Gateway use without a boiler

This Forum is about the Opentherm gateway (OTG) from Schelte

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Gateway use without a boiler

Postby xAPPO » Fri Aug 12, 2016 2:58 pm

Unfamiliar with Opentherm so I am not sure if it requires an active end to end acknowledge/handshake to work ? Or could I just attach this gateway to a 'thermostat' that outputs using the OT protocol and intercept its messages (with no boiler connected) ? My boiler does not currently have an OT interface but my next one might.

I am trying to get at the setpoint information output by a Honeywell evohome system. Currently it simply uses on/off relay control but I would like to try adding the Honeywell evohome Opentherm bridge and then extract the flow setpoint info and convert that to an analogue 0-10V signal to modulate my boiler to achieve that flow temperature. The latter aspect I know I can do as I have that feature currently.

https://theevohomeshop.co.uk/honeywell- ... r8810.html

Would a 'boilerless' OT interface work with this gateway or is the boiler endpoint required to maintain the OT communication ?

K
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Re: Gateway use without a boiler

Postby marcelr » Fri Aug 12, 2016 5:23 pm

I use an OTGW with the interface firmware to do just this. No boiler attached to the OTGW. A computer with USB-to-serial interface catches the OT messages from the thermostat and sends replies (using some homebrew code that I made).
Schelte sent me a newer version of the interface firmware (v1.1) The one on his site is still 1.0, IIRC, and does not work properly for this purpose.

grtz,

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Re: Gateway use without a boiler

Postby hvxl » Sun Aug 14, 2016 8:03 pm

With that confirmation that interface firmware v1.1 works fine, I've now published it on the web site.
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Re: Gateway use without a boiler

Postby marcelr » Sun Aug 14, 2016 9:07 pm

... interface firmware v1.1 works fine ...

Yes, used it for some months now, no glitches whatsoever.

grtz,

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Re: Gateway use without a boiler

Postby mike7 » Sat Aug 27, 2016 5:24 am

Schelte,

I would like to try interface firmware without thermostat, if I remove slave interface part from schematic how I should connect pins 3 & 17 of the PIC? Pull down pin 17 and pull up pin 3 with 4k7 resistors, right?

Thank you,
Mike
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Re: Gateway use without a boiler

Postby hvxl » Mon Aug 29, 2016 4:35 pm

Pin 3 is an output, so there's no need to pull it anywhere. If you pull pin 17 low, it looks to the firmware as if a thermostat is connected. If you pull it high it thinks there is not thermostat. The firmware only reports a change, but otherwise does not change its behaviour based on this information. So either should work fine. With the normal PCB it's easiest to pull the input low (by installing R6).

If you are not going to install the slave interface you don't need 24V. In that case you may want to consider using a transformer with a lower output voltage so the voltage regulator doesn't have to dissipate as much power.
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Re: Gateway use without a boiler

Postby Bogdan » Sat Dec 10, 2016 2:26 pm

Hello guys,

I have just bought an Evohome controller ATC928G3000 with OT bridge R8810. I have bind the system together and connected to the OTGW. I have OT Monitor v.4.3.0.2 for windows and firmware gateway v.4.2.5.

I don't have a boiler with OT interface so I didn't connect anything to OTGW X2 connector. All I want to do is to listen what Evohome controller is sending on OT interface.

The response I see is "T90800002 Write-Data Message ID 128: 2" constantly sent at 1 sec and nothing else. Is this behavior normal?

I have checked that the communication between Evohome controller and R8810 is good by sending RF check and the test passed: meaning the RED Led from R8810 was flashing 5 times (excellent signal) but on Evohome controller I didn't get any message like "Signal strength:Excellent" (which normally I receive in case of BDR91 connection check)

I have tried to rebind several times and noticed that when R8810 is unbound than the OTGW message is "T90800002 Write-Data Message ID 128: 0"
and immediately after bounding with controller the value changes back to "T90800002 Write-Data Message ID 128: 2".
What is strange for me is that R8810 LED flashes GREEN only 2 times at 10 sec. interval immediately after bounding and after that LED flashes
RED 3 times with 3 sec. pause and the cycle repeats but only with LED flashing RED.
Even if I switch OFF the Evohome controller (remove the batteries) I see the same messages on OTGW meaning R8810 somehow sends independently this message.
If it is bounded it sends "T90800002 Write-Data Message ID 128: 2"
If it is unbounded it sends "T90800002 Write-Data Message ID 128: 0"

I have run diagnostic v.1.1 firmware Test 2 and Test 5. For Test 2 I see a lot of numbers I don't understand and sometimes there are a few with
Red color. For Test 5 the voltage of Thermostat I suppose is within the limits

Thermostat: 0.79, 2.13
Boiler: 0.00
Reference: 1.21

So I am stuck now and don't know where the problem is and why I don't see other messages. Or maybe this is normal behavior?
Can someone give me some hints what to do next :?:
If needed I can provide a Log file.

Thank you very much!

Greetings,
Bogdan
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Re: Gateway use without a boiler

Postby hvxl » Sun Dec 18, 2016 5:39 pm

I don't think you report accurately what OTMonitor shows. It will not report different things for the same message T90800002. That will always be translated to "Write-Data Message ID 128: 2". "Write-Data Message ID 128: 0" would be T90800000.

In any case, if you don't have a boiler connected, the thermostat does not get a response to its T90800002 request. It then repeats the request every second. So what you observed is to be expected.

If you don't have an Opentherm boiler, you can load the interface firmware in the OTGW and then write some program that simulates the boiler's responses.
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Re: Gateway use without a boiler

Postby Bogdan » Sat Jan 07, 2017 4:48 pm

Schelte, thanks for your reply!
Can someone give me a hint on how to do the program that simulates the boiler response?

Greetings,
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