Spider boxes

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Isaiah

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Baton Rouge
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Electrical Inspector
Temp Construction power - they came off a 3ph 4W 60A branch circuit and ran app 250’ to a spider box. From there they ran to second box 100’ away from the first and then to a 3rd box at another 100’ from the second. Each box has 3-5 extension cords at 120Vac to intermittent loads such as grinders and drills. All receptacles at the spider boxes have GFCI protection but it seems there would be a large voltage drop and potential overload scenario having all loads tied to single source over 400’ away. However the 60A CB has not yet tripped. Should each box have its own branch circuit or is ok to dash chain 3 boxes together off a single branch CB?


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Are these the 3 phase spider boxes that use the blue pin and sleeve 60A connectors? Or are they 50 amp 1ph twistlock standard spider boxes?

It's fine to chain them together that's what theyre for. I doubt voltage drop even becomes an issue with the loads you describe.
 
Todd0x1 said:
Are these the 3 phase spider boxes that use the blue pin and sleeve 60A connectors? Or are they 50 amp 1ph twistlock standard spider boxes?

It's fine to chain them together that's what theyre for. I doubt voltage drop even becomes an issue with the loads you describe.
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Thanks Todd0x1. I figured it was ok. Basically it’s like a branch circuit off a panelboard that feeds multiple receptacles in a residence up to 13. Is there any limit as to how many receptacles on a 60A 3 phase branch circuit ??


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Isaiah said:
Thanks Todd0x1. I figured it was ok. Basically it’s like a branch circuit off a panelboard that feeds multiple receptacles in a residence up to 13. Is there any limit as to how many receptacles on a 60A 3 phase branch circuit ??


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The question here is are these the standard 50 amp boxes? if so, the 60 is to big to be compliant.
 
Isaiah said:
.....Is there any limit as to how many receptacles on a 60A 3 phase branch circuit ??


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If I understand correctly what Isaiah is asking a more accurate way to ask the question is - Is there any limit to the number of receptacles on a 20A branch circuit fed from a 60A source? And the answer is no.
 
ActionDave said:
If I understand correctly what Isaiah is asking a more accurate way to ask the question is - Is there any limit to the number of receptacles on a 20A branch circuit fed from a 60A source? And the answer is no.
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But it should be. Because if you limit the number of receptacles on a circuit, you limit a possible overload. I will save that for the next NEC code update.
 
mtnelect said:
But it should be. Because if you limit the number of receptacles on a circuit, you limit a possible overload. I will save that for the next NEC code update.
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No it shouldn't. That is a design issue and would violate 90.1. I can have two recepts on a circuit or 400, if I plug in four 1500W heaters I'm gonna overload the circuit.
 
It's not clear to me if each receptacles has proper OCP (unless the term "spider box" includes OCP). Is there OCP at each "spider" ??
 
augie47 said:
It's not clear to me if each receptacles has proper OCP (unless the term "spider box" includes OCP). Is there OCP at each "spider" ??
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Augie47. The spider box specification sheet does not indicate overcurrent protection is included within the box; but each receptacle has GFCI protection.


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Isaiah said:
Augie47. The spider box specification sheet does not indicate overcurrent protection is included within the box; but each receptacle has GFCI protection.


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You still didn't answer if these boxes are rated 60A or 50A...
 
Isaiah said:
Temp Construction power - they came off a 3ph 4W 60A branch circuit and ran app 250’ to a spider box. From there they ran to second box 100’ away from the first and then to a 3rd box at another 100’ from the second. Each box has 3-5 extension cords at 120Vac to intermittent loads such as grinders and drills. All receptacles at the spider boxes have GFCI protection but it seems there would be a large voltage drop and potential overload scenario having all loads tied to single source over 400’ away. However the 60A CB has not yet tripped. Should each box have its own branch circuit or is ok to dash chain 3 boxes together off a single branch CB?


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Click to expand...
We have daisy chained single phase 50 amp spider boxes but never more then 100' total. I would perform voltage readings in both 120 volt lines at furthest box when they are loaded the most. As long as the 60 amp circuit breaker never trips appears you are not overloading the circuit. Believe the NEC states that total voltage drop should not exceed 5% so you want to have 114 volts from ends of furthest extension cord.
 
The receptacles would b
Isaiah said:
Augie47. The spider box specification sheet does not indicate overcurrent protection is included within the box; but each receptacle has GFCI protection.


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The receptacles would be required to have OCP in accordance with 210.21. If they are 15 or 20 amp receptacles and the only protection O(other than being GFCI) is the 60 amp breaker it is definitely a violation.
 
augie47 said:
The receptacles would b

The receptacles would be required to have OCP in accordance with 210.21. If they are 15 or 20 amp receptacles and the only protection O(other than being GFCI) is the 60 amp breaker it is definitely a violation.
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Augie upon further review, the boxes do in fact have internal circuit breakers for protection for each of outlets …many thanks for your commentary.


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garbo said:
We have daisy chained single phase 50 amp spider boxes but never more then 100' total. I would perform voltage readings in both 120 volt lines at furthest box when they are loaded the most. As long as the 60 amp circuit breaker never trips appears you are not overloading the circuit. Believe the NEC states that total voltage drop should not exceed 5% so you want to have 114 volts from ends of furthest extension cord.
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I agree you should do a voltage reading. I would add, wait until the sun is on the cords and they have heated up.
 
Strathead said:
You still didn't answer if these boxes are rated 60A or 50A...
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They are rated 50A but there are three daisy chained together - 150A total. these are non-continuous loads and each box has internal branch CBs for protection of each outlet


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