Open Therm

[GBH]

I have an ATAG Q60 which ATAG say is 100% opentherm but they advise me there are problems with the Evohome connecting properly with the boiler which they admit is odd as Honeywell make there opentherm controls.
at the moment it just keeps the boiler ticking over all the time even when no heat is required.

[Richard]

There are issues going on with multiple boiler manufacturers and OpenTherm, but not from Honeywell's side (remember they created OpenTherm). If anything the likelihood is that ATAG have modified the protocol or not implemented it correctly. Do they have the OpenTherm logo on the boilers connections and are they registered with the OpenTherm Association? If so you could report this issue to them to investigate.

[GBH]

ATAG are adamant its Evo home that the fault lies with they say there are many other manufactures having similar problems as there controllers work correctly and are made by Honeywell, and Yes all ATAG current boilers are Opentherm. To be honest there seems to be a massive void of knowledge from the manufactures on both sides, which is very frustrating.

[Richard]

I know the guys personally who deal with this at Honeywell and the issue is not with evohome.

Ideal Vogue & Logic+ OpenTherm works 100% with evohome, as does Ravenheat's OpenTherm boilers. Vaillant with a VR33 adaptor also seems to work fine. Intergas currently doesn't work and I have heard of issues with Viessmann. The issue with OpenTherm is that the boiler manufacturers can pick and choose what they want as long as they comply with the basic requirements.

I would like to see everything uniform as it was intended to be. However, those manufacturers trying to sell their own controls will no doubt attempt to make this process difficult and this is damaging the OpenTherm brand and should be clamped down on by the OpenTherm Association.

[GBH]

Hi couldn't agree with you more ive bought a 3k boiler because it was 100% opentherm or supposed to be crazy part is that Honeywell make there controls im now left with a system that dosnt connect properly ive fitted extra large radiators so I can run at a much lower temperature and all that is impossible till I can sort this put.

[GBH]

Hi is there any chance you can email me a wiring diagram for a 2 port s-plan system with an opentherm bridge ive been on to EVO tech and they keep sending me anything but the right drawing I basically have a set up like page 42 drawing 2 and diagram on page 46 but instead of the BRD91 for the heating I have the R8810 opentherm bridge.

[a62vw]

I assume you have the OpenTherm bridge connected to terminals 20 & 21? On the boiler did you set Option 60 to 02 for OpenTherm? It comes factory set at 03.

[GBH]

Hi yes thats exactly how its wired, 20 & 21 with option 60 set to 02
ATAG claim the boiler needs version 4 from the opentherm connection ive asked Evohome and they keep avoiding answering what version the bridge and controller works

[Lexden]

I have an Atag is24 system boiler connected to Evohome via an Opentherm connection. Boiler control isn't an issue. I have a profile of 70C max and Evohome controls to this temperature when heating HW. It is too early to say much about CH as the boiler was installed in April. My only reservation to date is that Opentherm is slow to get the boiler into condensing mode. I am convinced that this is down to zones coming on at various times. Evohome tends to crank the boiler up when there is a discrepancy between HR92 target and actual temperatures. Is it significant; I do not know. Neither the boiler, bridge nor Evohome have the Opentherm logo as far as I can tell from looking at them. There is no logo in the is boiler manual.