Start-Up, Kilo- ohm, A50-7274ef | Carrier 50BV020-064 manual

Table 11 — Thermistor Resistance vs Temperature

Values for Supply-Air Temperature Sensor

(10 Kilo- ohm)

TEMP	TEMP	RESISTANCE
(C)	(F)	(Ohms)
–40	–40	335,651
–35	–31	242,195
–30	–22	176,683
–25	–13	130,243
–20	–4	96,974
–15	5	72,895
–10	14	55,298
–5	23	42,315
0	32	32,651
5	41	25,395
10	50	19,903
15	59	15,714
20	68	12,494
25	77	10,000
30	86	8,056
35	95	6,530
40	104	5,325
45	113	4,367
50	122	3,601
55	131	2,985
60	140	2,487
65	149	2,082
70	158	1,752

SMOKE DETECTOR/FIRE ALARM SHUTDOWN (FSD) — To allow a smoke detector to shut the 50BV down, remove the jumper from FSD to C and wire these terminals to a set of normally closed contacts on the smoke detector.

ALARM (ALARM) AND WARNING (WARN) OUT- PUTS — Two dry contacts output a discrete signal when the alarm and warning lights on the display are lit. To pick up the alarm output signal, wire between the ALARM and ALM-CM terminals. To pick up the warning output signal, wire between the WARN and ALM-CM terminals.

0.50

2.25

O0.187

65º

a50-7274ef

8.00

1.00

0.25

0.22

0.81 1.25

O0.187 (2 HOLES)

REMOTE OCCUPANCY (ROCC) — The 50BV unit may be commanded by another control system or a twist timer to become occupied and run when a set of dry contacts close. In order for this to occur, wire the contacts to ROCC and C and set the Local/Off/Remote switch to REMOTE.

RETURN AIR TEMPERATURE SENSOR (RAS) — The return/mixed air temperature sensor is a 5 kiloohm temperature sensor used as the space control point. For every degree that the RAS is below the set point, the supply air set point will be reset by the configured value in the custom configured RESET RATIO. Refer to Table 12 and Fig. 31.

Table 12 — Thermistor Resistance vs Temperature

Values for Return-Air Temperature

Sensor (5 kiloohm)

TEMP	TEMP	RESISTANCE
(C)	(F)	(Ohms)
–40	–40	167,835
–35	–31	121,098
–30	–22	88,340
–25	–13	65,121
–20	–4	48,487
–15	5	36,447
–10	14	27,648
–5	23	21,157
0	32	16,325
5	41	12,697
10	50	9,952
15	59	7,857
20	68	6,247
25	77	5,000
30	86	4,028
35	95	3,265
40	104	2,662
45	113	2,183
50	122	1,801
55	131	1,493
60	140	1,244
65	149	1,041
70	158	876
75	167	740
80	176	628

NOTE: All dimensions are in inches.

Fig. 31 — Return Air Temperature Sensor

(P/N HH79NZ079)

Wire the sensor to PCB1 connector J3, terminals 15 and 16. Change custom configuration as instructed in Configure the Custom Programming Selections section. Changing this con- figuration to YES changes the EWT input to be used as return air temperature input.

START-UP

General — Complete the Start-Up Checklist on page CL-1 before attempting system start-up.

CRANKCASE HEATERS — The 50BVT,U,V,W,X034-064 units include crankcase heaters. Crankcase heaters are ener- gized as long as there is power to the unit and the compressor is not operating.

Wait 24 hours before starting the compressors to permit warming by the crankcase heaters.

AFTER 24 hours, continue with the procedures below.

CONFIRM THE INPUT POWER PHASE SEQUENCE — The input power phase rotation sequence must be L1-L2-L3 = ABC (or forward or clockwise) as indicated with a phase rotation meter. Incorrect input phase rotation will cause the com- pressors to rotate in reverse, which results in no cooling capacity.

IMPORTANT: On VAV units, fan rotation direction can NOT be used for the phase sequence check; fan rotation for VAV units with a variable speed drive is independent of the unit input wiring sequence.

If the compressor is rotating in the wrong direction, it may: emit increased noise; shut down due to internal overload protection; have only a small decrease in suction pressure when it starts; or have only a small increase in discharge pressure