Heater turns on without actual demand for heat!

[RobK]

Hi all,

I use OTGW for half a year now, much to my liking.

However on two occasions now my USB OTGW has erractly started heating the house (thermostat at 14, house at 21 degrees in summer).

This ONLY happened with the USB connector disconnected.
I have bridged the MAX232 socket as per instructions, and use a Prolific PL2303 USB-serial convertor.
Also the thermostat (Honeywell Round Modulation) at that point reports an 'F'(ailure) sometimes.

Has anyone ever noticed the same behaviour?

Is it possible that the communication with the Opentherm thermostat gets garbled and OTGW goes into On/Off mode?

If so, could this be corrected by changing the comparator voltage?

Does a setting exists that prohibits the OTGW to go into simple On/Off-mode?

Curious as to your experiences, regards,
Rob

[Bwired]

I had the same problem!
Do you have a remeha?

For now i put my remeha in ecomode, only that stopped the heating....
Still have ro investigate further

[RobK]

I do have a Remeha Quinta 45.

Do you also have this problem ONLY with the USB cable disconnected? Otherwise everything works super.

So why bother and not just leave the USB connected? Because it is on a seperately powered TP-LINK-device. The same happens if someone pulls the plug on that... Thats exactly what happened the aforementioned two times!

I can't directly see the connection with having a Remeha. Any ideas?

[Bwired]

I have mine connected upon an ethernet device.
But i did not find out yet that its caused by the opentherm gateway
Could be another problem for me?
But i do know that my heating goes ON even when setpoint is set to 8

[hvxl]

Thinking about this issue, I realized that in case the gateway receives multiple invalid messages from the thermostat, it may present a low level OT signal to the boiler for some period of time. If this situation lasts longer than 15 seconds, the boiler may interpret that low level as a heat request. To prevent that, I have now added a variable that keeps track of when the last message was sent to the boiler. If that's over 5 seconds ago, the gateway will make the OT signal to the boiler high, thus preventing the unwanted heating.

You can download firmware 4.2.4 and check if that improves the situation.

Of course this change doesn't help with the communication problem. I have no idea how disconnecting the USB could cause such problems, but other users have reported similar observations in the past. My original design doesn't have the USB interface. It was an initiative of the person who started the web shop. I don't have such a setup, so I am unable to provide much support for that configuration.

@Bwired: Do you also see communication issues when this happens? How ecomode could have any effect on this is quite mysterious to me.

[Bwired]

Thanks Schelte!
agree I dont understand that also, so cant tell

I will sure test the firmware and get back here...
regards Pieter

[RobK]

Hi Schelte,

saw your message about the new firmware just now. Have installed it and will try and provoce the same situation in the forthcoming days.
Thanks for all the thinking & work you've put in this matter!

Rob

[RobK]

Regrettably the new firmware did not improve the issue. Within minutes after I disconnected the USB cable the boiler indicated a heat-demand.
The thermostat did not (yet?) indicate an F(ailure) at this point. There was definitely no demand for heat based on the thermostat (13 degrees, where the house was at 20).

I'm considering to decouple the USB-cable from the OTGW by removing the jumper-wires and inserting a MAX232. Must have something to do with the USB cable drawing a current from the PIC...

Any other clues anyone?
Rob

[hvxl]

Without the serial connection there's very little that can be done with regard to debugging. Do you have any LEDs connected? They could give some indication if the gateway is still receiving messages, detects lots of errors, etc. when this happens.

[RobK]

No LED's attached at the moment I'm afraid.