EvoHome - Hot Water Kit (unvented cylinder? Santon)

[hy288]

Hi,

Anyone using EvoHome controls in S-Plan Plus arrangement with Opentherm?

I'm considering the EvoHome setup with a new boiler upgrade (Baxi 800 System 2 boiler?).
We have S-Plan Plus - x2 CH zones, x1 HW; with an unvented cylinder - Santon Premier Plus 250L (PP250B).

Having investigated the EvoHome setup, I understand one needs the EvoHome Hot Water Kit (ATF500SDH) allowing the Evo system to control the HW.

Honeywell Home Evohome Hot Water Kit (ATF500DHW)

Honeywell Home Evohome Hot Water Kit (ATF500DHW) | Buy Honeywell Evohome Products From the Smart Thermostat Specialists @The Smart Thermostat Shop

thesmartthermostatshop.co.uk

The kit comprises of a battery cylinder thermostat sensor (to monitor HW temp); and a wireless relay which i believe gets wired to the HW zone valve along with the thermal cut out stat in the unvented cylinder. The existing cylinder thermostat likely gets bypass or replaced the thermostat sensor in this kit?

The kit appears to come with a insertion sensor, but i have no idea how you would install this on the unvented cylinder - Santon Premier Plus in my case?
The cylinder is fully encased plastic, and there isnt any obvious slot to attached the sensor.

Anyone have direct experience in the installation of such sensor for the Santon?

If anyone who is using a EvoHome in Opentherm/S-Plan Plus, then please let me know...

Cheers,
Hung

 

[muggles]

A suitable pocket can be made in the cylinder insulation using the immersion heater access panel.

I'd steer clear of the Baxi, especially if you're wanting to use OpenTherm which is very hit & miss on those boilers.

 

[hy288]

A suitable pocket can be made in the cylinder insulation using the immersion heater access panel.

I'd steer clear of the Baxi, especially if you're wanting to use OpenTherm which is very hit & miss on those boilers.

Thanks!
Just also got some feedback from Resido (Honeywell). They told me the same, by accessing the immersion heater panel.
They mentioned that the insertion sensor should wedged in between the moulded insulation foam ensuring that the sensor contacts the stainless steel immersion heater boss outer surface.
Does that sound about right? - however, just not entirely sure how secure that approach would be...

Yeah definitely want Opentherm. The issues you mentioned, are these perhaps based on older Baxi models or specific models?
I've been looking at the Baxi 800 System 2 boiler. It's their latest version and Baxi claim OpenTherm compatible. Surely it should work if its OpenTherm certified.

 

[flameport]

and a wireless relay which i believe gets wired to the HW zone valve along with the thermal cut out stat in the unvented cylinder.

The wireless relay is connected to activate the zone valve for normal operation.

The cylinder stat/cutout must be hard wired so that when opened it disconnects power to the zone valve for the cylinder.
You cannot have the thermal cutout operating via a wireless connection or any other device - it must physically interrupt the circuit for the zone valve regardless of any other controls.

 

[muggles]

Thanks!
Just also got some feedback from Resido (Honeywell). They told me the same, by accessing the immersion heater panel.
They mentioned that the insertion sensor should wedged in between the moulded insulation foam ensuring that the sensor contacts the stainless steel immersion heater boss outer surface.
Does that sound about right? - however, just not entirely sure how secure that approach would be...

Yeah definitely want Opentherm. The issues you mentioned, are these perhaps based on older Baxi models or specific models?
I've been looking at the Baxi 800 System 2 boiler. It's their latest version and Baxi claim OpenTherm compatible. Surely it should work if its OpenTherm certified.

View attachment 382778

Yes that's correct with the sensor

Ref OpenTherm, the answer is "sort of". The OpenTherm protocol has 256 control IDs but only a select few of them need to be implemented by a manufacturer in order to gain certification. They may have ironed out the issues but certainly a year or so ago people were experiencing difficulty with limited functionality when connecting Baxi to OT. Also their modulation is rubbish and they have very few installer parameters available to be able to set the boiler up to the system it's connected to.

 

[hy288]

Yes that's correct with the sensor

Ref OpenTherm, the answer is "sort of". The OpenTherm protocol has 256 control IDs but only a select few of them need to be implemented by a manufacturer in order to gain certification. They may have ironed out the issues but certainly a year or so ago people were experiencing difficulty with limited functionality when connecting Baxi to OT. Also their modulation is rubbish and they have very few installer parameters available to be able to set the boiler up to the system it's connected to.

I assume when you talk about opentherm functionality it would extend to things like:

• Flow temperature control (basic modulation)
• Burner status feedback
• Flow/return temperature reporting
• Fault code/status reporting
• DHW control (where applicable)
• External weather compensation integration (if supported via OpenTherm)
• and more??

So are you saying to get certification, the boiler just need to perform say the first bullet (basic modulation - by accepting flow temp requests from a controller and not really provide feedback etc).

I guess my follow-up question is there public information (somewhere) on specific boiler brands/models that detail how feature rich they are in terms of opentherm functionality?
Or do you know from direct experience which are the good boilers that have better opentherm support - feature wise?

Another alternative boiler i was considering was the Ideal Vogue MAX system boiler. Pretty sure its support opentherm but dont know to what extend feature wise? Do you know how good this would be?
I think Intergas HRE is supose to be a decent one for opentherm (but not sure exactly), plus there not many installers in my area for that. Plenty for Baxi or Ideal....Why is this so difficult?

End of the day I'm planning on the EvoHome controls but just need to pair this with a decent boiler for opentherm.
The Vogue MAX gets a good reviews, long warranty, good internals and believe installers like them for maintenance. Just dont know if the opentherm is decent enough and integration with EvoHome. Probably spawn a seperate post on this...
Any recommendations would be appreciated.

 

[muggles]

No, manufacturers don't generally publish their OT feature set, it's a case of engineers experience. Of the two you've mentioned I'd go for the Ideal, but the Vokera Pinnacle knocks the socks off both of them IMHO

 

[hy288]

No, manufacturers don't generally publish their OT feature set, it's a case of engineers experience. Of the two you've mentioned I'd go for the Ideal, but the Vokera Pinnacle knocks the socks off both of them IMHO

Thanks bro. Will give Vokera a look also...

I was concerned that may have been the case i.e. lack of public info on OT feature sets.
I'll probably sent out a specific post on EvoHome and OT boiler feedback.....someone must know which are good OT feature set boilers that work well with EvoHome.