Author Topic: Low power loads  (Read 2412 times)

tlveik

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Low power loads
« on: April 22, 2017, 09:21:09 PM »
I'm looking at the specs for the Ted Pro Home (I have a Ted 5000) and the 20 amp core for the spider has a minimum load of 60 watts.  Is that really true?  Is it not capable of seeing loads less than 60 watts?  My Ted 5000 can.

Tom

pfletch101

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Re: Low power loads
« Reply #1 on: April 22, 2017, 11:02:02 PM »
The primary CT/MTU channels of the Pro Home have similar specs to those of the 5000. The Spyder system for the Pro Home has no equivalent in the 5000. From what I can gather, it proved impossible to implement the same low current accuracy for multiple Spyder channels as for a single primary channel, within the constraints of cost and silicon real estate within which the designers were working. Rather than report spuriously accurate low power data whose actual error limits spanned zero, they chose to report such data as zero, so that users would know what they didn't know.  :)
Peter R. Fletcher
TED Pro Home - main MTUs monitoring utility and PV Solar feeds; 2 Spyders monitoring selected individual circuits

tlveik

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Re: Low power loads
« Reply #2 on: April 23, 2017, 10:01:33 AM »
That's a bummer.  I don't see any point in getting a spyder then since during low power times of the day, most of my sub-circuits will be less than 60 watts and they will all read zero.

Do you happen to know what the power resolution is for the 20 amp core?  I'm not asking about accuracy, just resolution.

Tom

pfletch101

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Re: Low power loads
« Reply #3 on: April 23, 2017, 02:05:39 PM »

Do you happen to know what the power resolution is for the 20 amp core?  I'm not asking about accuracy, just resolution.

Tom

I don't think that it is specified anywhere, but, eyeballing my data, it looks like about 30 W - slowly changing readings seem to jump or 'jitter' in steps of about this magnitude.
« Last Edit: April 23, 2017, 02:10:16 PM by pfletch101 »
Peter R. Fletcher
TED Pro Home - main MTUs monitoring utility and PV Solar feeds; 2 Spyders monitoring selected individual circuits

tlveik

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Re: Low power loads
« Reply #4 on: April 23, 2017, 05:27:26 PM »
Thanks, that helps.

Tom

lundwall_paul

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Re: Low power loads
« Reply #5 on: April 28, 2017, 01:33:53 PM »
That's a bummer.  I don't see any point in getting a spyder then since during low power times of the day, most of my sub-circuits will be less than 60 watts and they will all read zero.

Do you happen to know what the power resolution is for the 20 amp core?  I'm not asking about accuracy, just resolution.

Tom

Exactly why I removed the spyders from my panel. They just are not very useful in a typical home. Most of the homeowners are aware of the high ticket items that drive the cost up. I enjoy the overall TED Pro and I find it very accurate. My actual power bills vs what the TED records are typically within $10. 99% of the discrepancy is when the meter is actually read. Typically my meter is read on the 18th of the month, but if the 18th is on a weekend or holiday wont be read until the following workday.  FYI you can sell your spyders on eBay.

tlveik

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Re: Low power loads
« Reply #6 on: April 29, 2017, 08:27:11 PM »
As much as I like my Ted 5000, it would be nice to be able to see what is happening on sub-circuits.  Even though those low power loads don't contribute a lot to overall consumption, it would be useful to be able to see what is happening on those sub-circuits.

Tom

geekfarmer

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Re: Low power load
« Reply #7 on: July 29, 2017, 02:32:10 PM »
If they are measuring the current with an 8bit a to d, the minimum non-zero reading on a 20 amp line would be about 37 watts. So, depending on how they read the current, anything less than that would read 0.