Nest+need new opentherm wiring (keep existing programmer?)

[lucluc]

I have an Ideal system boiler (which supports opentherm) in the kitchen, cylinder upstairs on a 3-way valve. Existing digital programmer is on a diagonally opposite wall to the boiler in the kitchen (does not support OT, wires go an unknown route); analogue thermostat in the living room.

With the sales, I am thinking of getting Nest professionally installed, but only if it can be wired with opentherm, otherwise I'm guessing it would not save as much money since it can't adjust the CH flow temperature.

From what I understand, Heatlink normally replaces the programmer, but since I want OT, I'd need two extra wires for opentherm from the programmer to the boiler. That might be difficult/untidy given the layout of the kitchen due to doors, cupboards, etc.

An alternative, perhaps it is possible to just keep the existing programmer as "CH/HW always on", and then get Heatlink+OT professionally wired right next to the boiler and connect to whatever wire goes from the programmer to the boiler? But, looking at the manual, I'm guessing there is only a single "on" wire from the programmer to the boiler, so the boiler can't distinguish HW/CH so wouldn't be able to alter flow temperature?

Or do any of the Nest alternatives simplify opentherm installation for old installations like mine that aren't wired up for it?

Thanks.

 

[Dan Robinson]

Honeywell Evohome.

 

[dilalio]

Honeywell Evohome.

But change the TRV bodies

 

[lucluc]

On the evohome customer page, it says since I currently have a single zone I'd need wi-fi base pack (249) and hot water kit (85). For multizone I'd then add a trv per radiator (60) when I could afford it.

Presumably it's a case of the installer disconnecting the existing programmer, wiring the relay pack next to the boiler, disconnect all the wiring in the airing cupboard, put hot water kit on the tank to signal the temperature.

Is my understanding correct of my existing wiring correct that I couldn't easily have opentherm without extra wires from the programmer to the boiler?

 

[flameport]

t I couldn't easily have opentherm without extra wires from the programmer to the boiler?

With new controls, whether they be Nest, Honeywell or any others, your existing programmer is irrelevant. It would be removed along with the wiring to it.
Same for any existing thermostat - removed.
The new controller is wired in wherever the wiring box is, typically next to the boiler or in a cupboard where the valves and hot water cylinder are.

 

[lucluc]

Ah, I do have a wiring panel in the airing cupboard connected to the 3-way, etc.

So, kitchen programmer would be removed (and cables linked together so airing cupboard still wired to the boiler); then new controller wired in airing cupboard to that wiring panel. Make sense.

But, say the Nest Heatlink went in the airing cupboard, then the installer would need to run opentherm cables to the boiler (since I don't have OT yet). So, I'd still not get OT support.

It looks like with EvoHome I'd also need to buy an additional OT box (extra 100 pounds).

So, I guess the secondary question would be, are OT gas savings significant? Or is leaving the boiler front temperature panel on "eco 67C" 'near enough' savings.

I had wanted the whole "reduce flow temperature", but I can't see how I would make enough gas savings with EvoHome.

 

[lucluc]

Although, if the Nest Heatlink is wired in the airing cupboard, and the kitchen programmer removed, then would there be existing spare wires going from the old programmer to the airing cupboard that could be used to carry OT signal from airing cupboard to the old (to be removed) programmer, and then already wired to the boiler on the opposite wall?

Otherwise, how is OT wired in to airing cupboard in retrofits?

I'm not doing the work, just like to weigh up options before spending any money.

 

[dilalio]

Save money = use less gas.
Increase comfort levels = spend money.

That's pretty much the long and short of it.

 

[vulcancontinental]

Just how much do you expect to save?

 

[lucluc]

Good question. I see figures banded around of "save 10-15% over a regular thermostat". So, I was figuring that if it was really half at 5-10% then I could save 25-50 pounds a year, then Nest could break even after say five to ten years. That's acceptable to me given my old thermostat has been in place for 20+ years.

I was also hoping I'd save on overall boiler maintenance by running the boiler at lower temperatures, so perhaps delaying the boiler breaking by a year or two.

But then, ErP gives figures of 1%-3%, which if that's savings then it would mean I'd never break even and it wouldn't be worth it.

I read that the opentherm wires can be thin (slightly thicker than bell wire), so perhaps it could be routed around the kitchen walls, but it would be a bit ugly.

 

[hertsboilers]

More about comfortable heating than gas bill saving. Also from the internet some installers suggested Nest isn't good on Opentherm.

 

[Dan Robinson]

Nest, OpenTherm and y plan don't work.

Hence Evohome. You can buy many different configurations. Best talk to an installer/specialist who knows the system.

 

[vulcancontinental]

How much is your annual bill? Which model Ideal? Do you have radiators. Why do you think running cool makes a boiler last longer? ERP estimates 3%, 1% for straightforward stat, 2% TPI stat or weather comp.

 

[hertsboilers]

Nest, OpenTherm and y plan don't work.

Hence Evohome. You can buy many different configurations. Best talk to an installer/specialist who knows the system.

I am going to spend some time to read Evohome now.

 

[flameport]

I see figures banded around of "save 10-15% over a regular thermostat".

No thermostat to any thermostat is a big saving. It's also the cheapest thing to install.

Normal thermostat and timer to a Hive / Nest or other similar thing will save, but only for people who are in the habit of leaving the heating on all the time, the savings being from it switching off when you leave the building. Similar savings can be made by using the existing controls properly, but plenty of people are unable or unwilling to do that, and would rather spend £300 on a device to do it for them.

After that any other improvements from things like weather compensation are tiny, and are unlikely to ever cover the cost of the installation. Entirely pointless on an existing system, and only installed on new ones because they usually have to be.

Nest could break even after say five to ten years.

It will be either broken, obsolete or both by then.
Unlike your old thermostat, most of it's functionality depends on it being connected to remote servers and apps which could be switched off or discontinued at any time - that time being as soon as it's unprofitable for the manufacturer.