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Icon_missing_medium
Feb 19, 2016 10:36pm
8 posts

I am sending zwave "smart plug" and other energy reporting device info to SEG from an ISY home automation controller.  The zwave devices report current power (watts) and energy (kWh).  I belive the kwh is repported as total to date, meaning it is always a big number, vs the small incremental delta.

My question is: how to deal with this for SEG.  I would think there are two basic options:

1) use SEG settings to deal with the repettive total kwh being sent (but how and what settings?)

2) Only send current W data and have SEG translate into kwh data.  This could be via a single stream or by sending a duplicate stream of the W data with an E in the transmission packet.  Again there would be SEG configuration settings I dont fully understand.

Any advice would be greatly appriciated.  I have asked this in a thread kwh from a GEM, but it may not be relevent to that thread, so I am starting this specific thread.

 

THanks!!!!!!!

 

Thanks! 

 
Samotage_300_medium
Feb 19, 2016 11:10pm
555 posts

Hi,

There is no specific setting in SEG for this.  Both kinds of functionality were prototyped a long time ago, and found to have issues, particuarly converting W in to Wh as this is dependent on a time period - for which this is not reliably known between data points and the device can go offline, causing havoc in the calculations!

For subtractive processing, there are other problems as well.

The best advice is to calculate the subtraction on site before sending this data to SEG, that way you are in control of the subtraction processing and getting this right.

Hope this helps!

Sam, @samotage

 
Icon_missing_medium
Feb 19, 2016 11:24pm
8 posts

Hi Sam

 

THanks so much for your speedy reply!

If I understand correctly, you are saying

 

1) It is NOT feasible to send a duplicate P (w) transmission, even coded with an E, because the strnsmission interval would not be precise.  For the sake of discussion, assuming reliable transmission, what interval or calibration formula would one use?  

2) Sending E (kwh) data isnt viable, because SEG needs to receive "delta" (change) in kwh, not totak kwh. Is that the point?

 

I am not sure if the ISY controller can readilly do calculations to obtain change-in-kwh data for transmission.

Doesn't this issue come up frequently?  Would it be hard to implement a subtractive calculation in SEG?  I imagine so, or your would have done it.

Any more guidance you can suggest?  I have 6500 views on my thread in the ISY forums on my effort to send smart plug date to SEG.

Here is the recent post where I repoer SUCCESS...almost, but for this issue...

http://forum.universal-devices.com/topic/12682-...

 

Thanks!!

 

 

 
Icon_missing_medium
Feb 24, 2016 3:17am
8 posts

Sam: I 've on looked on SEG at the E data points sent from GEM/Dash and from ISY.  I've thought about your comment, below.  My question is:

As you state, sending incremental data points means: the total is made from the sum of the parts, which is very susceptible to errors.  For this exact reason, isn't it actually better/error-free to send cumulative data points along with time-stamp (As ISY does). This way:  the total always reconciles to date/time.  In other words, by always sending Total kWh to -date, it never matters if transmissions are lost because actual total is always correct (intermediate intervals might be off, but that's much less inmportant).

samatage said:

"...ound issues, converting W in to Wh as this is dependent on a time period data points and the device can go offline, causing havoc in the calculations!"

For subtractive processing, there are other problems as well."

Am I worong about this?

Can SEG receive data this way?

THanks!!

 

 
Samotage_300_medium
Feb 24, 2016 4:32am
555 posts

Right now, SEG can't, and you have a point.

SEGmeter is designed to continually calculate the interval energy consumption, and will store this up if the internet fails and forward when it returns.

In practice, there is minimal systematic error in this approach and it works very well.

I've been thinking about this, and may do an enhancement to deal with this situation.

Sam, @samotage

 
Icon_missing_medium
Feb 24, 2016 4:55am
8 posts

Thanks for another reply, Sam.

I'd think being able to tie to Total kWh (etc) by Date/Time is the cleanest of all solutions, but appriciate there may be more under the hood, making this not simple to implement.

At this time, here is my plan to send from ISY: (note I send all circuits from GEM/DASH and plugs, and other things from ISY (see below).

- P (W): send every 3-15 minutes depending on device.  It's not worth the ISY resource

overhead to get finer granularity (and I have perfect 20 sec data on circuits directly on GEM or current status on ISY)

- E (Wh): send every hour.  THis seems like a good balance between frequency and resources.  It also makes the Wh calc very easy.  If a transmission is missed, I have 23 more for eash day.  Looking at Wh with > 1hr granularity is pointless, look at P (W) instead.

Sound reasonable to you?

[Note: I send to SEG from GEM/Dash 32 circuits + V + T.  From ISY I send "smart plug" etc data.  For me having the plug data is critical as a few of my circuits feed most of what I want to track, e.g IT, AV, Mechanical.  The combo is perfect.  Also, as you likely know, many other streams could be sent from ISY to SEG, e.g plotting lock opening, motion-detector activity, home/away graphing, etc, etc, etc. Withe the two one could chart energy while home vs while away; irrigation duration vs water usage vs temp, etc.  ISY variables allow some math so the streams are basically up to the imagination. 

 
Samotage_300_medium
Feb 25, 2016 1:04am
555 posts

There is plenty of imagination as what can be done with the data.  A heap of unit types exist already, and new ones can be added easy enough. which has been done in the past :)

I would recommend sending your energy data more frequently than hourly, at least with every power data point. The aggregations are done on a half hour basis and hourly would be running against the grain - as the in between half hours will be missed!

There are reports and calculations in seg to allow you to summarise things by date as well!

Sam, @samotage

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