Specs
9
SELECTION PROCEDURE
I. DETERMINE COOLING AND HEATING
REQUIREMENTS AT DESIGN CONDITIONS
Given:
Required Cooling Capacity (TC 28,000 Btuh...........
Sensible Heat Capacity (SHC) 20,500 Btuh............
Required Heating Capacity 28,550 Btuh...............
Outdoor Entering--Air Temperature 95F(35C)........
Outdoor--Air Winter Design Temperature 20F(--6.7C)..
Indoor--Air Winter Design Temperature ............70F
(21.1C)
Indoor Entering--Air Temperature . . . . . . . . . . . . . 80F (26.7C)
edb, 67F ewb (19.4C)
Indoor--Air Quantity ........................1000 CFM
ExternalStaticPressure ...................0.20IN.W.C.
ElectricalCharacteristics(V--Ph--Hz)..........230--1--60
edb — entering dry bulb
ewb — entering wet bulb
II. SELECT UNIT BASED ON REQUIRED COOLING
CAPACITY
Enter Cooling Capacities table at condenser entering temperature
of 95F(35C), indoor air entering at 1000 cfm and 67F (19.4C)
ewb (entering wet bulb). The 030 unit will provide a total cooling
capacity of 28,800 Btuh and a sensible heat capacity of 21,600
Btuh.
For indoor--air temperature other than 80F edb (entering dry
bulb), calculate sensible heat capacity correction, as required, using
the formula found in Note 3 following the cooling capacities
tables.
NOTE: Unit ratings are net capacities.
III. SELECT ELECTRIC HEAT
Enter the 030 Heating Capacities table at 1000 CFM. At 70F
(21.1C) return indoor air and 20F(--6.7C) air entering outdoor
coil, the integrated heating capacity is 16,740 Btuh. (Select
integrated heating capacity value since deductions for outdoor--coil
frost and defrosting have already been made. No correction is
required.)
The required heating capacity is 28,550 Btuh. Therefore, 11,810
Btuh (28,550 -- 16,740) additional electric heat is required.
Determine additional electric heat capacity in kW.
11,810 Btuh
3414 Btuh/kW
=
3.46 kW of heat required
Enter the Accessory Electric Heater Usage table on page 4 for
208/240v. single--phase, 030 unit. The 5--kW heater at 240v most
closely satisfies the heating required. To calculate kW at 230v,
multiply the heater kW by multiplication factor 0.92 found in the
Multiplication Factors table on page 4.
5 kW x 0.92 = 4.6 kW
4.6 x 3414 = 15,704 Btuh
To calculate kW at 208 v, see Multiplication Factors table on page
4.
Total unit heating capacity is 32,444 Btuh (16,740 +15,704).
IV. DETERMINE FAN SPEED AND POWER
REQUIREMENTS AT DESIGN CONDITIONS
Before entering the air delivery tables, calculate the total static
pressure required. From the given, the Accessory Electric Heat
Pressure Drop table, and the Filter Pressure Drop table, find:
External static pressure 0.20 IN. W.C.
Filter 0.09 IN. W.C.
Electric heat 0.04
IN. W.C.
Total static pressure 0.33 IN. W.C.
Enter the table for Dry Coil Air Delivery — Horizontal Discharge
at 1000 CFM and 230v high speed. The blower will deliver 1036
CFM @ 0.40 IN W.C. static pressure. This will adequately handle
job requirements.
PH4Z