S-plan hot water migration from Honeywell EVOhome

[Chris Bartlett]

Hi everyone,

After a successful installation of Loxone for my lighting (migrating from an earlier proprietary whole-house lighting system) I’m planning on migrating my heating system which is using the Honeywell EVOHome wireless system. Initially, I want to try to migrate just the hot water system - partly as it seems something I can do with a few relay ports I’ve got free before I buy all the Air rad valves,  and partly because I’m having some trouble with the EVOHome system for hot water right now so would rather migrate than fix.

The current wiring is basically ’S plan’ - with the EVOHome grafted onto it. Here’s a logical plan of the heating part of it:



I think like what’s happening here is the EVOHome BD91 is told - because of the wireless thermostat -  that we need some hot water.  The black on the BD91 goes live which will complete the circuit through the tanks thermostat, engage the zone valve if the thermo is closed and then (once its open and the connection made) turn on the boiler to heat some water.

I’m supposing that having the two thermostats is because if there is a problem with the EVOHome system - such as when the wireless thermostat runs out of batteries, the tank thermostat will provide a backstop that stops the system running uncontrolled. So my main question is, if switching to Loxone how would I wire up the thermostat (s)? Do I need to do the same thing and find some wired thermostat on a Digital input - or can I just use the tank thermostat? I watched a couple of the loxone videos and in one Hugh was discussing running the thermostat on 24 volt (volt free) to read the NC switch on a digital input for a scheduled controller. I’m not sure my thermo will run that way at the moment (its one of these: https://www.plumbnation.co.uk/boiler-spares/product/ariston-60001652-indirect-thermostat-kit-duct-70/?gclid=Cj0KCQjwyLGjBhDKARIsAFRNgW_f65mKC8b--loIkPPi5rTdTVAcOWGfmVd8nyIvQugT7U0cmw0S9R4aAtTvEALw_wcB)

So really  - that’s Q1 - how to wire the thermostat(s) for Loxone hot water. Happy to buy a new thermostat if this one won’t do the job.

Q2, is more generic - I need to keep most of the S-plan for now, but how do people approach this sort of migration - can I simplify it to just put the boiler on a relay, the thermostat on a relay with a 24V digital input for open/cloded detection and the zone valve on a relay? Would really simplify it as the wiring centre is a complete mess at the moment. I've read that its good practice to keep the zone valve controlling the boiler - rather than adding it to a relay - is that true?

Any thoughts or help?

Cheers,

Chris

[Rob]

Hi Chris

For HW you’d only need one relay connected on a timed schedule to provide power to the cylinder stat. If the cylinder stat says the water needs to be heated it will close the circuit to the zone valve, this in turn closes the boiler firing connector. This ensures the boiler can’t fire unless the zone valve is open. You shouldn’t need to buy anything else to make the HW work via Loxone.

Generally, when designing heating/HW controls for clients I recommend using Loxone to take the place of time clocks and room thermostats and leave the system controls (zone valves, boilers, cylinder stat, pumps etc) to do what they are designed to do, in most cases using a standard wiring centre. This way, any plumber/heating engineer won’t need to be concerned about knowing their way around Loxone. In most (modern-ish) heating installations, the 230v mains power for your zone valves, pumps etc comes direct from the boiler. This is a safety feature as it means you have a single point of electrical isolation for the whole system when you turn the power off to the boiler. What you shouldn’t have (although I have seen it!) are mains supplies for zone valves, pumps etc from different parts of your mains wiring.

Do you have individually controlled heating zones, e.g. UFH with manifold actuators?

Cheers
Rob

[David Wallis]

Hw thermostat wiring doesn’t look right, feel like it prob should be showing a switched live rather than neutral? (Obv just a diagram issue and not reality!)

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[g...@camleyphotographic.com]

I have done this exact thing for an ASHP. I only use the Mitsubishi Ecodan controller to set the flow temperature from Loxone (using a modbus device). All the pumps/valves/ASHP/immersion are triggered are controlled using Loxone relays. Actually, I use a low voltage feed from the Loxone to turn on/off relays and a contactor within the area dedicated to the heating control. This avoided the need to run multiple 240v cables to the cabinet and could be replaced by a single 6 way ribbon cable.

 

It gives a huge advantage that I can switch between CH and DHW without triggering the ASHP to undertake a powerup cycle, which the Mitsubishi controller always does.

 

I suspect an ASHP might be more complex than a gas boiler. Anyway…

 

I think you will want to replace the thermostat trigger with something on your Loxone. This way the central controller can fire up your boiler when there is sufficient demand.

 

There is a nice video on the Loxone website on how to do all this. Very well worth watching.

 

Let me know if you want a link to it.

 

George

 

From: loxone-...@googlegroups.com <loxone-...@googlegroups.com> On Behalf Of Chris Bartlett
Sent: 23 May 2023 14:43
To: Loxone English <loxone-...@googlegroups.com>
Subject: S-plan hot water migration from Honeywell EVOhome

 

Hi everyone,

After a successful installation of Loxone for my lighting (migrating from an earlier proprietary whole-house lighting system) I’m planning on migrating my heating system which is using the Honeywell EVOHome wireless system. Initially, I want to try to migrate just the hot water system - partly as it seems something I can do with a few relay ports I’ve got free before I buy all the Air rad valves,  and partly because I’m having some trouble with the EVOHome system for hot water right now so would rather migrate than fix.

The current wiring is basically ’S plan’ - with the EVOHome grafted onto it. Here’s a logical plan of the heating part of it:

I think like what’s happening here is the EVOHome BD91 is told - because of the wireless thermostat -  that we need some hot water.  The black on the BD91 goes live which will complete the circuit through the tanks thermostat, engage the zone valve if the thermo is closed and then (once its open and the connection made) turn on the boiler to heat some water.

I’m supposing that having the two thermostats is because if there is a problem with the EVOHome system - such as when the wireless thermostat runs out of batteries, the tank thermostat will provide a backstop that stops the system running uncontrolled. So my main question is, if switching to Loxone how would I wire up the thermostat (s)? Do I need to do the same thing and find some wired thermostat on a Digital input - or can I just use the tank thermostat? I watched a couple of the loxone videos and in one Hugh was discussing running the thermostat on 24 volt (volt free) to read the NC switch on a digital input for a scheduled controller. I’m not sure my thermo will run that way at the moment (its one of these: https://www.plumbnation.co.uk/boiler-spares/product/ariston-60001652-indirect-thermostat-kit-duct-70/?gclid=Cj0KCQjwyLGjBhDKARIsAFRNgW_f65mKC8b--loIkPPi5rTdTVAcOWGfmVd8nyIvQugT7U0cmw0S9R4aAtTvEALw_wcB)

So really  - that’s Q1 - how to wire the thermostat(s) for Loxone hot water. Happy to buy a new thermostat if this one won’t do the job.

Q2, is more generic - I need to keep most of the S-plan for now, but how do people approach this sort of migration - can I simplify it to just put the boiler on a relay, the thermostat on a relay with a 24V digital input for open/cloded detection and the zone valve on a relay? Would really simplify it as the wiring centre is a complete mess at the moment. I've read that its good practice to keep the zone valve controlling the boiler - rather than adding it to a relay - is that true?

Any thoughts or help?

Cheers,

Chris

--

[g...@camleyphotographic.com]

This is the link to the video.

 

https://www.youtube.com/watch?v=k1LZ7kw1FXA

 

There are plenty on the Loxone website. Hugh is an excellent trainer, all his videos are very clear.

 

George

To view this discussion on the web visit https://groups.google.com/d/msgid/loxone-english/047101d98dbd%24a3ab2ce0%24eb0186a0%24%40camleyphotographic.com.

[Chris Bartlett]

Hi all,

There was indeed an error in my diagram (of course), but it is indeed pretty standard S-plan. Looking straight-forward after watching the video. Only think I’m still wondering is if I should replace the Evohome remote thermostat with say, the 1-wire thermostat from Loxone (i have 1-wire due to the Faradite switches). This then keeps the tank thermostat in line with the zone-valve/boiler (which i understand is a safety requirement) but lets us set the water temp in Loxone. If I were to do that, can I set the water temp on the schedule block or do i need an intelligent room controller (or some other block) to set the water temp?

Think I’m nearly there….

Chris

Sent from my iPad

On 25 May 2023, at 13:57, g...@camleyphotographic.com wrote:



This is the link to the video.

 

https://www.youtube.com/watch?v=k1LZ7kw1FXA

 

There are plenty on the Loxone website. Hugh is an excellent trainer, all his videos are very clear.

 

George

 

 

From: gck via Loxone English <loxone-...@googlegroups.com>
Sent: 23 May 2023 22:29
To: 'Chris Bartlett' <ch...@dahu.co.uk>; 'Loxone English' <loxone-...@googlegroups.com>
Subject: RE: S-plan hot water migration from Honeywell EVOhome

 

I have done this exact thing for an ASHP. I only use the Mitsubishi Ecodan controller to set the flow temperature from Loxone (using a modbus device). All the pumps/valves/ASHP/immersion are triggered are controlled using Loxone relays. Actually, I use a low voltage feed from the Loxone to turn on/off relays and a contactor within the area dedicated to the heating control. This avoided the need to run multiple 240v cables to the cabinet and could be replaced by a single 6 way ribbon cable.

 

It gives a huge advantage that I can switch between CH and DHW without triggering the ASHP to undertake a powerup cycle, which the Mitsubishi controller always does.

 

I suspect an ASHP might be more complex than a gas boiler. Anyway…

 

I think you will want to replace the thermostat trigger with something on your Loxone. This way the central controller can fire up your boiler when there is sufficient demand.

 

There is a nice video on the Loxone website on how to do all this. Very well worth watching.

 

Let me know if you want a link to it.

 

George

 

From: loxone-...@googlegroups.com <loxone-...@googlegroups.com> On Behalf Of Chris Bartlett
Sent: 23 May 2023 14:43
To: Loxone English <loxone-...@googlegroups.com>
Subject: S-plan hot water migration from Honeywell EVOhome

 

Hi everyone,

After a successful installation of Loxone for my lighting (migrating from an earlier proprietary whole-house lighting system) I’m planning on migrating my heating system which is using the Honeywell EVOHome wireless system. Initially, I want to try to migrate just the hot water system - partly as it seems something I can do with a few relay ports I’ve got free before I buy all the Air rad valves,  and partly because I’m having some trouble with the EVOHome system for hot water right now so would rather migrate than fix.

The current wiring is basically ’S plan’ - with the EVOHome grafted onto it. Here’s a logical plan of the heating part of it:

<image001.png>

I think like what’s happening here is the EVOHome BD91 is told - because of the wireless thermostat -  that we need some hot water.  The black on the BD91 goes live which will complete the circuit through the tanks thermostat, engage the zone valve if the thermo is closed and then (once its open and the connection made) turn on the boiler to heat some water.

I’m supposing that having the two thermostats is because if there is a problem with the EVOHome system - such as when the wireless thermostat runs out of batteries, the tank thermostat will provide a backstop that stops the system running uncontrolled. So my main question is, if switching to Loxone how would I wire up the thermostat (s)? Do I need to do the same thing and find some wired thermostat on a Digital input - or can I just use the tank thermostat? I watched a couple of the loxone videos and in one Hugh was discussing running the thermostat on 24 volt (volt free) to read the NC switch on a digital input for a scheduled controller. I’m not sure my thermo will run that way at the moment (its one of these: https://www.plumbnation.co.uk/boiler-spares/product/ariston-60001652-indirect-thermostat-kit-duct-70/?gclid=Cj0KCQjwyLGjBhDKARIsAFRNgW_f65mKC8b--loIkPPi5rTdTVAcOWGfmVd8nyIvQugT7U0cmw0S9R4aAtTvEALw_wcB)

So really  - that’s Q1 - how to wire the thermostat(s) for Loxone hot water. Happy to buy a new thermostat if this one won’t do the job.

Q2, is more generic - I need to keep most of the S-plan for now, but how do people approach this sort of migration - can I simplify it to just put the boiler on a relay, the thermostat on a relay with a 24V digital input for open/cloded detection and the zone valve on a relay? Would really simplify it as the wiring centre is a complete mess at the moment. I've read that its good practice to keep the zone valve controlling the boiler - rather than adding it to a relay - is that true?

Any thoughts or help?

Cheers,

Chris

[g...@camleyphotographic.com]

The loxone controller does not need a central thermostat.

 

It turns of based on the demand from room. You configure the threshold and the system turns on. It will take into account a number of factors (eg room size, number of rooms below temp, how far away from their target temp, warm up time, cycle time) and then manage the system.

 

I have my ASHP to run for a minimum of 40 minutes when at least two rooms (7%) demand heat. There is no cental thermostat. Just a room sensor in each and every room.

 

Hopefully that makes sense.

 

G

To view this discussion on the web visit https://groups.google.com/d/msgid/loxone-english/44EE97D3-A746-4467-8974-E4A4100FA438%40dahu.co.uk.

[Chris Bartlett]

Hi - I probably didn’t explain that well enough. I’m talking about using the 1-wire thermostat from Loxone along with the tank thermostat so that the hot water temp can be set/controlled from loxone. This would mirror what I have now with the Honeywell Evohone system. The tank thermostat remains as the over temp device, the loxone 1-wire controls the water temp. 

I know how to use a relay output to control the water zone valve (and the boiler) through the tank thermostat but I’m not sure what to use alongside the schedule block to control the hot water temp?

Chris

Sent from my iPhone

On 27 May 2023, at 19:20, g...@camleyphotographic.com wrote:



[Ewan Tait]

The schedule block can have an analogue value attached to it, so that when it's on, a value of 65 could be presented at O and when it's off, a value of 20. But you would need to couple it to a threshold switch, or similar, to avoid the hot water constantly going on and off constantly when it reaches temperature. You would want it to stay on until it hits 65, then go off, but stay off until it drops to, say, 60.

Cheers,

Ewan

[g...@camleyphotographic.com]

I am pretty sure that loxone has a hysteris controller to manage this. I use it for a dehumidifier controller which stops it cycling around the target level.

 

G

 

 

From: loxone-...@googlegroups.com <loxone-...@googlegroups.com> On Behalf Of Ewan Tait
Sent: 28 May 2023 10:44
To: Loxone English <loxone-...@googlegroups.com>
Subject: Re: S-plan hot water migration from Honeywell EVOhome

 

The schedule block can have an analogue value attached to it, so that when it's on, a value of 65 could be presented at O and when it's off, a value of 20. But you would need to couple it to a threshold switch, or similar, to avoid the hot water constantly going on and off constantly when it reaches temperature. You would want it to stay on until it hits 65, then go off, but stay off until it drops to, say, 60.

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[AndyB]

I use a 2 position controller for hot water (with hysteresis set at 5).

Connect the 1-wire probe to PV, and a schedule to SP.

I've got the schedule default value set at 35, then schedule for morning and evening at 50, and a Sunday morning 1/2hr 60degree for legionella (although not sure if thats required now).

Works reasonably well as max warm up is from 30C, so never without tepid water.  I did have the default set at 50 but realised I was heating water a lot of times when it wasn't used.  It would be nice for Loxone to work out when to turn the water on to get up to temperature, but never managed to get that to work.

[Lis Hilton]

Chris, sounds like you’re knee-deep in a serious wiring puzzle! If you’re simplifying to Loxone, sticking with the tank thermostat is probably easiest, but adding a 24V relay for detection sounds like a smart move too. As for keeping the zone valve on the boiler, yeah, that’s pretty standard to avoid overcomplicating. If you’re already dealing with a mess of wiring, might be worth calling in pros like https://plumbing-united.com/services/sewer-drain-cleaning/ to make sure everything’s clean and efficient.