Lennox XC20-036-230-01 Installation And Service Procedure page 76

GAUGE SET
CONNECTIONS FOR TESTING AND CHARGING
A. CLOSE MANIFOLD GAUGE SET VALVES AND CONNECT THE CENTER HOSE TO A CYLINDER OF HFC-410A SET FOR LIQUID PHASE CHARGING.
B. CONNECT THE MANIFOLD GAUGE SET'S LOW PRESSURE SIDE TO THE SUCTION LINE SERVICE PORT.
C. CONNECT THE MANIFOLD GAUGE SET'S HIGH PRESSURE SIDE TO THE LIQUID LINE SERVICE PORT.
D. POSITION TEMPERATURE SENSOR ON LIQUID LINE NEAR LIQUID LINE SERVICE PORT.
AIRFLOW
DRY
BULB
C
T
DROP
53º
19º
AIR
FLOW
ALL TEMPERATURES ARE
EXPRESSED IN ºF
ASSUME DT = 15 AND A TEMP. = 72º, BELOW C TEMPERATURES REQUIRE ACTION:
DT
Cº
T –
DROP
53º
19 – 15
58º
14 – 15
62º
10 – 15
Figure 55. Checking Indoor Airflow over Evaporator Coil using Delta-T Chart
XC20
CHARGE IN
LIQUID PHASE
D
TEMPERATURE
SENSOR
Figure 54. Gauge Set Connections
TEMPERATURE OF AIR
INDOOR COIL
ENTERING INDOOR COIL ºF
A
AIR
FLOW
INDOOR
COIL
=
ºF ACTION
=
4 INCREASE THE AIRFLOW
=
-1 (WITHIN +3º RANGE) NO CHANGE
=
-5 DECREASE THE AIRFLOW
MANIFOLD GAUGE SET
LOW
REFRIGERANT TANK
A
DIGITAL SCALE
C
TO LIQUID
LINE SERVICE
PORT
WET-BULB ºF
A
1. DETERMINE THE DESIRED DT — MEASURE ENTERING AIR
72º
TEMPERATURE USING DRY BULB (A) AND WET BULB (B).
DT IS THE INTERSECTING VALUE OF A AND B IN THE
TABLE (SEE TRIANGLE).
B
2. FIND TEMPERATURE DROP ACROSS COIL — MEASURE
64º
THE DRY BULB AIR TEMPERATURE ENTERING AND LEAV­
ING THE COIL (A AND C). TEMPERATURE DROP FORMULA:
(T
DRY BULB
3. DETERMINE IF FAN NEEDS ADJUSTMENT — IF THE DIF­
FERENCE BETWEEN THE MEASURED T
WET
SIRED DT (T
BULB
NEEDED. SEE EXAMPLE AT LEFT:
4. ADJUST THE FAN SPEED — SEE INDOOR UNIT INSTRUC­
TIONS TO INCREASE/DECREASE FAN SPEED.
NOTE - CHANGING AIR FLOW AFFECTS ALL TEMPERA­
TURES; RECHECK TEMPERATURES TO CONFIRM THAT THE
TEMPERATURE DROP AND DT ARE WITHIN +3º.
76
HIGH
B
SUCTION LINE
TEMPERATURE SENSOR
(LIQUID LINE)
DT
80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
78 23 23 23 22 22 21 21 20 19 18 17 16 15 14
76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
74 21 21 21 20 19 19 18 17 16 16 15 14 13 12
72 20 20 19 18 17 17 16 15 15 14 13 12 11 10
70 19 19 18 18 17 17 16 15 15 14 13 12 11 10
57 58 59 60 61 62 63 64 65 66 67 68 69 70
) = A MINUS C.
DROP
–DT) IS WITHIN +3º, NO ADJUSTMENT IS
DROP
OUTDOOR UNIT
B
AND THE DE­
DROP