A little help please

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memyselfandI

memyselfandI

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Hampton Roads, Virginia
I have in an industrial facility a 225A 277/480V 3PH 4W panel that feeds 14-3ph 30A receptacles, each one is on their own breaker. Calculated load on each device is 24A. Can I put those devices on a 30A breaker and be compliant with the code as far as demand factor? I was using Table 220.44. The panel is fed with a 225A breaker.
 
chris kennedy said:
T200.44 is for non-dwelling rec's calculated at 180va.
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Sorry I'll go ahead and omit that part. I have in an industrial facility a 225A 277/480V 3PH 4W panel that needs to feed 14-3ph 30A receptacles, each one is on their own breaker. Calculated load on each device is 24A. Can I put those devices on a 30A breaker and be compliant with the code, or do I need to add another panel? The panel is fed with a 225A breaker.
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It's an interesting question when I try to go to the Code and answer by Code reference.
Obviously, if all 14 outlets were used concurently, a 225 amp panel would not suffice. Sizing the panel is totally dependant on the projected load at any given time, and, so-far, I have no Code reference to address that.
 
What they are are these things called Aquatherms. They circulate water through a injection mold machine. They have heaters in them that keep the water a constant temperature. They cycle on and off as required to maintain heat. They generally only draw about 13A apiece but each machine has two, and other 480v equipment essential to its operation. These Aquatherms are portable and are connected with a cord and plug, 30A 3ph 480v. We have put two circuits to each machine to accommodate this equipment, but each circuit has 2 outlets on it so we can be flexible on where we place them. Sometimes we put two pieces of equipment on them and then the currnet goes up to no more than 20A. Not all of these heaters will be on at the same time. They are not continuos duty.
 
Someone may prove me wrong (not an unusual happening), but I don't think you are going to find a definite yes or no answer here or a Code "answer".
The Code simply states the circuit should be designed for the load and you have thrown in a lot of varibles. From "24 amps" we are now down to "no more than 20". The load is "not continuous", but it's seems almost impossible to determine how much would be concurrent.
From one standpoint, if you use a 225 amp feeder, properly protected, worse electrical scenerio, the breaker trips.
But, you also state the equipment is "essential to the operation", so you might not want to take the chance.
My experience with industrial would be that normally you would provide two panels or a larger panel, but that's based on my experience only.
In most industrial applications, loads are usually added periodically, so "overkill" can also be seen a "planning"
 
Here is my problem. We had a breaker in the panel that burned a hole in the buss. I feel the cause was a loose connection, others feel it was a overload. The load was recorded at 13A on a 15 a breaker. Now I know that if that is the case then that load should be moved to a 20A breaker. However, beacuse we have these other pieces of equipment that need to run, sometimes we share the circuit. In this situation, the second circuit has an Aquatherm and a grinder hooked up to the same circuit with a combined total of 18A.
 
memyselfandI said:
Here is my problem. We had a breaker in the panel that burned a hole in the buss. I feel the cause was a loose connection, others feel it was a overload. The load was recorded at 13A on a 15 a breaker. Now I know that if that is the case then that load should be moved to a 20A breaker. However, beacuse we have these other pieces of equipment that need to run, sometimes we share the circuit. In this situation, the second circuit has an Aquatherm and a grinder hooked up to the same circuit with a combined total of 18A.
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There's no reason that a 20a breaker should handle 13a or even 18a any better than a 15a breaker can (other than tripping as it's designed to.)

Just as with receptacles, the conductive parts are more than capable of carrying even 30a. If a breaker's contact has a poor connection with the bus stab, normal current can quickly damage the contacting surfaces.

There's no reason 'overload' current should damage the stabs with a properly-mating breaker-bus connection. Overcurrent melts plastic; arcing melts metal.
 
LarryFine said:
There's no reason that a 20a breaker should handle 13a or even 18a any better than a 15a breaker can (other than tripping as it's designed to.)

Just as with receptacles, the conductive parts are more than capable of carrying even 30a. If a breaker's contact has a poor connection with the bus stab, normal current can quickly damage the contacting surfaces.

There's no reason 'overload' current should damage the stabs with a properly-mating breaker-bus connection. Overcurrent melts plastic; arcing melts metal.
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That is interesting that you say that because I feel it was a loose connection from the factory. The breaker was never used until this piece of equipment was hooked up and even at 13A on a 15A breaker, the buss should not have burned up the way it did. I literally saw the connection glowing and arcing as the current was being pulled through it and the breaker didn't heat up enough to trip. This was a bolt in type breaker factory installed. As far as a 15 or 20 on the circuit, I know that they would protect the load at 13 or 18 amps, but sometimes not all the time, they plug in another Auatherm and at 13 amps a piece and a 30A breaker needs to be in place because how long will a 26A load last on a 15 or 20 amp breaker. This is the only reason why we use the 30A breakers, it allows us to be versatile when connecting this equipment because we can't pick and choose what mold goes where but when it is put into service we have to be ready to make sure it performs properly wherever it winds up.
 
"I literally saw the connection glowing and arcing as the current was being pulled through it and the breaker didn't heat up enough to trip."

"I feel it was a loose connection from the factory."

Based on these statements, did you or someone else remove the CB prior to checking for it being loose ?
I would agree with what you saw leaning towards to a loose connection, but was the fact of a loose connection established?

If the same 30A CB is used to supply various loads, have you considered adding O/Ls to the heaters for current control?
 
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VinceS said:
"I literally saw the connection glowing and arcing as the current was being pulled through it and the breaker didn't heat up enough to trip."

"I feel it was a loose connection from the factory."

Based on these statements, did you or someone else remove the CB prior to checking for it being loose ?
I would agree with what you saw leaning towards to a loose connection, but was the fact of a loose connection established?

If the same 30A CB is used to supply various loads, have you considered adding O/Ls to the heaters for current control?
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The breaker was never removed, replaced, or used prior to this application. As far as establishing the cause, the panel is still under warranty and we are sending it back to the manufacturer for them to determine the cause...which we all know it's not THEIR fault but ours because we were the last ones to touch it.
All the heaters have individual overload protection in each unit, designed this way by the manufacturer.
I guess what I should be asking is should I use Table 220.44 to determine feeder size for these receptacles?
 
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memyselfandI said:
That is interesting that you say that because I feel it was a loose connection from the factory. The breaker was never used until this piece of equipment was hooked up and even at 13A on a 15A breaker, the buss should not have burned up the way it did. I literally saw the connection glowing and arcing as the current was being pulled through it and the breaker didn't heat up enough to trip. This was a bolt in type breaker factory installed. As far as a 15 or 20 on the circuit, I know that they would protect the load at 13 or 18 amps, but sometimes not all the time, they plug in another Auatherm and at 13 amps a piece and a 30A breaker needs to be in place because how long will a 26A load last on a 15 or 20 amp breaker. This is the only reason why we use the 30A breakers, it allows us to be versatile when connecting this equipment because we can't pick and choose what mold goes where but when it is put into service we have to be ready to make sure it performs properly wherever it winds up.
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MM&I, What size wire are you connecting to the 30a breaker ? Also, how far

from the panel are the 30a recpts.
 
benaround said:
MM&I, What size wire are you connecting to the 30a breaker ? Also, how far

from the panel are the 30a recpts.
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I think we are going off in a direction that was not the intent of the original question. The first and last question that I asked was can I use Table 220.44 to size the feeders to feed that panel which supplies those receptacles. The size of the wire and the length of the runs are irrelevant, but if you must know then wire size is #10AWG THHN CU, 3 current carrying conductors in the raceway, ambient air temp of 30 DEG Cel, less that 75' away.
 
memyselfandI said:
The first and last question that I asked was can I use Table 220.44 to size the feeders to feed that panel which supplies those receptacles.
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Again IMO no.

Section 220.44 permits receptacle loads, calculated at not more than 180 volt-amperes per strap, to be computed by either of the following methods:
1. The receptacle loads are added to the lighting load. The demand factors (if applicable) in Table 220.12 are then applied to the combined load.
2. The receptacle loads are calculated (without the lighting load) with demand factors from Table 220.44 applied.
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You probally will have a hard time getting the factory to pony up, because they usually have that big sticker saying " Recheck connections that may be loose from vibrations of shipping" or something simular. The assembler probally crossthreaded the screw, or bad threads in the buss.
 
chris kennedy said:
Again IMO no.
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I guess I was thinking I could use that table for what I needed but I see that the table is for receptacles in general areas and not definate purpose. I know that the connected load can't exceed the rating of the equipment or device, all the searching I have done on this keeps pointing back to this. It's kind of like it "runs back home to momma". It's hard to determine a panel size in an industrial situation when machinery data is not yet available.
 
memyselfandI said:
It's hard to determine a panel size in an industrial situation when machinery data is not yet available.
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That applies to just about every installation.
 
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