Maximum Distance Between Branch CB and Control Panel

[james.lightfoot]

Hello,

1st time posting. I am working on a dehumidification system with (5) control panels, (3) of which have large heater loads, (1) w/ a 7 VFD's, and (1) control panel. Between the 575kW of heaters and (5) 25 Hp motors, this unit (48'L x 14'W x 13'H)will have a 480VAC/1,200 Amp service; hence, I've laid out a power distribution scheme and had a switchboard quoted. The switchboard, 30KVA 480VAC Delta to 208Y/120VAC XFMR and 150 Amp lighting distribution panel are going to inside an electrical service closet at the end of the unit. Following are the panels.

Panel	Description	FLA	MCA*1	MOCPcalc	CBMOCP*10
1 (14)	Process Fans (4+1), React Fan & Wheel/Rotor	178.60	223.25	217.16	225
2 (15)	Reactivation Heaters	361.12	451.40	361.12	500
3 (16)	Pre-Heat	211.48	264.35	211.48	300
4 (17)	Post-Heat	121.28	151.60	121.28	175
5 (18)	Control Panel	15.00	18.75	15.00	20

Question: It's been a long time, but I recall a code that said a disconnect must be w/in 50' of the load (control panels in this instance). Is this correct or do I need another breaker, matching the noted trip ratings? Either way, would you point me to the code section so that I may note in my drawings please?

Thank you

 

[charlie b]

My book is not handy. But I believe Article 100 defines "within sight" along the lines of being visible (i.e., not blocked from view by some machine or other) and within 50 feet. Also, I believe that does apply to motors and their controllers, but not to heaters and not in general to control panels. Someone else will need to confirm or refute this.

 

[GoldDigger]

Also, if a secondary, closer, disconnect it required it does not have to be a breaker, although that may end up being the cheapest option.
And if it is a breaker, it may not have to be sized to protect the wiring or the load.

 

[TX+ MASTER#4544]

My book is not handy. But I believe Article 100 defines "within sight" along the lines of being visible (i.e., not blocked from view by some machine or other) and within 50 feet. Also, I believe that does apply to motors and their controllers, but not to heaters and not in general to control panels. Someone else will need to confirm or refute this.

2023 NEC
hello, charlie b

Article 100 Definitions
"In Sight From (Within Sight From) Equipment that is visible .........."
Equipment, key word here

110.29 In Sight From (Within Sight From, Within Sight)

Thanks for reading.
Comments accepted.
TX+MASTER#4544

 

[james.lightfoot]

Thank you all for the help. There has been a slight change to the design that I think will require that my "sub-panels" will need breakers.
The "electrical service closet" that was to be 50" deep at the end of the 50' long unit is now an "electrical service room", which will be walked into; hence, I don't think the breakers in the 480V distribution panel will no longer satisfy "In Sight From (Within Sight From) Equipment that is visible .........." Equipment, key word here
110.29 In Sight From (Within Sight From, Within Sight)

Did the change to the walk-in room just force the sub-panels to require CB's/disconnects?

Thanks again.

 

[TX+ MASTER#4544]

Thank you all for the help. There has been a slight change to the design that I think will require that my "sub-panels" will need breakers.
The "electrical service closet" that was to be 50" deep at the end of the 50' long unit is now an "electrical service room", which will be walked into; hence, I don't think the breakers in the 480V distribution panel will no longer satisfy "In Sight From (Within Sight From) Equipment that is visible .........." Equipment, key word here
110.29 In Sight From (Within Sight From, Within Sight)

Did the change to the walk-in room just force the sub-panels to require CB's/disconnects?

Thanks again.

2023 NEC
I don't know enough info about your sub panels but it's highly possible you will need a disconnect perhaps where it enters a building or imediately inside backed up to where it enters the building. The electrical room is for electrical equipment only. And you must have Code clearance for depth of working space as T. 110.26(A)(1) under 1,000 volts.
What do you mean.." which will be walked into; hence....'

TX+MASTER

 

[james.lightfoot]

Panel (all of which are attached to the outside of the unit in the numbered locations) & "room" callouts:
(13) "Electrical room" about 9" wide x 4' deep {the box to the right of the man is the 480V 1,200A switchboard}
(14) 225A VFD Panel
(15) 500A - 300KW Reactivation Heaters Panel
(16) 300A - 175KW Pre Heaters Panel
(17) 175A - 100KW Post Heater Panel
(18) 30A Controls Panel

Once someone steps inside to "room" to actuate the CB's, they are no longer "in line of sight" of any panels. This leads me to the conclusion that each panel now requires a means of deenergizing (disconnect or breaker). Am I leading myself down the wrong path?

 

[petersonra]

My take is it might be the thing serves an integrated machine of some sort thus requires only one disconnect.

 

[james.lightfoot]

In the past, on smaller units, I used distribution blocks in the sub-panels and placed stickers on each them noting that the panel was energized/disconnect located elesewhere.

 

[TX+ MASTER#4544]

Panel (all of which are attached to the outside of the unit in the numbered locations) & "room" callouts:
(13) "Electrical room" about 9" wide x 4' deep {the box to the right of the man is the 480V 1,200A switchboard}
(14) 225A VFD Panel
(15) 500A - 300KW Reactivation Heaters Panel
(16) 300A - 175KW Pre Heaters Panel
(17) 175A - 100KW Post Heater Panel
(18) 30A Controls Panel

Once someone steps inside to "room" to actuate the CB's, they are no longer "in line of sight" of any panels. This leads me to the conclusion that each panel now requires a means of deenergizing (disconnect or breaker). Am I leading myself down the wrong path?
View attachment 2572185

View attachment 2572183
View attachment 2572184

2023 NEC
When you

 

[TX+ MASTER#4544]

2023 NEC

When you got your permit what type of occupancy was listed?

james. lightfoot

I think your Code Article will be 670 and 670.4(B).........." which states that a machine will be an individual unit and shall be provided with disconnecting means" I think that means it will be provided at the factory and factory installed. And you will wire it according to the motor load.

TX+MASTER+4544

 

[jaggedben]

As Charlie alluded to, whether you need a disconnecting means within sight depends on the particular equipment supplied by that circuit. There is no general requirement. The answer is likely not the same for all five of your control panels. The motor control center with the VFDs requires one (Article 430), but the rest is pretty unclear from the info given. We would just be guessing what articles of the code govern the other four control panels. Maybe Article 425 or 427 for the heaters, or maybe 670, or maybe other articles.

 

[Jraef]

Don’t forget
430.102.B (2) exceptions:

(b) In industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure that only qualified persons service the equipment

This allows for using the source breaker or disconnect as the lock out point. I don’t know if there are similar exceptions allowed for other than motor loads. This is why MCC breakers are often the only LO/TO point in most industrial facilities.

 

[james.lightfoot]

Thanks to everyone for sharing their thoughts and especially experience. This has been of great help.