Bohn SWN0075M2, R-507, R404A, R-22 Installation Manual
Refrigeration
Systems
H-IM-64L September 2007 Part No. 25001201
Replaces H-IM-64L (11/05)
Installation and
Operation Manual
H-IM-64L-0907 | Version 002
Table of Contents
General Safety Information...............................................................................2
Inspection ...............................................................................................................2
Warranty Statement ............................................................................................2
Unit Cooler Placement .......................................................................................3
Unit Cooler Mounting .........................................................................................4
Defrost Thermostat ..............................................................................................5
Expansion Valves and Nozzles .....................................................................5-8
Condensate Drain Lines .....................................................................................9
Air Cooled Condensing Unit and Condenser Space and Location
Requirements ..........................................................................................10
Remote and Water Cooled Condensing Units Requirements ........... 11
Condensing Unit Rigging and Mounting ................................................. 12
Condensing Unit Accessories ................................................................13-17
Suction Filters, Driers, Sight Glasses ........................................................... 13
Demand Cooling ...............................................................................................14
Head Pressure Control .....................................................................................15
Refrigerant Oils ...................................................................................................16
Phase Loss Monitor ...........................................................................................17
Recommended Refrigerant Piping Practices ..........................................17
Refrigeration Pipe Supports ......................................................................... 17
Suction Lines ....................................................................................................... 18
Suction Line Risers ............................................................................................ 18
Liquid Lines .........................................................................................................18
Hot Gas Defrost Systems ..........................................................................19-20
Unit Cooler Piping ............................................................................................. 21
Line Sizing Charts ........................................................................................22-29
Weight of Refrigerants in Copper Lines During Operation ................30
City & Tower Water Connections ..................................................................31
Evacuation and Leak Detection ...................................................................31
Refrigerant Charging Instructions ...............................................................32
Field Wiring ..........................................................................................................32
Check Out and Start Up ..................................................................................32
Operational Check Out ....................................................................................33
System Balancing - Compressor Superheat .............................................33
Evaporator Superheat ......................................................................................34
General Sequence of Operation ..................................................................34
Electric Defrost Troubleshooting ................................................................. 35
Unit Cooler Troubleshooting Guide ...........................................................36
System Troubleshooting Guide .................................................................... 37
Preventive Maintenance Guidelines .....................................................38-39
InterLink Replacement Parts ......................................................................... 39
Typical Wiring Diagrams ...........................................................................40-45
Service Record .................................................................................................... 46
General Safety Information
1. Installation and maintenance to be performed only by
qualied personnel who are familiar with this type of
equipment.
2. Some units are pressurized with dry air or inert gas.
All units must be evacuated before charging the system
with refrigerant.
WARNING: Refrigerant can be harmful if it is inhaled. Refrigerant must be used and recovered responsibly.
Failure to follow this warning may result in personal injury or death.
Inspection
Responsibility should be assigned to a dependable individual at the
job site to receive material. Each shipment should be carefully checked
against the bill of lading. The shipping receipt should not be signed
until all items listed on the bill of lading have been accounted. Check
carefully for concealed damage. Any shortage or damages should be
reported to the delivering carrier. Damaged material becomes the
delivering carrier’s responsibility, and should not be returned to the
manufacturer unless prior approval is given to do so. When uncrating,
care should be taken to prevent damage. Heavy equipment should be
left on its shipping base until it has been moved to the nal location.
Check the serial tag information with invoice. Report any discrepancies
to your Heatcraft Refrigeration Products Sales Representative.
3. Make sure that all eld wiring conforms to the requirements
of the equipment and all applicable national and local codes.
4. Avoid contact with sharp edges and coil surfaces.
They are a potential injury hazard.
5. Make sure all power sources are disconnected before any
service work is done on units.
area available through the distributor; the second through fth years,
the purchaser must submit a proof-of-purchase of a compressor and
supply it to Heatcraft Refrigeration Products Warranty Claims for
reimbursement.
Seller makes no express warranties except as noted above. All implied
warranties are limited to the duration of the Express Warranty. Liability
for incidental and consequential damages is excluded.
The forgoing is in lieu of all other warranties, express or implied,
notwithstanding the provisions of the uniform commercial code, the
Magnuson-Moss Warranty - Federal Trade Commission Improvement
Act, or any other statutory or common law, federal or state.
Warranty Statement
Seller warrants to its direct purchasers that products, including Service
Parts, manufactured by SELLER shall be of a merchantable quality, free
of defects in material or workmanship, under normal use and service
for a period of one (1) year from date of original installation, or
eighteen (18) months from date of shipmen
first occurs. Any product covered by this order found to Seller’s
satisfaction to be defective upon examination at Seller’s factory will
at SELLER’s option, be repaired or replaced and returned to Buyer
via lowest common carrier, or SELLER may at its option grant Buyer
a credit for the purchase price of the defective article. Upon return
of a defective product to SELLER’s plant, freight prepaid, by Buyer,
correction of such defect by repair or replacement, and return freight
via lowest common carrier, shall constitute full performance by SELLER
of its obligations hereunder.
SELLER shall have no liability for expenses incurred for repairs made by
Buyer except by prior, written authorization. Every claim on account
of breach of warranty shall be made to SELLER in writing within the
warranty period specied above – otherwise such claim shall be
deemed waived. Seller shall have no warranty obligation whatsoever if
its products have been subjected to alteration, misuse, negligence, free
chemicals in system, corrosive atmosphere, accident, or if operation
is contrary to SELLER’s or manufacturer’s recommendations, or if the
serial number has been altered, defaced, or removed.
MOTOR COMPRESSORS:
Motor compressors furnished by SELLER are subject to the standard
warranty terms set forth above, except that motor compressor
replacements or exchanges shall be made through the nearest
authorized wholesaler of the motor compressor manufacturer (not at
SELLER’s factory) and no freight shall be allowed for transportation of
the motor compressor to and from the wholesaler. The replacement
motor compressor shall be identical to the model of the motor
compressor being replaced. Additional charges which may be incurred
throughout the substitution of other than identical replacements
are not covered by this warranty. An optional, non assignable, four
(4) year extended compressor warranty may be purchased within
the boundaries of the United Sates of America, its territories and
possessions, and Canada. With this extended compressor warranty,
replacements are administered by an authorized compressor
distributor only. Replacements within the rst year of the warranty
2
t by SELLER, whichever
SELLER makes no warranty, express or implied, of fitness for any
particular purpose, or of any nature whatsoever, with respect
to products manufactures or sold by seller hereunder, except as
specically set forth above and on the face hereof. It is expressly
understood and agreed that SELLER shall not be liable to buyer,
or any customer of buyer, for direct or indirect, special, incidental,
consequential or penal damages, or for any expenses incurred by
reason of the use or misuse by buyer or third parties of said products.
To the extent said products may be considered "consumer products,"
As dened in Sec. 101 of the Magnuson-Moss Warranty - Federal Trade
Commission Improvement Act, SELLER makes no warranty of any kind,
express or implied, to "consumers," except as specically set forth above
and on the face hereof.
The following conditions should be adhered to when installing this
unit to maintain the manufacturers warranty:
(a) System piping must be in accordance with good
refrigeration practices.
(b) Inert gas must be charged into the piping during
brazing.
(c) The power supply to the unit must meet the
following conditions:
A. Three phase voltages must be +/ 10% of nameplate ratings. Single
phase must be within +10% or
-5% of nameplate ratings.
B. Phase imbalance cannot exceed 2%.
(d) All control and safety switch circuits must be
properly connected according to the wiring diagram.
(e) The factory installed wiring must not be changed
without written factory approval.
(f) All equipment is installed in accordance with
Heatcraft Refrigeration Products specied minimum
clearances.
© 2007, Heatcraft Refrigeration Products LLC
Unit Coolers
Recommended Unit Cooler Placement
Some general rules for evaporator placement which must be
followed are:
1. The air pattern must cover the entire room.
2.
NEVER locate evaporators over doors.
3. Location of aisles, racks, etc. must be known.
4. Location relative to compressors for minimum
pipe runs.
5. Location of condensate drains for minimum run.
The size and shape of the storage will generally determine the
type and number of evaporators to be used and their location. The
following are some typical examples:
Minimum Unit Clearances
Figure 1. Medium Prole and Large Unit Coolers
NOTE:
W = Total width
of evaporator
coil surface.
One evaporator
Figure 2. Low Prole Unit Coolers
NOTE:
H = Total height
evaporator
coil surface.
NOTE: Leave space equal to unit height between bottom of unit and
product. Do not stack product in front of fans.
Two evaporators
One evaporator
Figure 3. Center Mount Unit Coolers
Recommended Maximum - Minimum Dimensions for
E S M T
Max. Min. Max. Min. Max. Min. Max. Min.
25' 2' 20' 3' 40' 3' 40' 6'
Two evaporators
Center Mount Unit Cooler Installations.
3
Unit Cooler Mounting
Most evaporators can be mounted with rod hangers, lag screws, or
bolts. Use 5/16" bolt and washers or rod for up to 250 pounds, 3/8" for
up to 600 pounds and 5/8" for over 600 pounds. Care should be taken
to mount the units level so that condensate drains properly. Note that
some unit cooler designs achieve drain pan slope by using dierent
height mounting brackets. In this situation, the top of the mounting
brackets should be level. Adequate support must be provided to hold
the weight of the unit.
When using rod hangers, allow adequate space between the top of
Figure 4. Large Coolers and Freezers Placement.
the unit and the ceiling for cleaning. To comply with NSF Standard 7,
the area above the unit cooler must be sealed or exposed in such a way
to facilitate hand cleaning without the use of tools. When lagging or
bolting the unit ush to the ceiling, seal the joint between the top and
the ceiling with an NSF listed sealant and ends of open hanger channels
must be sealed to prevent accumulation of foreign matter.
When locating unit coolers in a cooler or freezer, refer to Figures 1
through 4 for guidelines.
NOTE: Always avoid placement of Unit Coolers
directly above doors and door openings.
Baed Unit
Whe re o ne wa ll e vap orato r
mounting is satisfactory.
Cooler or Freezer with Glass
Display Doors
Cooler or Freezers where one wall
will not accommodate all required
evaporators or where air throw
distance must be considered.
Bae
Glass
Display
Door
Allow sucient space between
rear of Unit Cooler and wall to
permit free return of air. Refer to
Figures 1 through 3 for proper
space.
Elevation view of glass display door
cooler or freezer. Be sure air discharge
blows above, not directly at doors.
Provide bae if door extends above
blower level.
Defrost
Many types of control arrangements can be used. In some applications,
it may not be necessary to have scheduled defrost periods. The normal
“o cycle” of the compressor may be adequate to keep the evaporator
coil clear of frost. In other applications, a defrost timer may be necessary
to help assure a clear coil. In a medium temperature environment, “air
defrost” is initiated by the timer, but the evaporator fans continue to
operate to facilitate the melting of frost on the n surface. Other types
of defrost schemes require that the fans on the evaporator shut o
4
during the defrost period.
For most applications, two to four defrost cycles per day should be
adequate. The defrost requirements will vary on each installation so
the defrost settings should be determined by observing the system
operation.
Defrost Thermostat
Adjustable (F25-209 Series)
The defrost duration is determined by the setting of the defrost
termination thermostat. Initially, the thermostat should be set at midrange. This will terminate the defrost at about a 60°F bulb temperature
which will be satisfactory for most applications. A somewhat longer or
shorter defrost can be obtained by adjusting the control clockwise for a
shorter defrost and counterclockwise for a longer defrost. The fan delay
temperature setting of the thermostat is factory set at 25°F. It can be
adjusted upward by turning the adjusting screw next to the duration
adjustment with a small screwdriver. Each complete clockwise rotation
of this screw raises the setting approximately 3°F. This screw should not
be adjusted more than four turns. Making this adjustment also raises
the defrost termination temperature setting of the thermostat by a
similar amount. For example, with the duration setting at mid-range,
the termination temperature would be approximately 60°F. Turning
the adjusting screw one turn would raise the fan delay temperature to
about 28°F as well as changing the termination temperature from 60°F to
63°F. On medium temperature applications it may be necessary to raise
the setting to assure that the thermostat will reset after a defrost.
Adjustable (060-100-00 Series)
This control has an adjustable defrost termination setpoint and an
adjustable dierential for controlling the fan delay. A typical termination
setting is 60°F with a 25°F dierential. Termination setting may be
adjusted to increase/decrease the length of defrost. The dierential
should be adjusted to turn on the fans at 30 to 35°F (Fan Temperature
= Termination Temperature – Dierential). Actual coil temperature will
be 5 to 10°F below this value. Some unit coolers are preset and labeled
at the factory with special settings.
Note: Defrost controls are positioned as determined
by engineering test. Job conditions may require
the sensing device to be relocated for optimal
defrosting.
Bimetal Disc
A bimetal disc type thermostat is wired to the control circuit to terminate
the defrost cycle when the coil temperature reaches approximately 55°F.
The bimetal disc thermostat provides a fan delay to allow moisture on
the coil to freeze after defrost termination.
Note: On systems where the suction temperature is
above approximately 25°F, the fans may not
start for an extended period of time.
On freezer applications, it may be necessary to apply a jumper to the
fan delay on a warm box. This can be corrected by jumping the fan
switch contacts. This will allow the fans to start immediately after
defrost termination. This will disable the fan delay.
If moisture blow-o is encountered without the fan delay, a higher
temperature defrost thermostat can be ordered. This thermostat
terminates defrost at 60°F and prevents the fans from running when
the coil temperature is above 40°F. Refer to the replacement parts list
for the correct number to order.
Table 1. Expansion Valve Selection For 100# Head Pressure Valve
BTUH R-507/R404A R-507/R404A R-22 R-22
at about -20
10° T.D. Sporlan ALCO Sporlan ALCO Sporlan ALCO Sporlan ALCO
3,000-5,000 EGSE 1/2 ZP HFESC-1/2-RZ EGSE 1/2 C HFESC-1/2-RC EGVE 1/2 Z HFESC-1-HZ EGVE 1/2 C HFESC-1/2-HC
5,500-7000 EGSE 1/2 ZP HFESC-1/2-RZ EGSE 1 C HFESC-1/2-RC EGVE 1 ZP HFESC-1-HZ EGVE 1 C HFESC-1-HC
7500-8000 EGSE 1 ZP HFESC-1/2-RZ EGSE 1 C HFESC-1-RC EGVE 1 ZP HFESC-1 1/2-HZ EGVE 1 C HFESC-1-HC
8500-10,000 EGSE 1 ZP HFESC-1-RZ EGSE 11/2 C HFESC-1 1/4-RC EGVE 11/2 ZP HFESC-1 1/2-HZ EGVE 1 C HFESC-1-HC
10,500-11,000 EGSE 1 ZP HFESC-1 1/4-RZ EGSE 11/2 C HFESC-1 1/4-RC EGVE 11/2 ZP HFESC-2-HZ EGVE 11/2 C HFESC-1-HC
11,500-13,000 EGSE 11/2 ZP HFESC-1 1/2-RZ EGSE 11/2 C HFESC-1 1/4-RC EGVE 11/2 ZP HFESC-2-HZ EGVE 11/2 C HFESC-1-HC
13,500-15,000 EGSE 11/2 ZP HFESC-2-RZ EGSE 2 C HFESC-1 1/2-RC EGVE 2 ZP HFESC-2 1/2-HZ EGVE 11/2 C HFESC-2-HC
15,500-17,000 EGSE 2 ZP HFESC-2-RZ EGSE 2 C HFESC-2-RC EGVE 2 ZP HFESC-2 1/2-HZ EGVE 2 C HFESC-2-HC
17,500-20,000 EGSE 2 ZP HFESC-3 1/2-RZ SSE 3 C HFESC-2-RC EGVE 3 ZP HFESC-3-HZ EGVE 2 C HFESC-2 1/2-HC
20,500-24,000 SSE 3 ZP HFESC-3 1/2-RZ SSE 3 C HFESC-3-RC SVE 3 ZP HFESC-3-HZ SVE 3 C HFESC-3-HC
24,500-28,000 SSE 3 ZP HFESC-3 1/2-RZ SSE 4 C HFESC-3-RC SVE 4 ZP HFESC-5 1/2-HZ SVE 3 C HFESC-3-HC
28,500-34,000 SSE 4 ZP HFESC-5-RZ SSE 4 C HFESC-3-RC SVE 5 ZP HFESC-5 1/2-HZ SVE 4 C HFESC-5 1/2-HC
34,500-40,000 OSE 6 ZP HFESC-5-RZ SSE 6 C HFESC-5-RC SVE 8 ZP HFESC-5 1/2-HZ SVE 4 C HFESC-5 1/2-HC
40,500-50,000 OSE 8 ZP HFESC-7-RZ OSE 8 C HFESC-5-RC SVE 10 ZP HFESC-8-HZ SVE 5 C HFESC-5 1/2-HC
50,500-60,000 OSE 9 ZP HFESC-10-RZ OSE 9 C HFESC-7-RC SVE 10 ZP HFESC-8-HZ SVE 8 C HFESC-8-HC
60,500-70,000 OSE 9 ZP HFESC-10-RZ OSE 9 C HFESC-10-RC OVE 15 ZP HFESC-10-HZ SVE 8 C HFESC-8-HC
70,500-80,000 OSE 12 ZP HFESC-10-RZ OSE 12 C HFESC-10-RC OVE 15 ZP HFESC-15-HZ SVE 10 C HFESC-10-HC
80,500-90,000 OSE 12 ZP HFESC-13-RZ OSE 12 C HFESC-10-RC OVE 15 ZP HFESC-15-HZ SVE 10 C HFESC-10-HC
90,500-100,000 OSE 12 ZP HFESC-13-RZ OSE 12 C HFESC-13-RC OVE 15 ZP HFESC-15-HZ OVE 15 C HFESC-15-HC
100,500-110,000 OSE 21 ZP TRAE-20-RZ OSE 21 C HFESC-13-RC OVE 20 ZP HFESC-20-HZ OVE 15 C HFESC-15-HC
110,500-120,000 OSE 21 ZP TRAE-20-RZ OSE 21 C HFESC-13-RC OVE 20 ZP HFESC-20-HZ OVE 15 C HFESC-15-HC
120,500-130,000 OSE 21 ZP TRAE-20-RZ OSE 21 C TRAE-20-RC OVE 20 ZP HFESC-20-HZ OVE 15 C HFESC-15-HC
NOTES:
1. Valve selections assume standard conditions and 100°F vapor-free liquid.
2. Equivalent valve may be used in place of selection.
3. For "Medium Temp R-507," valve designation will use “P” for refrigerant code.
˚F/-29˚C Evap. +25˚F/-4˚C Evap. -20˚F/-29˚C Evap. +25˚F/-4˚C Evap.
5
Table 2. Expansion Valve Selection 180# Head Pressure Valve
BTUH R-507/R404A R-507/R404A R-22 R-22
at about -20
10˚ T.D. Sporlan ALCO Sporlan ALCO Sporlan ALCO Sporlan ALCO
3,000-5,000 EGSE 1/2 ZP HFESC-1/2-RZ EGSE 1/2 C HFESC-1/2-RC EGVE 1/2 ZP HFESC-1/2-HZ EGVE 1/2 C HFESC-1/2-HC
5,500-7000 EGSE 1/2 ZP HFESC-1-RZ EGSE 1 C HFESC-1/2-RC EGVE 1 ZP HFESC-1-HZ EGVE 1/2 C HFESC-1-HC
7500-8000 EGSE 1 ZP HFESC-1-RZ EGSE 1 C HFESC-1/2-RC EGVE 1 ZP HFESC-1-HZ EGVE 1 C HFESC-1-HC
8500-10,000 EGSE 1 ZP HFESC-1-RZ EGSE 1 C HFESC-1-RC EGVE11/2 ZP HFESC-1 1/2-HZ EGVE 1 C HFESC-1-HC
10,500-11,000 EGSE 1 ZP HFESC-1 1/4-RZ EGSE 11/2 C HFESC-1-RC EGVE 11/2 ZP HFESC-1 1/2-HZ EGVE 1 C HFESC-1-HC
11,500-13,000 EGSE 1 1/2 ZP HFESC-1 1/4-RZ EGSE 11/2 C HFESC-1 1/4-RC EGVE 11/2 ZP HFESC-2-HZ EGVE 1 C HFESC-1 1/2-HC
13,500-15,000 EGSE 2 ZP HFESC-1 1/2-RZ EGSE 11/2 C HFESC-1 1/4-RC EGVE 2 ZP HFESC-2-HZ EGVE 11/2 C HFESC-1 1/2-HC
15,500-17,000 EGSE 2 ZP HFESC-2-RZ EGSE 2 C HFESC-1 1/2-RC EGVE 2 ZP HFESC-2 1/2-HZ EGVE 11/2 C HFESC-1 1/2-HC
17,500-20,000 EGSE 2 ZP HFESC-2-RZ EGSE 2 C HFESC-1 1/2-RC EGVE 3 ZP HFESC-2 1/2-HZ EGVE 11/2 C HFESC-2-HC
20,500-24,000 SSE 3 ZP HFESC-3-RZ SSE 3 C HFESC-2-RC SVE 3 ZP HFESC-3-HZ SVE 2 C HFESC-2-HC
24,500-28,000 SSE 4 ZP HFESC-3-RZ SSE 3 C HFESC-2-RC SVE 4 ZP HFESC-3-HZ SVE 3 C HFESC-2 1/2-HC
28,500-34,000 SSE 4 ZP HFESC-5-RZ SSE 4 C HFESC-3 1/2-RC SVE 4 ZP HFESC-5 1/2-HZ SVE 3 C HFESC-3-HC
34,500-40,000 SSE 6 ZP HFESC-5-RZ SSE 6 C HFESC-3 1/2-RC SVE 5 ZP HFESC-5 1/2-HZ SVE 3 C HFESC-3-HC
40,500-50,000 OSE 9 ZP HFESC-7-RZ SSE 6 C HFESC-3 1/2-RC SVE 8 ZP HFESC-5 1/2-HZ SVE 4 C HFESC-5 1/2-HC
50,500-60,000 OSE 9 ZP HFESC-7-RZ OSE 9 C HFESC-5-RC SVE 10 ZP HFESC-8-HZ SVE 5 C HFESC-5 1/2-HC
60,500-70,000 OSE 9 ZP HFESC-10-RZ OSE 9 C HFESC-7-RC OVE 15 ZP HFESC-8-HZ SVE 5 C HFESC-5 1/2-HC
70,500-80,000 OSE 12 ZP HFESC-10-RZ OSE 12 C HFESC-7-RC OVE 15 ZP HFESC-10-HZ SVE 8 C HFESC-8-HC
80,500-90,000 OSE 12 ZP HFESC-10-RZ OSE 12 C HFESC-10-RC OVE 15 ZP HFESC-10-HZ SVE 8 C HFESC-8-HC
90,500-100,000 OSE 12 ZP HFESC-13-RZ OSE 12 C HFESC-10-RC OVE 15 ZP HFESC-15-HZ SVE 10 C HFESC-8-HC
100,500-110,000 OSE 12 ZP HFESC-13-RZ OSE 12 C HFESC-10-RC OVE 20 ZP HFESC-15-HZ SVE 10 C HFESC-10-HC
110,500-120,000 OSE 12 ZP HFESC-13-RZ OSE 12 C HFESC-10-RC OVE 20 ZP HFESC-15-HZ SVE 10 C HFESC-10-HC
120,500-130,000 OSE 21 ZP HFESC-13-RZ OSE 12 C HFESC-13-RC OVE 20 ZP HFESC-15-HZ OVE 15 C HFESC-10-HC
˚F/-29˚C Evap. +25˚F/-4˚C Evap. -20˚F/-29˚C Evap. +25˚F/-4˚C Evap.
Figure 5. Bulb and Contact Location
Figure 6. Multiple Evaporators
6
Distributor Nozzles
Nozzles supplied with unit coolers are selected for numerous
refrigerants at cataloged operating conditions and 95˚F liquid entering
the expansion valve. If mechanical or another method of subcooling
is used, the nozzle and expansion valve selection should be checked.
For conditions outside those cataloged, use the charts to select a
proper nozzle. Nozzle capacity should be within 135% to 180% of
unit operating condition for optimum coil performance. Nozzles are
available from Sporlan Wholesalers or from Heatcraft Refrigeration
Products. A small nozzle can be drilled larger using the I.D. column in
table 3, page 8. The hole must be accurately centered in the nozzle. A
lathe is preferred for accurate drilling.
may occur and poor evaporator operation may be experienced.
For peak performance, it is important to select an expansion valve with
the correct capacity and selective charge. Thermostatic expansion
valves may be mounted in any position, but they should be installed
as close to the evaporator as possible. For best performance, the outlet
of the expansion valve should be installed directly to the distributor
body. If this is not possible, the distance between the valve outlet and
distributor should not exceed 24 inches. Elbows located between the
expansion valve and distributor will hinder proper distribution and
therefore, are not recommended. Some accessories may, however,
necessitate the use of elbows.
Expansion Valves and Distributor Nozzles
Before installing the expansion valve on the distributor of the
evaporator, the proper distributor nozzle must be installed. Two
nozzles are normally shipped with each evaporator for dierent
refrigerants. Select the nozzle for the refrigerant that will be used.
The size of the nozzles shipped with each evaporator is based on
ordinary conditions, usually 95˚F liquid temperature and a maximum
of 15˚F evaporator TD*. If a mechanical subcooler is to be used in
your system, consult the factory or a representative for distributor
nozzle sizing. This is very important as the nominal capacity of the
nozzle increases as the liquid refrigerant temperature is lowered.
If the correct size nozzle is not installed, poor refrigerant distribution
*Temperature Dierence
(design room temperature minus saturated suction temperature)
Selecting Distributor Nozzle at the Job Site
You must know 4 things:
1. Refrigerant
2. Evaporating Temperature
3. Tons or BTUH
4. Highest Liquid Temperature
Locate the expansion valve bulb on a horizontal length of suction
line as close to the suction header as possible. The bulb should be
clamped tightly on the suction line and insulated with a waterproof
type of insulation. The bulb should never be placed on a coupling or
other obstruction so as to not make 100 % contact with the suction line.
The bulb should never be placed in a trap or downstream of a trap in
a suction line. Locating the bulb on the bottom of a suction line is not
recommended. The bulb should be installed at the 3, 4 or 8, 9 o’clock
position on the suction line. See Figure 5 on page 6.
EXAMPLE: Select a nozzle for R404A, -20˚F suction; 9,400
BTUH, 60˚F liquid entering TXV.
9,400
12,000
= .78 Tons
[1.83 Factor
for 60˚F Liquid]
EXAMPLE: Select a nozzle for R22, 20˚F suction; 67,000
BTUH, 100˚F liquid entering TXV.
67,000
12,000
From Table 3 on page 8 select Size 4 rated at 3.84 tons. We prefer
selecting at 135% - 180% of nominal rating. This is typically two sizes
smaller than the closest tonnage in Table 3.
5.58
3.84
= 5.58 Tons
= 145% of Nominal Rating - okay.
0.78
1.83
From Table 3 on page 8 select Size 3/4 rated at 0.29 tons.
0.42
0.29
Typical selections would be between 135% and 180%.
= .42 Corrected Tons
= 145% of Nominal Rating - okay.
7
Worksheet:
Given Values
Refrigerant ____________________________
Suction Temperature ___________________˚F
BTUH _______________________________
Liquid Temperature _____________________˚F
Calculations: _____ BTUH ÷ 12,000 = _____ Tons
Liquid Correction Factor:
_____________˚F liquid = _____________ Factor
_____ Tons ÷ _____ Factor = ____Corrected Tons
Nozzle Selections (Table 3)
______ Tons ÷ _______ Nozzle Capacity = ______%
(if within 135% to 180%, it is acceptable)
Table 3. Distributor Nozzle Capacities in Tons of Refrigeration
Nozzle Evaporator (Saturated Suction) Temperature °F
Orice R22
No. I.D. (in.) 40° 20° 0° -20° -40° 40° 20° 0° -20° -40° 40° 20° 0°
1/4 0.052 0.34 0.26 0.21 0.18 0.15 0.23 0.17 0.13 0.11 0.09 0.20 0.15 0.12
1/3 0.060 0.44 0.34 0.28 0.23 0.20 0.30 0.23 0.18 0.14 0.11 0.26 0.20 0.15
1/2 0.070 0.61 0.48 0.38 0.32 0.27 0.41 0.31 0.24 0.19 0.16 0.36 0.27 0.21
3/4 0.086 0.92 0.72 0.58 0.48 0.41 0.62 0.47 0.37 0.29 0.24 0.54 0.41 0.32
1 0.100 1.23 0.96 0.78 0.64 0.55 0.83 0.63 0.49 0.39 0.32 0.72 0.54 0.43
1-1/2 0.120 1.79 1.40 1.13 0.94 0.80 1.20 0.92 0.71 0.57 0.46 1.05 0.79 0.63
2 0.141 2.46 1.92 1.55 1.29 1.10 1.65 1.26 0.98 0.78 0.64 1.44 1.09 0.86
2-1/2 0.157 3.07 2.39 1.93 1.60 1.37 2.06 1.57 1.22 0.97 0.79 1.79 1.35 1.07
3 0.172 3.68 2.87 2.32 1.93 1.65 2.47 1.88 1.47 1.17 0.95 2.15 1.63 1.28
4 0.199 4.92 3.84 3.10 2.58 2.20 3.31 2.52 1.96 1.56 1.27 2.88 2.18 1.72
5 0.221 6.07 4.74 3.83 3.18 2.72 4.08 3.11 2.42 1.93 1.57 3.55 2.68 2.12
6 0.242 7.28 5.68 4.59 3.81 3.26 4.89 3.72 2.91 2.31 1.88 4.26 3.22 2.54
8 0.266 8.77 6.84 5.52 4.59 3.93 5.89 4.49 3.50 2.79 2.27 5.13 3.88 3.06
10 0.281 9.83 7.67 6.19 5.15 4.40 6.60 5.03 3.92 3.12 2.54 5.75 4.35 3.43
12 0.313 12.10 9.47 7.65 6.36 5.43 8.16 6.21 4.84 3.86 3.14 7.10 5.37 4.24
15 0.348 15.10 11.70 9.48 7.88 6.74 10.10 7.70 6.01 4.78 3.89 8.81 6.65 5.25
17 0.368 16.80 13.10 10.60 8.81 7.54 11.30 8.61 6.72 5.35 4.35 9.85 7.44 5.87
20 0.404 20.30 15.80 12.80 10.60 9.08 13.60 10.40 8.10 6.45 5.24 11.90 8.97 7.08
25 0.453 25.50 19.90 16.10 13.40 11.40 17.10 13.10 10.20 8.11 6.60 14.90 11.30 8.91
30 0.484 29.20 22.80 18.40 15.30 13.10 19.60 14.90 11.60 9.27 7.54 17.10 12.90 10.20
R404A, R507, R402A R134a, R401A
Note: Based on 100°F liquid entering expansion valve.
(1 ton = 12,000 BTU/H)
Table 4. Liquid Temperature Correction Factor
Liquid Temperature
Correction Factor 3.02 2.55 2.10 1.83 1.59 1.37 1.17
NOTE: Tons X Correction Factor = Nozzle Capacity Nozzle Capacity (Tons) X 12,000 = BTUH Rating
˚F 30˚ 40˚ 50˚ 60˚ 70˚ 80˚ 90˚ 95˚ 100˚ 110˚ 120˚
1.06 1.00 0.85 0.72
Table 5. Pressure Drop vs. Nozzle Loading
Actual Load at a Percent of Above Rating
Group 80% 90% 100% 110% 120% 130% 140% 150% 160% 170%
Nozzle PSI *M 10 12 15 18 20 22 24 27 29 31
Drop
* M Group = R12, MP39, R134a.
†
H 16 20 25 30 35 38 40 43 46 49
†
H Group = R22, R404A, R502, R507, HP80.
8
Condensate Drain Lines
DRAIN LINE MIN.
PITCH - 1/4”/ FT.
VAPOR SEAL
TRAP
OPEN
DRAIN
Either copper or steel drain lines should be used and properly protected
from freezing. In running drain lines, provide a minimum 1/4 inch per
foot pitch for proper drainage. Drain lines should be at least as large as
the evaporator drain connection. All plumbing connections should be
made in accordance with local plumbing codes. All condensate drain
lines must be trapped, and run to an open drain. They must never be
connected directly to the sewer system. Traps in the drain line must be
located in a warm ambient. We recommend a trap on each evaporator
drain line prior to any tee connections. Traps located outside, or extensive
outside runs of drain line must be wrapped with a drain line heater.
The heater should be connected so that it operates continuously. It
is recommended that the drain line be insulated to prevent heat loss.
A heat input of 20 watts per linear foot of drain line for 0˚F (-18˚C)
room applications and 30 watts per linear foot for -20˚F (-29˚C) rooms
is satisfactory. In freezers, the evaporator drain pan tting should be
included when heating and insulating the drain line.
Inspect drain pan periodically to insure free drainage of condensate.
If drain pan contains standing water, check for proper installation. The
drain pan should be cleaned regularly with warm soapy water.
Figure 7. Condensate Drain Lines
WARNING: All power must be disconnected before clean-
Traps on low temperature units must be outside of refrigerated
enclosures. Traps subject to freezing temperatures must be wrapped
with heat tape and insulated.
NOTE: Always trap single evaporator system drain
lines individually to prevent humidity migration.
ing. Drain pan also serves as cover of hazardous
moving parts. Operation of unit without drain
pan constitutes a hazard.
9
Space and Location Requirements for
Air Cooled Condensing Units and Remote Condensers
The most important consideration which must be taken into account
when deciding upon the location of air-cooled equipment is the
provision for a supply of ambient air to the condenser, and removal of
heated air from the condensing unit or remote condenser area. Where
this essential requirement is not adhered to, it will result in higher
head pressures, which cause poor operation and potential failure of
equipment. Units must not be located in the vicinity of steam, hot air
or fume exhausts. Corrosive atmospheres require custom designed
condensers.
Figure 8. Space and Location Requirements for Condensing Units and Remote Condensers
Another consideration which must be taken is that the unit should be
mounted away from noise sensitive spaces and must have adequate
support to avoid vibration and noise transmission into the building.
Units should be mounted over corridors, utility areas, rest rooms and
other auxiliary areas where high levels of sound are not an important
factor. Sound and structural consultants should be retained for
recommendations.
Walls or Obstructions
The unit should be located so that air may circulate freely and not
be recirculated. For proper air ow and access all sides of the unit
should be a minimum of “W” away from any wall or obstruction. It
is preferred that this distance be increased whenever possible. Care
should be taken to see that ample room is left for maintenance work
through access doors and panels. Overhead obstructions are not
permitted. When the unit is in an area where it is enclosed by three
walls the unit must be installed as indicated for units in a pit.
Units in Pits
The top of the unit should be level with the top of the pit, and
side distance increased to “2W”.
If the top of the unit is not level with the top of pit, discharge
cones or stacks must be used to raise discharge air to the top of
the pit. This is a minimum requirement.
Multiple Units
For units placed side by side, the minimum distance between
units is the width of the largest unit. If units are placed end
to end, the minimum distance between units is 4 feet.
Decorative Fences
Fences must have 50% free area, with 1 foot undercut, a “W”
minimum clearance, and must not exceed the top of unit.
If these requirements are not met, unit must be installed as
indicated for “Units in pits”.
10
Walls or Obstructions for Horizontal Air Flow
* “W” = Total width of the condensing unit or condenser.
Multiple Units with Horizontal Air Flow
Requirements for Remote and Water Cooled
Condensing Units
General Installation
The indoor compressor units are designed to be used with a remote
condenser. The water cooled units are similar, except that they have
an integral water cooled condenser. Inlet and outlet water connections
are to be made in the eld. On units having a compressor water jacket,
incoming water shall be routed through the jacket prior to entering
the condenser. For cleaning purposes, condenser end plates can be
removed to give access to the water tubes. Cleaning is accomplished
by a simple spiral tool powered by an ordinary electric drill. During
installation, allow space for cleaning the condenser. Commercial
equipment of this type is intended for installation by qualified
refrigeration mechanics.
Typical Arrangements
Diagram 1 illustrates a typical piping arrangement involving a remote
condenser located at a higher elevation, as commonly encountered
when the condenser is on a roof and the compressor and receiver are
on grade level or in a basement equipment room.
In this case, the design of the discharge line is very critical. If properly
sized for full load condition, the gas velocity might be too low at
reduced loads to carry oil up through the discharge line and condenser
coil. Reducing the discharge line size would increase the gas velocity
suciently at reduced load conditions; however, when operating at
full load, the line would be greatly undersized, and thereby creating an
excessive refrigerant pressure drop. This condition can be overcome
in one of two of the following ways:
1. The discharge line may be properly sized for the desired pressure
drop at full load conditions and an oil separator installed at the bottom
of the trap in the discharge line from the compressor.
2. A double riser discharge line may be used as shown in Diagram 2.
Line “A” should be sized to carry the oil at minimum load conditions and
the line “B” should be sized so that at the full load conditions both lines
would have sucient ow velocity to carry the oil to the condenser.
Water Regulating Valve
Using this control on the water cooled condensing units, the head
pressure can be maintained by adjusting the ow of water through
the condenser section. This type control is most often located on the
water entering side of the condenser and is regulated by the refrigerant
condensing pressure.
Subcooler
Diagrams 1 and 2 below show typical subcooler piping. Diagram 1
is the preferred connection with receiver as it provides maximum
subcooling. Diagram 2 may be used if the receiver is located far from
the condenser.
Notes:
1. All oil traps are to be as short in radius as possible.
Common practice is to fabricate the trap using three
90 degree ells.
2. Pressure relief valves are recommended at the condenser
for protection of the coil.
3. A pressure valve at the high point in the discharge line is
recommended to aid in removing non-condensables.
4. The placement of a subcooler should be that it does not
interfere with normal airow of the condenser. Increased
static of the unit could cause a decrease in system capacity
and fan motor damage.
GPM Requirements
The GPM Requirements table below can be used as a guide for
determining water ow requirements of the condenser. Operation
below the minimum ow rates may result in excessive fouling and
poor heat transfer. Operation above the maximum ow rates risk
premature impingement corrosion and tube failure.
Water Cooled Condenser GPM Requirements
Model Min GPM Max GPM Rated GPM*
SWN0075H2 0.7 5 1.25
SWN0075M2 0.7 5 1.5
SWN0090H2 0.7 5 2
SWN0090M6 0.7 5 2.25
SWN0100H2 0.7 5 2
SWN0150H2 0.7 5 2.5
SWN0150L6 0.7 5 1.5
SWN0199M6 0.7 5 4
SWN0200H2 2 18 4
SWN0200L6 2 18 2
SWN0200M2 2 18 5
SWN0200M6 2 18 7
SWN0210L6 2 18 3
SWN0310E6 4 18 5
SWN0300H2 4 18 6
SWN0310L6 4 18 4
SWN0310M6 4 18 9
SWN0311L6 4 18 6
SWN0400H2 4 18 11
SWN0400L6 4 18 7
SWN0499H2 7.5 23 10
SWN0500H2 7.5 23 12.5
SWN0500M6 7.5 23 15
SWN0599L6 7.5 23 7.5
SWN0600L6 7.5 23 10
SWN0601L6 7.5 23 10
SWN0750H2 10 25 12.5
SWN0750L6 10 25 10
SWN0760H2 10 25 15
SWN0761H2 10 25 20
SWN0900L6 20 67 20
SWN1000H2 20 67 30
SWN1000L6 20 67 20
SWN1500H2 20 80 35
SWN1500L6 20 80 20
SWN2000H2 20 80 40
SWN2200L6 20 80 25
* Low Temp. Rating Point: -20°F SST, 85°F EWT, 105°F CT, 5°F SC
* Medium/High Temp. Rating Point: 25°F SST, 85°F EWT, 105°F CT,
5°F SC
Diagram 1
Diagram 2
11
Condensing Unit Rigging and Mounting
Rigging holes are provided on all units. Caution should be exercised
when moving these units. To prevent damage to the unit housing
during rigging, cables or chains used must be held apart by spacer
bars. The mounting platform or base should be level and located so
as to permit free access of supply air.
Ground Mounting
Concrete slab raised six inches above ground level provides a suitable
base. Raising the base above ground level provides some protection
from ground water and wind blown matter. Before tightening mounting
bolts, recheck level of unit. The unit should in all cases be located with
a clear space in all directions that is at a minimum, equal to the height
of the unit above the mounting surface. A condensing unit mounted in
a corner formed by two walls, may result in discharge air recirculation
with resulting loss of capacity.
Roof Mounting
Due to the weight of the units, a structural analysis by a qualied
engineer may be required before mounting. Roof mounted units should
be installed level on steel channels or an I-beam frame capable of
supporting the weight of the unit. Vibration absorbing pads or springs
should be installed between the condensing unit legs or frame and
the roof mounting assembly.
Access
Provide adequate space at the compressor end of the unit for servicing.
Provide adequate space on the connection side to permit service of
components.
Spring Mounted Compressor
Compressors are secured rigidly to make sure there is no transit damage.
Before operating the unit, it is necessary to follow these steps:
a. Remove the upper nuts and washers.
b. Discard the shipping spacers.
c. Install the neoprene spacers. (Spacers located
in the electrical panel or tied to compressor.)
d. Replace the upper mounting nuts and washers.
e. Allow 1/16 inch space between the mounting nut/
washer and the neoprene spacer. See Figures 9
and 11 below.
Rigid Mounted Compressor
Some products use rigid mounted compressors. Check the compressor
mounting bolts to insure they have not vibrated loose during shipment.
See Figure 10 below.
Figure 9. Spring Mount
Figure 10. Solid Mount for Mobile or Deep
Sump Application.
Figure 11. Spring Mount
12
Condensing Unit Accessories
Suction Filters, Driers, Sight Glasses
There are two types of suction and liquid lter/driers used on
Heatcraft Refrigeration Products units. Replaceable core and/or
sealed units are used, dependent upon the option package ordered.
Suction lters, regardless of type, are always installed upstream of
the compressor suction service valve, and any accumulators or other
options that may be installed. Suction lters are equipped with
“Schrader” type access valves to allow eld measurement of pressure
drop across the device. This allows plugged lters and elements to
be identied very quickly and easily so they can be replaced when
the pressure drop is excessive. Refer to the specic manufacturers’
recommendation on servicing these units by make and model.
Liquid lter/driers, regardless of type, are always installed downstream
of the receiver outlet service valve, and upstream of the liquid line
solenoid valve (if supplied). Liquid line driers may or may not have an
access valve, dependent on the size and application.
The basic servicing of these units is similar to suction lters. Liquid
line driers should be replaced whenever there is evidence of excessive
pressure drop across the lter, or the system becomes contaminated
due to system leaks, compressor burnouts, acid formation, or
moisture accumulation as indicated by the liquid line sight glass.
The sight glass is installed in the main liquid line assembly, downstream
from the receiver outlet service valve, and immediately after the liquid
line drier. The sight glass is designed to give a visual indication of
system moisture content with refrigerant owing. Slight color indication
on a new system is common and will be eliminated during system
evacuation. Generally, it requires no eld service. However, in cases of
extreme acid formation in a system after a compressor burnout, the
acid may damage the sensing element or etch the glass. This would
require that the sight glass be replaced, along with the liquid line drier
after any compressor motor burnout.
Table 6. Recommended Low Pressure Control Settings for Outdoor Air Cooled Condensing Units
R-22 R-404A/R-507 R-134a
*Minimum Cut-In Cut-Out Cut-In Cut-Out Cut-In Cut-Out
Temp. ˚F PSI PSI PSI PSI PSI PSI
50 70 20 90 35 45 15
40 55 20 70 35 35 10
30 40 20 55 35 25 10
10 30 10 45 25 13 0
0 15 0 25 7 8 0
-10 15 0 20 1 --- ---
-20 10 0 12 1 --- ---
-30 6 0 8 1"Hg. --- ---
* Minimum ambient or box temperature anticipated, high pressure control setting: R-22, 360 PSI; R-404A, R-507, 400 PSI; R-134a, 225 PSI
* The standard preset low pressure switch used for pumpdown is set for 15 PSI cut in / 4 PSI cut out and is a good setting for most pumpdown systems
* ZB Scroll compressors should be set for 25 PSI cut in / 17 PSI cut out (R-404A / R-507)
CAUTION: Fans closest to the headers should not be
cycled on standard temperature or pressure
controls. Dramatic temperature and pressure
changes at the headers as a result of fan
action can result in possible tube failure.
Fan motors are designed for continuous
duty operation.
Fan cycling controls should be adjusted to maintain a mini
mum of (5) minutes on and (5) minutes o. Short cycling of
fans may result in a premature failure of
motor and/or fan blade.
Compressors operating below +10°F SST must have air
owing over the compressor at all times when the compres
sor is running.
-
-
13
Evaporating Temperature (ºF)
Condensin
g
T
emper
atu
r
e (ºF)
Copeland Demand Cooling for Discus L2 Models
R-22, when used in a properly designed and controlled refrigeration
system, is a realistic low temperature refrigerant alternative to R-502,
which was phased out due to its high ozone depletion potential.
However, experience has shown R-22 can present problems as a low
temperature refrigerant because under some conditions the internal
compressor discharge temperature exceeds the safe temperature limit
for long term stability of refrigeration oil. For this reason suction to liquid
heat exchangers are not recommended unless they are necessary to
prevent another potential problem.
The Copeland Demand Cooling System
Copeland's demand cooling system uses modern electronics to provide a
reliable, cost-eective solution to this problem. It is required for all single
stage R-22 applications with saturated suction temperatures below -10˚F.
The Demand Cooling module uses the signal of a discharge head
temperature sensor to monitor discharge gas temperature. If a critical
temperature is reached, the module energizes a long life injection valve
which meters a controlled amount of saturated refrigerant into the
compressor suction cavity to cool the suction gas. Refer to Figure 13.
This process controls the discharge temperature to a safe level. If, for
some reason, the discharge temperature rises above a preset maximum
level, the Demand Cooling module will turn the compressor o (requiring
a manual reset) and actuate its alarm contact. To minimize the amount
of refrigerant which must be injected, the suction gas cooling process
is performed after the gas has passed around and through the motor.
Operating Range
Demand Cooling is designed to protect the compressor from high
discharge temperatures over the evaporating and condensing
temperature ranges shown in Figure 12 at a maximum return gas
temperature of 65˚F.
When Demand Cooling operates, it “diverts” refrigeration capacity
in the form of injected saturated refrigerant from the evaporator to
the compressor. The eect of this diversion on evaporator capacity is
minimal because the diverted capacity is used to cool the gas entering
the compressor. As the gas is cooled, it naturally becomes more
dense, increasing the mass ow through the compressor, which partly
compensates for the capacity diverted from the evaporator.
1. Compressor Return Gas Temperature: Suction lines
should be well insulated to reduce suction line heat gain.
Return gas superheat should be as low as possible
consistent with safe compressor operation. Minimum 20˚F
superheat at the compressor is required.
2. Condensing Temperatures: It is important when using
R-22 as a low temperature refrigerant that condensing
temperatures be minimized to reduce compression ratios
and compressor discharge temperature.
3. Suction Pressure: Evaporator design and system control
settings should provide the maximum suction pressure
consistent with the application in order to have as low a
compression ratio as possible.
In most cases, with floating head systems where condensing
temperatures are low during most of the year, Demand Cooling will
operate primarily as a compressor protection control much as the
oil failure control protects the compressor during periods of low oil
pressure. Demand Cooling will be allowed to operate only during those
periods when condensing temperatures and return gas temperatures
are high or in periods where a system failure (such as an iced evaporator,
an expansion valve which does not control superheat, blocked
condenser, or a failed condenser fan) raises condensing temperatures
or return gas temperatures to abnormally high levels or lowers suction
pressure to abnormally low levels.
Demand Cooling System Design
Figure 12. Demand Cooling Injection
Figure 13. Single Stage Internal Refrigerant Injection
14
Head Pressure Control
Several types of head pressure control systems are available on
condensing units:
A. Dual Valve System. (See section on operation
and adjustment.)
B. Single Valve system. No adjustments are necessary.
(See section on operation.)
C. Ambient Fan Cycle Control. (See section on operation
and adjustment.)
D. No Control.
A. Dual Valve System
Operation and Adjustment
Condensing units with dual valves require sucient charge to partially
ood the condenser during low ambient conditions.
Valve adjustment should be made with gauges connected to the
discharge port of the compressor. Adjustments should be made during
mild or low ambient conditions. Turning the valve stem “clockwise” on
the ORI valve will increase the discharge pressure, while turning the
valve stem “counterclockwise” will decrease the discharge pressure.
If adjustments are made during warm ambient conditions, it may not be
possible to adjust the regulator valve as low as desired. Readjustment
may be necessary once cooler conditions prevail.
The system employs an ORI (open on rise of inlet pressure) valve and
an ORD ( open on rise of dierential pressure) valve. The high pressure
discharge gas is introduced above the liquid in the receiver tank. The
receiver discharge is regulated by the ORI valve.
The discharge pressure of the ORI valve must be adjusted to regulate
the unit for proper operating conditions. Adjust the ORI valve shown
on the following diagram to maintain a discharge pressure of 160 to
180 PSIG.
B. Single Valve System
The standard valve used on high pressure refrigerant systems controls
the head pressure at approximately 180 PSIG. There is no adjustment
for this valve. On low pressure refrigerant systems the valve controls
pressure at approximately 100 PSIG. For energy eciency, the 100 PSIG
valve is sometimes used on high pressure refrigerant systems. When this
is done, refer to Table 1 on page 5 for expansion valve selections.
At condensing pressures above the valve setting, ow enters Port C
and leaves Port R. When the condensing pressure falls below the valve
setting, the valve modulates to permit discharge gas to enter Port D.
Metering discharge gas into the refrigerant ow leaving the condenser
produces a higher pressure at the condenser outlet, reduces the ow,
and causes the level of liquid refrigerant to rise in the condenser.
This “ooding” of the condenser with liquid refrigerant reduces the
available condensing surface, holding the condensing pressure at
the valve setting.
Figure 14. Dual Valve Piping Arrangement
Figure 15. Single Valve Flooding Valve Piping
Arrangement
C. Ambient Fan Cycle Control
This is an automatic winter control method which will maintain a
condensing pressure within reasonable limits by cycling fan motors
in response to outside air temperature. The thermostat(s) should be
eld adjusted to shut o the fan when the condensing temperature
is reduced to approximately 90˚F. Table 7 lists approximate settings
for several system T.D.’s. These settings are approximate as they do not
take into account variations in load.
CAUTION: Under no circumstance should all condenser
motors be allowed to cycle o on one control.
At least one motor shall be wired to operate
at all times. Under most circumstances, the
condenser motor nearest the inlet header
should remain on whenever the compressor
is operating.
Table 7. Ambient Fan Cycle Thermostat Settings
Design Thermostat Settings
Models T.D. T1 T2 T3
30 60
2-fan units: 25 65
20 70
4-fan units: 15 75
30 60 40
3-fan units: 25 65 55
20 70 60
6-fan units: 15 75 65
30 60 50 30
8-fan units: 25 65 55 40
20 70 65 50
15 75 70 60
NOTE: Cycle pairs of fans on double wide units.
15
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