Three Phase site - multiple electrical issues.

[hurk27]

This just does not sound like a ground or neutral switched issue. Normally the only thing that happens then if GFCIs trip.

But it is typically pretty consistent.

I agree because multiwire circuits have been used for years and if installed correctly should not cause the problems in the OP case, but if this EC short changes the customer on this who knows what other kind of work was done, hopefully the customer can still go after the bond of the original EC and or his insurance company that was in effect at the time, but most states only have a 2 year statue of limitations for civil claims like this???

 

[karlmax1103]

good post!

 

[Sparty D]

You did mention you have rs232 and rs485 circuits. they are usually not isolated. you might want to install isolaters in those lines. not a solution, but maybe a bit of a bandaid.

I can't imagine that a suggestion that they shut off the power as part of diagnosis would go over real well.

Linear power supplies usually have a high degree of isolation and ride through so whatever is downstream of them should be fairly clean. did you ground one leg of the DC for some reason? if you did, and there is some weird voltage coming through the ground wires, it could get past the DC power supplies since the isolation would be defeated.

I would be checking the ground wires coming into all of the panel boards and seeing if there is current flow in any of them. record what you find, but don't worry all that much about it for the time being.

get a long wire, maybe a couple hundred feet and an analog meter (do not use a high impedance digital meter). measure the voltage between an EGC at one end of the building to an EGC at the other end of the building.

Thanks for the suggestions. I agree that current on the ground is a strong possibility. The owners maintenance man touched ground and neutral while replacing a light and tripped a breaker. I can only think of current causing a breaker to trip. Something causes the emergency lights and PC ups units to think power has been lost. A loose neutral comes to mind and even more so now knowing it is spliced in the emergency breaker box sub panel. The first EC was short by a foot. That is the only box feed from the transfer switch.

 

[Sparty D]

I agree because multiwire circuits have been used for years and if installed correctly should not cause the problems in the OP case, but if this EC short changes the customer on this who knows what other kind of work was done, hopefully the customer can still go after the bond of the original EC and or his insurance company that was in effect at the time, but most states only have a 2 year statue of limitations for civil claims like this???

The EC's GL was notified and listened in on the most recent conf. call too. They also have a Forensic Investigator retained, but has never done anything I know of. Thanks and it goes to show that you should do things right the first time.

 

[Fordean]

light

light

Is the lighting 120 volt or 208 volt? If the latter, it would not be directly affected by an unreliable neutral. (But I would not expect you to be blowing ballasts on such fixtures either.)

If it is a high resistance or intermittent neutral, it could be made worse by single phase loads with a high inrush current like large motors. Motors which are on steadily and are wired in wye may actually have a stabilizing effect on the neutral voltage.

Do the lights constantly Blink, That what a neutral would do. Very noticeable.

 

[Fordean]

I agree because multiwire circuits have been used for years and if installed correctly should not cause the problems in the OP case, but if this EC short changes the customer on this who knows what other kind of work was done, hopefully the customer can still go after the bond of the original EC and or his insurance company that was in effect at the time, but most states only have a 2 year statue of limitations for civil claims like this???

Sounds like the nuts on the Inside of the Switchboard they bond the bus bars together was never tightened.

 

[Sparty D]

Sounds like the nuts on the Inside of the Switchboard they bond the bus bars together was never tightened.

Since we are the low voltage group, we personally have not checked for lugs being tight, but have said it needed to be checked. The GC and his buddy EC have said it was done, but also said they "verified neutrals" and when they are not in the breaker box would have meant a lot of tracing. I am skeptical of everything they say and that is my nature anyway. No proof one way or the other. The emergency lights come and go at random and it maybe days or hours between trips. They have a 10 min timer on them so when they "think" power failed it is obvious as they stay on for 10 mins.

The lights I believe are 120 and the major 208 would be the PTAC (room heater/AC).

 

[Sparty D]

HELP Checking for neutral short to ground on three phase.

HELP Checking for neutral short to ground on three phase.

I was looking and can't say I found exactly what I was looking for. The GC is installing Ferrups to isolate the low voltage from the high voltage. So the high voltage is being addressed. The door units on this low voltage system use earth ground to dissipate static and the shield of the RS485 is also connected to earth ground. If the ground is a current carrying conductor then 60hz is on the RS485 shield and the chassis and parts of the door controller circuit board. Bad and could explain the comm issues. 12vdc is derived from step down AC transformers (output 18vac) and then converted to 12VDC by a power supply board. The 120vac to these come from a subpanel on the Emergency Generator feed. There is one box with 200amp disconnect and it feeds one building and has two 100 amp three pole breakers to feed the other two buildings. One of these breaker boxes has 37 hots and 27 neutrals in violation of the plans dedicated neutral clause.

I think because the transformers draw so little current (1-2amps) when I put a Fluke 43b on to measure the harmonics it was 30 and 40% at the branch outlet.

My question and concern is the ground at the moment. What steps/troubleshooting can be done to see if there is a short between ground and neutral (other than the required bond.) A planned power outage is not out of the question where we could ohm the two after breaking the one bond at the service. Assuming there is only one bond point, but who knows with the EC that short changed seemingly everything else. Links welcome.

 

[GoldDigger]

I read and article Mike Holts wrote on bonding and grounding for 3 phase systems. I went to our outlet that is a dedicated run to the subpanel and measured the voltage between ground and neutral. .2 to .4vac. Based on the article I was expecting to see 4.5vac. 3vac for the panelboard and 1.5vac for the branch. Can you let me know if I am missing something?

Also the owner let me know that nearly all the electronic thermostats in the complex for the residents HVAC unit have been replaced due to failure and some of the replaced ones have gone out again.

One possibility, since you mentioned the substation across the street, is that there is a substantial voltage gradient from one side of the building to the other.
One thing this can cause is strong earth currents near the surface going into the substation.
Any electronics which is not connected to a solid thick EGC could pick up substantial voltage from local earth contact. This contact could be from metal plumbing stubs which transition to non-metallic for the long runs, from incidental contact with structural metal which is not effectively bonded, etc. or from misguided attempts to connect the equipment to a local ground instead of the EGC.
This could in turn cause large end-to-end currents in data cables like RS-232 or coax which has no dielectric isolation, control wiring, etc.
One way to test for this is to disconnect the data cable at one end and measure the voltage from the ground or shield wire(s) to the ground of the equipment you disconnected from.
As some of our members along with Mike Holt have opined, a good safe ground system can be built with one or more good earth electrodes which are bonded together and a solid EGC network above ground, and only ONE point at which the two are connected together.
That avoids current flowing in the EGCs.


Sent from my XT1080 using Tapatalk

 

[Sparty D]

One possibility, since you mentioned the substation across the street, is that there is a substantial voltage gradient from one side of the building to the other.
One thing this can cause is strong earth currents near the surface going into the substation.
Any electronics which is not connected to a solid thick EGC could pick up substantial voltage from local earth contact. This contact could be from metal plumbing stubs which transition to non-metallic for the long runs, from incidental contact with structural metal which is not effectively bonded, etc. or from misguided attempts to connect the equipment to a local ground instead of the EGC.
This could in turn cause large end-to-end currents in data cables like RS-232 or coax which has no dielectric isolation, control wiring, etc.
One way to test for this is to disconnect the data cable at one end and measure the voltage from the ground or shield wire(s) to the ground of the equipment you disconnected from.
As some of our members along with Mike Holt have opined, a good safe ground system can be built with one or more good earth electrodes which are bonded together and a solid EGC network above ground, and only ONE point at which the two are connected together.
That avoids current flowing in the EGCs.


Sent from my XT1080 using Tapatalk

GoldDigger thanks for hanging with this one.

Okay, I think I understand. Since we have not seen where the ground wire that leads from the ground buss bar (in the phone closet where we pickup EG) ultimately ends up at on the 1600 service, that is questionable and should be checked but does require opening the big box. This is a wood frame construction and we have pulled new wires so a unintentional grounding of the wires twice would not be probable and since there is technically three separate systems (one in each building) doing the same thing that makes it even less likely in my opinion. We believe, along with the engineer who did the plans, that there IS more than ONE connection/short between neutral and ground.

If I measured the voltage between the shield and the devices case ground as you suggest (these are tied to the same point) do have any idea what the value would read? Analog or Digital VOM? Also, would a logging meter connected between our ground and neutral or outlet ground prove anything? Measure voltage? Measure Current?

 

[rlundsrud]

Ok, This was a LOT to read, but I tried to read through all of the threads so I don't post anything redundant. With that said, I am curious about the generator, specifically the bonding of the neutral. I am wondering if the neutral was done incorrectly and it is double bonded. You would have to check to see how the neutral was run through the ATS, and whether it was bonded at the generator. If it was bonded at the generator it needs to disconnect from the main system at the ATS. There are some very nice threads on this forum that show how it should be done. I am just spit balling on this, but it would be easy to check and even if it isn't the fix for this, it may well be wrong anyway given the original EC's issues and should be corrected.

Bob

 

[Open Neutral]

When entering the building a radio in the 120mhz area breaks squealch.

This is surely wrong. 120 Mhz is in the middle of the aircraft band. I suspect these are 150 Mhz business band radios. Their breaking squelch may just mean there is lots of EMI in the area; that could be just the lighting...

 

[GoldDigger]

Some people do carry aircraft band radios or monitors. And since the aircraft band is AM it is a lot easier to break squelch with noise.
So 120 MHz is possible, just less likely.


Sent from my Droid Maxx

 

[hurk27]

This is surely wrong. 120 Mhz is in the middle of the aircraft band. I suspect these are 150 Mhz business band radios. Their breaking squelch may just mean there is lots of EMI in the area; that could be just the lighting...

I also asked this at the top of post 17, and he replied in post 19 at the bottom that he is a pilot.

Also much of the aircraft bands are AM or amplitude modulation, so they would be susceptible to any EMI

Gold beat me too it LOL

 

[Open Neutral]

I also asked this at the top of post 17, and he replied in post 19 at the bottom that he is a pilot.

Also much of the aircraft bands are AM or amplitude modulation, so they would be susceptible to any EMI

Sorry I missed that point.

If an AM handheld, it's subject to any kind of RFI; so ignore it.

 

[PetrosA]

Just a thought, but after reading this thread's development for the last few months, I started wondering if part of the issue could be ground loops (even NEC compliant ones) inducing current from the nearby high voltage lines. If, in all three buildings, you have grounds originating from both the regular feeders and generator panel feeder, you would have these two grounded systems creating a loop between buildings because their grounds are getting bonded to each other at either end (compliantly) through whatever they're installed in and the building metal or conduit or wherever you have cables from both systems landing in a common j-box (where their grounds would get tied together). These loops could be large enough to induce a serious amount of ground loop current with regards to the low voltage systems installed. I could be wrong, but there's something in this story that reminds me of that case study a few years back of the residential neighborhood next to the train tracks where the cable company's loop around the block was inducing enough current from the HV lines on the railroad to burn out the cable drops where they were bonded to the POCOs ground and wreaking havoc for the customers.

 

[Sparty D]

Good point - Shared Neutrals on AFCI or GFCI

Good point - Shared Neutrals on AFCI or GFCI

Just a thought, but after reading this thread's development for the last few months, I started wondering if part of the issue could be ground loops (even NEC compliant ones) inducing current from the nearby high voltage lines. If, in all three buildings, you have grounds originating from both the regular feeders and generator panel feeder, you would have these two grounded systems creating a loop between buildings because their grounds are getting bonded to each other at either end (compliantly) through whatever they're installed in and the building metal or conduit or wherever you have cables from both systems landing in a common j-box (where their grounds would get tied together). These loops could be large enough to induce a serious amount of ground loop current with regards to the low voltage systems installed. I could be wrong, but there's something in this story that reminds me of that case study a few years back of the residential neighborhood next to the train tracks where the cable company's loop around the block was inducing enough current from the HV lines on the railroad to burn out the cable drops where they were bonded to the POCOs ground and wreaking havoc for the customers.

Thanks for the input and the site still has on going issues. Eaton power conditioners were installed by others and I don't think a isolated ground was used. In other words our low voltage system, including the data (RS485), are tied to electrical ground even after the hot and neural go through the power conditioner.

Regarding the cable TV feeder, it is literally connected to the same bus bar in one of the buildings our ground connection is made. So is it a thought the cable TV could be causing a ground loop as it attaches to the electrical ground and POCO electrical ground?

Also, the second EC traced circuits after we advised them the number of neutrals in the panels did not equal the number of hots. Pretty simple stuff if you can count to 42. They finally put in writing that all the residential units (assuming bedrooms) were wired with 12/3 and two circuits share a neutral. This is against the plans and spec's no shared neutral language. What I don't know and understand at the moment is if the EC's report accurately states GFI when the bedrooms have Siemens AFCI breakers. Did he interchange GFI with AFCI? My understanding is to use a shared neutral on a AFCI would require a double pole AFCI breaker so the one leg does not sit out there without a neutral. The only place a GFCI would be is next to the sink in the bathrooms. I don't recall double pole AFCI's and believe them to be rare.

They have said the installation meets code. Not adding it indeed does not meet spec. Any thoughts on shared neutrals on either circuit and the cable TV connection?

 

[Sparty D]

Ok, This was a LOT to read, but I tried to read through all of the threads so I don't post anything redundant. With that said, I am curious about the generator, specifically the bonding of the neutral. I am wondering if the neutral was done incorrectly and it is double bonded. You would have to check to see how the neutral was run through the ATS, and whether it was bonded at the generator. If it was bonded at the generator it needs to disconnect from the main system at the ATS. There are some very nice threads on this forum that show how it should be done. I am just spit balling on this, but it would be easy to check and even if it isn't the fix for this, it may well be wrong anyway given the original EC's issues and should be corrected.

Bob

I appreciate the idea. I have wondered too if it was done right. The second EC "should" have checked that, but not disclosing shared neutrals two years back makes one wonder.

 

[gar]

140326-1944 EDT

The RS485 circuits need isolation. RS485 chips do not have a large common mode capability. Just in the few volt range.

On I232 isolators I make RS232 is optically isolated and converted to RS422, and then with another unit back to RS232. With this arrangement RS232 data can be sent error free at 115.2 kbaud while a 1000 V RMS 60 Hz sine wave is applied to the RS422 common relative to the RS232 common. The 1000 V limitation is base on the maximum voltage capability of the optical coupler. RS422 and RS485 are essentially the same type of signal. RS485 is a half-duplex connection whereas RS422 is full-duplex.

.

 

[PetrosA]

Thanks for the input and the site still has on going issues. Eaton power conditioners were installed by others and I don't think a isolated ground was used. In other words our low voltage system, including the data (RS485), are tied to electrical ground even after the hot and neural go through the power conditioner.

Regarding the cable TV feeder, it is literally connected to the same bus bar in one of the buildings our ground connection is made. So is it a thought the cable TV could be causing a ground loop as it attaches to the electrical ground and POCO electrical ground?

Also, the second EC traced circuits after we advised them the number of neutrals in the panels did not equal the number of hots. Pretty simple stuff if you can count to 42. They finally put in writing that all the residential units (assuming bedrooms) were wired with 12/3 and two circuits share a neutral. This is against the plans and spec's no shared neutral language. What I don't know and understand at the moment is if the EC's report accurately states GFI when the bedrooms have Siemens AFCI breakers. Did he interchange GFI with AFCI? My understanding is to use a shared neutral on a AFCI would require a double pole AFCI breaker so the one leg does not sit out there without a neutral. The only place a GFCI would be is next to the sink in the bathrooms. I don't recall double pole AFCI's and believe them to be rare.

They have said the installation meets code. Not adding it indeed does not meet spec. Any thoughts on shared neutrals on either circuit and the cable TV connection?

My first thought on shared neutrals is that it shouldn't be an issue if it was done correctly. I don't know if they would have been required to be AFCI protected at the time of installation - you'd need to know what code cycle it was engineered to.

The cable TV connection could be a part of a ground loop problem. If your LV systems and the facility's electrical systems are still having issues and the electrician who's been working with you on this hasn't found the problem or come up with any theories yet, you might want to look for a specialist troubleshooter. Otherwise the facility owners are just going to keep throwing money at repairs and possibly have a dangerous issue bite them at some point.