Carrier WeatherExpert 48N2 - Page 57

57
75 Ton Standard Efficiency
Circuit B
Contactor OFM(s)
Coils
Software Board Conrolled Controlled
A CONDFAN1 MBB Rly 6 OFC1 OFM1
Comp A1 or A2 ON
B CONDFAN2 MBB Rly 5 OFC2 OFM6 Comp B1, B2, or B3 ON
Common CONDFAN3 RCB Rly 1 OFC3 OFM3,4 Circuit A or B SCT or OAT
# of Fans ON
Fans ON # of Fans ON Fans ON
Stage 1 OFC1 1 OFM1 Stage 1 OFC2 1 OFM6 Stage 2 OFC1,3 2 OFM1,3,4 Stage 2 OFC2,3 2 OFM3,4,6
Low Ambient Prestart 1 (OAT ≤ 50 F) = Stage 1 Low Ambient Prestart 2 (50 F < OAT < 70 F) = Stage 2
Circuit A
High Ambient Prestart (OAT ≥ 70 F) = Stage 2
Coils
High Saturated Condensing Temp (SCT>130) = Stage 2
Stage down allowed if SCT<SCT_MIN Stage up allowed if SCT_MAX<SCT<130 Current stage if SCT_MIN<SCT<SCT_MAX
75 Ton High Efficiency
Circuit B
Contactor OFM(s)
Coils
Software Board Conrolled Controlled
A CONDFAN1 MBB Rly 6 OFC1 OFM2 B CONDFAN2 MBB Rly 5 OFC2 OFM5
Common CONDFAN3 RCB Rly 1 OFC3 OFM1,6 Common CONDFAN4 RCB Rly 2 OFC4 OFM3,4
# of Fans ON
Fans ON # of Fans ON Fans ON
Stage 1 OFC1 1 OFM2 Stage 1 OFC2 1 OFM5 Stage 2 OFC1,3 2 OFM1,2,6 Stage 2 OFC2,3 2 OFM1,5,6 Stage 3 OFC1,3,4 3 OFM1,2,3,4,6 Stage 3 OFC2,3,4 3 OFM1,3,4,5,6
Circuit A
Low Ambient Prestart 1 (OAT ≤ 50 F) = Stage 1
Coils
Low Ambient Prestart 2 (50 F < OAT < 70 F) = Stage 2 High Ambient Prestart (OAT ≥ 70 F) = Stage 3 High Saturated Condensing Temp (SCT>130) = Stage 3
Stage down allowed if SCT<SCT_MIN Stage up allowed if SCT_MAX<SCT<130 Current stage if SCT_MIN<SCT<SCT_MAX
Allow Fan Staging if OAT < 70 F and:
Logic
Circuit
Controlling Output
Circuit
Controlling Output
Logic
Comp A1 or A2 ON
Comp B1, B2, or B3 ON
Circuit A or B SCT or OAT
Circuit A or B SCT or OAT
Circuit A
Circuit A Circuit B
Circuit B
Allow Fan Staging if OAT < 70 F and:
POWER BOX
3
MM
2
6
MM
5
A2
A1
B2
B1
B3
1
4
POWER BOX
3
MM
6
A2
A1
B2
B1
B3
MM
1
4
Fig. 10 — 75 Ton Unit Condenser Fan Staging Sequence
a48-8696
LEGEND
MM — Motormaster OAT — Outdoor Air Temperature OFC — Outdoor Fan Contactor OFM — Outdoor Fan Motor