Author Topic: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit  (Read 3230 times)

Offline nathanhall

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Couldn't find the answer or this debate in search so here goes:

Is there any way to accurately report power for a multi zone/multi tstat environment with one one-stage furnace and A/C?

If my AC kicks on for zone 1, the AC is on and consuming around 2300W.  If it then kicks in for zone 2 as well (while zone 1 is receiving air) there is no significant change in power consumption - a few dampers open but the AC unit itself is still on and consuming roughly the same amount of power regardless of the number of zones requesting air.

If I enter "2300,2300,750" into the "energy used" section of my tstats Vera accurately reports 2300W of usage when the AC or heat kicks on when requested by one tstat/zone.  If the second zone/tstat kicks on as well, into which I have entered the same "2300,2300,750" stats, Vera now reports my wattage usage as 4600W (reading 2300 from both tstats which are on). 

Is there a way to get Vera to post 2300W of usage if any number of zones/tstats are active?  Something like 0 tstats active = 0W, 1 through X tstats active = 2300W cumulative?

Offline nathanhall

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Re: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit
« Reply #1 on: January 26, 2013, 11:07:38 am »
I'm surprised no one has an answer to this so far - the heat or A/C is such a dominant energy consumer in any house that looking at overall house energy use is nearly useless without getting this part right.  It's frustrating that I've got pretty much all other 80+ z-wave devices reporting correctly, but can't figure this critical portion out.

The only progress I've made is to use the Combination Switch plugin to switch on whenever either tstat is consuming energy - but this plugin doesn't have a field for energy used so that's been no help so far.  Maybe I'll investigate the "virtual thermostat" plugin to see if that could help.

Offline guessed

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Re: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit
« Reply #2 on: January 26, 2013, 05:11:27 pm »
The simple power [simulation] options in Vera assume that a Single device controls a single power sink.  In the case of HVAC, that's not the case.

If you want to continue with simulated power modelling, you could create/register a Device with Vera to represent the actual HVAC unit, then register power usage (2200w) against the new device instead of the discrete T-Stats.

The easiest type of device would be a virtual switch.

You'd have to write script, or use one of newer Scene plugins, to automate keeping the state of the Virtual switch in sync with both T-Stat units.

This will give you approximate usage data, since these things vary depending upon which components of the HVAC system are running at any given moment.



The alternative option is to add a Power measurement device to the HVAC itself, instead of a simulation.  This could be a Brultech, CurrentCost, or similar device as long as it can accurately record the data.

In practice, using a Brultech GEM, I see a lot of variation in the physical power readings from my central fan unit, so I'm not sure how useful "fixed" values are for this type of device.

Offline nathanhall

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Re: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit
« Reply #3 on: January 28, 2013, 05:03:44 pm »
Ok - I've created a virtual switch which turns on whenever either tstat is on.  Is there a way to force an "energyused" field to objects (like virtual switches) that do not have this field in the GUI?

The Brultech looks like a great longer-term option - however I just became a dad and need to keep my projects a little less ambitious for now, or at least things I can stop working on and easily pick up later.

Offline guessed

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Re: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit
« Reply #4 on: January 29, 2013, 12:40:39 am »
If the Virtual switch doesn't have the "Energy used" field, normally in the Settings tab, then you can manually add one by using the Advanced Tab and setting(s) as follows:

New Service: urn:micasaverde-com:serviceId:EnergyMetering1
New Variable: UserSuppliedWattage

But what's displayed in the status line is this:

New Service: urn:micasaverde-com:serviceId:EnergyMetering1
New Variable: Watts

... which will likely need to be filled in with a value when the HVAC unit is actually on (2200W in your case).  I did modify the VSwitch device to indicate it impl the S_EnergyMetering1.xml (even though it didn't) but I don't think that part is necessary for the UI to change to display the value.

Offline nathanhall

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Re: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit
« Reply #5 on: February 08, 2013, 05:49:05 pm »
Thank you very much - I tried your suggestions above and now everything's working - I set my power consumption on the actual tsats to 1,1,1, and I have my virtual/combination switch turn on whenever it detects power consumption from either stat.  The virtual switch is set to ~2800W for the Watts field and that shows up in both the Vera native energy reporting and dataMine.

One last nagging thing of minimal importance - I'm not certain how to convert the virtual switch from a light/binary switch to a climate device.  I don't want or need to do this for the GUI, but so that the Vera native energy tracking tool will show the virtual switch energy consumption as being from a climate device vs. a binary light.

Offline garrettwp

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Re: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit
« Reply #6 on: February 08, 2013, 05:54:16 pm »
This is not possible. Changing the type of the device will cause the virtual switch to be inoperable.

- Garrett

Offline Brientim

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Re: Accurately Reporting Power With 2 Tstats/Zones For One HVAC Unit
« Reply #7 on: February 08, 2013, 06:30:38 pm »
Have a look at this thread. A similar request was raised recently
http://forum.micasaverde.com/index.php/topic,13300.msg99038.html#msg99038