EMF summary report

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ghostbuster

Senior Member
With a 1200 amp service near this bed nighstand area,in our experience 1mg. is never going to be achieved ( no matter what you do-even shielding) unless you turn off all the power.Someone is dreaming in tecnicolour.
 

mwm1752

Senior Member
Location
Aspen, Colo
Thanks Ron, my confusion come from his analysis of no current on the grounded conductor of the the service. This would indicate that the loads are balanced & not something that is baffling or alarming. a balanced 120/208 system would not have EFL's I presume. I get parallel paths & shared neutrals of different circuits & how that would in fact unbalance the conduit/cable & emit EFL's. The service is also where the electrode system would bond to the grounded conductor and all metal surfaces as required. So the video stresses the net currents which should equal 0 when placing an amprobe around all circuit conductors of a feeder/branch circuit.
 
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mwm1752

Senior Member
Location
Aspen, Colo
With a 1200 amp service near this bed nighstand area,in our experience 1mg. is never going to be achieved ( no matter what you do-even shielding) unless you turn off all the power.Someone is dreaming in tecnicolour.

The residents are not willing to move the bed to the other side of the room. Go figure.
 

ron

Senior Member
Thanks Ron, my confusion come from his analysis of no current on the grounded conductor of the the service. This would indicate that the loads are balanced & not something that is baffling or alarming. a balanced 120/208 system would not have EFL's I presume. I get parallel paths & shared neutrals of different circuits & how that would in fact unbalance the conduit/cable & emit EFL's. The service is also where the electrode system would bond to the grounded conductor and all metal surfaces as required. So the video stresses the net currents which should equal 0 when placing an amprobe around all circuit conductors of a feeder/branch circuit.

Maybe there is an inappropriate N-G bond and the current normally expected on the grounded conductor is on the grounding conductor (or shared) causing imbalance.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
I am voting for ron's analysis: that current which should be returning on the neutral is instead being carried by some other conductive material (eg. a water pipe).

It is also possible that the load is simply well balanced... was any measurement of net current on the service conductors made?

-Jon
 

mwm1752

Senior Member
Location
Aspen, Colo
Maybe there is an inappropriate N-G bond and the current normally expected on the grounded conductor is on the grounding conductor (or shared) causing imbalance.

Even if that was true - the current would take all paths -- he states supply side nuetral which is my service conductors & technically the only path back to the utility -- I was not present that is why reading the report without actual hands on the report seems odd. I believe this is a service with a single disconnecting means controling a stack meter assembly. I'll go by today & get pics.
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Even if that was true - the current would take all paths -- he states supply side nuetral which is my service conductors & technically the only path back to the utility --
I look forward to any pictures you'll get.

One thing to consider, on the power company (PoCo) side, the building service drop or lateral grounded conductor has a high likelihood of being bonded to the PoCo earth grounding, the bond of which is also used by the primary neutral. So, even though this building with the 1200 Amp service is the only premises connected to the supply transformer bank, the grounded service conductor connection to the PoCo earth ground will in turn connect to the PoCo primary grounded conductor that goes to any adjacent transformer banks, then through the bond there to the grounded service conductor of other premises and then through the Grounding Electrode Systems of any supplied buildings to the metallic municipal water system, which, connects back to your OP building.

As you say: "all available paths". Depending upon the lay of the neighborhood, municipal conductive water distribution, PoCo distribution wiring, and neighboring transformer banks, there could be multiple parallel paths back to the 1200 A secondary side bond sufficiently reducing their resistance ( in parallel ), resulting in a passible over all end user experience and no historical complaints of flicker or fluctuation.
 

ghostbuster

Senior Member
In one condo building we were involved in, there was over 80 amps of current flow on the copper water pipes throughout the building.This current was neutral current.We found all the electric stoves in the building still had the neutral ground link installed as well as the neutral bonded to ground in the splitters and disconnect switches.
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
EMF & Net Currents

EMF & Net Currents

Some more EMI required reading by Riley and others:
 

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  • EMI Net Current wiring protocol.pdf
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  • EMI Guide 29page.pdf
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  • EMI Computer Jitter.doc
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  • EMI Net Current Article.txt
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  • EMI Magnetic Fields 101.txt
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ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
I found this field report from a job we did years ago. The customer complained of "jitter" on the work station computer screens. It turned out to be the mis-matching of
the modular partitions between different manufacturers. This resulted in the crossing of the grounds and neutrals
when the power strips were connected together producing
net currents and EMI causing the screen jitter.
 

Attachments

  • EMI _Net Currents_Mega Path Report_JJ & TT.doc
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mwm1752

Senior Member
Location
Aspen, Colo
Phase A = 119 Amps, Phase B = 101 Amps, Grounded Conductor = 16 Amps
4 Parallel runs each pipe contains A, B, GC - measured ?Net Current? each run
Pipe 1 = .06 Amps, Pipe 2 = 6.2 Amps, Pipe 3 = 4 amps, Pipe 4 = .09 Amps
Did not have an amp loop long enough to encompass the complete service lateral
For unknown reasons my readings do not match the report readings, still curious why 2 out of 4 parallel runs show a significant net current reading. Service has an UFER grounding system & water piping CU. The gas service piping has no reading and the transformer is within 50? of the service equipment and has its own GES. The only connection to the GC & GEC is in the Main disconnect.
 

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  • 100 East Cooper Street 2015-02-24  01.JPG
    100 East Cooper Street 2015-02-24 01.JPG
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    100 East Cooper Street 2015-02-24 02.JPG
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    100 East Cooper Street 2015-02-24 03.JPG
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mbrooke

Batteries Included
Location
United States
Occupation
Technician
You need to find where current is flowing... Sorry for the late reply.

You either have one or more of the following:


1. subpanel with bonding jumper


2. 3 wire subpanel (was never code complaint in the same building as you service disconnect)


3. Grounds one the neutral bar or neutrals on a ground bar in subpanels.


4. Neutral to ground faults in branch circuits (this is really, really common)

5. defective appliance

6. Open service neutral

All of the above are code violations and have been for decades.

7. 3 wire dryers and ranges touching something metal, like a dryer connected to a metal exhaust duct.


8. Normal GEC, ground rod, water pipe current. This is about the only thing that is difficult to correct in that removing such is a code violation, and may not stop current since a water loving EGC appliance may be another path to water pipes. If you really want to fix it in a code complaint way call the water company and install an isolation fitting after 12 feet (or what ever the code length was for pipe electrodes) of water pipe. This will stop most of the current (99% of it), but not all of it.


Also of note POCO may have a broken MGN or neighbor may have a broken neutral (or you might) if GEC currents are excessive.

Further note panel boards and transformers naturally have elevated EMFs so only option is to move them.
 

mwm1752

Senior Member
Location
Aspen, Colo
Why would only 2 of 4 parallel sets of service lateral that tie together at both ends have unsual readings. wouldn't all paths be taken & divided somewhat equally? The path of pipes 1,2,3,4 all lead to the same termination point as you can see in the picture(line side of fusing).
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Phase A = 119 Amps, Phase B = 101 Amps, Grounded Conductor = 16 Amps
4 Parallel runs each pipe contains A, B, GC - measured ?Net Current? each run
Pipe 1 = .06 Amps, Pipe 2 = 6.2 Amps, Pipe 3 = 4 amps, Pipe 4 = .09 Amps
Did not have an amp loop long enough to encompass the complete service lateral
For unknown reasons my readings do not match the report readings, still curious why 2 out of 4 parallel runs show a significant net current reading. Service has an UFER grounding system & water piping CU. The gas service piping has no reading and the transformer is within 50? of the service equipment and has its own GES. The only connection to the GC & GEC is in the Main disconnect.

OK good info.

You will have to divide your net currents into 2 categories: the service (incoming feeds, GECs, main disconnect) and the feeder to the apartments.

I mention individual feeders because there is a very good chance in the very least one or two of those apartments has an improperly done subpanel, ditto with a standing neutral to ground fault on a branch circuit. Every other apartment Ive seen has an improperly done subpanel where the bonding screw want removed or something along those lines. This would cause current to flow on the metal conduits and in turn the chassis of the meter bank creating elevated magnetic fields. Current will also be forced onto EGCs in the subpanel traveling to appliances with metal water lines back to the water bond (which again creates elevated EMF).



For the service I recommend multiple clamps to determine the ratio of net current between the service conductors and the GECs. If the ratio is high, for both, than that would indicate an problem with the service like an open neutral.



In a perfect world I would go in there and trip the main and analyze circuit by circuit and megger, but considering apartments and impossible to go into each one this has to be done entirely via amp clamps and logic.
 

mwm1752

Senior Member
Location
Aspen, Colo
OK good info.

You will have to divide your net currents into 2 categories: the service (incoming feeds, GECs, main disconnect) and the feeder to the apartments.

I mention individual feeders because there is a very good chance in the very least one or two of those apartments has an improperly done subpanel, ditto with a standing neutral to ground fault on a branch circuit. Every other apartment Ive seen has an improperly done subpanel where the bonding screw want removed or something along those lines. This would cause current to flow on the metal conduits and in turn the chassis of the meter bank creating elevated magnetic fields. Current will also be forced onto EGCs in the subpanel traveling to appliances with metal water lines back to the water bond (which again creates elevated EMF).



For the service I recommend multiple clamps to determine the ratio of net current between the service conductors and the GECs. If the ratio is high, for both, than that would indicate an problem with the service like an open neutral.



In a perfect world I would go in there and trip the main and analyze circuit by circuit and megger, but considering apartments and impossible to go into each one this has to be done entirely via amp clamps and logic.

Can I get accurate reading clamping around the feeder pipe on the load side of the OCPD? or will the metal piping hinder the measurement
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Can I get accurate reading clamping around the feeder pipe on the load side of the OCPD? or will the metal piping hinder the measurement

Metal piping will not give you an accurate measurement since if only one feeder is leaking to ground as soon as the pipe hits the support strut current will get on all of them. Rather a general consensus but nothing exact. Clamping the Hots and neutrals with ground excluded will give you true net current.


Also bear in mind the current will fluctuate as loads are switched on and off. So at one point the service may be well balanced then at next point less, so when doing individual service conduit readings keep this in mind, which may explain why the conduits read different net currents.
 
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