Ideal Logic 24H Condensing + 2 Zones + Nest

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Hello folks,

I have purchased 2 x Nest 3rd Generation Learning Thermostats in the Black Friday sales.

I currently have an Ideal Logic 24H condensing boiler with a KingSpan hot water tank. These are connected to 2 thermostats.

• Thermostat 1 controls hot water, and heating for the ground floor. We still have the radiators installed.
• The ground floor also has a 6 zone wet UFH system running off a Heatmiser 8-RF, with the ProWarm NeoAir thermostats. This is currently not electrically connected to the boiler. It operates on a schedule 10mins behind Thermostat 1.
• Thermostat 2 controls heating for floors 1 and 2 which have radiators.

Questions:

1. Given my boiler supports OpenTherm, what wires would I need to run to the Nest Heat Link?
2. How will the wiring change with the introduction of the Heatmiser 8-RF?

Images:
Boiler - left side

Boiler - Right Side

Manuals:
https://nest.com/support/images/mis...Nest-Learning-Thermostat-Install-Guide-UK.pdf

https://www.mrcentralheating.co.uk/...ogic 24 (ErP) Heat Boiler Only - installation

https://www.heatmiser.com/en/download/211/english/7486/uh8-rf-manual.pdf



Any advice would be greatly appreciated.

 

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I should add, the existing Thermostat 1 and Thermostat 2’s are Danfoss TP One-M

 

[ericmark]

As far as I am aware only one OpenTherm device can connect to the boiler, I don't have an OpenTherm boiler so for me it does not really matter, I was rather disappointed with Nest Gen 3, I thought it would connect to my Energenie MiHome TRV heads, but it seems support has been withdrawn. So it will change with one command from phone, but not the scheduled changes.

However the wall thermostat does seem to work out how long of a burn is required not to over shoot, I am not however over impressed Nest says how the TRV heads work but as yet don't seem to be making any of there own.

However it was only this year when Hive intruded their own TRV's to work with their wall thermostats, so maybe Nest will release one soon.

 

[MeldrewsMate]

One possible solution:
Nest One will control heating and hot water, use it's Opentherm connection to the boiler. Connect the HW output to the boiler's SL2, as seems to be the present case.
The Opentherm control will adjust the downstairs radiator temperatures to achieve the room temperature required from Nest One, when HW generation is demanded all bets are off and the rad temps will rise until the cylinder 'stat is satisfied.

Nest Two will control only the upstairs rads, it's HW output being unused. Thie demand for this zone will connect to SL1 or SL2, for the following reasons:
1. To SL1...uptairs rad temps will be dictated by Nest One's Opentherm output, if Nest One is 'satisfied' you can expect upstairs rads to be less than hot, or even cool.
2. To SL2...(I'd prefer this) upstairs rads go to the boiler temperature that is used for hot water generation, in other words, the more traditional operation.
In this way the Opentherm will not adversely and inadvertantly affect upstairs.

I hope this helps, MM

 

[ianmcd]

you say you have two zones but it sounds like the zone with the HW and 1 zone CH are controlled by a 3 port valve is this correct ?

 

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MeldrewsMate

Nest One:
If I have understood you correctly, I am to wire the L N E to the Heatlink as usual.

Do I take these from the mains coming in, split them with one set heading to the boiler and 1 set to the Heatlink?

On the OpenTherm side, I assume I remove the purple loop and wire these into the Heatlink.

For the HW, there are 3 connections documented in the Nest manual: Call to Heat, Common and Satisfied. Common appears to link to Live. Is it the Call to Heat I attach to SL2?

 

[-WildCard-]

you say you have two zones but it sounds like the zone with the HW and 1 zone CH are controlled by a 3 port valve is this correct ?

I see 2 motorised valves attached to the KingSpan upstairs and a pump. Image attached if it helps.

 

[ericmark]

From picture I can see three motorised valves and a pump, but not sure if the tank is a heat store? With a heat store the boiler runs at most efficient rate for a long burst rather than needing to modulate, and the variable speed pump can supply radiators as an when required even if only wanting 2 kW I have never worked on a system like this, I only know they exist.

My brother-in-law had it with his old house, main advantage was 4 heat sources all running one central heating system, back boiler on wood burner, solar panels, immersion heaters connected to solar panels, and a LPG boiler all fed in as required.

There are many reasons for having motorised valves and pumps, one house I stayed at had circulation pump for domestic hot water so you did not need to wait for hot water to arrive at taps.

It does seem from the instructions the boiler does not have an internal pump, so to be a heat store I would expect at least two pumps. So I may be completely wrong, so I suggest you wait and see what others say who may recognise the system. Personally I would not fit any replacement thermostat without being totally sure what I have.

 

[-WildCard-]

Progress

Reading this thread: https://www.diynot.com/diy/threads/nest-boiler-issues.533486/

It appears we have the same system. S-Plan, KingSpan HW Cylinders and Idea Logic Boilers, though mine is a 24H vs 15. Homes made by the same builders.

It appears the Heatlinks fit in at the top control panel on the HW cylinder.

Just need to decipher the attached photos to figure out where the 2 Heatlinks plug in.

 

[ianmcd]

yes you do indeed have 3 motorised valves as I suspected