Is Smart meter this smart?

[glennrichard]

Client I replaced an a/c unit for called and said Edison got some warning from her smart meter about high wire temperatures. He said the disconnect for one of the older units was at 800 degrees and the house could start on fire. Anyway I went out and all three units were running. I pulled the disconnects on each and we both felt them. Two were just above outside temps. Sure enough the one old unit was very hot! I checked connections at breaker and replaced the contactor and disconnect and that solved it.

So heres the question that I did not get an answer to at the service providers page(Edison). What the heck alerted Edison to come out and start sniffing around with a thermometer? I can't see it being the amp draw as they have no idea what it would be in the home at any certain time. That unit draws about 9/10 amps max. Secondly even with that disconnect running hot once it drew 20 amps either the breaker would trip or the 15 or 20 amp cartridge fuses in the disconnect would go. Typically they left no paperwork and she only said her kid was told they came out from some smart meter alert/warning. Confused what alert a smart meter would have sent

 

[LarryFine]

"How do it know?!"

 

[kwired]

Sounds more effective than AFCI's

 

[Russs57]

That is interesting. The one thing the smart meter knows for sure is KWH norms and load profile. If we assume voltage is a constant that leaves current as the variable.

Say they see a sudden load equating to LRC of said compressor repeating every couple of minutes that happens several times in a row until compressor finally starts. They only know load profile is abnormal and investigate. They run up on unit going HUM/CLICK repeatedly until it takes off and runs normally. You have only seen it running so took no note of it.

Best I can come up with but technology is getting better and smarter all the time. That can be a good thing. Proof is in the pudding and they were right.

 

[kwired]

That is interesting. The one thing the smart meter knows for sure is KWH norms and load profile. If we assume voltage is a constant that leaves current as the variable.

Say they see a sudden load equating to LRC of said compressor repeating every couple of minutes that happens several times in a row until compressor finally starts. They only know load profile is abnormal and investigate. They run up on unit going HUM/CLICK repeatedly until it takes off and runs normally. You have only seen it running so took no note of it.

Best I can come up with but technology is getting better and smarter all the time. That can be a good thing. Proof is in the pudding and they were right.

I can see abnormal load profile causing such a notification, but how will it know a connection is hot, especially if not one of the connections to the meter itself?

 

[glennrichard]

I can see abnormal load profile causing such a notification, but how will it know a connection is hot, especially if not one of the connections to the meter itself?

That's what I don't understand. Obviously there were some connections going south which caused that disconnect to feel hot. The old contractor was pretty bad as were the contacts in that fused disconnect. Even still it would have tripped the cartridge fuses or breaker. I should have had her get Edison on the phone while I was working on the thing to get it straight from them.

I suppose it would not be all that tricky to have some temp sensor monitoring the meter contacts but no way is this meter knowing what's happening in a disconnect that's probably been going on for 10 years.

 

[Craigv]

If the meter reads waveforms as afci's do, it could pick up a poor connection causing some arcing that doesn't match any known profile. This would create the alert that brought them out to investigate.

 

[Ingenieur]

weird

perhaps the saw a 240 load start and saw an unbalanced v drop per leg?
or saw the load current decrease over time due to the hi Z?

 

[Ingenieur]

I could see a few ways to detect this
how many 240 motor loads in a typ home? 1?

assume 10 nml fla and 60 starting, 6:1
R nml 24, starting 4 Ohm
suppose the bad connection adds 2 Ohm nml (200 W, 20 vdrop) and 4 when starting
new fla ~ 9.2 and starting 30, 3.2:1, this could be flagged for investigation
also starting vdrop would be lower

or v drop
since i i the same on both legs so should v drop ref to neut
if the R on one leg is higher so will vdrop on that leg ref to neut

kind of scary the data they could gather or the load profile that could be developed

 

[Jraef]

That's what I don't understand. Obviously there were some connections going south which caused that disconnect to feel hot. The old contractor was pretty bad as were the contacts in that fused disconnect. Even still it would have tripped the cartridge fuses or breaker. I should have had her get Edison on the phone while I was working on the thing to get it straight from them.

I suppose it would not be all that tricky to have some temp sensor monitoring the meter contacts but no way is this meter knowing what's happening in a disconnect that's probably been going on for 10 years.

If the meter reads waveforms as afci's do, it could pick up a poor connection causing some arcing that doesn't match any known profile. This would create the alert that brought them out to investigate.

weird

perhaps the saw a 240 load start and saw an unbalanced v drop per leg?
or saw the load current decrease over time due to the hi Z?

Probably all of the above, fed into an algorithm that has learned, over the very high number of connected units and a database of service tech experiences, that ultimately eliminated the vast majority of other possibilities. Since the meter is the total SOURCE for all power to the circuit and it absolutely knows what it has been delivering, it can immediately eliminate all possibilities of line side causes. That’s something we can’t do when we go out to troubleshoot, and they can lie to us, claiming there were no line side issues. There is no need for them to lie to themselves so their database of possibilities is much smaller than ours.

 

[mbrooke]

Its a guess, but as the disconnect heated up, the metal tab expanded, arced a little, broke the connection, then cooled down and reconnected starting the AC unit. Enough times the cycling goes beyond normal thermostat cycling and a red flag is raised to check further like long current ripples accounting it.

Remember that an AC unit, even drawing 9-10 amps has an inrush of over 80amps. Multiple inrushes repeatedly every few minutes or less would raise a red flag easily. I know that when my neighbors lost a cap in the AC unit, the compressor was short cycling every minute and I could see the dimming at my house. Sure enough 2 days latter there was an AC tech out front.

 

[kwired]

If the meter reads waveforms as afci's do, it could pick up a poor connection causing some arcing that doesn't match any known profile. This would create the alert that brought them out to investigate.

I can understand it being able to detect a current signature that is abnormal but how are they able to give the information I boldfaced below?

Client I replaced an a/c unit for called and said Edison got some warning from her smart meter about high wire temperatures. He said the disconnect for one of the older units was at 800 degrees and the house could start on fire. Anyway I went out and all three units were running. I pulled the disconnects on each and we both felt them. Two were just above outside temps. Sure enough the one old unit was very hot! I checked connections at breaker and replaced the contactor and disconnect and that solved it.

So heres the question that I did not get an answer to at the service providers page(Edison). What the heck alerted Edison to come out and start sniffing around with a thermometer? I can't see it being the amp draw as they have no idea what it would be in the home at any certain time. That unit draws about 9/10 amps max. Secondly even with that disconnect running hot once it drew 20 amps either the breaker would trip or the 15 or 20 amp cartridge fuses in the disconnect would go. Typically they left no paperwork and she only said her kid was told they came out from some smart meter alert/warning. Confused what alert a smart meter would have sent

 

[glennrichard]

I can understand it being able to detect a current signature that is abnormal but how are they able to give the information I boldfaced below?

I think what took place is the guy started poking around with an infrared thermometer after he was alerted to come out and that's when he found the disconnect heating up. BUT the girl claims they were alerted to come by because of the meter sending a high temp reading.

Aside from that disconnect running hot the unit itself was running without issue the whole day I was replacing the other unit.

 

[mbrooke]

I think what took place is the guy started poking around with an infrared thermometer after he was alerted to come out and that's when he found the disconnect heating up. BUT the girl claims they were alerted to come by because of the meter sending a high temp reading.

Aside from that disconnect running hot the unit itself was running without issue the whole day I was replacing the other unit.

Probably the meter alarmed for arcing/short cycling of a motor load- guy came out and did some IR to check it wasn't the meter jaws- found the disconnect to be the culprit after he noticed one of the ACs kicking on and off randomly. Its a guess. I know one guy on here told a story that they busted someone for power theft because after linemen pulled the meter, the AC units kept churning.

 

[Craigv]

I can understand it being able to detect a current signature that is abnormal but how are they able to give the information I boldfaced below?

There is no way a meter can detect temperature. But it can detect any waveform that is created by the circuit. As the OP surmised, I also think they saw a "bad" waveform created by a loose arcing connection, or a too-frequent motor start and sent a human to inspect.

 

[mbrooke]

There is no way a meter can detect temperature. But it can detect any waveform that is created by the circuit. As the OP surmised, I also think they saw a "bad" waveform created by a loose arcing connection, or a too-frequent motor start and sent a human to inspect.

Yup- and just to add something complimenting your post:


Smart meters have a bad rap for fires, usually due to the jaws getting stretched or damaged after a replacement. I could understand a protocol of immediate alarm if they suspected anything resembling bad jaws in the meter base.

 

[kwired]

There is no way a meter can detect temperature. But it can detect any waveform that is created by the circuit. As the OP surmised, I also think they saw a "bad" waveform created by a loose arcing connection, or a too-frequent motor start and sent a human to inspect.

I agree, my comments have been based on OP that says "Edison got some warning from her smart meter about high wire temperatures". I don't see that being very likely. I can see unusual current being detected and prompting them to check into it, but no way they are going to use any data they have to confidently tell customer something is hot.