Help with Evohome / Opentherm / Intergas

[top brake]

Because this is not a mandatory part of OpenTherm spec.

[blowlamp]

Because this is not a mandatory part of OpenTherm spec.

I see, but that seems to imply it must be a mandatory part of the spec for the boiler, although I admit I don't know if it is or it isn't.

[Dan_Robinson]

Because this is not a mandatory part of OpenTherm spec.

Seems a shame not to make the most of a feature set.

Agreed. If it was my previous post that you had in mind, then what I meant to convey was that the flame would modulate by vertue of OpenTherm requesting a specific flow temperature from the boiler. & do.

It only reminded me that it had been mentioned by a couple of posters.

[blowlamp]

I've cut & pasted a few things below from tinternet.

Quote:
While shopping for Opentherm equipment with home automation in mind, it can be useful to have some idea to which extent boilers and thermostats support the opentherm protocol. Only some messages are mandatory (ID's 0, 1, 3, 14, 17, and 25), all others may or may not implemented. (Yes Daalderop, support for MsgID 14 is mandatory.)

Which I think refers to things in this picture.

Capture.jpg

So is one to conclude that MsgID 14 governs the maximum flow temperature and is required in both boilers and controllers?

[paulockenden]

Perhaps having the original question would have helped

Many people asked what the Intergas problem was. I've seen the question several times now.

Nobody ever said that it was that Evohome wouldn't pair with the internals directly. And someone, can't remember who, said on another forum that the problem was that Intergas couldn't support the data rate. And that it was to do with multiple vs single zones.

[HenGus]

Many people asked what the Intergas problem was. I've seen the question several times now.

Nobody ever said that it was that Evohome wouldn't pair with the internals directly. And someone, can't remember who, said on another forum that the problem was that Intergas couldn't support the data rate. And that it was to do with multiple vs single zones.

Quote:

It works well, but doesn't appear to modulate with multiple zones. Investigations and upgrades are in progress.

In the mean time (as OpenTherm is an upgrade anyway) you can use weather comp and Evohome together. Unquote

Read more: https://www.diynot.com/diy/threads/i...#ixzz4pYoucZn6

[StephenC]

Because this is not a mandatory part of OpenTherm spec.

It seems to me that neither the boiler (slave), or controller (master) have this as mandatory to be able to set max ch flow temp.

That’s a recipe for disaster (reality in this case).

Leading me to observe either:

1. OpenTherm specifications are flawed (this is my current opinion)

Or

2. Certification and governance of OpenTherm products is flawed leading to incompatible products on the market



I did look at this when I was troubleshooting my Viessmann OpenTherm problem with max temps.

See my response on this page to Bruce where I have referenced the OpenTherm spec where I believe I found that Viessmann were probably not at fault (if I was understanding the spec document correctly - which I seems to be as I had confirmation from OpenTherm association):

http://www.wordpress-1219309-4387497.cloudwaysapps.com/vbulletin/showthread.php?5133-Opentherm-EvoHome-Viessmann-111-W-overshoots/page10

I’ve reported these issues directly to the OpenTherm association and did not really get much out of them in the way of help or that they would liaise with Viessmann on the issue. They suggested I contact Viessmann who in turn told me to get their OpenTherm controller or go back to BDR91 on/off control.......

I got this in response to my report of interoperability issues:

“Dear Stephen,

I’m chairman of the Technical Committee of the OpenTherm Association. I do agree with you statement that the maximum supply set point is an option for a master device (room control).
The boiler should also work properly with a OpenTherm controller without the possibility to set the maximum supply temperature.
I propose you contact Viessman to solve this issue in a for you acceptable way.

Regards,
Twan Smets”


Stephen.

[top brake]

It seems to me that neither the boiler (slave), or controller (master) have this as mandatory to be able to set max ch flow temp.

That’s a recipe for disaster (reality in this case).

Leading me to observe either:

1. OpenTherm specifications are flawed (this is my current opinion)

Or

2. Certification and governance of OpenTherm products is flawed leading to incompatible products on the market



I did look at this when I was troubleshooting my Viessmann OpenTherm problem with max temps.

See my response on this page to Bruce where I have referenced the OpenTherm spec where I believe I found that Viessmann were probably not at fault (if I was understanding the spec document correctly - which I seems to be as I had confirmation from OpenTherm association):

http://www.wordpress-1219309-4387497.cloudwaysapps.com/vbulletin/showthread.php?5133-Opentherm-EvoHome-Viessmann-111-W-overshoots/page10

I’ve reported these issues directly to the OpenTherm association and did not really get much out of them in the way of help or that they would liaise with Viessmann on the issue. They suggested I contact Viessmann who in turn told me to get their OpenTherm controller or go back to BDR91 on/off control.......

I got this in response to my report of interoperability issues:

“Dear Stephen,

I’m chairman of the Technical Committee of the OpenTherm Association. I do agree with you statement that the maximum supply set point is an option for a master device (room control).
The boiler should also work properly with a OpenTherm controller without the possibility to set the maximum supply temperature.
I propose you contact Viessman to solve this issue in a for you acceptable way.

Regards,
Twan Smets”


Stephen.

Interesting thanks for sharing

It is precisely to assure interoperability that the ch tmax is not mandatory

Twan advised you in the correct way

Customers need to lobby the boiler manufacturers to comply with the OT protocol spec and follow the spirit of OpenTherm standard rather than closing access or being protectionist by not selling OpenTherm compatible boilers in the UK market

It tends to be the German boiler manufacturers that are resisting adoption of OpenTherm in the UK.

[blowlamp]

Interesting thanks for sharing

It is precisely to assure interoperability that the ch tmax is not mandatory

Twan advised you in the correct way

Customers need to lobby the boiler manufacturers to comply with the OT protocol spec and follow the spirit of OpenTherm standard rather than closing access or being protectionist by not selling OpenTherm compatible boilers in the UK market

It tends to be the German boiler manufacturers that are resisting adoption of OpenTherm in the UK.

My boiler & controller are from different manufacturers in the Netherlands. The boiler allows the controller to set the CH maximum temperature and the controller has the ability to do it. It seems logical to me - the boiler's the slave and the controller is its master. So it's an odd thing in my view when a CH boiler master controller can't set a maximum CH water temperature limit.

[The EVOHOME Shop]

My boiler & controller are from different manufacturers in the Netherlands. The boiler allows the controller to set the CH maximum temperature and the controller has the ability to do it. It seems logical to me - the boiler's the slave and the controller is its master. So it's an odd thing in my view when a CH boiler master controller can't set a maximum CH water temperature limit.

As top brake has said, the spec does not require the master to set Tmax. As much as we stamp our feet, Honeywell have followed the spec laid down by the OpenTherm Association. Don't you have an Intergas boiler and can set Tmax at the boiler anyway?

[blowlamp]

As top brake has said, the spec does not require the master to set Tmax. As much as we stamp our feet, Honeywell have followed the spec laid down by the OpenTherm Association. Don't you have an Intergas boiler and can set Tmax at the boiler anyway?

Ok, so it's not mandatory, but is it optional?

To answer your question: I do have an Intergas boiler and I set Tmax on the master controller in the hallway.

[The EVOHOME Shop]

I've cut & pasted a few things below from tinternet.

Quote:
While shopping for Opentherm equipment with home automation in mind, it can be useful to have some idea to which extent boilers and thermostats support the opentherm protocol. Only some messages are mandatory (ID's 0, 1, 3, 14, 17, and 25), all others may or may not implemented. (Yes Daalderop, support for MsgID 14 is mandatory.)

Which I think refers to things in this picture.

[ATTACH=CONFIG]1059[/ATTACH]

So is one to conclude that MsgID 14 governs the maximum flow temperature and is required in both boilers and controllers?

ID 57 is Max CH Water Setpoint, not ID 14, which is the modulation of the boilers fan I believe... Limiting the fan modulation wouldn't stop the boiler hitting 88 degrees before you ask, it would only limit it doing it as fast...

[Dan_Robinson]

ID 57 is Max CH Water Setpoint, not ID 14, which is the modulation of the boilers fan I believe...

I figured this out the other night buggered if I can remember exactly what it was.... Not fan speed though

[top brake]

My boiler & controller are from different manufacturers in the Netherlands. The boiler allows the controller to set the CH maximum temperature and the controller has the ability to do it. It seems logical to me - the boiler's the slave and the controller is its master. So it's an odd thing in my view when a CH boiler master controller can't set a maximum CH water temperature limit.

Not every boiler allows the ch Tmax to be set. So to avoid conflict Honeywell controls don't try to.

Remember the best selling OpenTherm thermostat in NL has a Honeywell logo on it... Honeywell are experts in OpenTherm as they invented it...

[StephenC]

Not every boiler allows the ch Tmax to be set. So to avoid conflict Honeywell controls don't try to.

Remember the best selling OpenTherm thermostat in NL has a Honeywell logo on it... Honeywell are experts in OpenTherm as they invented it...

But boilers (slave) don’t have to set the max ch flow temp according to the OpenTherm spec either!!


When both sides (master and slave) components of the control system are designed to set no value (which is possible and allowed within the specs - Honeywell/Viessmann) so the control system as a whole is not fit for purpose as has been shown. Finger pointing occurred in both directions in this case, and both were right unbelievably. (Honeywell vs Viessmann). That’s what led me to start assessing OpenTherm itself as a specification.

OpenTherm specification is flawed as it stands (the version I assessed)

What I’m saying is the OpenTherm specification must be updated to dictate that one or the other (master or slave) sets a value.

It’s irrelevant at this point taking about Honeywell EvoHome, Nest or Intergas or Viessmann etc. Fundamentally it’s a spec problem that will manifest itself again and again. Because the spec allows for it.

P.S. I still think EvoHome with BDR91 is great.

;-)

Stephen