Allowable fuse size - disagreement

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Miked56

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West Chester, PA, USA
Here is the set-up....

A mechanic responded to a lighting circuit that had blown a fuse. In the control cabinet, (6) 2-pole 30A lighting contactors feed (12) fused lighting circuits - 277v, single phase. Blown fuse was a 15A time delay. All other fuses were 20A or 30A time delay. Thinking the 15A fuse was installed incorrectly, mechanic installed 30A time delay fuse to restore circuit. No special labeling indicating any fuse size withing the cabinet. Mechanic was cited for negligent "unsafe work practices" for installing the 30A fuse.

Knowns:

Circuit draw is - less than 9 A
Each light pole protected with 2 Amp fuses at base of pole
All contactors protected with up-stream 30A double pole circuit breakers
#10 solid THHW wiring throughout cabinet and branch circuits to poles

Aside from voltage drop calculations (which should have been considered at install), no special labeling for required fuse size, or conduit fill de-rating (again, install calculations)... all of which are unknown to a maintenance mechanic.... I ask the following:

With 30A breakers protecting #10 wiring, and 30A contactors...
Did mechanic violate NEC sectors 240 or 310?
Without specific labeling, was a 30A fuse allowed within the scope of NEC?
With fusing at fixtures, was the circuit under-protected by his actions?

My opinion was no, he did not. From a "users point of view", he based his decision on observable variables, ie. wire size, contactor rating, breaker sixe. Given the circumstances of breaker size, wiring size, no special labeling, and measured load, a 30A fuse was the MAXIMUM he could have gone to.

Was the mechanic negligent? Your thoughts?
 
Assuming the 15A fuse had been installed incorrectly IMHO requires a lot more backup work to confirm that before casually replacing with a 30A fuse.
That circuit might have had different wire sizes downstream or some other justification for the smaller fuse. He apparently did not know that one way or another.
If the current measured out to 9A, then a 15A fuse should have held and an exact replacement would seem to be appropriate pending further investigation.
JMO
 
I think he may have some level of if not negligence perhaps inappropriate action. If the total current draw is only 9 amps there is no way a 15 amp fuse should open unless it was a fast blow fuse which would not be appropriate.

He probably should have investigated why the fuse opened rather than replacing it with a higher-rated fuse. Personally I do not think it is ever appropriate for a "mechanic" to be replacing a fuse with a higher-rated fuse. It does not appear to me that he is properly trained if he is changing the rating of a fuse like this and therefore it would appear to me he is not electrically qualified to be doing this work as required by OSHA rules.

However, I am thinking that this is approaching being asked for a legal opinion as it seems possible that what is being described is some kind of Union grievance and I don't think that the rules would allow us to comment directly on such a case.
 
GoldDigger said:
Assuming the 15A fuse had been installed incorrectly IMHO requires a lot more backup work to confirm that before casually replacing with a 30A fuse.
That circuit might have had different wire sizes downstream or some other justification for the smaller fuse. He apparently did not know that one way or another.
If the current measured out to 9A, then a 15A fuse should have held and an exact replacement would seem to be appropriate pending further investigation.
JMO
Click to expand...

My question revolves around violations of code. Did he violate the regulations?
 
petersonra said:
I think he may have some level of if not negligence perhaps inappropriate action. If the total current draw is only 9 amps there is no way a 15 amp fuse should open unless it was a fast blow fuse which would not be appropriate.

He probably should have investigated why the fuse opened rather than replacing it with a higher-rated fuse. Personally I do not think it is ever appropriate for a "mechanic" to be replacing a fuse with a higher-rated fuse. It does not appear to me that he is properly trained if he is changing the rating of a fuse like this and therefore it would appear to me he is not electrically qualified to be doing this work as required by OSHA rules.

However, I am thinking that this is approaching being asked for a legal opinion as it seems possible that what is being described is some kind of Union grievance and I don't think that the rules would allow us to comment directly on such a case.
Click to expand...


No Union grievance, nothing like that. Current draw was measured after fuse install.
Just asking if he violated code requirements.
 
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In hindsight, he did not violate the code by over fusing for the conductors and equipment connected.
But he had no assurance that he might not be violating the code when he acted.
Hard to pin it down farther than that.
The original installing electrician could have put a 30 in initially, because he knew the installation details.

Sent from my XT1585 using Tapatalk
 
petersonra said:
I think he may have some level of if not negligence perhaps inappropriate action. If the total current draw is only 9 amps there is no way a 15 amp fuse should open unless it was a fast blow fuse which would not be appropriate.

He probably should have investigated why the fuse opened rather than replacing it with a higher-rated fuse. Personally I do not think it is ever appropriate for a "mechanic" to be replacing a fuse with a higher-rated fuse. It does not appear to me that he is properly trained if he is changing the rating of a fuse like this and therefore it would appear to me he is not electrically qualified to be doing this work as required by OSHA rules.

However, I am thinking that this is approaching being asked for a legal opinion as it seems possible that what is being described is some kind of Union grievance and I don't think that the rules would allow us to comment directly on such a case.
Click to expand...

infinity said:
What is the maximum allowable size of OCPD permitted for this type of circuit?
Click to expand...

30A
 
Miked56 said:
My question revolves around violations of code. Did he violate the regulations?
Click to expand...

You question didn't revolve around whether he violated code, it revolved around whether he was negligent, and was cited for negligence due to unsafe work practices. Here in Florida, we have a State code that requires us to follow 2% feeder and 3% branch circuit voltage drop. So, without further investigation he would have violated code here. That said, he did practice unsafe work practices. He was negligent in that he didn't find out why the one fuse was 15 amp rated. An employer certainly has a right to determine what they consider "unsafe" , especially when their determination is in excess of standard practice, when they are paying the bills.
 
Cow said:
It may not be logical but to call it unsafe?

Please explain.
Click to expand...

If an electrician shuts the breaker off, tags it out and then proceeds to the "dead" panel, and removes the covers and starts working without suiting up and doing a voltage test, is he being perfectly safe because the panel was actually dead even though he didn't prove it? My answer is no. With no investigation or knowledge of why the fuse was 15A to decide to change it to 30A is unsafe until proven otherwise. In my opinion the burden of proof isn't on the other side. Things are not unsafe only after an accident occurs. Simple as that, in my mind.
 
suppose the fuses for the individual luminares are only supplemental in nature and the listing for them requires a branch OCPD with a rating not greater than 15A. did he even check for such a possibility before just changing the fuse rating?
 
GoldDigger said:
Assuming the 15A fuse had been installed incorrectly IMHO requires a lot more backup work to confirm that before casually replacing with a 30A fuse.
Click to expand...

True, but with an existing mix of sizes and no markings about which to use in a given circuit, it's not a far stretch to assume that all of them should be 30's (or 20's). If one circuit specifically required a 15amp fuse, the negligence started when the panel was installed without labels.

As a side note, it's not uncommon in the world of maintenance to for someone to substitute in a smaller fuse when the right one isn't available and not leave a note about it ("was a 30, only had a 15, replace this later").
 
Thanks to all who commented so far. Allow me to clear up a few assumptions.

The mechanic is a general maintenance mechanic, not an electrician.
The 15A fuse blew because a mechanic on an earlier shift left open the in-ground j-box, allowing water to pool and shorted the circuit.
The mechanic saw no labels indicating any fuse sizes, and no drawings were available to confirm circuitry.
The mechanic accepted the corrective action, knowing the company can define "un-safe" however it wants to.
The mechanic asked only, "Did I violate the National Electric Code?"... given the circumstances, my opinion was he did not.
Myself, as a registered electrician, would have investigated the circuitry, calculated load, and install the standard sized fuse based on "next size up", meaning a 9 amp draw would have been a 15A fuse. I also would have labeled the fuse holder as such.

As a general maintenance mechanic, it's not uncommon for mistakes to happen. I'm not interested in debating his qualifications, etc.

Thanks again! Everyone work safe and get home whole!
 
Unless there is derating involved, a 30A OCPD, whether fuse or breaker, is permissible for #10 wire of any type. istm the problem is a maintenance man with perhaps less than acceptable qualifications "fixed" it rather than an electrician. this seems to me a failure of procedure and rules than what he did.

In the industrial environment where I worked previously, a maintenance man would never even attempt what the OP described. As soon as a problem electrical in nature was discovered, the electrical department would be called to fix it.

imo, the mechanic was not negligent, he did what he thought he needed to do to keep the eqpt running. He may have overstepped his bounds and qualifications, but I dont see negligence here.
 
I don't think I have a problem with a maintenance mechanic replacing a blown fuse when the reason for the fuse being blown is known, assuming the mechanic knew the reason for the blown fuse prior to replacing it, which is not clear. It's not all that hard to train him on how to replace a blown fuse. However it does not seem to me that he is qualified to determine that is acceptable to change the rating of the fuse.

It seems to me there are several failures of perhaps practice and policy in play here. First off is why the mechanic thought it was acceptable to change the rating of a fuse. This appears to me to be their failure of training or supervision or both. It may be that it's also a failure policy because there is no written policy that says what he can and cannot do as far as electrical work goes. That would seem to be a gross violation of what constitutes a qualified worker.

The second problem though is at a higher level I think. Why is there no marking indicating what this fuse rating should be. Is there no drawing? There is no drawing it seems to me that that the very least the ratings of the fuses are to be marked on the panel next to the fuse holders.
 
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