Question on remote overwrite functionality

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jan341
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Question on remote overwrite functionality

Post by jan341 »

Reading the OTGW documentation, I interpret that the F2 thermostat function under options must somewhere store the overwrite setpoint.
Upon a read Id=9 from the thermostat the OTGW sends a read-ack with the stored value. If a real temp, the thermostat will take this value as its room setpoint, if a zero the thermostat cancels its overwrite state.

This function comes in two flavors, a mandatory where the thermostat user can not change the overwrite setpont and a flavor where the thermostat user is allowed to overrule the overwrite. This also comes in two flavors: manually and programmatically. This setting is communicated to the themostat with Read-Ack message id= 100 from the OTGW.

Question: what is the default enable overwrite value ?

In the F2 function you can choose for "temporary" or "constant". Than the OTGW must somewhere store a value for the Id=100 message, as the thermostat does a read and the OTGW should than send its stored value. So, if I understand it correctly, the F2 function does two things: store remote overwrite setpoint and store the overrule enable flags.

From the F2 function you can stop the overwrite with the button "schedule". I presume it stores a zero in the rem overwrite setpoint and, it sets the overrule on allowed.

Question: If the thermostat user overrules the remote setpoint, than the OTGW should not send upon read id=9 the remote overwrite setpoint (if it does, the thermostat once again comes in overwrite state). So, how does OTGW know that it should "reset" the remote overwrite setpoint to zero (as zero would reflect the non overwrite state of the thermostat) ? And I presume also enable the overrule ?
hvxl
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Re: Question on remote overwrite functionality

Post by hvxl »

You are right. When issuing a TT or TC command, the OTGW stores the requested temperature along with a bit for whether a TT or TC command was used. Whenever the thermostat reads MsgID 9, the override temperature is returned. When the thermostat reads MsgID 100, the TT/TC bit is examined to return the Program change priority bit. The OTGW always returns the Manual change priority bit as set (enabled).

The OTGW monitors MsgID 16 to check that the thermostat picked up the override remote setpoint. Unfortunately some thermostats don't set the room setpoint exactly to what was requested, so the OTGW allows for a deviation of 0.125 degrees. If MsgID 16 doesn't match the requested override setpoint within 3 tries, the override gets cancelled.

Once the override setpoint has been accepted by the thermostat, the OTGW keeps monitoring MsgID 16. If a user or the schedule changes the setpoint, the value in MsgID 16 will no longer match the stored override setpoint. At that point the OTGW firmware also cancels the override.

The "schedule" button sends a TT=0 command. As a 0 temperature cancels the override, it doesn't matter whether TT=0 or TC=0 is used.
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