
46 VAV-PRC011M-EN
Single-Duct VAV Terminal Units
Minimum Circuit Ampacity (MCA) Equation
• MCA = heater amps x 1.25
Maximum Over Current Protection (MOP) Equation
• MOP = heater amps
• However since MOP is less than or equal to MCA, then choose next fuse greater than MCA.
• Units without electric reheat would use smallest fuse sizing.
Standard Fuse Sizes: 15, 20, 25, 30, 35, 40, 45, 50, and 60.
Example–For MOP of Single-Duct Unit
A model VCEF, electric reheat unit size 14 has 480/3 phase 15 kW electric reheat with 2 stages.
15 kW – 480/3 heater
15x1000/480x1.73=18.06
MCA = 18.06 x 1.25 = 22.58 amps. Since MOP is less than or equal to MCA, then MOP = 25.
Useful Formulas
kW = 1214 X L/s X ATD
ATD = kW / 1214 X L/s
kW
Cfm ATD×
3145
--------------------------------
=
3φamps
kW 1000×
PrimaryVoltage 3×
------------------------------------------------------------------
=
ATD
kW 3145×
Cfm
-------------------------------
=
1φamps
kW 1000×
PrimaryVoltage
--------------------------------------------------- -
=
Komentarze do niniejszej Instrukcji