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UH-PRC001-EN18
Selection
Procedure
Motor and Fan Speeds
Motor and fan speeds are selected to
provide efficient performance. The
solid-state speed control will provide an
infinite number of speeds between the
highest and the lowest cataloged fan
speeds. The speed control is not
calibrated in specific fan speeds. For use
on units with 115 volt/60 cycle/
1 phase, 1/8 hp and smaller standard
motors only.
Standard and Bypass Units
Standard models meet most
requirements and are most economical.
Bypass units meet conditions as
mentioned above, and are also used
where low final temperature is specified.
25 and 50 Cycle Unit Heat Capacities
Table SP-8 shows the Btu, cfm, and the
hp required on unit heaters when
operated on 25 or 50 cycle circuits.
The multipliers in Table SP-8 may be
applied to standard 60 cycle unit
capacities to determine the capacities of
the same unit when operating on
25 or 50 cycle current. These multipliers
may be used on units cataloged at
1050 to 1150 RPM.
For the smaller Trane Unit Heaters
cataloged at 1550 RPM, the capacity data
in the catalog may be applied to either
25 or 50 cycle service.
Table SP-7 – Factors For Determining Steam Capacity Of Model P Projection Unit Heaters At Various Pressures And Temperatures
Table Based on 2 PSIG and 60 F Entering Air
Steam Temperature of Entering Air (F)
Pressure PSIG -10 0 10 20 30 40 50 60 70 80 90 100
0 1.49 1.41 1.33 1.25 1.18 1.11 1.03 0.96 0.90 0.83 0.76 0.69
2 1.52 1.45 1.37 1.29 1.22 1.15 1.07 1.00 0.93 0.86 0.80 0.73
5 1.58 1. 50 1.42 1.34 1.27 1.20 1.12 1.05 0.98 0.91 0.85 0.78
10 1.64 1.57 1.49 1.41 1.34 1.27 1.19 1.12 1.05 0.98 0.91 0.85
Draw- 15 1.70 1.62 1.55 1.47 1.40 1.32 1.25 1.18 1.11 1.04 0.97 0.90
Through 20 1.75 1.67 1.60 1.52 1.45 1.37 1.30 1.23 1.16 1.09 1.02 0.96
Unit 30 1.83 1.75 1.68 1.61 1.53 1.46 1.39 1.32 1.25 1.18 1.11 1.04
40 1.90 1.82 1.75 1.68 1.61 1.53 1.46 1.39 1.32 1.25 1.18 1.11
50 1.96 1.87 1.81 1.74 1.67 1.59 1.52 1.45 1.38 1.31 1.24 1.17
60 2.02 1.94 1.87 1.79 1.72 1.64 1.57 1.50 1.43 1.36 1.29 1.22
70 2.07 1.99 1.92 1.84 1.76 1.69 1.62 1.55 1.47 1.40 1.33 1.27
75 2.10 2.02 1.94 1.86 1.79 1.71 1.64 1.57 1.49 1.42 1.36 1.29
Note:
To determine the Btu per hour capacity of a Model P projection unit heater at any steam pressure and entering air temperature, multiply rated capacity at 2 psig steam 60 F entering air (Table
SP-5) by factor from above table.
Model P Nomenclature
UHP A 0 4 2 P 4 C A A 1 T A R C A D B E
123 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Digits 1,2,3 – Product Type
Digit 4 – Development Sequence
Digits 5,6,7 – Unit Size
Digit 8 – Coil Type
Digit 9 – Fin Series
Additional Selection Data
Digit 10 – Design Sequence
Digit 11 – Tube Material
Digit 12 – Fin Material
Digit 13 – Voltage
Digit 14 – Motor Type
Table SP-8 – Factors for Determining Unit
Heater Capacities at 25 or 50 Cycles
Multiplier To Be Applied To
RPM 60-Cycle 1100 RPM Ratings
25 CY 50 CY BTU CFM HP
1425 1425 1.17 1.25 1.95
950 .87 .833 .572
710 710 .7 .623 .242
Table SP-9 – Properties of Steam
Gauge Pressure Temp. Latent
Lbs. F Heat
2 219 965
5 227 960
10 239 952
15 250 945
20 259 939
25 267 933
30 274 928
40 287 919
50 298 911
60 307 904
70 316 897
75 320 891
Digit 15 – Fan Guard
Digit 16 – Unit Coating
Digit 17 – Diffuser
Digit 18 – Manual Starter
Digit 19 – Speed Controller (115/60/1
standard motors)
Digit 20 – Thermostats
Digit 21 – Subbase