green/Yellow with a brown sheath covering (Hot water off (NC))
2 - Empty (Heating off (NC))
3 - Black (Hot water on (NO))
4 - Grey (Heating on (NO))

On the Nest I thought that this would go from Hive to Nest as:


HW OFF 1 > 4
CH OFF 2 (Not used)
HW ON 3 > 6
CH ON 4 > 3

Additionally for the nest I suspect I'd need live going to sockets 2 and 5

This gives me hot water but no heating. I have a British Gas 330+ boiler.

Any ideas where I'm going wrong?

 

[ianmcd]

more info needed sounds like you have a Y plan but we dont have crystal balls well some do

 

[uumai]

Hi,

Thanks for the reply.

I'm not sure but I think it is a Y-Plan. Flow from the condenser boiler (British Gas 330+) goes through a Grundfos Alpha 2 circulator pump and then into a 'Mid Position Actuator Code - BGMVSP-23'. Looking at the side of the actuator, the switch seems to stay on the W.



Please let me know what other information may be useful if anything.

Edit:
Image of the old Hive box Model SLR2 - Boiler Interface.


Edit 2:
When calling for hot water the MPA goes to W as expected. When calling for heat it changes to M but never goes to H only. I don't know how this worked with Hive maybe this is a symptom of my setup.

 

[stem]

Did you have an existing room thermostat? If it is still there set it to 'maximum' and try the Nest. On the other hand, if you have just disconnected it, the the heating circuit will be open circuit and will not work. They need decommissioning properly.

 

[uumai]

Hi Stem,

Only the hive when I moved which uses a wireless room thermostat as the Hive heat link is removed I suppose subsequently disconnected.

I have seemingly managed to get a little heat on my radiators when i first ran power and then lost it for the day. Today I think I'm managed to get it working. I think some of the power wiring was loose.

 

[uumai]

Think I have now resolved this. Thanks for the questions they helped me to better understand my system