How is "Heat On" establshed?

Posted on
Thu Nov 03, 2016 2:23 pm
jh71283 offline
Posts: 125
Joined: Jun 16, 2014

How is "Heat On" establshed?

Hello

I was wondering how the plugin establishes the heat on / off status... is it a simple check if target < actual then heat = on?

The reason I ask is I am pretty sure that my heating comes on / off regularly to maintain the temperature, but the events I have connected to the heat on event don't fire.

On reviewing my temperature logs, the temp is not actually dropping below the target, so I am guessing the evohome is doing some clever stuff to maintain the temperature.

Thanks!

Posted on
Thu Nov 03, 2016 9:18 pm
ELWOOD offline
Posts: 214
Joined: Feb 11, 2007
Location: Ramsey, NJ

Re: How is "Heat On" establshed?

State of heat on indicates the system is set for heating. What you want is when the system is calling for heat.
Make a trigger for device state changed use "heater equipment state" That should fire when the furnace burner
turns on and off.

Elwood

Posted on
Sat Nov 05, 2016 10:16 am
jh71283 offline
Posts: 125
Joined: Jun 16, 2014

Re: How is "Heat On" establshed?

OK, cool. Will give that a shot.

Thanks!

Posted on
Sat Nov 05, 2016 10:18 am
jh71283 offline
Posts: 125
Joined: Jun 16, 2014

Re: How is "Heat On" establshed?

Ugh. It looks like the Heating Equipment State is the one I have been using all along.

It just doesn't seem to tie up with when I hear the heating pump running.

Posted on
Sat Nov 05, 2016 5:22 pm
ELWOOD offline
Posts: 214
Joined: Feb 11, 2007
Location: Ramsey, NJ

Re: How is "Heat On" establshed?

This can get somewhat confusing depending on the type of heating system you have. Heating Equipment State comes from the thermostat and says the room is cold and tells your
furnace to start producing heat, when the room temperature is satisfied the Heating Equipment State changes to off and the thermostat tells the furnace to stop heating. What happens
in the furnace depends on the type. With a hot water system when the thermostat says give me heat it opens a zone valve, the zone valve opening turns on the circulator pump and the
radiator starts getting worm. Now the water in the furnace starts dropping in temperature so an other thermostat in the furnace now turns on the burner and heats up the water. When
the furnace get the water hotter the burner stops but the zone valve may still be open if the room is not up to temperature. So the burner may be turning on and off until the room reaches
the set temperature. The heat pump is similar in that the compressor can be turning on and off when heating, to complicate things more heat pumps also have a backup electric heating
element for when it gets colder out doors and the compressor does not produce the required heat. If you listen for the fan you will see that it turns on when the thermostat calls for heat
and stops when the room reaches the set point.
Hope I haven't made this to confusing.

Elwood

Posted on
Sun Nov 06, 2016 9:47 am
jh71283 offline
Posts: 125
Joined: Jun 16, 2014

Re: How is "Heat On" establshed?

Thanks Elwood, that does make sense.

Now I just wish that my boiler was connected via a standard plug so that I could just install a power meter to get a definitive count on when the boiler is running :)

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