Advice/confirmation for Nest install for Greenstar 30DCi classic boiler with Integral Diverter Value

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Brownjamesa

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Hi all,

I have read several posts and searched the internet and believe I have now got the correct procedure to install a Nest for my Greenstar 30DCi classic boiler with an Integral Diverter Value with a DT20 timer.

If I could just get a second opinion, before I proceed it would be really appreciated


Current setup:
01-Current-Setup.png


Phase 1: Replace HW Cylinder temp sensor with Honeywell L641A1039

1. Turn off boiler
2. Switched off power to boiler
3. Replace HW cylinder temp sensor with Honeywell L641A1039:
a. Blue: 1
b. Brown: C​
4. Switch on power to boiler
5. Turn on boiler
6. Perform a factory reset to allow boiler to recognise cylinder thermostat
a. Select “spanner” button
b. Select “eco” and “suitcase” button, until you see “8.A”
c. Select “eco” button, until you see “8.E”
d. Select “chimney” button, this will then display “00”
e. Hold “chimney” button, until the display shows “[ ]”​
7. Test hot water, by calling for heat and temporally increasing the temp on the HW cylinder

02-Phase1.png


Phase 2: Install Nest thermostat

1. Turn off boiler
2. Switched off power to boiler
3. Looking at the boiler, amend wire configuration as per below:
a. ST10:Lr – remove wire and move to Nest:T1
b. ST10:Lr – connect new wire to Nest:3
c. ST10:Ls – remove wire and move to Nest:T2
d. ST10:Ls – connect new wire to Nest:2
e. ST17: remove plug
f. ST8:7: connect blue wire from HW cylinder cable
g. ST8:9: connect new wire to Nest:5​
4. Looking at the Nest Heatlink, amend wire configuration as per below:
a. Nest:N – connect mains N
b. Nest:L – connect mains L
c. Nest:6 – connect brown wire from HW cylinder cable
d. Nest:E – connect mains E​
5. Looking at the Nest Heatlink, confirm the wire configuration as per below:
N: from mains N
L: from mains L
1: N/A
2: from ST10:Lr
3: from ST10:Ls
4: N/A
5: from ST8:9
6: from L641:C
OT1: N/A
OT2: N/A
Earth: from mains E
T1: from old room stat (black)
T2: from old room stat (red)​
6. Remove DT20 timer from boiler and insert blanking plate
7. Switch on power to boiler
8. Turn on boiler
9. Configure Nest and confirm Heating & Hot Water

03-Phase2.png


Many thanks in advance.

James
 
Last edited:
You'd be better off keeping the cylinder sensor. You can wire it in parallel with terminals 4 & 5 on the Heat Link to provide time control of the hot water (DO NOT link the mains Live to 5).

Your description of the heating side is correct
 
Thanks for your reply Muggles, so you what you are saying is, its not worth adding the HW thermostat and I should just do the following and keep my existing HW compoents?


1. Turn off boiler
2. Switched off power to boiler
3. Looking at the boiler, amend wire configuration as per below:
a. ST10:Lr – remove wire and move to Nest:T1
b. ST10:Lr – connect new wire to Nest:3
c. ST10:Ls – remove wire and move to Nest:T2
d. ST10:Ls – connect new wire to Nest:2
e. ST17:brown - connect to new wire to Nest:4
f. ST17:blue - connect to new wire to Nest:5​
4. Looking at the Nest Heatlink, amend wire configuration as per below:
a. Nest:N – connect mains N
b. Nest:L – connect mains L
c. Nest:E – connect mains E​
5. Looking at the Nest Heatlink, confirm the wire configuration as per below:
N: from mains N
L: from mains L
1: N/A
2: from ST10:Lr
3: from ST10:Ls
4: from ST17:brown
5: from ST17:blue
6: N/A
OT1: N/A
OT2: N/A
Earth: from mains E
T1: from old room stat (black)
T2: from old room stat (red)​
6. Remove DT20 timer from boiler and insert blanking plate
7. Switch on power to boiler
8. Turn on boiler
9. Configure Nest and confirm Heating & Hot Water

04-Phase0-update.png
 
Yep, you've got it. You might need to insert a link somewhere to provide continuity once the DT20 is removed, but you'll soon know if it doesn't work without one!
 
I doubt the boiler will work properly when the nest interrupts the cylinder sensor but you can always reconnect the cylinder stat if that happens.
 
picasso said:
I doubt the boiler will work properly when the nest interrupts the cylinder sensor but you can always reconnect the cylinder stat if that happens.
Click to expand...
It's wired to the Common & NC terminals on Nest, which creates a short across the NTC wires. The boiler interprets this as the cylinder being satisfied, so it switches over to the heating demand. When Nest calls for hot water, the relay breaks the link between C and NC, allowing the boiler to read the correct resistance of the sensor and thus know the temperature of the cylinder. It'll then heat the cylinder until either the NTC's resistance tells the boiler that the cylinder has reached setpoint, or the timer switches off, restoring the short which the boiler will interpret as cylinder satisfied.

It's hot water priority, Worcester style
 
Depends on how the boiler interprets no signal from the sensor, be interested to see if it works as intended.
 
Hi Guys,

Just finished installing the Nest and my system boiler is flashing a blue light and displaying the code "Ad"?

The nest is connected OK and I am calling for heat and the radiators are getting hot.


Cheers
James
 
Last edited:
You might have discovered a new code there, don't think that's in the book :LOL: is your cylinder heating OK?
 
Its all sorted now... :)

As soon as I told the Nest I wanted to control the Hot water, that code went away and the temperature was then displayed on the boiler :D.

For others that have this issue, I did the following on the Nest dial:

1. Settings
2. Equipment
3. Pro setup
4. System Boiler
5. Hot Water, switch to On/Off.
6. Done.

Muggles/Andrew... about that beer I owe you, you have two options:

1. DM your email address and I will send you beer money via PayPal
2. Tell me a charity of your choice and I will donate.

Thanks again for all your help, its working as described, when I turn on the call the water, it takes priority like it already did :)

Cheers
James


Edit:

I did find this on a Google search, which then pointed me to look at the hot water controls:

Screenshot-2020-12-06-192731.png


Screenshot-2020-12-06-193106.png
 
Last edited:
Just came back from a walk and the error message has re-appeared :-(

If I turn the hot water on via Nest, the error message goes away and the boiler status is normal.

If I just have the heating on, the error message appears.

I can't leave the hot water on all the time, as it takes piority over the heating.

I am safe to leave the message on the boiler as I know it works or do I need to change the wiring?

05-minor-issue.png
 
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