Monitoring Total Residual Current (TRC)

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1

Originally Posted By: Don Kerwin
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icon_question.gif I have been doing alot of research on the cause & effect of stray voltages, and here is a summary: If stray voltages exist within a home’s electrical system, then a portion of the current that should be returning through the neutral path is actually flowing through a different path - most likely via bonding /grounding connections back to the source - and due to some sort of insulation breakdown.


There are literally hundreds of regulations published by the NEC, NESC and OSHA to ensure a relatively consistent and substantial path from each electrical load back to the neutral connection on the utility?s meter. All involved with electrical work in residential and commercial installations are reminded over and over that the ground was never intended to be (nor should be wired as) a return path for neutral current.

So, why do residual (leakage) currents still exist? A simple answer is that the applicable codes were not followed, and that existing circuit connections were somehow overlooked or 'grandfathered? as newer codes were established.

That being said, wouldn't it be prudent to measure the total residual current (TRC) of a home to get an idea of the baseline TRC value? Then, monitor that quantity over a day, week and month to see if there are changes (loss of insulation) due to switching loads, weather, etc.?

A few other questions:
1) Does anyone know whether the utility is responsible for the level of TRC existing within a facility?
2) Has TRC ever been used as part of a pass/fail test during any electrical or building inspections?
3) Has any residential or commercial building owner ever used TRC as a tool for identifying faulty electrical or mechanical installations? (i.e. drywall screw or stud nail semi-piercing cable insulation).
4) Is there a maximum level of TRC which could be considered unsafe for residents or employees of a facility?

We have all recommended that prospective owners have homes tested for Radon, lead paint, termites, asbestos, UF insulation, etc. Should we add monitoring of TRC to this list of test to be performed before the signing of the final purchasing agreement?

Any feedback would be appreciated.

--
Don Kerwin
Hunter Engineering

2

Originally Posted By: Scotty Lee
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Sounds like you have a lot of spare time icon_wink.gif


This would be way outside the scope of a home inspection. As for the fees that would be required for this service, you would be talking more than most would be willing to pay.

3

Originally Posted By: Don Kerwin
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icon_wink.gif Yeah - I have too much time on my hands - especially when I get answers like yours.


Since you haven't really answered any of my questions, I will try to address some of your concerns:

"This would be way outside the scope of a home inspection."
Of course it is. However, as an inspector, do you not recommend other tests be performed like Radon, asbestos, water quality, etc.? If, in fact, this monitoring were to be a valuable tool in determining the electrical safety of a property, who would you recommend do the testing?

"As for the fees that would be required for this service, you would be talking more than most would be willing to pay."
Unless this monitoring provides some sort of value to the buyer, I wouldn't expect any fee would be low enough. I am just doing some preliminary research. What kind of fees exist for Radon testing, water quality, etc.?

Any 'constructive' feedback would be helpful......

--
Don Kerwin
Hunter Engineering

4

Originally Posted By: Blaine Wiley
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Don,


Scotty is correct that this is WAY outside the scope of a normal home inspection. Radon is offered or recommended as a normal standard part of a home inspection in areas where Radon is highly occurring and is a concern. In fact, the EPA has a Radon map that shows where the highest concentrations of Radon are. Asbestos tests are recommended only when we see something (visual inspection) that tells us that asbestos may be present. Water quality inspections are rare, at least in both states that I have operated an HI business in.

TRC measurement is an item in the HI industry which would be considered Technically Exhaustive. The great majority of home inspectors don't do things like load calculations, gas line btu capacity, thermal loss imaging, microwave leak detection, EMF detection, etc.

Also, in the case of Radon, Asbestos, Lead , etc. , there are published guidelines as to the acceptable level. What are the guidelines for TRC?

Fees could be anything. I've seen inspectors do free Radon tests to get more inspections. When title X was originated, XRF lead testing was in the high hundreds, now I can find it for my clients for $79. I would think until there is a general public panic which is proven by TRC being a significant present health hazard, and one that occurs with some frequency, there will be no market.

I haven't ever heard of anyone getting a shock or dying from TRC, but then, I ate lead paint as a child.

Blaine ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

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Originally Posted By: Don Kerwin
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Thank you for the reply - and the reasoning behind it!

–
Don Kerwin


Hunter Engineering

6

Originally Posted By: jpeck
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Don,


You are asking for the impractical.

And total residual current caused from loose, poor, etc., connections in the electrical system will be dependent on the load on that electrical system and. specifically, on those affected circuits.

The only way to monitor this would be to stand there 24/7 and watch it as equipment came on and went off. Or install a rather expensive monitoring device which would, on paper, track the current versus time (or an even more expensive digital one). Besides, you you only measure the total through the ground rod, or the total fo all grounds combined?

A few other questions:
1) Does anyone know whether the utility is responsible for the level of TRC existing within a facility?

JP: I would say no, because it would, based on your descriptions, be caused by the interior wiring system.

2) Has TRC ever been used as part of a pass/fail test during any electrical or building inspections?

JP: Not that I am aware of, but it could be used as an indication that there was an improper ground by measuring the current on the main grounding electrode conductor going to the ground rod.

3) Has any residential or commercial building owner ever used TRC as a tool for identifying faulty electrical or mechanical installations? (i.e. drywall screw or stud nail semi-piercing cable insulation).

JP: I have no idea if they have or not.

4) Is there a maximum level of TRC which could be considered unsafe for residents or employees of a facility?

JP: As measured where? This would get down to individual circuits, then the combinded total, then the concentrated total (how much in one localized area), etc.

Don, you've raised some good and interesting points, but to do anything worth reviewing and discussing, this would have to be a wide spread, long duration, montioring of each circuit 24/7/365 for several years (for seasonal variations).

Interesting idea though. Who would fund it? Talking major $$$$ here.

--
Jerry Peck
South Florida

7

Originally Posted By: psabados
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Don


We know the actions levels for Radon, Lead, CO. The feds can not even make up the minds about the mold situation and action levels associtated with it.

Why should or would Joe home owner be concerned about TRC? There would be absolutely no short term test that could be used to guage that situation. Which would be required in a real estate transaction.

My question is! Whats the long term effect on the occupants of the dwelling and on the dwelling itself? Who's setting the limits and how can an accurate test be performed within a short real estate sale time frame?

Paul

8

Originally Posted By: Bob Badger
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Don Kerwin wrote:
So, why do residual (leakage) currents still exist? A simple answer is that the applicable codes were not followed, and that existing circuit connections were somehow overlooked or 'grandfathered? as newer codes were established.


Hi guys I am new here but far from new in the electrical trade.

First and foremost you will almost always have some current flow on the grounding electrode conductor even in a building that has code compliant wiring.

The ground is bonded to the neutral at the panel and the utility bonds their transformer neutral to ground also.

Because of this some of the current that should be flowing on the combination neutral ground from the utility will flow through the earth and or water pipes back to the utility transformer.

This is unavoidable with the distribution system here in the US.

--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum
9

Originally Posted By: Mike Parks
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Bob’s answer is why when a water service line is used as an electrode, that connection needs to be made with the first 5’ of entering the structure.


This is so no current is on the interior water lines.

This is different from the bond to the waterlines.

Get a book like Stallcup's Electrical Grounding and Bonding Simplified ITEM# SEG02 on the NFPA.org page.

Be real careful when addressing grounding/bonding issues. Many electricians do not understand this topic.

Mike P.

10

Originally Posted By: Bob Badger
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Mike Parks wrote:

Be real careful when addressing grounding/bonding issues. Many electricians do not understand this topic.


Mike sadly that is very true, I have been in the trade for quite a while and I would be lying if I told you I did not have to use reference books for some of these issues.

Of course when you have "Equipment Grounding Conductors" "Grounding Electrode Conductors" "Grounded Conductors" "Ungrounded Conductors" "Main Bonding Jumpers" "Bonding Jumpers" etc. each with different requirements it is easy to get lost. ![icon_confused.gif](upload://qv5zppiN69qCk2Y6JzaFYhrff8S.gif)

--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum
11

Originally Posted By: Mike Parks
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Don


Why did you bring http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=12;t=000099 here?

Karl ,and others, is the best source for this info.

Some of the code concerns you have have been in effect since 1934.

This is not a home inspector topic "EMF".

Mike P. EMF Consultant

12

Originally Posted By: Bob Badger
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Mike I could not remember the name of Karl’s book, but I agree that Karl and the others have much to offer on this subject.


These guys make their living dealing with just this issue.

Karl flies around the country identifying the problems and creating reports so local electricians can fix it.


Quote:
This is not a home inspector topic "EMF".


So you feel that a home inspector is wrong to ask questions?

IMO the more well rounded you are in all aspects of electrical work, the more you will understand the basic stuff.

--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum
13

Originally Posted By: Mike Parks
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Bob


He is not a home inspector. Go to Mike's site and look. The link is in my above post.

Karl's book is in the post.

Mike P.