How
to Design Walk-in Cooler
Heat Load Calculations
Electrical Load Calculations
Mechanical Installation
Electrical Wiring
Note:
I had errors putting pictures, charts, tables and other images.
Pls. see Youtube Video here:
https://www.youtube.com/watch?v=74aUw3ZrFgE
I had errors putting pictures, charts, tables and other images.
Pls. see Youtube Video here:
https://www.youtube.com/watch?v=74aUw3ZrFgE
References:
-
ASHRAE
Tables
-
Carrier
charts
-
Paragon
Company
-
Sumit
Products Inc
-
Eaton/Cutler
Hammer
-
Penn/Johnson
Controls
-
Keeprite
Refrigeration
-
Encore
Wire Corporation
-
Coldmatic
Refrigeration
-
Thomson
Delmar Learning
-
NATIONAL
REFRIGERANTS INC
-
Tecumseh
Products Company
-
Industrial
Controls – Eriks company
-
Sporlan
– Parker Hannifin Corporation
-
Modern
Refrigeration and Air-conditioning – Althouse
-
…
and many more (if I forget you, I don’t mean it…sorry)
Walk-in
cooler Design, sizing and selection Process:
Ø
Heat
load calculation
Ø
How
to Size Evaporator
Ø
How
to size compressor and condensing unit
Ø
How
to select liquid receiver
Ø
How
to select TXV (thermostatic expansion valve)
Ø
How
to select filter/drier
Ø
How
to select sight glass
Ø
How
to select liquid line solenoid valve
Ø
How
to size refrigerant lines and piping
Ø
How
to calculate electrical load input
Ø
How
to size copper wire conductors
Ø
How
to wire refrigeration walk-in cooler
Ø
How
to wire evaporator
Ø
How
to wire condensing unit
Ø
How
to wire compressor, condenser fan motor
Ø
How
to wire defrost timer
Ø
How
to wire thermostat
Ø
How
to wire liquid line solenoid valve
Ø
How
to wire low pressure control/switch
Ø
How
to calculate and set low pressure switch settings
Ø
How
to prepare estimate bill of materials – electrical
Ø
How
to prepare estimate bill of materials – mechanical
Ø
How
to prepare order information and specification
Given:
PROJECT WALK-IN
COOLER:
Walk-in Cooler Room
Temp = 35 F
Outside Temp = 75
F (walk-in cooler is inside
air-conditioned building)
TD = 75 F – 35 F
TD = 40 F
Two Evaporator/Cooler
Fans = 1/8 HP (100 watt) each
Lights = 40 watt Lamp
working 8 hrs per day
Occupancy Load =
2 persons working 8 hrs per day
CABINET:
Cabinet
Dimensions: 26 GA White Stucco embossed finish int/exterior
Length = 6.5 ft
Width = 6.5 ft
Height = 8.25 ft
Cabinet Material
Characteristics:
Outside air film factor, Fo = 6.0
Inside air film factor, Fi = 1.65
Cabinet
insulation characteristics:
1/4 inch thick Polyurethane, K = 0.16 Btu in./sq
ft/hr/F
1 inch thick Particle Board, K = 0.94 Btu in./sq
ft/hr/F
1/2 inch thick Celotex, K = 0.31 Btu in./sq
ft/hr/F
PRODUCT:
Product Load
(meat) = 500 lbs (storage quantity -
newly added)
Product Stock
Shift = 250 lbs (regularly placed in
walk-in cooler)
Total Product
Load = 500 + 250
Total Product
Load = 750 lbs
Product (Meat,
brined) specific heat above freezing = 0.75
Btu/lb-F
Product entering
temp = 45 F
Walk-in Cooler Room
Temp = 35 F
TD product = 45 –
35
TD product = 10 F
Other Design
Factors/Considerations:
1. Ventilation/Infiltration Loss Factor = Normal
(Note: Heavy Usage is 4 or more door
openings per hour)
2. Loading Percentage = 100 % (design for Full Load scenario)
3. Walk-in Cooler has No Windows
4. Walk-in Cooler is not exposed to the sun
(no solar load)
5. No Defrost
6. Split (TD between refrigerant & air)
is 10 F
for wet produce & meat
7. Total System Running Time is 20 hrs
8. Add 20% Reserve Capacity
Cold Room Calculator (ALFA
LAVAL) results:
Transmission
losses = 264 watt
Ventilation
losses = 299 watt
Other heat
sources = 303 watt
Cooling
down/congel = 23 watt (Cool
down/Congel. Time = 24 hr)
SUBTOTAL = 889 watt
SUBTOTAL = 889
watt x 3.41 Btu/hr per watt
SUBTOTAL = 3031
Btu/hr
REQUIRED CAPACITY
= 3031 Btu/hr + 20 % Reserve Capacity
REQUIRED CAPACITY
= 3031 x 1.2
REQUIRED CAPACITY
= 3638 BTU/HR
SPECIFIC CAPACITY
= 108 Watt/cu. m
SPECIFIC CAPACITY = 10.4 Btu/hr per cu. ft
Approximate Conversion:
1 Btu/hr
per cu. ft ~ 10
Watt/cu. m
Solution:
TOTAL HEAT LOAD =
HEAT LEAKAGE (TRANSFER) LOAD +
HEAT USAGE (SERVICE) LOAD
HEAT LEAKAGE LOAD:
HEAT LEAKAGE LOAD
= HEAT walls +
HEAT ceiling +
HEAT floor +
HEAT windows
HEAT LEAKAGE LOAD
= U x A x TD
where:
U = overall (combined) heat
transfer coefficient of walls, ceiling,
floor, windows of
cabinet
A = total outside area of
cabinet/refrigerated space
TD = temperature difference
between outside and inside of
refrigerated space
U = 1/R
total
R = 1/C
R = t/K
R total = R1 + R2
+ R3 +
R4 + R5
R total = 1/C1 +
1/C2 + t3/K3
+ t4/K4 +
t5/K5
R total = 1/Fo + 1/Fi
+ t3/K3 +
t4/K4 + t5/K5
where:
R = thermal resistance of a material
R total =
total thermal resistance of cabinet (composite,
made of different materials)
R1, R2, R3, R4, R5 = individual thermal
resistances of
materials
C1, C2 =
individual thermal conductance of materials
(given thickness)
t3, t4, t5 =
individual thickness of materials (inch)
K3, K4, K5 =
individual thermal conductivity of materials
(per inch of
thickness)
Calculate U, the overall (combined) heat transfer
coefficient:
U = 1/R total
R total = 1/Fo + 1/Fi
+ t3/K3 +
t4/K4 + t5/K5
From the given Cabinet
Material Characteristics:
Outside air film factor, Fo = 6.0
Inside air film factor, Fi = 1.65
From the Cabinet
insulation characteristics:
t3 = 1/4 inch thick Polyurethane, K3 =
0.16 Btu in./sq ft/hr/F
t4 = 1 inch thick Particle Board, K4 =
0.94 Btu in./sq ft/hr/F
t5 = 1/2 inch thick Celotex, K5 = 0.31
Btu in./sq ft/hr/F
Substituting to
the formula,
R total =
1/6 +
1/1.65 + 0.25/0.16
+ 1/0.94 +
0.5/0.31
R total =
0.167 +
0.606 + 1.562
+ 1.064 +
1.613
R total =
5.012
U = 1/R total
U = 1/5.012
U = 0.2 Btu/sq ft/hr/F
HEAT walls:
HEAT walls = U x
A x TD
HEAT walls = 0.2
Btu/sq ft/hr/F x A(walls) x 40 F
Length = 6.5 ft
H=8.25
Width = 6.5 ft
Height = 8.25 ft
L=6.5
W=6.5
Area of Walls:
A(walls) = ( 2
x W x H ) + ( 2 x L x H )
A(walls) = ( 2
x 6.5 x 8.25 ) + ( 2 x 6.5 x 8.25 )
A(walls) =
214.5 sq ft
HEAT walls = 0.2 x 214.5 x
40
HEAT walls = 1716
Btu/day
HEAT ceiling and floor:
A(ceiling and
floor) = 2 x
L x W
A(ceiling and
floor) = 2 x
6.5 x 6.5
A(ceiling and
floor) = 84.5 sq ft
HEAT ceiling and
floor = 0.2 x
84.5 x 40
HEAT ceiling and
floor = 676 Btu/day
HEAT windows:
HEAT windows = 0
HEAT LEAKAGE LOAD:
HEAT LEAKAGE LOAD
= HEAT walls +
HEAT ceiling and floor +
HEAT windows
HEAT LEAKAGE
LOAD =
1716 + 676
+ 0
HEAT LEAKAGE
LOAD =
2392 Btu/day
HEAT USAGE LOAD:
HEAT USAGE LOAD =
HEAT product +
HEAT air change (infiltration) +
HEAT motors +
HEAT lights +
HEAT occupants +
HEAT defrost +
HEAT solar
HEAT product:
HEAT product = m x
Cp x TD
Substituting
values below,
Total Product Load = 750 lbs
Product (Meat, brined) specific heat
above freezing = 0.75 Btu/lb-F
TD product = 10 F
HEAT product
= 750
x 0.75 x 10
HEAT product
= 5625
Btu/day
HEAT air change (infiltration):
HEAT air change
(infiltration) = Inside Volume
x Air Change x Heat
Inside Volume:
Total thickness =
1 +
0.5 + 0.25
Total thickness
= 1.75
inches (0.146 ft)
Inside Length =
6.5 -
( 2 x 0.146 )
Inside Length =
6.21 ft
Inside Width =
6.5 -
( 2 x 0.146 )
Inside Width =
6.21 ft
Inside Height =
8.25 -
( 2 x 0.146 )
Inside Height =
7.96 ft
Inside Volume =
Inside Length x Inside Width
x Inside Height
Inside Volume = 6.21 x 6.21
x 7.96
Inside Volume = 307 cu ft
Using the Inside
Volume and ASHRAE tables,
corresponding to
Inside Volume of 307 cu ft, we find
Air Changes per
24 hr = 34.5
For Normal Ventilation/Infiltration Loss Factor
(Long Storage): 0.6
Air Changes per
24 hr = 34.5 x 0.6
Air Changes per
24 hr = 20.7
Properties of
Air:
The given Outside
Temperature is 75 F (walk-in cooler is
inside air-conditioned building), however, to be on the safe side, we will use:
Outside Air
at: 85 F 80% RH
Cold Storage Room
Temp: 35 F 60% RH
Heat to be
Removed from Air:
From ASHRAE
Table,
Heat to be
removed from air at 85 F 80% RH to 35
F 60% RH
Heat to be
Removed = 1.70 Btu/cu ft
HEAT air change
(infiltration) = 307
x 20.7 x 1.7
HEAT air change
(infiltration) = 10,803
Btu/day
HEAT motors :
HEAT motors = No.
of Motors x Btu/motor
x HP x 24
hr
No. of Motors
(Evaporator/Cooler Fans) = 2
HP of Motors
(each) = 1/8 HP
From the Table,
for 1/8 HP motor,
Btu/motor =
4600 Btu/HP-hr
HEAT motors =
2 x
4600 x 1/8
x 24
HEAT motors =
27,600 Btu/day
HEAT lights:
HEAT lights = No.
of Lamps x Watts/lamp
x Operation hr x 3.42
Btu/watt
No. of Lamps = 1
Lamp wattage = 40
watts
Lamp operation = 8
hrs per day
HEAT lights =
1 x
40 x 8
x 3.42
HEAT lights =
1094 Btu/day
HEAT occupants:
HEAT occupants = No. of Occupants x
Heat/occupant x Hours of Work
No. of Occupants
= 2 persons
Hours of Work
= 8 hrs per day
Heat/occupant:
From the Table,
we can interpolate the Heat/occupant:
Heat/occupant
= ( 840
+ 950 )/2
Heat/occupant =
895 Btu/hr
HEAT occupants = No. of Occupants x
Heat/occupant x Hours of Work
HEAT occupants
= 2
x 895 x 8
HEAT occupants
= 14,320
Btu/day
HEAT defrost:
HEAT defrost = 0
(Note:
Heat of Defrost is typically for Storage
Temperature of 32 F or lower,
in which case, 10% of Defrost Heat Input is
added to the Heat Load.)
HEAT solar:
HEAT solar = 0
(Note:
Illumination (solar) heat from the sun is
typically 15 watt/sq m of surface.)
HEAT USAGE LOAD:
HEAT USAGE LOAD =
HEAT product +
HEAT air change (infiltration) +
HEAT motors +
HEAT lights +
HEAT occupants +
HEAT defrost +
HEAT solar
HEAT USAGE LOAD =
5625 +
10,803 + 27,600
+ 1094 +
14,320 + 0
+ 0
HEAT USAGE LOAD =
59,442 Btu/day
TOTAL HEAT LOAD:
TOTAL HEAT LOAD =
HEAT LEAKAGE (TRANSFER) LOAD +
HEAT USAGE (SERVICE) LOAD
TOTAL HEAT LOAD = 2392
+ 59,442
TOTAL HEAT LOAD
= 61,834
Btu/day
Based on Total
System Running Time of 20 hrs:
TOTAL HEAT
LOAD/20 hr = 61,834/20
TOTAL HEAT
LOAD/20 hr = 3092
Btu/hr
Adding 20%
Reserve Capacity (R.C.):
TOTAL HEAT LOAD
with R.C. = 3092
x 1.2
TOTAL HEAT LOAD
with R.C. = 3710
Btu/hr
TONNAGE:
TONNAGE = 3710/12,000
TONNAGE = 0.31 TON
TONNAGE ~
1/3 TON
Split (TD between refrigerant & air):
In a walkin cooler
with mixed products, the product requiring the highest humidity will determine
the split.
Pork requires
85% to 90% RH and beans 90% to 95% RH.
To prevent
moisture loss and product damage, we will select 10 °F split to maintain high humidity.
SIZING THE EVAPORATOR:
Evaporator Size
at 1 °F TD = TOTAL HEAT LOAD with R.C. /Split
TOTAL HEAT LOAD
with R.C. = 3710
Btu/hr
Split = 10 F
Evaporator Size
at 1 °F TD = 3710/10
Evaporator Size
at 1 °F TD =
371 Btu/hr-F
From KeepRite Refrigeration tables, evaporators are available at 10 F
TD, therefore, we will multiply the Evaporator Size at 1 °F TD
by 10 °F.
Evaporator Size
@ 10 °F TD = Evaporator Size at 1 °F TD x 10 °F
Evaporator Size
@ 10 °F TD =
371 x 10
Evaporator Size
@ 10 °F TD =
3710 Btu/hr
Selecting Evaporator Capacity at Evaporator Temperature:
With Box
Temperature of 35 F and Split of 10 F,
Evaporator
Temperature (temperature of refrigerant entering evaporator) is calculated as,
Evaporator
Temperature = 35 – 10
Evaporator
Temperature = 25 F
Using the
calculated Evaporator Size @ 10 °F TD of 3710 Btu/hr
and the calculated Evaporator Temperature of 25 F, we select
KLP Model 104M with 4300 Btu/hr
Air Defrost model: A
Power supply is 115 Volts, 1-phase, 60
Hz: S1
Generation (2nd): B
Evaporator Order
Information: KLP104MA-S1B
SIZING THE CONDENSING UNIT AND COMPRESSOR:
Based on good design engineering practice, we
will select a condensing unit
that will match the capacity of the
evaporator model that was chosen on the
previous step.
Using the
nomenclature and the table
TECUMSEH
AIR-COOLED CONDENSING UNITS,
the closest match
we found is
CDU Model
AKA9440ZXAXC with a capacity of 4000 Btu/hr,
having compressor
model AKA9438ZXA with a capacity of 3800 Btu/hr,
1/2 HP using
Refrigerant R-404A.
Condensing Unit
Order Information: AKA9440ZXAXC
Evaporator Range and Condenser Ambient Range:
HOW TO CALCULATE
REFRIGERANT LIQUID RECEIVER CAPACITY:
Specification
from Tecumseh Cond. Unit:
Liquid Receiver Tank capacity = 33 cubic inch
Tank Design Pressure = 500 psig
Calculate mass
flowrate of R404A refrigerant:
Q = m x Cp x TD
m = Q/Cp x TD
Q = 3710 Btu/hr
Cp = Specific
Heat from NRI = 0.36 Btu/lb-F
TD = 40 F
m = 3710/(0.36 x
40)
m = 258 lb/hr
mass flowrate per
minute = 258/60 = 4.3 lb/min
The general rule
of thumb for R22 and R404a charge per ton is 2-4 lbs/ton.
Tonnage = 1/3 ton
Since we are
using short lines, we will use Charge per Ton of 2 lbs/ton,
Calculate Refrigerant Charge:
Charge = 2 lbs/ton x 1/3 ton
Charge =
0.67 lbs
Charge in ounce
(oz) = 0.67 lbs x
16 oz/lbs
Charge in oz
= 11 oz.
Calculate Volume
of R404A refrigerant charge:
D = m/v
v = m/D
D = Density from
NRI = 66.37 lb/cu ft
v = 0.67/66.37
v = 0.01 cu ft
Convert cubic
feet to cubic inches:
v = 0.01 x 1728
v = 17.28 cu in.
The liquid
receiver capacity from Tecumseh Condensing Unit is 33 cu in.
However, it can
only be filled up to 80% capacity according to code and for safety reasons.
Max effective
capacity = 33 x 0.80
Max effective
capacity = 26.4 cu. in.
Since the
calculated volume of refrigerant charge of
17.28 cu. in. is LESSER than the Maximum Effective Capacity
of 26.4 cu.in., the liquid receiver size
is appropriate.
FILTER DRIER SIZE SELECTION:
From Sporlan
Tables, we select the
1/4 inch
Catch-All C-032 Flared filter drier
SELECTION OF SIGHT GLASS:
Using recommended
Sporlan sight glass tables, we select
1/4 inch
SA-12FM Female X Male Flare sight
glass
SELECTING TEV/TXV – THERMOSTATIC EXPANSION VALVE:
Application: Medium Temperature Refrigeration
Design Evaporator
Temperature: 25 F
Design Ambient
Temperature: 90 F (from Tecumseh Condensing Unit)
Design TD
(condenser & ambient): 35 F
Design Condenser
Temperature = Design Ambient +
Design TD
Design Condenser
Temperature = 90
+ 35
Design Condenser
Temperature = 125 F
Design Condenser
Sub-cooling: 10 F
Design System
Capacity: 1/3
TON
Refrigerant
Liquid Temperature = Design Condenser
Temperature -
Design Condenser Sub-cooling
Refrigerant
Liquid Temperature = 125
- 10
Refrigerant
Liquid Temperature = 115 F
Calculate
Available Pressure Drop across TEV:
Design Condenser
Temperature: 125 F
Design Evaporator
Temperature: 25 F
From
R404A PT chart, determine:
Condensing Pressure @ 125 F: 333
psig
Evaporating Pressure @ 25 F:
63 psig
Pressure drop due
to friction, accessories, lines, and others:
50 psig
Available
Pressure Drop across TEV = 333 -
63 - 50
Available
Pressure Drop across TEV = 220 psig
Using the table
with interpolation, we find the correction factor (CF)
CF Liquid
Temperature @ 115 = ( 0.89 + 0.77 )/2
CF Liquid
Temperature @ 115 = 0.83
Using the
following information & using the table to find the closest match:
Design Evaporator Temperature: 25
F
Available Pressure Drop across TEV: 220
psig
CF Pressure Drop
= 1.34
VALVE TYPE
SELECTION:
The following
tables will help us choose a TEV that is most suitable for the Walk-in Cooler
project application:
Based on project
requirements, given data, and recommendations from the tables, we decide to
choose the following valve type and characteristics:
Valve Type: G
Valve Body: Forged Brass
(for superior strength and durability)
Connection
Type: SAE flare
Capacity
Adjustment: Externally adjustable valve
Thermostatic
Element: Replaceable
Strainer: Removable 100 mesh strainer at inlet
connection
Valve Type: G
Design System Capacity: 1/3
TON
Design Evaporator Temperature: 25 F
Using these
information, we can now determine from the R404A table,
TEV Rating =
0.59 TON
TEV Capacity =
TEV Rating x CF
Liquid Temperature x CF Pressure Drop
CF Liquid Temperature
= 0.83
CF Pressure Drop
= 1.34
TEV Capacity =
0.59 x
0.83 x 1.34
TEV Capacity
= 0.66
TONS
Inlet connection,
Outlet connection and External line connection sizes are determined from the
Type G valve body Specifications table for R404a
---
Sporlan
Nomenclature/Order: GSE-1/2-SC 1/4” x 1/2” x 1/4” SAE
flare x 5’
Body Type: G
Sporlan
Refrigerant R404A Code: S
External
equalizer: E
Nominal
Capacity: 1/2 TON
Thermostatic
Charge: SC
Inlet
Connection: 1/4 in.
Outlet
Connection: 1/2 in.
External
Equalizer Connection: 1/4 in. SAE flare
Capillary Tubing
Length: 5 ft
SELECTION OF LIQUID LINE SOLENOID VALVE:
From Sporlan
chart, we select the corresponding Liquid Line solenoid valve
model A3F1 – normally close, 1/4 inch,
MKC-1 coil 120 Volts, 50-60 Hz
Bill of Materials Estimate: Refrigerant Lines and Mechanical Components
ACR Copper line
1/2 in. x 25 ft for suction line and
drain line
ACR Copper line
1/4 in. x 15 ft for liquid line and equalizer line
Armaflex black
insulation size 1/2 in
Armaflex black
insulation size 1/4 in
1/2 in. vibration
isolator
1/2 in.
refrigerant line clamps x 10
1/4 in.
refrigerant line clamps x 10
1/2 in. 90 degree
elbow x 10
1/4 in. 90 degree
elbow x 6
Unistrut 1-5/8
inch width x 3 ft
length
2 in. width flat bar
x 3 ft length
1/2 in. x 8 ft
threaded rod
1/2 in. nuts x 4
1/2 in. washers x
4
1/2 in. flares x
8
1/4 in. flares x
8
ELECTRICAL LOAD CALCULATION - WALK-IN
COOLER:
Notes:
1. Electrical
wiring is to be sized in accordance with minimum circuit ampacity (MCA) rating.
2. Use 75 Celsius
wire or higher.
3. Overcurrent
protection for evaporator fan motors and defrost heaters must not exceed
maximum value shown on evaporator nameplate.
4. Size fuses
used must not exceed the Maximum Fuse Size ratings.
CALCULATE TOTAL
ELECTRICAL LOAD IN VOLT-AMPERES (VA) INPUT:
I. Lighting Load
Watts
Output: 40 watt lamp x 1
Voltage:
120 Volts (Input Voltage)
Amperage:
0.67 Amps (Amp draw or Input Current)
LED Light Bulb efficiency: 50%
Power Output = Volts x Amps x Efficiency
40 watts = 120 volts x Amps x Efficiency
Amps = 40/(120 x 0.5)
Amps = 0.67 Amps
Input Volt Ampere (VA) = 120 Volts x 0.67
Amps
Input Volt Ampere (VA) = 80 VA
II. Motor Load -
Evaporator Fan Motor
Electrical Data for Evaporator Model
KLP104MA-S1B:
HP:
1/15 HP
Watts:
100 watts PSC Motor x 1
Voltage: 115 Volts
MCA: 1.3 Amps
Max. Fuse: 15 Amps
Max. Overcurrent Protection (MOP): 15
Amps
Full Load Amps (FLA): 1 Amp
Motor Efficiency: 100 watts/115 watts =
87%
Input Volt Ampere (VA) = 115 Volts x 1 Amp
Input Volt Ampere (VA) = 115 VA
III. Motor Load -
Condensing Unit Compressor & Fan Motor
Electrical Data for Condensing Unit Model
AKA9440ZXAXC:
a. Compressor
HP: 1/2 HP ( 373 watts )
Rated Load Amperage (RLA): 9.2 Amps
Locked Rotor Amps (LRA): 58.8 Amps
Voltage: 115 Volts
Compressor Efficiency: 373
watts/1058 watts = 35%
Input Volt Ampere (VA) = Voltage x RLA
Input Volt Ampere (VA) =
115 Volts x 9.2 Amps
Input Volt Ampere (VA) =
1058 VA
b. Condenser Fan Motor
Output Watts: 35 watts
Voltage: 115 Volts
Amperes: 1.4 Amps
Motor efficiency: 35/161 = 22%
Input Volt Ampere (VA) = 115 x 1.4
Input Volt Ampere (VA) = 161 VA
c. Condensing Unit
Voltage: 115 Volts
MCA: 12.9 Amps
Max Fuse Size: 20 Amps
Heating Air Conditioning Refrigeration (HACR)
Breaker: 20 A
IV. Motor Load -
Defrost Timer Motor
From Paragon 9145 Defrost Timer
specifications,
Voltage: 120 Volts
Power Consumption: 6 VA
Input Amps: 0.05 Amps
Input Volt Ampere (VA) = 6 VA
V. Controls Load
- Thermostat
From PENN/Johnson Controls A419 Thermostat
specifications,
Voltage: 120 Volts
Power Consumption: 1.8 VA
Input Amp: 0.015 A
Input Volt Ampere (VA) = 1.8 VA
VI. Controls Load
- Low Pressure Control
From Ranco Low Pressure Control model
O10-1483,
Input Voltage: 120 Volts
Input Current: 24 Amps
Input Volt Ampere (VA) = 120 X 24
Input Volt Ampere (VA) = 2880 VA
VII. Solenoid Valve Load - Liquid Line
Solenoid Valve
From Sporlan A3F1 MKC-1 Coil model,
Voltage: 120 Volts
Watts: 10
Watts
Magnetic Coil Efficiency: 70%
Power Output = Volts x Amps x Efficiency
10 watts = 120 volts x Amps x Efficiency
Amps = 10/(120 x 0.7)
Amps = 0.12 Amps
Input Volt Ampere (VA) = 120 Volts x 0.12
Amps
Input Volt Ampere (VA) = 14.4 VA
TOTAL INPUT VA:
80 VA - I. Lighting Load
115 VA - II. Motor Load - Evaporator Fan Motor
1058 VA - III.
Motor Load - Condensing Unit Compressor
161 VA Motor Load - Condensing Unit Condenser Fan
Motor
6
VA - IV. Motor Load - Defrost Timer Motor
1.8
VA - V. Controls Load - Thermostat
2880 VA - VI.
Controls Load - Low Pressure Control
14.4 VA - VII. Solenoid Valve Load - Liquid
Line Solenoid Valve
--------------------------
4316.2 VA TOTAL
ADDING 20%
RESERVE ELECTRICAL LOAD
4316.2 x 1.20 = 5179.4 VA
DIVIDE TOTAL INPUT VA BY LINE VOLTAGE
5179.4 VA/120 V = 43.16 A
FIND SERVICE AMP:
USE TABLE 310.15(B)(16) with Copper 75 C
50 Amp Service
(disconnect switch)
AWG 8 Service
Conductors (service wire)
Order
Information:
60-Amp Eaton
Cutler-Hammer
Lockable
Indoor/Outdoor Air Conditioner Disconnect
ALLOWABLE
AMPACITY: not less than 83% of the service rating
50 Amp x 0.83
= 41.5 A
COPPER CONDUCTOR WIRE
SIZES FOR WIRING:
Use Max Fuse Amp
recommended by Manufacturer
Low Pressure
Control 30 A : AWG 10
Condensing
Unit 20 A : AWG 12
Evaporator 15 A : AWG 14
Light Bulb 15 A : AWG 14
L.L. Solenoid
Valve 15 A : AWG 14
Defrost
Timer 15 A : AWG 14
Thermostat 15 A : AWG 14
TABLE
310.15(B)(16):
Estimate Bill of Material - Electrical: Condensing Unit, Fan Motor:
Defrost timer –
Paragon model 9145-00
Thermostat –
Johnson Controls model A419
Liquid line
solenoid valve – Sporlan model A3F1
Low pressure
control – Ranco model O10-1483
Disconnect Switch
60-Amp – Eaton Cutler-Hammer
Evaporator Drain
Line Heater
Junction box,
square x 2
AWG 8 Wire x 15
ft
AWG 10 Wire x 5
ft
AWG 12 Wire x 15
ft
AWG 14 Wire x 40
ft
1-1/2 in. x 15 ft
flexible conduit
1-1/2 in.
straight fittings for flexible conduit x 12
1-1/2 in. 90
degree fittings for flexible conduit x 8
1-1/2 in. flexible conduit clamps x 20
1/2 in. x 15 ft
BX cable
1/2 in.
pipe/tubing clamps for BX cable x 20
Wire connectors x
40
BX cable Anti-shorts
x 10
Electrical data -
Evaporator
Condenser fan
motor input 115 Volt, 1.4 Amp
Paragon 9145
Defrost Timer
Johnson Controls
A419 Thermostat
Evaporator Installation:
Ceiling mounted
evaporators are best located on the upper corner of the cabinet as far as
possible from the entrance door.
LOW PRESSURE CONTROL (LPC) CUT-IN, DIFFERENTIAL, CUT-OUT:
(note: Cut-in is High Event, Cut-out is Low
Event)
LPC CUT-IN Temperature = Evaporator
Temperature – 5 F
LPC CUT-IN Temperature = 25 – 5
LPC CUT-IN Temperature = 20 F
From PT chart for R404a,
Pressure @ 20 F = 57 psig
LPC CUT-IN Pressure = 57 psig
Differential (Diff.) = 10 psig
LPC CUT-OUT Pressure = LPC CUT-IN Pressure –
Differential
LPC CUT-OUT Pressure = 57 – 10
LPC CUT-OUT Pressure = 47 psig
From P/T Chart for R404a,
LPC CUT-OUT Temperature @ 47 psig = 12 F
[Note:
Adjust/Fine tune the differential.
If it short cycles (run time is too short),
adjust differential to 15 psig]
TYPICAL WALKIN REFRIGERATOR (R-22) TEMPERATURES/PRESSURE:
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Pls. see Youtube Video here:
Pls. see Youtube Video here:
