Loading Ckts to 60%

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Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
When they say to only load fire alarm circuit to 60% how is that figured without knowing power supply or how much each device draws? Trying to determine how devices on a ckt. TY!
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
What kind of circuits? Are you referring to the tap connections of FA panels to a riser?
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
When they say to only load fire alarm circuit to 60% how is that figured without knowing power supply or how much each device draws? Trying to determine how devices on a ckt. TY!
Typically it is based on the capacity of the circuit. On a Siemens Firefinder XLS SLC loop, for example, you can have 252 addressable devices. If you limit the design to 60%, that would be only 151 devices allowed in your design. For notification appliance circuits, the limit would be based on current draw. Again, the Siemens ZIC-4A card has 4 notification appliance circuits on it with a max of 3 amps per circuit. Your design can't put more than 1.8 amps worth of notification appliances on any circuit.
 

farmantenna

Senior Member
Location
mass
you can't design a circuit without knowing what you are using, It's like anything else we do.

look up the amp draw of the devices and then your panel or power supply and go from there. I never knew the circuit load could not be more than 60 %. I thought it was 20 or 25% extra reserve capacity.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
you can't design a circuit without knowing what you are using, It's like anything else we do.

look up the amp draw of the devices and then your panel or power supply and go from there. I never knew the circuit load could not be more than 60 %. I thought it was 20 or 25% extra reserve capacity.
Please see post #4.
 
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