Nailor Industries, Inc. reserves the right to change any information concerning product or specification without notice or obligation.
Minimum Circuit Ampacity
MCA = 1.25 x (Load 1 + Load 2 + Load 3 + Load 4)
Maximum Overcurrent Protection
MOP = (2.25 x load 1) + load 2 + load 3 + load 4
If the calculated MOP does not equal the standard current rating of an overcurrent protective device (typically even multiples of 5),
then the marked MOP is the next lower standard rating.
Exceptions:
1. The marked MOP will be the next higher standard rating than the computed value, if the next lower standard rating is less than
125 percent of the current rating of an electric heater load when such heater is involved.
2. If the computed value for MOP is less than the MCA, then the marked MOP is increased to the largest MOP appropriate for the
MCA.
3. If the MCA does not correspond to a standard protective device rating, the next higher standard rating of the protective device
will be marked if this rating does not exceed 800 A.
For Nailor Fan Powered Terminal Units and Fan Powered Chilled Water Terminal Units,
Load 1
is the largest motor current,
Load 2
is the sum of all other motor currents, and
Load 3
is the heater current.
Load 4
is used for other loads greater than 1.0 ampere and
can be considered zero for most standard products.
For Nailor Variable Air Volume Units,
Load 1
and
Load 2
are considered zero.
Load 3
is the heater current
Load 4
is used for other loads greater than 1.0 ampere and can be considered zero for most standard
products.
(Motor currents are determined by product application test in accordance with UL 1995 and may not be the same as the motor
manufacture’s FLA marking.)
All formulae, definitions, and exceptions are cited from Underwriters Laboratories Inc. Standard for Safety for Heating and Cooling Equipment, UL
1995 Fourth Edition (Sec. 37.14, 37.15) CAN/CSA-C22.2 No. 236 Fourth Edition
Appendix A – MCA and MOP Calculations
OL
CLH
HLH
OL
CLH
HRH
OL
CRH
HLH
OL
CRH
HRH
CRH
OR
HRH
CLH
OR
HRH
CRH
OR
HLH
CLH
OR
HLH
AIRFLOW
LEFT HAND CONTROLS
AIRFLOW
RIGHT HAND CONTROLS
9/18 IOM-DOAS
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Model 33SZ • Orientations
