Lennox SSB036H4S4 Installation Instructions Manual page 23

CHECKING AIR FLOW AT INDOOR COIL
Temp.
80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
of air
entering
78 23 23 23 22 22 21 21 20 19 18 17 16 15 14
indoor
76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
coil ºF
74 21 21 21 20 19 19 18 17 16 16 15 14 13 12
A 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
Wet-bulb ºF
57 58 59 60 61 62 63 64 65 66 67 68 69 70
T
Drop
C
19º
53º
air flow
DRY
BULB
All temperatures are
expressed in ºF
Figure 19. Checking Indoor Airflow over Evaporator Coil using Delta-T Chart
START: Determine how refrigerant is metered
WHEN TO CHARGE?
S
Warm weather best
S
Can charge in colder weather
CHARGE METHOD? Determine by:
S
Metering device type
S
Outdoor ambient temperature
WEIGH-IN
CHARGING METHOD FOR LONG LINE SETS
64ºF (17.7ºC) and Below
Adjust amount for variation in
line set length and liquid line
Amount specified
diameter using table below.
on nameplate
+
Liquid Line
Set Diameter
5/16"
3/8"
1/2"
DT
B
A
72º
B
air flow
64º
DRY
BULB
INDOOR
WET
BULB
COIL
REQUIREMENTS:
S
Sufficient heat load in structure
S
Indoor temperature between 70‐80ºF (21-26ºC)
S
Manifold gauge set connected to unit
S
Thermometers:
- to measure outdoor ambient temperature
- to measure liquid line temperature
- to measure suction line temperature
Figure 20. Determining Charge Method
Total charge
=
HFC-410A
[(Line set oz./ft. x total length) ­ (factory charge for line set)] = charge adjustment
(ounces per foot)
Example: Units are factory­charged for 15 feet (4.6 meters) of 3/8" line set.
0.40
Factory charge for 3/8" is 0.60 oz/ft x 15 = 9.0 ounces.
0.60
1.00
Figure 21. Using HFC-410A Weigh-In Method
1. Determine the desired DT—Measure entering air temperature
using dry bulb (A) and wet bulb (B). DT is the intersecting value of
A and B in the table (see triangle).
2. Find temperature drop across coil
entering and leaving air temperatures (A and C). Temperature Drop
Formula: (T ) = A minus C.
Drop
3. Determine if fan needs adjustment
and the desired DT (T
measured T
Drop
adjustment is needed. See examples: Assume DT = 15 and A
temp. = 72º, these C temperatures would necessitate stated ac­
tions:
DT =
T –
Cº
Drop
=
19 – 15
53º
=
14 – 15
58º
=
10 – 15
62º
—See indoor unit instructions to increase/de­
4. Adjust the fan speed
crease fan speed.
Changing air flow affects all temperatures; recheck temperatures to
confirm that the temperature drop and DT are within +3º.
WEIGH‐IN
NOTE - Insulate liquid line when it is routed through areas where the
surrounding ambient temperature could become higher than the
temperature of the liquid line or when pressure drop is equal to or
greater than 20 psig.
NOTE - The above nameplate is for illustration purposes only. Go to
actual nameplate on outdoor unit for charge information.
Charging Formula for Liquid Line Charge Adjustments
Page 23
—Measure the coil's dry bulb
—If the difference between the
–DT) is within +3º, no
Drop
ºF ACTION
4 Increase the airflow
-1 (within +3º range) no change
-5 Decrease the airflow
TXV
65ºF (18.3ºC)
64ºF (17.7ºC)
and Above
and Below
APPROACH OR
SUBCOOLING
SSB*H4 SERIES