Open leg of 240V single phase 3W residential/commercial service -- odd results

[lakee911]

Hi All,

I was called out to troubleshoot a system yesterday. 240/120V, 3W, 200A commercial install. Customer complains that when he turns off the 240V water heater, the lights go off. Also, exterior motion detector causes inside lights to flicker. Everything appears to be wired properly. Water heater and A/C do not work.

Main CB closed. Voltages read were L1 to N: approx 120V; L2 to N: approx 120V; :L1 to L2: approx 1.2V :?
Opened the meter enclosure. Line side of meter voltages were L1 to N: approx 120V; L2 to N: approx 120V; :L1 to L2: approx 240V
Main CB opened. Voltages read (on line side of main CB, load side of meter) were L1 to N: approx 120V; L2 to N: approx 21V; L1 to L2: approx 94V. :?

I told the customer that he likely has a problem with the meter and to call the utility and let them know that he has either lost one of the two legs or the neutral. I figured likely the first and not the latter. Everything from the transformer on the pole to the meter, from the meter to the main CB, and all branch circuits looked just fine.

By the way, the building has two services and the other works just fine.

Customer sends me an email stating, "The problem with the box was that it was not in service. I had not started an account for that one. Why it was getting any power at all is a mystery to me." Why it was getting any power was a mystery to me too. The meter was installed--one of those new digital ones.

Any idea what's going on here? I'd assumed that if the meter was present it would work. Are the new digital ones capable of interupting service, and if so, could it be faulty? I couldn't fully check, but i'm ruling out a cross connection between the two services.

Thx,
Jason

 

[kwired]

Hi All,

I was called out to troubleshoot a system yesterday. 240/120V, 3W, 200A commercial install. Customer complains that when he turns off the 240V water heater, the lights go off. Also, exterior motion detector causes inside lights to flicker. Everything appears to be wired properly. Water heater and A/C do not work.

Main CB closed. Voltages read were L1 to N: approx 120V; L2 to N: approx 120V; :L1 to L2: approx 1.2V :?
Opened the meter enclosure. Line side of meter voltages were L1 to N: approx 120V; L2 to N: approx 120V; :L1 to L2: approx 240V
Main CB opened. Voltages read (on line side of main CB, load side of meter) were L1 to N: approx 120V; L2 to N: approx 21V; L1 to L2: approx 94V. :?

I told the customer that he likely has a problem with the meter and to call the utility and let them know that he has either lost one of the two legs or the neutral. I figured likely the first and not the latter. Everything from the transformer on the pole to the meter, from the meter to the main CB, and all branch circuits looked just fine.

By the way, the building has two services and the other works just fine.

Customer sends me an email stating, "The problem with the box was that it was not in service. I had not started an account for that one. Why it was getting any power at all is a mystery to me." Why it was getting any power was a mystery to me too. The meter was installed--one of those new digital ones.

Any idea what's going on here? I'd assumed that if the meter was present it would work. Are the new digital ones capable of interupting service, and if so, could it be faulty? I couldn't fully check, but i'm ruling out a cross connection between the two services.

Thx,
Jason

Some meters I believe are capable of interrupting service via remote control so a POCO service tech does not need dispatched to disconnect a service - this is desired for customers that are frequent disconnects for non payment, and not sure they would put that type of meter on every service.

Even if it is not that type if the service has been disconnected they often still leave meter in place and simply put non metallic sleeves over the tabs so they are insulated from the jaws when plugged in. If there is a tear in the sleeve you could have a "bypass" of their intended open circuit. They will generally put the sleeve on the load side of meter so that an electonic meter is still powered for purposes of reading.

Also if there is two services and there is any interconnection between them (even if unintentional) you could be getting backfeed voltage from the other service .

 

[Sierrasparky]

If the poco fixed it without removing the meter then it sounds like the meter has solid state relays that are not working properly.

 

[lakee911]

I didn't notice any sleeves, but I also didn't pull the meter.

I'd expect a malfunction, but I'm surprised that it would be able to disconnect/reconnect a load as great as 200A.

Thanks

 

[Sierrasparky]

I didn't notice any sleeves, but I also didn't pull the meter.

I'd expect a malfunction, but I'm surprised that it would be able to disconnect/reconnect a load as great as 200A.

Thanks

The wonders of Smart meters and solid state relays!

 

[Besoeker]

The wonders of Smart meters and solid state relays!

A current of 200A though a solid state relay would generate a fair bit of heat.

 

[kwired]

I know nothing about meters that may be cabable of turning off the load, but I do know that a typical contactor intended to switch a 200 amp load will likely be larger than the typical 200 amp plug in meter, so I am guessing these meters either have more depth to them to contain this, or are not designed to same standards as a typical contactor. For one thing they typically will only be operated a maximum of once open and once closed every month, and in most cases also will not be transitioning with a full 200 amps of load, and even more likely to be less than 60 amps most of the time.

 

[lakee911]

Here is some info that I found on smart meters. Apparently they do have disconnect switches.

http://www.wired.com/threatlevel/2010/03/smart-grids-done-smartly/

http://stopsmartmeters.org/

 

[gar]

120910-9150 EDT

What was the input impedance of the meter used to measure the voltages 120, 21, and 94 of post 1? Note: 120-21 is 99 and this is close enough to 94 to imply these measurements are consistent.

It looks like one side of the contactor in the meter is open. This is almost certainly DPST. Yes the meters do have contactors (relays). These are electromechanical. With any known semiconductors there is no way you are going to put a two pole solid-state switch, that can handle a continuous 200 A current (power dissipation about 400 W), in the package of a standard meter. Further it may have to handle a 10,000 A transient.

From indirect information I understand there is a very wimpy coil for the contactor. This means it has to be a pulsed contactor.

Fires are likely a real possibility because of this contactor.

The stop smart meters has a lot of scare information that is probably unsupportable.

Security, or vulnerability, is possibly a major concern from an attack perspective that could cause a major grid problem. I would not worry about someone monitoring my power usage. In all probability there is a cumulative KWH register in the meter equivalent to the present gear train mechanism. Thus, lost or incorrect data from a meter on a single or a few data transmissions is no problem over a long time period, but does require the electronics within the meter to be reliable.

Jamming of RF communication would be the major concern. Breaking the encryption code is probably difficult. In a major outage jamming could prevent rapid detection of where problems are located. But that is no worse than the present system,

I do not have my smart meter yet, but all my neighbors do. DTE brought a plug-in meter for me, but mine is a bolt on. This was two weeks ago, and no one has returned with the correct meter.

.

 

[hillbilly1]

I have seen where customers rocked the meter back and forth enough to tear the sleeves and make contact in order to steal power.

 

[texie]

I have seen where customers rocked the meter back and forth enough to tear the sleeves and make contact in order to steal power.

I'm not commenting on the OP. But since the subject of sleeves was mentioned (we used to call them "boots" in my area), I've often wondered about the wisdom and safety of the POCO to use them. Your comments seem to be one good reason to question the safety. After all, they are only a cheap piece of plastic with no rating as far as I understand.

 

[Hv&Lv]

Hi All,

I was called out to troubleshoot a system yesterday. 240/120V, 3W, 200A commercial install. Customer complains that when he turns off the 240V water heater, the lights go off. Also, exterior motion detector causes inside lights to flicker. Everything appears to be wired properly. Water heater and A/C do not work.

Main CB closed. Voltages read were L1 to N: approx 120V; L2 to N: approx 120V; :L1 to L2: approx 1.2V :?
Opened the meter enclosure. Line side of meter voltages were L1 to N: approx 120V; L2 to N: approx 120V; :L1 to L2: approx 240V
Main CB opened. Voltages read (on line side of main CB, load side of meter) were L1 to N: approx 120V; L2 to N: approx 21V; L1 to L2: approx 94V. :?

I told the customer that he likely has a problem with the meter and to call the utility and let them know that he has either lost one of the two legs or the neutral. I figured likely the first and not the latter. Everything from the transformer on the pole to the meter, from the meter to the main CB, and all branch circuits looked just fine.

By the way, the building has two services and the other works just fine.

Customer sends me an email stating, "The problem with the box was that it was not in service. I had not started an account for that one. Why it was getting any power at all is a mystery to me." Why it was getting any power was a mystery to me too. The meter was installed--one of those new digital ones.

Any idea what's going on here? I'd assumed that if the meter was present it would work. Are the new digital ones capable of interupting service, and if so, could it be faulty? I couldn't fully check, but i'm ruling out a cross connection between the two services.

Thx,
Jason

Could be that the boots were installed earlier, and someone that the POCO hired to change out the meter didn't realize what they were doing when they changed it. Ask the POCO to come check.

 

[kwired]

I have seen where customers rocked the meter back and forth enough to tear the sleeves and make contact in order to steal power.

The meter still records what was used, so they are stealing service, yet they are not getting free power unless they never pay the bill again and POCO never checks it again.

 

[hillbilly1]

The meter still records what was used, so they are stealing service, yet they are not getting free power unless they never pay the bill again and POCO never checks it again.

It was recording, but the POCO wasn't reading it, it was off the beaten path, so the meter reader wasn't going out of his/her way to check it.

 

[kwired]

It was recording, but the POCO wasn't reading it, it was off the beaten path, so the meter reader wasn't going out of his/her way to check it.

Well I guess POCO is the loser if they do not want to ensure there is no service available when in a "disconnected" status. If power is on because user rocked the meter until it wore a hole in the sleeve, how are they going to prove that actually happened? If off beaten path and has only one service on the transformer - it is much more reliable to disconnect the transformer primary, if anyone is stupid enough to try to reconnect that they usually will be caught - still laying at the base of the pole.

 

[Open Neutral]

Agree re: the SSR and dissipation.

The other reason for the relay is delay on turn-up. Wanna bet when you restore power to it, there's a delay of say 1-100 seconds, a random one? That way it's easier for POCO to bring up the feeder, and then the loads kick in over the next few minutes.

Does it have another output to HVAC/water heaters to shed those loads during peak demands?

 

[gar]

120925-1536 EDT

My smart meter was installed last Saturday.

Prior to this I measured voltage change at the main panel with a moderate 240 V load. Then after the Smart meter was installed a similar measurement was made. There is essentially no significant difference between the two meters. This is proof of no solid state contactor for the two hot lines. Further there is no great amount of power dissipation from current flowing thru the meter.

There have been reports of smart meters catching fire. Are these reports true? I have no idea. I certainly do not expect my new meter to burn up from load current. There was apparently a discussion of this in a Spectrum on-line thread.

.

 

[Hv&Lv]

120925-1536 EDT

My smart meter was installed last Saturday.

Prior to this I measured voltage change at the main panel with a moderate 240 V load. Then after the Smart meter was installed a similar measurement was made. There is essentially no significant difference between the two meters. This is proof of no solid state contactor for the two hot lines. Further there is no great amount of power dissipation from current flowing thru the meter.

There have been reports of smart meters catching fire. Are these reports true? I have no idea. I certainly do not expect my new meter to burn up from load current. There was apparently a discussion of this in a Spectrum on-line thread.

.

I would like to see some reports like this for comparison. We actually have a few that are melted in the back at the lugs. Load wasn't a factor. Peak demand was around 12kW.

 

[texie]

I would like to see some reports like this for comparison. We actually have a few that are melted in the back at the lugs. Load wasn't a factor. Peak demand was around 12kW.

I have a colleague down in Florida that works under contract to the POCO to be called in to replace/repair meter sockets when they find issues at meter change out for new smart meters. He reports that some are just old and when they yank the old meter it is sometimes problematic. But he indicates that he gets failures on some well after the change out due to less than ideal clamping of the old socket jaws that lead to failure and sometimes fire.
He said that in many cases the POCO is paying to replace the customer owned meter sockets in this event to avoid the backlash from consumers and bad press. This can be a costly endeavor as the AHJ makes them bring the whole service up to date. I think in his case the POCO is doing something like 5 million of them and when you mess with meters that may not have been touched in 20-30 years your going to get some of this.

 

[Open Neutral]

I know nothing about meters that may be cabable of turning off the load, but I do know that a typical contactor intended to switch a 200 amp load will likely be larger than the typical 200 amp plug in meter, so I am guessing these meters either have more depth to them to contain this, or are not designed to same standards as a typical contactor.

Consider the solid-state meter innards would be far smaller than a moving coil's. There could easily be enough space left over....