Circuit overload and shock questions

[jischr]

I'm in safety and have a couple electrical questions.

Q1 ? Two UL approved portable space heaters, each rated 1500W, are on one power strip. The two users only use them on ?low? because it has tripped the power strip when they both use them at higher settings. It could still be fire hazard if the power strip failed closed and additional load is put on the circuit, at least until the supply breaker tripped. Is administrative control acceptable to the electrical code or is a known potential overload unacceptable?

Q2 ? a 480V cabinet and 120/208V power distribution panel that are properly grounded is subject to water from a leak on the floor above. The enclosures are not rated for wash down. Water is coming out under the room access door. Presuming the circuits are properly grounded there is no risk of shock when touching other metal parts, e.g. the door, or even the enclosures while standing in the water correct? This is to respond to a question from one of the people who walked through water and was too busy to notify anyone of the leak.

Thanks in advance,

John

 

[petersonra]

I'm in safety and have a couple electrical questions.

Q1 ? Two UL approved portable space heaters, each rated 1500W, are on one power strip. The two users only use them on ?low? because it has tripped the power strip when they both use them at higher settings. It could still be fire hazard if the power strip failed closed and additional load is put on the circuit, at least until the supply breaker tripped. Is administrative control acceptable to the electrical code or is a known potential overload unacceptable?

Q2 ? a 480V cabinet and 120/208V power distribution panel that are properly grounded is subject to water from a leak on the floor above. The enclosures are not rated for wash down. Water is coming out under the room access door. Presuming the circuits are properly grounded there is no risk of shock when touching other metal parts, e.g. the door, or even the enclosures while standing in the water correct? This is to respond to a question from one of the people who walked through water and was too busy to notify anyone of the leak.

Thanks in advance,

John

A1: IMO the OCPD either on the branch circuit or the power strip is more than adequate to deal with the potential risk. I do not think that an administrative control is warranted since the device protects itself via its built in OCPD from the potential risk. The fact that they are choosing to run their heaters on low is a convenience for the users by not having to reset the strip or BC OCPD, not a safety issue.

A2: Grounding in this case provides no particular protection from whatever additional risk of electrocution there might be from the floor being wet. Neither the door or the enclosures would be energized under any normal conditions, so where would the hazard come from?

 

[Little Bill]

This is to respond to a question from one of the people who walked through water and was too busy to notify anyone of the leak.

If they had time to ask the question, it seems they would also have had the time to report the leak!:roll:

 

[RichB]

:thumbsup: to both the above!

 

[charlie b]

Q1: If the two users each had their heater at or above 80%, and if the power strip failed to protect itself (these things tend to be cheaply made), the circuit breaker could take the resulting current for far, far longer than the power strip could take the same current. The circuit breaker might not even trip at all. So yes, I would call this a safety hazard, specifically a fire hazard.

Q2: If the panels are properly bonded, then a person touching the enclosure could not initiate a shock situation. If the enclosure had somehow become energized (e.g., due to some loose wires inside the panel), the upstream breaker would have tripped right away. So water on the floor would not have a bearing on any electrical safety consideration. It might create a slipping hazard, but not a shock hazard.

 

[Sahib]

Q2 ? a 480V cabinet and 120/208V power distribution panel that are properly grounded is subject to water from a leak on the floor above. The enclosures are not rated for wash down. Water is coming out under the room access door. Presuming the circuits are properly grounded there is no risk of shock when touching other metal parts, e.g. the door, or even the enclosures while standing in the water correct? This is to respond to a question from one of the people who walked through water and was too busy to notify anyone of the leak.

There might be reduction in your body resistance when standing in water on floor than when standing on dry floor. So if there is a partial insulation breakdown in the panel due to water seepage, which though do not operates the OCPD, may be adverse enough to shock you when standing in water but may not shock you when standing on dry floor!

 

[Ponchik]

There might be reduction in your body resistance when standing in water on floor than when standing on dry floor. So if there is a partial insulation breakdown in the panel due to water seepage, which though do not operates the OCPD, may be adverse enough to shock you when standing in water but may not shock you when standing on dry floor!

IMO your statement may be true assuming the person is bare feet. Usually people have shoes on and that will prevent shock.

Even if they are bare footed and the flooring has some water on it, it may still be a nonconductive material (wood flooring) then I don't see any additional harm.

 

[K8MHZ]

Q1: Do the instructions or label say not to use the heaters with extension cords or outlet strips? I have seen the receptacles in outlet strips burnt totally up from using an electric space heaters on them and the little breaker never tripped. So I am against such a practice, and the manufacturer of the heater may be, as well.

Q2: Is based on a presumption. That presumption being that all metal is bonded and grounded properly. What effect will the water have on the metal to metal connections as it relates to a fault? What assures there is no potential, or potential for potential, between the non metal (concrete?) floor and the metal cabinets? Everything may be electrically safe right now, but what will happen as time goes on? Water may eventually form a conductive path with enough impedance not to trip a breaker, but enough conductivity to create a shock. My take is to stop the leak immediately, if that hasn't already been done.

The above is my personal opinion based on experience and gut feeling. I prefer to err on the side of caution when it comes to electricity.

 

[WorkSafe]

Space heaters and other high current items are not allowed to be used with power strips (DoD policy). To many issues with the strip burning up. I'm surprised that a safety professional would even allow it in the workplace.

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[Ponchik]

Space heaters and other high current items are not allowed to be used with power strips (DoD policy). To many issues with the strip burning up. I'm surprised that a safety professional would even allow it in the workplace.

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What is "DoD" policy?

 

[WorkSafe]

What is "DoD" policy?

I was just saying we don't allow them in the air force, aka DoD department of defense.

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[Ponchik]

I was just saying we don't allow them in the air force, aka DoD department of defense.

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I had a feeling that is what it meant.

But that only applies to DOD.

In my opinion I don't see any difference between the power strip having two heaters on it vs one wall receptacle having two heaters on it. If the circuit overloads the breaker should open up the circuit. If the power strip overloads then the auxiliary OCPD will open up the circuit. Now, I know there are cheap power strips and good power strips. So we can have a system that is 100% safe. You can not control what the consumer plugs into their strip.

 

[petersonra]

Space heaters and other high current items are not allowed to be used with power strips (DoD policy). To many issues with the strip burning up. I'm surprised that a safety professional would even allow it in the workplace.

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Given the tens of millions of power strips in use and the very few (if any) fires caused by using them appropriately, my guess is this is just bureaucratic over reach.

 

[WorkSafe]

Given the tens of millions of power strips in use and the very few (if any) fires caused by using them appropriately, my guess is this is just bureaucratic over reach.

I agree, but the keywords are "using appropriately." We don't live in a world where workers will know what appropriate is. It's easier for everyone to disallow high current items on power strips.

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[Ponchik]

I agree, but the keywords are "using appropriately." We don't live in a world where workers will know what appropriate is. It's easier for everyone to disallow high current items on power strips.

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What what are you going to do if a person needs space heaters in their office or under their cubicle??

2nd you are going to do an inspection every week to see who uses the heaters? I don't think it is possible to keep people from using space heaters or using power strips.

3rd, some people have common sense and some don't. Some just don't simply understand what is an overload and what can cause or not cause fire. Has nothing to do with common sense they simply do not understand.

 

[petersonra]

I agree, but the keywords are "using appropriately." We don't live in a world where workers will know what appropriate is. It's easier for everyone to disallow high current items on power strips.

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my guess is there are very few if any fires caused by power strips that are overloaded that have built in CBs. the CB will just trip and prevent any issue that the overload might otherwise have caused.

damaged power strips might well be a problem, but any damaged electrical equipment has potential for problems, not just power strips.

I just do not see any special hazard here. So called safety experts make a huge deal out of things like this that are not especially hazardous but allow all kinds of electrical issues to exist that truly are a problem. Look at all the moronic yellow lines put on the floor in front of lighting panels. No hazard there at all. Just a convenience issue.

 

[WorkSafe]

Bob,

I tell them to just use the power strip according to it's rating, but then another inspector comes in behind me saying it has to go and it's a major fire hazard. Even our Fire Department comes through and writes these people up.

 

[petersonra]

Bob,

I tell them to just use the power strip according to it's rating, but then another inspector comes in behind me saying it has to go and it's a major fire hazard. Even our Fire Department comes through and writes these people up.

If this is a DoD facility and there is a DoD rule against what they are doing, I can understand getting a write-up.

Just because something is against the rules does not mean it is unsafe. You still have to follow the rules whether it is really a safety hazard or not. in any case, it is doubtful that the FD is in a position to make a determination as to whether something is or is not an electrical hazard likely to cause a fire.

My guess is more people are harmed from tripping over them than are harmed by fires that are started by them.

 

[WorkSafe]

Bob,

You gotta remember, I work for the guberment. If it makes sense to private industry, it definitely does not makes sense for the government.

Sorry if I derailed this thread.