Author Topic: TED Pro + Spyder unusual reading (newbie, first install)  (Read 3133 times)

dduffey

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TED Pro + Spyder unusual reading (newbie, first install)
« on: May 17, 2015, 07:08:50 AM »

Just hooked up my TED Pro w/ Spyder today and noticed something unusual.

My upstairs AC circuit says it is drawing .6kw all the time, even when off (whole house is .7kw).  If I unplug the AC compressor that circuit (as measured by the spyder) drops to 0, but home usage (ECC) still says .7kw)... I I don't think it is REALLY drawing .6kw.  I haven't debugged or double checked the wiring yet but wanted to get some ideas of what might be causing that behavior.

About my system:
 * I don't have spyders on all curcuits
 * The AC has "two tied 30amp" breakers, I've a 60amp CT onto one
 * I don't know if it is balanced/unbalanced
 * I also have a downstairs unit w/ similar setup (but seems to work fine)
 * When I turn on/off the compressor (even when off) it does throw off minor sparks (suggesting there is some power?!?... but then why does't it seem to effect the ECC overall readings when unplugging it)


Could it be:
 * I've clamped onto the wrong phase?
 * I've used the wrong size of CT?
 * Some other cross wiring in the house?

Thanks,

dduffey

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #1 on: May 18, 2015, 01:14:32 AM »
I did some more troubleshooting today, and wasn't able to figure it out.  But I've eliminated the spyder port, CT, pole, and direction of current as culprints.

That particular AC circuit always reads 600'ish watts when the AC is "off".  I even went around the house and turned most everything else off... the main clamps were reading 300 watts but the AC was reading 600... which shouldn't be possible.
If I manually pull the plug on the compressor the spyder reads 0 watts, but it doesn't effect the main clamps (which should "reduce" by 600 watts).  So it seems like it is not really using 600 watts.

One more thing, when I listen closely to the compressor when the AC is off, I do hear some electrical hum/noise... could there be some noise/ground loop on the line that is causing the reading?  As I said earlier, when I use the manual override switch by the compressor it does create a minor arc even though it shouldn't be getting any power (AC is not "on").

Thanks,

pfletch101

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #2 on: May 18, 2015, 01:20:13 AM »
One of the things that may be going on is a mains loop - you may have a connection between the live wire on one circuit and the live wire of another. While this setup is not immediately disastrous, it is very dangerous, since a supposedly isolated circuit won't be (if you have only turned one of the breakers feeding the loop off).
Peter R. Fletcher
TED Pro Home - main MTUs monitoring utility and PV Solar feeds; 2 Spyders monitoring selected individual circuits

RussellH

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #3 on: May 18, 2015, 07:18:02 AM »
I suspect that your AC unit is drawing reactive current.  The current is "real" in the sense that you can measure it, but it's not "real power".  Your utility meter will ignore it.  However, the TED doesn't always do so well and while it's designed to deal with the issue, it seems to fall short of perfect.  Others have observed this with the main units and the small capacitors in solar inverters.  The cheaper spyders may not fair so well.

I'm curious as to your main unit showing 300W.  You might want to repeat your shutdown test and observe your utility meter.  You may have a load you've overlooked.

dduffey

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #4 on: May 18, 2015, 04:45:25 PM »
One of the things that may be going on is a mains loop - you may have a connection between the live wire on one circuit and the live wire of another. While this setup is not immediately disastrous, it is very dangerous, since a supposedly isolated circuit won't be (if you have only turned one of the breakers feeding the loop off).

Thanks for the help.

What is the best way to troubleshoot that?

I could turn off all circuits except the AC, verify that it reads 0, then turn on other breakers until it reads "incorrectly"?  Since it is a 1-minute reading, I would probably just do a binary search for the potential cross wiring.  Is there are better way?

dduffey

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #5 on: May 18, 2015, 05:10:43 PM »
I suspect that your AC unit is drawing reactive current.  The current is "real" in the sense that you can measure it, but it's not "real power".  Your utility meter will ignore it.  However, the TED doesn't always do so well and while it's designed to deal with the issue, it seems to fall short of perfect.  Others have observed this with the main units and the small capacitors in solar inverters.  The cheaper spyders may not fair so well.

I'm curious as to your main unit showing 300W.  You might want to repeat your shutdown test and observe your utility meter.  You may have a load you've overlooked.

I didn't turn off everything, in particular the home office (where the ECC is), kitchen computer (where I was monitoring), fridge, etc., so the 300W actually sounds about right to me.  I just turned off enough that I could see it drop below the reading for the AC.

Thanks for the explanation of reactive current, that really helps explain some of the other readings in TED, I have a power factor of about 70-80%.

If the AC (compressor) is not on though, it shouldn't be creating a reactive load, should it?

Thanks for all the suggestions!

pfletch101

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #6 on: May 18, 2015, 05:29:04 PM »
One of the things that may be going on is a mains loop - you may have a connection between the live wire on one circuit and the live wire of another. While this setup is not immediately disastrous, it is very dangerous, since a supposedly isolated circuit won't be (if you have only turned one of the breakers feeding the loop off).

Thanks for the help.

What is the best way to troubleshoot that?


Turn all breakers off; confirm with a voltage probe that the A/C socket is dead, then turn on breakers singly until you confirm/find the one (or, ex hypothesi, ones) that feed it. If there is a loop, locating the false connection may be more challenging!
Peter R. Fletcher
TED Pro Home - main MTUs monitoring utility and PV Solar feeds; 2 Spyders monitoring selected individual circuits

RussellH

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #7 on: May 18, 2015, 09:51:30 PM »
If the AC (compressor) is not on though, it shouldn't be creating a reactive load, should it?

Reactive load could be caused by capacitors or maybe even control relays (which would explain the hum you hear).  I'd try unplugging the AC and seeing if the PF at the main clamps changes. 

dduffey

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Re: TED Pro + Spyder unusual reading (newbie, first install)
« Reply #8 on: July 09, 2015, 10:05:13 PM »
Sorry for the delay, I was out of the country for a few months (that's why I bought the TED!) and just got back.  Here is what I found.

MAIN LOOP TEST: I don't think I have a main-loop.  I turned of the breaker to the AC unit, then measured the voltage at the AC disconnect (near the compressor) and it measured about 1V (normally 240V when the breaker is ON).  I'm guessing that is normal, let me know otherwise.  (where does that 1V come from?).

PF @ AC UNIT TEST: When I had the breaker ON (and AC was off) and I pulled the plug from the AC disconnect my PF at the MAINs when from low 70s to low 90s.  Suggesting the low PF was coming from the "off" AC.

CAPACITOR TEST: The AC has three capacitors... I tested just one of them (the easiest one to get to) and I think it is starting to fail (7.5mF rated and was reading something much below that... don't recall exactly but definitely beyond 10%).  I didn't test they were harder to get to and couldn't easily read the ratings anyway.

The AC is old anyway (24 years old... capacitors are newer but not sure how newer) so I'm thinking to just have it replaced anyway.

Thanks for your help/suggestions, I consider it case-closed unless you think I'm missing something.