FORM 145.05-EG2 (618)
16
JOHNSON CONTROLS
13.
Select appropriate fan for the unit to deliver design air flow at required static pres
-
sure. There may be more than one supply air fan option available for the unit being
selected.
14. Add 5% belt drive losses to the motor BHP calculated, and select next available sup-
ply fan motor.
15.
Supply fan motor heat gain in MBH, based on 93.5% motor efficiency, may be cal
-
culated by multiplying above BHP plus the belt drive losses by 2.72.
16. Minimum Circuit Ampacity (MCA) of the unit may be calculated, using electrical
data in
Table 27 and Table 28 on page 68
, as follows:
a. For units without electric heat:
MCA = 1.25 * (largest motor RLA or FLA) + (FLA or RLA of all the rest of the
motor) + two transformers FLA
b. For units with electric heat, MCA is the lower of the heating and cooling mode
MCA. Cooling mode MCA is as shown in step a above.
• Electric heat less than 50 kW
Heating mode MCA = 1.25 * (electric heat FLA + supply fan motor FLA)
+ two transformers FLA.
• For units with electric heat 50 kW or more, MCA is the lower of the heating
and cooling mode MCA
Heating mode MCA = 1.25 * supply fan motor FLA + electric heat FLA +
two transformers FLA.
17. Maximum Overcurrent Protection (MOP) for the unit is calculated as follows:
a. For units without electric heat:
• MOP = 2.25 * (largest motor RLA or FLA) + (FLA or RLA of all the rest
of the motor) + two transformers FLA.
b. For units with electric heat, MOP is the lower of the heating and cooling mode
MOP. Cooling mode MOP is as shown in step a above.
• Heating mode MOP = 2.25 * (electric heat FLA + supply fan motor FLA)
+ two transformers FLA.
c. MOP is equal to next lower fuse size available of the higher of the values cal-
culated above, unless:
• Value in step c is lower than MCA, in which case the MOP value is the next
size higher than the MCA.
18. The component weights are in
Table 30 on page 69 and Table 31 on page 70
.
Add weights of the components covered by the options selected. To obtain operat-
ing weight, add water weights corresponding to the option selected carrying water
weights.
Selection Procedure (Cont’d)
Summary of Contents for L-Series
Page 1: ...FORM 145 05 EG2 618 ENGINEERING GUIDE Water Cooled Self Contained Units L Series Vertical ...
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Page 35: ...FORM 145 05 EG2 618 JOHNSON CONTROLS 35 OVERVIEW OF SERVICE CLEARANCES LSWU025 040 MODELS ...
