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Type: Posts; User: wbdvt

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1. ## Thread: NFPA 70E compliance- automation programmimg engineers

by wbdvt
Replies
9\$\$
Views
881

### NFPA 70E-2018 is Table 130.7(C)(15)(a) which...

NFPA 70E-2018 is Table 130.7(C)(15)(a) which lists Category 1 for equipment rated 240V and below as long as the parameters of maximum available fault current is no greater than 25kA and the maximum...
2. ## Thread: Calculating Arc Flash by Hand

by wbdvt
Replies
5\$\$
Views
416

### Depends on the sophistication of the utility...

Depends on the sophistication of the utility system but they should be able to give you a max/min value or an average value as they need to know this information themselves to operate the system.
3. ## Thread: POCO transformer 4 feet from service

by wbdvt
Replies
14\$\$
Views
748

### possibly but there is not enough detail to know...

possibly but there is not enough detail to know for sure. For example: is this in a residential development with a decent size padmount feeding multiple houses?

Not likely since the panel is...
4. ## Thread: Calculating Arc Flash by Hand

by wbdvt
Replies
5\$\$
Views
416

### In order to calculate the available bolted fault...

In order to calculate the available bolted fault current in your system, you need to get the available fault current from the utility. When you initially ask, a customer service rep will look at a...
5. ## Thread: Diesel Generator Breaker

by wbdvt
Replies
4\$\$
Views
307

### Unless it is an extremely large genset, the...

Unless it is an extremely large genset, the function of the generator breaker is really no different than any other breaker which is to protect the conductor and possibly overloading of the...
6. ## Thread: NFPA 70E compliance- automation programmimg engineers

by wbdvt
Replies
9\$\$
Views
881

### Is the highest voltage in the area you are...

Is the highest voltage in the area you are working 120V? I ask since you mention MCC and they are typically 480V. Are you in a cubicle where the 480V breaker is?

If only 120V, then you need...
7. ## Thread: Arc Flash Labelling for Service Equipment

by wbdvt
Replies
5\$\$
Views
386

### In order to calculate the incident energy at the...

In order to calculate the incident energy at the service equipment, you need to model back to the utility protective device. Typically this would start with:

Utility available fault current and...
8. ## Thread: Arc Flash Kit Recommendations

by wbdvt
Replies
4\$\$
Views
1,778

### In order to properly select arc rated PPE (or any...

In order to properly select arc rated PPE (or any PPE for that matter), you need to know the hazard level that you are exposed to. This means that if working in an industrial/commercial facility,...
9. ## Thread: Arc Flash Labels/ Motor Control Center

by wbdvt
Replies
11\$\$
Views
696

### Agreed with everything said. I have been doing...

Agreed with everything said. I have been doing arc flash studies for over 10 years and am amazed sometimes at what I see done. That is clearly incorrect on the labels on each MCC cubicle and I...
10. ## Thread: Relay Co-ordination Approach

by wbdvt
Replies
2\$\$
Views
397

### Not sure about your use of the term relay for the...

Not sure about your use of the term relay for the coordination. Are there actual relays you are trying coordinate? If also including the molded case circuit breakers, breakers with electronic trip...
11. ## Thread: SC Rating of Panel

by wbdvt
Replies
8\$\$
Views
664

### Typically the purchaser will specify what SCCR...

Typically the purchaser will specify what SCCR panel rating is needed based on the short circuit at the location of the panel. The breakers that come with the panel are then sized for an AIC rating...
12. ## Thread: SC Rating of Panel

by wbdvt
Replies
8\$\$
Views
664

### as noted above, the panel rating is independent...

as noted above, the panel rating is independent of the breaker ratings. It is based on the panel being able to hold together during a fault due to the magnetic forces of a fault.
13. ## Thread: Voltage rated gloves

by wbdvt
Replies
10\$\$
Views
3,818

### Doesn't matter what NFPA 70E says as OSHA...

Doesn't matter what NFPA 70E says as OSHA 1910.137 has the requirements for rubber insulating gloves as well as blankets and sleeves. OSHA requires that gloves be tested before first issue and every...
14. ## Thread: DC Arc Flash calculation

by wbdvt
Replies
5\$\$
Views
793

### did you look to see the specs on the rectifier...

did you look to see the specs on the rectifier circuit? The electronics may have a max short circuit rating and time before the internal protective circuits operate to protect the electronics. you...
15. ## Thread: AIC panel ratings

by wbdvt
Replies
6\$\$
Views
474

### When utilities are asked for short circuit, they...

When utilities are asked for short circuit, they will provide you with the infinite bus short circuit on the transformer secondary terminals based on transformer size and impedance. This will...
16. ## Thread: MV short circuit values above 10ka

by wbdvt
Replies
26\$\$
Views
1,049

### For three phase work, a faceshield is required...

For three phase work, a faceshield is required for 5-8 cal/cm^2 and a arc rated hood or faceshield with balaclava for 9 cal/cm^2 and higher. Since no faceshield was used, this would indicate that...
17. ## Thread: MV short circuit values above 10ka

by wbdvt
Replies
26\$\$
Views
1,049

### Not entirely accurate. The wearing and rating of...

Not entirely accurate. The wearing and rating of the arc rated faceshield depends on whether it is a single phase open air exposure and the cal/cm2 hazard level. Refer to OSHA 1910.269 Appendix E,...
18. ## Thread: MV short circuit values above 10ka

by wbdvt
Replies
26\$\$
Views
1,049

### I don't believe the fault current has any impact...

I don't believe the fault current has any impact on working with the exception of arc flash hazard. It is possible that with the higher fault current the incident energy levels may be low based on...
19. ## Thread: Arc Flash Labels

by wbdvt
Replies
3\$\$
Views
327

### There is not an OSHA requirement to have arc...

There is not an OSHA requirement to have arc flash labels. The requirement and details of what is on labels is in NFPA 70E-2018. This is standard is referenced by OSHA as a means of meeting the...
20. ## Thread: Arc Flash Study on full load or worse case scenairo acceptable to OSHA standards?

by wbdvt
Replies
3\$\$
Views
427

### I will be blunt. The questions you are asking...

I will be blunt. The questions you are asking indicate that you have not done an arc flash study before and really do not have a good grasp on what is needed for a study. This is dangerous as the...
21. ## Thread: Arc Flash study analysis Course

by wbdvt
Replies
3\$\$
Views
307

### You will get many opinions on software for arc...

You will get many opinions on software for arc flash studies. If your company already has a software product it is using for short circuit studies, you may be stuck with that. I believe the two...
22. ## Thread: UTILITY TRANSFORMER DAMAGE CURVES

by wbdvt
Replies
19\$\$
Views
982

### I wasn't clear on the point I was trying to make....

I wasn't clear on the point I was trying to make. I am aware of the difference between SMD & SMU. However, the OP stated the utility just said SM-20 and the OP assumed that meant a 20A fuse. ...
23. ## Thread: UTILITY TRANSFORMER DAMAGE CURVES

by wbdvt
Replies
19\$\$
Views
982

### One reason to coordinate the main bkr with the...

One reason to coordinate the main bkr with the utility fuse is to aid in troubleshooting. If the fuse goes, then the issue could be the transformer or secondary cable if coordinated. If not the...
24. ## Thread: UTILITY TRANSFORMER DAMAGE CURVES

by wbdvt
Replies
19\$\$
Views
982

### Your secondary protective device is not going to...

Your secondary protective device is not going to protect the transformer from any transformer internal faults or faults in the secondary conductors. The secondary may prevent a transformer overload...
25. ## Thread: Reducing arc flash chances

by wbdvt
Replies
7\$\$
Views
698

### Why do you think there will be an arc flash with...

Why do you think there will be an arc flash with the fuse? An arc flash will occur when a person makes contact with energized terminals or buses with a conducting object, among other causes. So for...
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