Standby generator ATS breakers feed camlock

hhsting

Senior Member
See attached sketch. I have 25kw, 240/120V single phase standby generator for cell site.
The 240V, 2 poles ATS has two breakers in it. One for cam lock 200A breaker and the other for the generator 125A breaker. The ATS feeds the downstream 200A panelboard.

When the ATS flips to generator it would be powering both the cam lock as well as 200A panelboard having demand load of 93A at present.

When the ATS flips to the utility the generator can still power the camlock.

The generator is not separately derived and normal utility power source is 240/120V single phase.

Following question:

1. Does the NEC 2014 say anything about cam locks anywhere?

2. Does the NEC 2014 say anything about cam lock ratings?

3. When ATS flips to generator, the 25kW full load amps is 104A. Panelboard demand amps is 93A. Is not the generator too small with comlock? Is their section in regards to how to size the standby generator?

4. When ATS flip to utility the generator FLA is 104A however downstream breaker provided is 200A is that ok?


 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
The camlock and generator breakers need to be mechanically interlocked. Since the panel, and I assume the transferswitch is rated at 200 amps, I see no issue there. There should be load shedding so the generator is not at max output. (With cell towers, there is usually redundant A/C’s that can be shed.)
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Those things are usually well engineered. Other than the interlok that hillbilly1 mentioned, I wouldn't give it a 2nd thought. Seems compliant.
 

hhsting

Senior Member
The camlock and generator breakers need to be mechanically interlocked. Since the panel, and I assume the transferswitch is rated at 200 amps, I see no issue there. There should be load shedding so the generator is not at max output. (With cell towers, there is usually redundant A/C’s that can be shed.)
What exactly is camlock? Are camlock like portable generator power production inlet? I dont follow camlock are they used to generate power or are they used to power an external load?

Also is it in code camlock breaker need to have interlock with generator breaker?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Google "camlock".... full story.....
off the top of my head 700.5 is likely the relevant Code Section.
 

hhsting

Senior Member
Google "camlock".... full story.....
off the top of my head 700.5 is likely the relevant Code Section.
Nothing in NEC 2014 about camlock inter lock? I didn’t see it for standby generator. Would NEC 2014 section 702.5 exception be for interlock camlock? No wait that says for normal power supply nothing about non normal power supply. Is it in NEC 2014?

Did google camlock seems like receptacles or connection for additional temporary power sources

Thanks
 
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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Since you are adopting the '17, use 702.12(C)
It's pretty much common sense that one wants to prevent back-feeds from any power sources.

Your concern is likely "beating a dead horse". I've seen a number of these set-ups and they all had mechanical interlocks. I doubt this is a unique install.
 

tom baker

First Chief Moderator
Staff member
camlocks a very common connection for generators and event power. Go to leviton and find product literature.
cam lock mfgs name like erickson. See what levitom calls them or what listed as, go from there.
 

hhsting

Senior Member
I am still confused. Some sites say camlock are used for power distribution entertainment, theater while other sites say camlock are used to connect portable generator.

What exactly is camlock purpose? Anyone know or care to share
 

hhsting

Senior Member
So in post #1 attachment lets say camlock is used for load bank testing then it would not be required to have interlock between generator breaker and camlock breaker? However if camlock is used to hookup portable generator then interlock would be required?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
So in post #1 attachment lets say camlock is used for load bank testing then it would not be required to have interlock between generator breaker and camlock breaker? However if camlock is used to hookup portable generator then interlock would be required?
i think you have got it exactly.
Hopefully the gender of the camlocks corresponds to the direction of power flow.
Only exception I can think of would be if temporary generator will be synced to the stationary one to provide more power.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
i think you have got it exactly.
Hopefully the gender of the camlocks corresponds to the direction of power flow.
Only exception I can think of would be if temporary generator will be synced to the stationary one to provide more power.
Or if the stationary fails, and they want an alternate option.
 
If a set of cams were installed for load-bank testing (and it's not that common, esp for a generator that small), they're be on the generator leg outside the panel, not on a separate breaker from the panel.

Case 1- generator supplies ATS
Case 2 - source connected to the cams supplies ATS
Case 3 - (v. rare) generator is being load-tested (which would usually be a temp connection on the non-bus side of the 125a panel breaker

Given all that, the pair of breakers in the panel should be mechanically interlocked (which might be removed for load testing).

Don't over-complicate things.
 
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