Thermo Products R-410A installation manual Section V System Operation

835961-UIM-D-0213
	RUN TIME		TEST
XL	90 30	TEST					RUNTIME 90 60 30	MIN. SEL
XL						Test
R
	RUN TIME
R
C
C						ALTERNATE
Y
Y						CONFIGURATION
O
O
W
W
W1/66
W1/66
R3
K2	K1			K3	COND.	FAN
REV	PRESSURE		DFST	M
VALVE	SWITCH		T’STAT	M
REV	PRESSURE	COMP RLY			DFST
OM						ALTERNATE

FIGURE 11: Time/Temp Control Module

will not energize any additional relays until the voltage level increases. If the voltage drops below approximately 16 VAC, the control will imme- diately de-energize the relay outputs and will not energize any relays until the voltage level increases.

TEST INPUT

The control includes a TEST input connector that can be used for vari- ous testing functions during installation and service. The TEST input connector is shown in Figures 11 & 12. The following table summarizes the behavior of the control when the two TEST pins are connected. More detailed descriptions of the various functions are included in other sections of this document.

TABLE 2: TEST Input Functionality

Duration of Connection (seconds)		Control Behavior
Time-Temp	Demand Defrost
Less than 2	Less than 2	No response
		Bypass ASCD. If Y is present
2-9	2-6	and pressure switch is closed,
		contactors will be energized.
		Clear lockout
		Initiate defrost cycle. (Demand
More than 9	More than 6	only: Energize X/L with active
		defrost curve flash code)
Connection	removed	Terminate defrost as normal
		Continue defrost cycle (Demand
Connection not removed		only: and X/L flash code) until

DEMAND DEFROST CURVE SELECTION JUMPER

X/L R C Y O W W1/66

PTEST

1

2

3

4

X/L

R

C

Y

O

W

W1/66

REV PRESSURE

COIL COIL G AMBG AMBIENT

HIGH	COND
VOLTAGE	FAN

TEST connection removed.

FAULT CODE DISPLAY

X/L Output

The X/L terminal of the heat pump control is typically connected to the X/L input of the room thermostat. The thermostat uses this signal to notify the homeowner of a problem with the heat pump using an LED or LCD display. When the control energizes the X/L terminal, the thermo- stat displays the flash code so the homeowner can see it.

TABLE 3: X/L Output Categories
Condition	X/L
Pressure Switch lockout - last mode of operation was heating	2 flashes
Pressure Switch lockout - last mode of operation was defrost	3 flashes
Incorrect Defrost Curve - jumper selection	On

When the control locks out the compressor because of a pressure switch lockout, it will energize the X/L output as shown in Table 3. The

VALVE SWITCH M

FIGURE 12: Demand Defrost Control Module

SECTION V: SYSTEM OPERATION

ANTI-SHORT CYCLE DELAY

The control includes a five-minute anti-short cycle delay (ASCD) timer to prevent the compressor from short cycling after a power or thermo- stat signal interruption. The ASCD timer is applied when the control is first powered from the indoor unit thermostat and immediately following the completion of a compressor run cycle. The compressor and the out- door fan will not operate during the five minutes that the timer is active.

The ASCD timer can be bypassed by connecting the TEST terminals for three seconds while the thermostat is calling for compressor opera- tion (Y input signal energized).

LOW VOLTAGE DETECTION

The control monitors the transformer secondary (24 VAC) voltage and provides low voltage protection for the heat pump and its components. In particular, the control prevents contactor chatter during low voltage conditions. If the voltage drops below approximately 19 VAC, the con- trol will continue to energize any relays that are already energized but

control has a three second delay between fault code flashes.

If the conditions above exist during cooling mode, the system could be in the loss of charge condition.

DEFROST OPERATION

Time/Temperature Defrost (13 Seer 2-5 Ton)

The defrost control is a time/temp. control which includes a field-select- able (tap located at board edge) time period between defrost cycle (30, 60, and 90 minutes). The jumper is factory set at 60 minutes. See Fig- ure 13.

The electronic timer and the defrost cycle will start only when the con- tactor is energized and the defrost thermostat is closed. The defrost thermostat is closed when the liquid temperature falls below approxi- mately 31° F.

The defrost mode is identical to the cooling mode except that the out- door fan motor stops and the first stage of heat is turned on through W1 / 66 to continue warming the conditioned space.

The defrost cycle will be terminated when the defrost thermostat is opened at 55° F or 10 minutes of compressor accumulated run time, whichever comes first.

10 Johnson Controls Unitary Products