In addition to some bug fixes, the following changes have been made since 5.1:
Handle Smart Power level changes while in monitor mode.
- Before, the OTGW would detect a Smart Power request and invert the output of the comparator. In monitor mode, that also invert the output to the boiler, resulting in an invalid Smart Power request to the boiler. Depending on how the boiler interpreted the invalid request, things could stop working, or the thermostat and boiler would still communicate, with the OTGW reporting lots of Error 03. In monitor mode, the OTGW now always passes on the line levels unaltered. This means that the boiler must support Smart Power for a thermostat to be able to use Smart Power when the OTGW is used in monitor mode. The OTGW will still recognize Smart Power requests. But it will now only invert the levels for its own use. This means that it will now be able to correctly decode the messages.
- Some boilers would spontaneously turn on Smart Power without a request from the thermostat, if they recognized the master MemberID code. The OTGW will now invert its receive mode when a boiler switches its idle current level. The OTGW will also invert its receive mode on the thermostat interface when the thermostat switches its idle voltage without first establishing Smart Power support. This should help the OTGW to understand messages from either side when they unexpectedly switch to Smart Power.
- Some people use the OTGW to drive the boiler differently than what the thermostat says, using the CS and CH commands. Or maybe they don't even have a thermostat connected. A risk with that is that the controlling program may crash or lose the connection after setting a high control setpoint. That could lead to the house being heated way above the desired temperature and a lot of wasted gas. The OTGW will now clear a remotely provided setpoint after just over a minute. People using this functionality must now make sure the CS command is repeated at least once per minute as long as the modified control setpoint is wanted. This should not be an issue in most cases because a proper PID controller will produce a new control setpoint more frequently than once per minute.
Due to resource scarceness, this feature uses the same timer as the SC command. So both the CS and SC commands will restart the timer. When using both, it is advised that they are generated by the same application. Otherwise the risk remains that a high control setpoint is kept active by the application that updates the clock after the heating application has gone offline. For this reason OTmonitor v5.2 now implements its own 1 minute timeout if it detects a CS command when OTmonitor is configured to periodically update the clock.
- The initial voltage reference value has been changed to 1.458V (4), which translates to a line voltage that lies closer to the midway point between the high and low voltage levels defined by the Opentherm specification. This only affects users with freshly installed gateway firmware. When upgrading the firmware, the old settings will normally be copied, unless the user specifically disables that. Or if they don't use the appropriate OTmonitor version.
- The OTGW used to consider a line voltage above 19.11V as a sign that the thermostat was disconnected. This value was chosen to work with a 20V power supply. However, the calculated voltage was only accurate with perfect component values. With 10% tolerance on most components, some people would get false positives. For a long time the advise has been for the 24V rail to be at least 24V. So the disconnect threshold could be made less tight.
- When the OTGW doesn't have an active setpoint override, it used to respond to an override request with "No override". However, the boiler or a downstream gateway might have a different opinion. In this situation, the OTGW will now pass on the information it receives from the downstream device.