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Alwayslearningelec

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When sizing motor conductors do you need to do 125% of FLA if its not a continuous load?
The motor FLA is 150A. It's temporary hoist for construction.
I have a fused switch feeding in a switchboard feeding it. Can fuse be 150a?
Do I need a separate disconnect switch near the hoist? I read that short circuit ground fault device must be 150-300% of motor FLA?
Thank you.
 
This is hoist electrical data. I'd say a hoist is def not continuous duty. I'm concerned with ordering the correct size fuse and stand alone disconnect of needed.
 

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Have you checked a manufacturer's website? Both Mersen and Bussman have sizing tables.

The fuses need go someplace. Is there aalready a switch?
 
jim dungar said:
Have you checked a manufacturer's website? Both Mersen and Bussman have sizing tables.

The fuses need go someplace. Is there aalready a switch?
Click to expand...
Yes there's a fused switch in a switchboard we are going to use. It's spare. I want to make sure I size the fuses correctly for the 150A FLA load.
 
From what you posted it appears you are feeding a control panel (possibly with drives) rather than a "30HP motor".
The manufacturer should provide you with data for selecting the SCGF protection.
IMO, Art 610.32 would apply for your disconnect.
.
 
horsegoer said:
When sizing motor conductors do you need to do 125% of FLA if its not a continuous load?
The motor FLA is 150A. It's temporary hoist for construction.
I have a fused switch feeding in a switchboard feeding it. Can fuse be 150a?
Do I need a separate disconnect switch near the hoist? I read that short circuit ground fault device must be 150-300% of motor FLA?
Thank you.
Click to expand...


Is this what you are looking for. 430.22(E)

1662665134894.png
 
augie47 said:
From what you posted it appears you are feeding a control panel (possibly with drives) rather than a "30HP motor".
The manufacturer should provide you with data for selecting the SCGF protection.
IMO, Art 610.32 would apply for your disconnect.
.
Click to expand...
Because it says "frequency drive"? It's a motor for a construction hoist.
Would I have a 2nd means of disconnect?
1. Obviously I have the fused switch in the switchboard.
2. Would I need a 2nd "loose" disconnect switch?
 
horsegoer said:
Because it says "frequency drive"? It's a motor for a construction hoist.
Would I have a 2nd means of disconnect?
1. Obviously I have the fused switch in the switchboard.
2. Would I need a 2nd "loose" disconnect switch?
Click to expand...
If it's a hoist, as I read Art 610,. you need a disconnect "in sight from"... might ask you design engineer,.
 
augie47 said:
If it's a hoist, as I read Art 610,. you need a disconnect "in sight from"... might ask you design engineer,.
Click to expand...
Thanks. I can't get a hold of the hoist company. I also can't if I need to use the FLA or the frequency drive info in the data sheet?
Also don't know about using 430.52 for sizing OCPD? Wow is it NOT straightforward.
 
I think I need to use table 610.14

I don't understand the OCPD section. It seems to reference TWO OCPD's. Fuse or inverse time breakers then mentions feeder OCPD. If you have a circuit from switchboard to hoist motor isn't it either a branch circuit or a feeder? Either or, not both?

Overcurrent protection​

You have to size the branch circuit OCPDs before you can size the feeder OCPDs; you will see why, momentarily.

Part V presents the requirements for feeder conductors and OCPDs [610.41], branch-circuit OCPDs [610.42], and motor overload protective devices (ODPs) [610.43]. It’s helpful that this sequence follows a logical workflow.

Protect each branch circuit with fuses or inverse time breakers; use the rating indicated by Table 430.52. Where two or more motors operate a single motion, add up their total nameplate ratings and use that sum as the rating [610.42(A)].

Now, size your feeder OCPD [610.41(A)]. To do this:

1. Sum up all loads other than the largest rating or setting branch OCPD.

2. Add in the largest rating or setting branch OCPD.

3. Apply the demand factors from Table 610.14(E).

The NEC isn’t clear whether step 2 or step 3 comes first. To divine the intent, we look at Art. 430 requirements and use the same logic.
 
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horsegoer said:
That not is dumb. It basically saying it should be considered continuous unless it's non continuous??
Click to expand...
The way I read it is that it is considered continuous unless no operational condition it can ever experience will make it continuous.
 
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