Opentherm on 2 zones installation

Ant1 · 24 Sep 2021

Hi all,

I am about to get a new Intergas Rapid 32 Plus boiler installed. I need 2 zones and my original plan was simply to have 2 zone valves , controlled by my 2 Google Nest Thermostats as On/Off thermostats.

However I came across something interesting page 26 of the boiler manual (refer to screenshot below), it seems I can have the main zone working as On/Off and the second one as opentherm.

I did not know it was possible, I thought opentherm was not possible on multi zones.

I understand that in such scenario I will not be able to control both zones independently (having zone 2 active will automatically activate zone 1), however I struggle understanding how opentherm can work.

If zone 2 is active, does this mean both zone then act as opentherm making thermostat 1 redudant? Effectively meaning it is not really a 2 zones set-up?

PS: I am planning zone 1 to be the warmest one for the kitchen & living room, and have zone 2 for the bedrooms.

muggles · 24 Sep 2021

Use the Honeywell T6R two-zone kit and you can have two independent OT zones through one receiver. It's the perfect match for this application.

You'll need https://theintergasshop.co.uk/honey...rt-thermostat-t6h700rw5001-5025121380027.html

And

https://theintergasshop.co.uk/honey...-wall-mounted-y6h920rw5031-5025121380171.html

Or the table stand versions of the same if you don't have existing thermostat wires you can use.

vulcancontinental · 24 Sep 2021

Multi zone OpenTherm (I think up to 6) is possible on any OT boiler with EPH controls including DHW.

muggles · 24 Sep 2021

vulcancontinental said:
Multi zone OpenTherm (I think up to 6) is possible on any OT boiler with EPH controls including DHW.

Yeah Kim has been playing around with this a bit but he'd not quite finished building his test rig last time I saw him. Be interesting to see how well it works and get some live data off it on a real system

vulcancontinental · 24 Sep 2021

muggles said:
Yeah Kim has been playing around with this a bit but he'd not quite finished building his test rig last time I saw him. Be interesting to see how well it works and get some live data off it on a real system

Well it's working well on my let property, two zones and DHW, remote control by me. Coming up for a year soon, be interesting to compare consumption. ON/OFF controlled Viessmann out OT controlled Vokera system boiler in.

Mr Chibs · 24 Sep 2021

I’ve the same boiler, rapid 32, with 2 x two port valves... what’s the advantage of opentherm?
Don’t think Mine is set up that way.

One zone valve runs kitchen ufh, other one the house. These work independently.

vulcancontinental · 24 Sep 2021

Mr Chibs said:
I’ve the same boiler, rapid 32, with 2 x two port valves... what’s the advantage of opentherm?
Don’t think Mine is set up that way.

One zone valve runs kitchen ufh, other one the house. These work independently.

In terms of boiler efficiency? Comfort? Monetary saving? Remote control of boiler?

Too many variables; the manufacturers qualify everything with those magic words 'up to' 10% saving for example but don't ever give a 'down to' minimum saving that they'll guarantee.

An EU technical committee came up with a figure of 3% to e added to the seasonal space heating efficiency of the boiler for a load compensating control which is what OpenTherm is.

I have it, would always have it but will not put a figure on savings; comfort, features and convenience, certainly.

Mr Chibs · 24 Sep 2021

How do you measure ‘comfort’?

I was just curious, will have to have a read up, but not sure it seems worth the effort, remote turn on not a big seller for me, as I never go out

CBW · 24 Sep 2021

You don’t measure comfort per se, just how comfortable the end user is, as opposed to being too hot, as quite often on/off controls will overshoot the temperature, so will turn off at say 21 degrees, but in effect heating to 23 degrees because of pump over run

Ant1 · 24 Sep 2021

muggles said:
Use the Honeywell T6R two-zone kit and you can have two independent OT zones through one receiver. It's the perfect match for this application.

You'll need https://theintergasshop.co.uk/honey...rt-thermostat-t6h700rw5001-5025121380027.html

And

https://theintergasshop.co.uk/honey...-wall-mounted-y6h920rw5031-5025121380171.html

Thanks, so I should be able to use opentherm on 2 zones independently using those 2 Honeywell thermostats (instead of my 2 Google Nest thermostats) with 2 zone valves, is that correct? It is a bit annoying I cannot use my Google Nest thermostats for multizone & opentherm...

Regarding the diagram I included in my original post (i.e. the first one), it looks like it will be more expensive to run than having 2 zones with 2 zone valves, would you agree?

CBW · 24 Sep 2021

Is there a reason you “need” 2 zones? If not, could you just run the whole system off Nest on OT?

Ant1 · 24 Sep 2021

CBW said:
Is there a reason you “need” 2 zones? If not, could you just run the whole system off Nest on OT?

The ground floor of the house is the main living area (living room, kitchen, office) and the first floor is for the bedrooms; it would make sense to split the CH into 2 zones as the first floor is not used that much during daytime.

vulcancontinental · 24 Sep 2021

Mr Chibs said:
How do you measure ‘comfort’?

I was just curious, will have to have a read up, but not sure it seems worth the effort, remote turn on not a big seller for me, as I never go out

How do you measure comfort? Simple, subtract the times you're uncomfortable.

You never go out? Then the OpenTherm operation will suit keeping everything ticking over.

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Opentherm on 2 zones installation

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