CORRECTION FACTORS | 43
Correction Factors
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THREE-PHASE
Entering DB (ºF)
19.4 23.0 26.6 32.0 37.4 41.0 44.6
Derate factor
0.98 0.95 0.93 0.86 0.93 0.96 1.0
Table 7: Outdoor Unit Frost Accumulation Factor (Heating)
1
.
Defrost Correction Factor for Heating Operation
Capacity tables do not take into consideration capacity reduction
when frost has accumulated on the condenser coil, nor during
defrost operation. Integrated heating capacity values can be
obtained as follows:
Formula: A = B x C
Where: A = Integrated heating capacity
B = Heating capacity value given in table of capacity
characteristics
C = Integrated correction factor for frost accumulation
There will be temporary reduction in capacity when snow piles up on the outside surface of the outdoor unit heat exchanger. The level of capacity
reduction depends on a number of factors, for example, outdoor temperature (°F DB), relative humidity (RH), and the amount of frost present.
1
At 85% outdoor air relative humidity.
The correction factors shown below are calculated in the LATS Multi V software program.
CORRECTION FACTORS
Elevation Correction Factors
For each outdoor unit, calculate the equivalent length of the liquid line from the outdoor unit to the farthest indoor unit. Also, determine the
elevation difference of farthest indoor unit above or below the outdoor unit. Find corresponding cooling capacity correction factor in the table
below. Multiply the cooling correction factor by standard cooling capacity. The resultant is the NET cooling capacity.
The correction factors shown below are calculated in the LATS Multi V software program.
Table 8: Cooling Correction Factors.
* ELF = Equivalent Pipe Length—Sum of the actual pipe length plus allocations for pressure drop through elbows, valves, and other fittings in equivalent length.
Elevation Differences (ft.)
Equivalent Length (ELF)
1
25
33
66
98
131
164
197
230
263
295
328
HU—Indoor units above Outdoor Unit (ft.)
0
1.00
0.99
0.97
0.95
0.93
0.91
0.88
0.87
0.85
0.83
0.83
0.82
25
1.00
0.99
0.97
0.95
0.93
0.91
0.88
0.87
0.85
0.83
0.83
0.82
33
-
0.99
0.97
0.95
0.93
0.91
0.88
0.86
0.85
0.83
0.82
0.82
66
-
-
0.96
095
0.93
0.90
0.88
0.86
0.85
0.83
0.82
0.82
98
-
-
-
0.94
0.92
0.90
0.88
0.86
0.84
0.83
0.82
0.82
131
-
-
-
-
0.92
0.90
0.88
0.86
0.84
0.83
0.82
0.82
164
-
-
-
-
-
0.90
0.88
0.86
0.84
0.83
0.82
0.82
HL—Outdoor Unit Above Indoor Units (ft.)
0
1.00
0.99
0.97
0.95
0.93
0.91
0.90
0.87
0.88
0.84
0.86
0.84
25
1.00
0.99
0.97
0.95
0.93
0.91
0.90
0.87
0.88
0.84
0.86
0.84
33
-
0.99
0.98
0.95
0.93
0.91
0.90
0.88
0.88
0.84
0.86
0.84
66
-
-
0.98
0.95
0.93
0.91
0.90
0.88
0.88
0.84
0.86
0.84
98
-
-
-
0.96
0.93
0.91
0.90
0.88
0.89
0.84
0.86
0.84
131
-
-
-
-
0.93
0.91
0.90
0.88
0.89
0.84
0.86
0.84
