Carrier 38VMA Series Service Manual page 25

Table 9 - Outdoor unit heating capacity calculation
Outdoor Unit Capacity x 1000 BTU
72
96
120
144
QHo: Outdoor Unit Heating Capacity
QHo = QHi x D/∑D（Round number）
T2A correction factor E
T = 102⁰F (default)
QHr: Outdoor Unit Real Heating Capacity
QHr = QHo + E
For example：
Outdoor Unit 72 + 96，Heating Indoor Unit (12K x 6) + (18K x 6)，T1 = 63⁰F，TS = 70⁰F，T4 = 45⁰F，T2A (average) = 93⁰F
T1 – TS = 63 – 70 = -7，so B = 2
T4 = 45，so C = 100%
T2A (average) = 93⁰F，so E = 6
QHi = ∑(AxB) x C =（1.2 x 2 x 6 + 2.0 x 2 x 6）x 100% = 38.4，Round number：39
72 outdoor unit capacity：QHo = QHix D / ∑D = 39 x 8 /（8 + 10）= 17.3，Round number：18
96 outdoor unit capacity：QHo = QHix D / ∑D = 39 x 10 /（8 + 10）= 21.6，Round number：22
72 outdoor unit actual capacity：QHr = QHo + E =18 + 6 = 24，From the frequency table：70Hz
96 outdoor unit actual capacity：QHr = QHo + E = 22 + 6 = 28，From the frequency table：78Hz
NOTES:
TS: Indoor unit setting temperature
T1: Room temperature
T2A: Temperature of evaporator inlet
T2B： Temperature of evaporator outlet
T4: Ambient temperature
Outdoor Unit Capacity (HP) D
8
10
12
14
25