Carrier 50VT-A Defrost Control, Quiet Shift, Interface Fan Board IFB, 50VT--A

50VT-- A

HIGH

STD DEHUM

LOW

COM

QC5

QC4

QC3

KZ

KL

QCR

DCR

R13

C8

R11

Q1

C

CDM/C

07

09

0L0

08

ALO

D2

QC1

Q3

AL2

24VAC/R

C9

C4

G1

RL

01

G2

3AMP

QIL

Z2

06

04

A7

R9

AB

A15

C0

F1

U1

Z1

C3

R4

RL4

D5

D3

C7

JWZ

P3

R2

JW5

R3

R5

R6

P2

JW3

QCB

P4

SDL

Y

R

W2 Y

C

W3 W3 W2 W2 C

JW4

SSTZ-8

P1

Y2

Y1 C

W3 W2

G

R

DH

Y

A09059

Fig. 16 - Interface Fan Board (IFB)

ACCUMULATOR COMPRESSOR

OUTDOOR COIL INDOOR COIL

TXV in Bypass

Position

LCS

HP S

			Metering
	LEGEND		Position
	HPS – High Pressure Switch
	LCS – Loss of Charge Switch
		Accurater®Metering De vice
		Arrow indicates direction of flow	C03012
		Fig. 17 - Typical Heat Pump Operation, Heating Mode
Step 3 — Defrost Control			If defrost thermostat is closed, speed-up pins (J1) must be shorted
Quiet Shift			by placing a flat head screw driver in between for 5 sec and
			releasing, to observe a complete defrost cycle. When the Quiet
Quiet Shift is a field-selectable defrost mode, which will eliminate
			Shift switch is selected, compressor will be turned off for two 30
occasional noise that could be heard at the start of defrost cycle and			sec intervals during this complete defrost cycle, as explained
restarting of heating cycle. It is selected by placing DIP switch 3			previously. When Quiet Shift switch is in factory default OFF
(on defrost board) in ON position.			position, a normal and complete defrost cycle will be observed.
When Quiet Shift switch is placed in ON position, and a defrost is			If defrost thermostat is in open position, and speedup pins are
initiated, the following sequence of operation will occur. Reversing			shorted (with a flat head screw driver) for 5 sec and released, a
valve will energize, outdoor fan will turn off, compressor will turn			short defrost cycle will be observed (actual length is dependent
off for 30 sec and then turn back on to complete defrost. At the			upon the selected Quiet Shift position). When Quiet Shift switch is
start of heating after conclusion of defrost reversing valve will			in ON position, the length of defrost is 1 minute (30 sec
de-energize, compressor will turn off for another 30 sec, and the			compressor off period followed by 30 sec of defrost with
outdoor fan will stay off for 40 sec, before starting in the Heating			compressor operation). On return to heating operation, compressor
mode.			will again turn off for an additional 30 sec and the outdoor fan for
Defrost			40 sec. When the Quiet Shift is in OFF position, only a brief 30
The defrost control is a time/temperature control which includes a			sec. cycle will be observed.
			NOTE: Unit will remain in defrost until defrost thermostat
field-selectable time period (DIP switch 1 and 2 on the board)
between defrost cycles of 30, 60, 90, or 120 minutes (factory set at			reopens at approximately 65_F (18_C) coil temperature at liquid
60 minutes). To initiate a forced defrost, two options are available			line or remainder of defrost cycle time.
depending on the status of the defrost thermostat.
			20