McQuay OAC 003G Installation Manual

Installation and Maintenance Manual IM 777-4

Skyline Air Handler

Models OAC/OAH 003G – 090G

Group: Applied Air Systems

Part Number: IM 777

Date: May 2009

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

General Information . . . . . . . . . . . . . . . . . . . . . . . 3

Receiving and Handling . . . . . . . . . . . . . . . . . . . . 3

Unit Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Nomenclature. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Installation Guidelines . . . . . . . . . . . . . . . . . . . . . 3

Mechanical Installation . . . . . . . . . . . . . . . . . . . . . . 4

Service Clearances . . . . . . . . . . . . . . . . . . . . . . . 4

Rigging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Curb Mounting and Unit Leveling. . . . . . . . . . . . . 4

Assembling Sections . . . . . . . . . . . . . . . . . . . . . . 5

Shipping Sections . . . . . . . . . . . . . . . . . . . . . . 5

Panels, Frame Channels, and Doors . . . . . . . . . . 7

Panel Removal . . . . . . . . . . . . . . . . . . . . . . . . 7

Frame Channel Removal . . . . . . . . . . . . . . . . 7

Access Doors and Panels. . . . . . . . . . . . . . . . 7

Fan Section Doors . . . . . . . . . . . . . . . . . . . . . 7

Injected-Foam Insulated Panels . . . . . . . . . . . 8

Field Mounting Junction Boxes and

Other Components. . . . . . . . . . . . . . . . . . . . . . . . 8

Duct Connections. . . . . . . . . . . . . . . . . . . . . . . . . 8

Dampers and Hoods . . . . . . . . . . . . . . . . . . . . . . 9

Mounting Actuators . . . . . . . . . . . . . . . . . . . . . . . 9

Face and Bypass Section Mounting. . . . . . . . . . 10

Piping Vestibules . . . . . . . . . . . . . . . . . . . . . . . . 10

Piping and Coils . . . . . . . . . . . . . . . . . . . . . . . . . 10

Water Cooling Coils . . . . . . . . . . . . . . . . . . . 10

Direct Expansion Coils . . . . . . . . . . . . . . . . . 10

Steam Coils. . . . . . . . . . . . . . . . . . . . . . . . . . 11

Water Heating Coils . . . . . . . . . . . . . . . . . . . 13

Drain Pan Traps . . . . . . . . . . . . . . . . . . . . . . . . . 13

Internal Isolation Assembly Adjustment . . . . . . . 14

Electrical Installation . . . . . . . . . . . . . . . . . . . . . . 16

Wiring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Operation Guidelines . . . . . . . . . . . . . . . . . . . . . . 17

Startup Checks . . . . . . . . . . . . . . . . . . . . . . . . . 17

Before Starting the Unit: . . . . . . . . . . . . . . . . . . 17

Fan Wheel Alignment . . . . . . . . . . . . . . . . . . 18

Operating Limits. . . . . . . . . . . . . . . . . . . . . . . . . 19

Fan Vibration Levels . . . . . . . . . . . . . . . . . . . . . 21

Vibration Causes . . . . . . . . . . . . . . . . . . . . . 21

Service and Maintenance . . . . . . . . . . . . . . . . . . . 22

Periodic Maintenance . . . . . . . . . . . . . . . . . . . . 22

Ball Bearing Lubrication. . . . . . . . . . . . . . . . . . . 22

Motor Bearings . . . . . . . . . . . . . . . . . . . . . . . 22

Fan Shaft Bearings. . . . . . . . . . . . . . . . . . . . 22

Fan Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

VM and VP Variable Pitch Key Type Sheaves 23

LVP Variable Speed Sheaves . . . . . . . . . . . 24

MVP Variable Speed Sheaves . . . . . . . . . . . 25

Fan Drive Belt. . . . . . . . . . . . . . . . . . . . . . . . 26

Front Load Filter Option. . . . . . . . . . . . . . . . . . . 28

Filter Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Coils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Winterizing Water Coils . . . . . . . . . . . . . . . . 29

Removing and Replacing Components . . . . . . . 29

Removing the Fan Section . . . . . . . . . . . . . . 29

Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Replacement Parts . . . . . . . . . . . . . . . . . . . . . . 31

Service and Warranty Procedure . . . . . . . . . . . . 32

Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Warranty Return Material Procedure . . . . . . . . . 32

Check, Test, and Start Procedure Form . . . . . . . 33

Quality Assurance Survey Report. . . . . . . . . . . . 35

Introduction

OAH 003 G D A C

Model

OAH = Outdoor air handler OAC = Outdoor air component

Nominal Unit Size (nominal square foot of coil)

003, 004, 006, 008, 010, 012, 014, 017, 021, 025, 030, 035, 045, 055, 065, 080, 085, 090

Vintage of McQuay Air Handling Unit

Unit Cross Section

C = Standard unit cross section M = Custom size cross section

Motor Location

A = Motor along side of fan housing D = Motor downstream of belt drive plenum fan F = Motor on inline fan G = Motor downstream of direct drive plenum fan T = Motor behind twin housed fans

Unit Type/Coil Position

B = Blow-thru cooling coil location D = Draw-thru cooling coil location H = Heating only V = Vent only

Introduction

General Information

The system design and installation must follow accepted industry practice as described in the ASHRAE Handbook, the National Electric Code, and other applicable standards. Install this equipment in accordance with regulations of authorities having jurisdiction and all applicable codes.

Installation and maintenance must be performed by qualified personnel familiar with applicable codes and regulations and experienced with this type of equipment. Sheet metal parts, self-tapping screws, fins, clips, and such items inherently have sharp edges; the installer should exercise caution.

CAUTION

Sharp edges and coil surfaces are a potential injury hazard. Avoid contact with them.

ATTENTION

Les bords tranchants et les surfaces des bobines sont un risque de blessure. Ne les touchez pas.

Receiving and Handling

1 Carefully check items against the bills of lading to verify

all crates and cartons have been received. Carefully

inspect all units for shipping damage. Report damage immediately to the carrier and file a claim.

2 Skyline air handler units are constructed of galvanized or

painted steel and are inspected thoroughly before leaving the factory. Take care during installation to prevent damage to units.

3 Take special care when handling the blower section. All

fans are dynamically balanced before leaving the factory. Rough handling can cause misalignment or a damaged bearings or shaft. Carefully inspect fans and shaft before unit installation to verify this has not happened.

Note: Screws, bolts, etc., for assembling sections are supplied

in a bag attached to each section. All necessary gasketing is applied in the factory for section-to-section mounting, unless the unit has a curb ready base. Units require caulk sealant between sections.

Unit Storage

Store unit on a level surface. If air handling units are stored for any period of time, periodically rotate the fan wheel to prevent permanent distortion of drive components. In addition, grease may settle in the lower part of the bearing, which can lead to oxidation on the upper portion of the bearing surface. Keep the fan bearings lubricated.

Nomenclature

Installation Guidelines

McQuay IM 777-4 3

Mechanical Installation

4 . 0 0 " b a s e r a i l e x t e n s i o n

W i d t h

3 0 . 0 0 "

4 . 0 0 "

W i d t h o f c o i l s e c t i o n

W i d t h o f

f a n s e c t i o n

3 0 . 0 0 "

H e i g h t

5 4 "

1 2 "

Mechanical Installation

Service Clearances

Rigging

In addition to providing adequate space around the unit for piping coils and drains, access to at least one side of the unit is always required to allow for regular service and routine maintenance, which includes filter replacement, drain pan inspection and cleaning, fan bearing lubrication, and belt adjustment. Provide sufficient space—at least equal to the length of the coil—on the side of the unit for coil removal. See

Figure 1 for servicing space requirements.

Maintain at least 54" of clearance in front of electrical power devices. Electrical power devices that are mounted on the side of the unit typically are up to 12" deep (Figure 2).

Figure 1: Servicing Space Requirements

Skyline air assembled, or in modules of assembled sections.

handlers ship as separate sections, completely

The unit must be rigged as it ships from the factory. Do not rig units after assembly.

and the corners of each shipping section.

Units are

provided with a factory-installed base rail

can be lifted using the 2" diameter lifting holes located in

To prevent damage to the unit cabinetry, use spreader bars. Position spreader bars to prevent cables from rubbing the frame or panels. Before hoisting into position, test lift for stability and balance. Avoid twisting or uneven lifting of unit.

Figure 3: Unit and Section Rigging

Figure 2: Service Clearance for Electrical Power Devices

Curb Mounting and Unit Leveling

Do not place a Skyline unit over an open curb unless it is equipped with a curb-ready base. Installation instructions for mounting units on a roof curb are provided in IM 770. For a copy, contact your local McQuay representative or visit www.mcquay.com. Make provisions under the unit to divert any moisture from entering the building below.

For units without roof curb mounting, place the equipment on a flat and level surface. Where surface irregularities exist, shim the base of the unit at one or more points along the length of the rails to prevent distortion or sagging of the support rails. Uneven or distorted sections cause misfit or binding of the doors and panels and improper draining of drain pans (Figure 4).

4 McQuay IM 777-4

Mechanical Installation

S h i m t o p r e v e n t d i s t o r t i o n i f w i d t h i s o v e r 1 0 8 "

S h i m s e c t i o n s u n t i l t h e y a r e s t r a i g h t a n d l e v e l

1 / 4 " d i a m e t e r b e a d c e n t e r e d i n f a c e o f c l e a r a n c e

U s e S p l i c e J o i n t a s a g u i d e

R e m o v a b l e L i f t i n g B r a c k e t

Figure 4: Leveling the Unit

Assembling Sections

If the unit is shipped in more than one shipping section, rig each section into position separately. Shipping sections are provided with a connection splice joint attached on the leaving air side of the shipping section that seals against the frame channel on the entering-air side of the adjoining. The splice joint is insulated and provides an air-tight seal between two sections once they are assembled together. Align the splice joint to seat into the mating gasket to provide an air seal. If the splice joint was bent during shipping or rigging, restore it to its original position (Figure 8).

Pull sections together to fasten. Use straps and a ratchet to help pull the sections together securely. Apply sealant to any gaps that may admit moisture.

3 Fasten base rails together first using the 3/8"-16 × 5"

bolts located in the splice kit provided with the unit (Figure 7).

a To fasten two shipping sections together, four bolts

are needed (two on each side of the unit). The bolts are run from one base rail into the other and fastened with a nut. Complete each section bottom and top before attaching additional sections.

b If desired, shipping sections for non curb-ready units

can be fastened together internally. To fasten internally, run field-provided #10 sheet metal screws or drill screws (4" long, maximum) through the interior frame channel of one unit into the splice joint of the neighboring section.

c Handle units with curb-ready bases and vestibules so

the lifting bracket can be removed after the unit is placed on the curbing.

Note: Remove the lifting bracket that projects inward over

the curbing. Save the self tapping screws. When the adjacent section is placed in position, use self tapping screw to secure the bases together.

Figure 6: Remove Vestibule Lifting Bracket

Shipping Sections

Figure 5: Apply Sealant to Mating Faces

McQuay IM 777-4 5

1 Caulk all assembly joints of the unit—Before joining the

sections, apply at least 1/4 inch diameter bead of sealant to the mating faces of the cabinet. Use the splice joint as a guide for applying the sealant (Figure 5).

Mechanical Installation

S p l i c e C o l l a r m u s t b e a l i g n e d t o s e a l t o g a s k e t .

5 / 1 6 - 1 8 N u t

S p l i c e P l a t e

5 / 1 6 - 1 8 B o l t

S l i d e S p l i c e C a p o n a n d b e n d e n d s d o w n

Figure 7: Fasten Bottom of Section

“D”

Gasket

3/8" x 1" Bolt and Nut

d A length of “D” gasket is attached to each section

(Figure 7). This gasket MUST be installed to the unit base section.

IMPORTANT

The gasket is to be installed in an arc shape with the ends lower than the center, so that any moisture that may reach the gasket will be drained to the outside of the unit.

e Handle units with curb-ready bases and vestibules so

the lifting bracket can be removed after the unit is placed on the curbing.

Note: Remove the lifting bracket that projects inward over

the curbing. Save the self tapping screws. When the adjacent section is placed in position, use self tapping screw to secure the bases together.

Figure 8: Internal Fastening

1 Check that the sealant is compressed between the mating

channels when the unit sections are joined. Touch up any places where gaps are noted.

2 After sections are seated tightly together, slip the splice

cap over the top panel flanges. Bend the ends of the splice cap down to secure in place (Figure 9).

3 Assemble the small splice plate at the top rail to secure

the sections together at the top. Use 5/16" bolts (Figure 9).

Figure 9: Splice Cap and Splice Plate

6 McQuay IM 777-4

Mechanical Installation

Remove panel to remove frame

Remove any panel screws that engage frame

OPEN

View from inside door

Jam Nuts

Do Not Rotate Cup

Panels, Frame Channels, and Doors

Panel Removal

To remove a side or top panel, remove the flat head Torx 30 fasteners along the sides of the panel. Lift off the panel after removing all fasteners.

Frame Channel Removal

Frame channels that run the length of the unit along the top can be removed to allow access to both the side and top of the unit. To remove the frame channel, first remove the side panel(s). Once the side panel is off, remove the flat head Torx 30 fasteners in the corner of the frame channels. Then pull the frame channel out the side. Remove any panel screws that are within one inch of the of the frame since they are engaged into the gasketed flange of the frame (Figure 10).

Figure 10: Removing Panel Screws

that require the “use of tools” to access compartments containing moving parts or electrical wiring. See

Figure 11.

Remove padlock if one is present.

CAUTION

Sharp edges and coil surfaces are a potential injury hazard. Avoid contact with them.

ATTENTION

Les bords tranchants et les surfaces des bobines sont un risque de blessure. Ne les touchez pas.

CAUTION

DO NOT attempt to rotate the cup. Damage to the unit will occur.

ATTENTION

NE PAS tenter de faire tourner la cuvette (cup). Ceci va dendomagger l’unité.

2 Insert 1/2" socket into cup and rotate 1/4 turn clockwise

as shown in Figure 11. If the cup and handle are on the left side of the door, rotate 1/4 turn counterclockwise.

3 Rotate the door handle 1/4 turn clockwise and then 1/4

turn counterclockwise to release any internal pressure or vacuum and open the door. If the cup and handle are on the left side of the door, rotate the door handle 1/4 turn counterclockwise and then 1/4 turn clockwise.

4 To prevent air leakage, tighten the door panels by

adjusting the jam nuts.

Access Doors and Panels

For routine maintenance, access normally is obtained through access doors or by removing side panels. Removing all flat head fasteners along the sides of a panel allow it to be removed.

Fan and filter sections are always provided with a service door on one side of the unit. If requested on order, doors can be provided on both sides of the unit. Optional service doors are available for most section types and are provided based on customer request.

Fan Section Doors

Note: Opening fan section doors requires using a 1/2" socket

wrench, which satisfies ANSI standards and other codes

Figure 11: Opening Fan Section Door

McQuay IM 777-4 7

Mechanical Installation

D i s c h a r g e

P l e n u m

Injected-Foam Insulated Panels

Skyline air handlers now are furnished with double-wall, injected-foam insulated panels. Foam panels are stronger, more rigid, and lighter than panels with fiberglass insulation. The insulation R-value is improved to 13. However, foam insulation can burn when exposed to flame or other ignition sources and release toxic fumes. Take care in cutting and sealing all field-cut openings in these panels.

Panel Cutting Procedure

1 Determine the number and location of holes required for

electrical conduit, piping, and control wiring as follows:

a Check that adequate space is available inside the unit

for conduit or pipe routing.

b Do not locate holes in a panel that provides access to

key maintenance components such as filters and fan assemblies.

c Do not locate where the conduit or piping blocks

airflow or obstructs hinged access doors.

2 Once a proper location is determined, drill a small pilot

hole completely through the panel. Then use a sharp hole saw or a saber saw and cut from each side of the panel.

3 Seal the double-wall panel on each side with an

industrial/commercial grade silicone sealant or duct seal compound. It is extremely important to seal each panel hole or penetration securely so it is airtight, watertight, and so that there is no exposed insulation.

Figure 12: Cutting/Sealing Injected-Foam Insulated Panels

Seal completely with silicone

Cut hole from both sides of panel

Prop 65—Substances in fuel or from fuel combustion can cause personal injury or death, and are known to the State of California to cause cancer, birth defects or other reproductive harm.

sealant or duct seal compound

Field Mounting Junction Boxes and Other Components

For field mounting 4" × 4" or smaller junction boxes to the standard panel exterior, use a minimum quantity of four, 3/16" diameter pop rivets. Do not use self-tapping drill screws.

They will not tighten nor secure properly and panel damage can occur.

If larger, heavier components require mounting on unit panels, use through-bolts with flat washers through both outer and inner panels. To maintain panel integrity, seal both ends with an industrial/commercial grade silicone sealant or duct seal compound.

WARNING

Flame and smoke can cause equipment damage, severe personal injury, or death.

Before operating unit, seal all piping and wiring holes on both inner and outer panels with an industrial grade silicone sealant or duct seal compound. Do not use a cutting

torch or expose panel to fire. Panel damage can occur.

WARNING

La fumée et les flammes peuvent endommager le matériel et causesr des blessures graves ou la mort. Avant d’utiliser le dispositif, obturer tous les trous de passage de tubulures et de fils ménagés dans les panneaux intérieurs et extérieurs au moyen d’une pâte à base de silicone ou d’un mastic d’étanchéite â conduits de qualité industrielle. Ne pas se servir d’un chalumeau coupeur ni exposer les pannequx à une flamme nue pour ne pas risquer de les endommager.

The unit frame channel is another excellent location for securing heavier components; self-tapping screws are not acceptable. Ensure that the location permits the full operation of all access doors and panels and does not interfere with other vital components.

Duct Connections

Use flexible connectors on the outlet and inlet duct connections of all units. Do not position down flow fans over air ducts that are routed down into the building. Use a discharge plenum when bottom connections are necessary (Figure 13).

Figure 13: Discharge Plenum

8 McQuay IM 777-4

Mechanical Installation

F l a s h i n g

D u c t

F l a s h i n g

U n i t t o p p a n e l

F l a s h i n g

D u c t

F l a s h i n g

Remove screws and panel to access damper control shaft.

Hood

E x h a u s t

I n t a k e

B a r r i e r

If the unit has a top mixing box or economizer damper or a top duct connection, field fabricate and install flashing to divert moisture from the connection. The flashing must lap over the standing seams of the top panels. The flashing also must lap over the side edges of the unit (Figure 14).

Figure 14: Flashing Over Top Panels and Sides of Units

Dampers and Hoods

Side dampers may be provided in the mixing box and economizer sections of units. When dampers are provided, a removable panel is located above the weather hood to provide access to the damper drive shaft. Other access may be available depending on the specific construction of the unit (Figure 15).

Figure 15: Filler Panel Over the Weather Hood

Figure 16: Field-Installed Barrier Between Hoods

Mounting Actuators

The installing contractor is responsible for the mounting of all field-installed actuators. No provisions are made for the location of these actuators due to the number of options and arrangements available and the variety of specific applications. Typically, actuators are mounted inside the cabinet. Provide proper support for the actuator to avoid excessive stress in the cabinet, linkage, or damper shafts.

Note: Damper blades are at full flow when open to 70 degrees.

Do not open blades further than 70 degrees.

Fresh air and return air dampers can be linked together and driven from the same actuator if the dampers are the same size. If the dampers are different sizes, they must be driven by separate actuators and controlled appropriately. Exhaust dampers are always driven by a separate actuator.

A typical rotary electric actuator can handle up to 40 sq. ft. of damper. For pneumatic actuators, allow 5 in-lb per square foot of damper area.

CAUTION

Maximum damper rotation is 70°. Maximum shaft torque is 205 inches/pound. Greater rotation or torque can cause equipment damage.

La rotation maximale des volets est de 70°. Le couple (torque) maximum de l’arbre est de 205po/lb. Une plus grande rotation (ou torque) peut endommager l’équipement.

ATTENTION

When units are ordered with exhaust hoods and intake hoods adjacent to each other, install a field-supplied barrier to prevent recirculation of exhaust air into the intake openings. (Figure 16).

McQuay IM 777-4 9

Mechanical Installation

Seal holes cut for piping

Face and Bypass Section Mounting

Internal and external face and bypass sections are mounted together using the instructions for horizontal components and do not require additional instruction. Skyline air handlers are provided with a bypass duct that is integral to the unit construction and requires no field assembly.

Face and bypass dampers may or may not be linked together. When dampers are placed before a single bank of coils, they always are linked together and require a single actuator. When dampers bypass a stacked or staggered coil, the dampers are not linked and require multiple actuators.

Face and bypass dampers have a torque requirement of 10 in-lbs per square foot of damper face area.

Piping Vestibules

For units that include a piping vestibule, cut the openings for routing the field piping as required in the field. Carefully seal passages cut through the panels to prevent air leakage. A single metal thickness pan is provided in the bottom of the curb-mounted vestibule. The pan can be removed if necessary. If holes are cut into the pan for a piping passage, seal the holes to prevent moisture leakage (Figure 17).

Figure 17: Seal Holes for Piping—Curb Mounted Units

Piping and Coils

When designing and installing piping:

• Follow applicable piping design, sizing, and installation

information in ASHRAE handbooks.

• Observe all local codes and industry standards.

• Do not apply undue stress at the connection to coil headers;

always use a backup pipe wrench.

• Support pipework independently of the coils.

Water Cooling Coils

Note: Use glycol in water coils for outdoor air handlers. Power

failures and other mechanical issues can expose coils to freezing temperatures.

• Water supply, water return, drain, and vent connections

extend through the end panel of the coil section. All connections are labeled on the end panel.

• Water supply and water return connections are typically

male NPT iron pipe.

• When installing couplings, do not apply undue stress to the

connection extending through unit panel. Use a backup

pipe wrench to avoid breaking the weld between coil connection and header.

• Follow recommendations of the control manufacturer

regarding types, sizing, and installation of controls.

For units with standard base rails, the vestibule is open to the coil section; therefore, seal all holes to prevent air leakage.

Figure 18: Seal Holes for Piping—Standard Base Rail Units

Direct Expansion Coils

• The coil distributor and suction connection extend through

the end panel of the coil section.

• Check nozzle in distributor for proper tonnage.

• When a (field supplied) thermostatic expansion valve is

located outside the unit and connected directly to the distributor (except on units with piping vestibules). Do not apply heat to the body of the expansion valve.

• The thermostatic expansion valve must be the external

equalizer tube type. Connect the 1/4-inch diameter external equalizer tube provided on the coil to the connection on the expansion valve.

• Use care when piping the system, making sure all joints are

tight and all lines are dry and free of foreign material. For typical refrigerant piping, see condensing unit product manual.

10 McQuay IM 777-4

Mechanical Installation

Steam Coils

Piping (see Figure 19)

• Steam supply and steam return connections typically are male NPT iron pipe and are labeled on the end panel of coil section. Connections extend through the coil section end panel.

• When installing couplings, do not apply undue stress to the connection extending through unit panel. Use a backup

pipe wrench to avoid breaking the weld between coil connection and header.

• Support piping independently of coils and provide adequate

piping flexibility. Stresses resulting from expansion of closely coupled piping can cause serious damage.

• Do not reduce pipe size at the coil return connection. Carry return connection size through the dirt pocket, making the reduction at the branch leading to the trap.

Coils

• Pitch all steam coils in units toward the return connection.

• Do not drip supply mains through the coil.

• Do not attempt to lift condensate when using modulating or

on/off control.

• Install vacuum breakers on all applications to prevent retaining condensate in the coil. Generally, connect the vacuum breaker between the coil inlet and the return main. The vacuum breaker should be open to the atmosphere and the trap design should allow venting of large quantities of air.

Traps

Note: Do not place steam traps outdoors.

• Size traps in accordance with the manufacturers’ recommendations. Make sure the required pressure differential is always available. Do not undersize.

• Use float and thermostatic or bucket traps for low pressure steam. On high pressure steam, use bucket traps. Use thermostatic traps only for air venting.

• Use bucket traps for on/off control only.

• Locate traps at least 12 inches below the coil return

connection.

• Multiple coil installation—individually trap each coil or group of coils.

• Coils in series—use separate traps for each coil, or a bank of coils.

• Coils in parallel—a single trap can be used, but an individual trap for each coil is preferred.

• Do not attempt to lift condensate when using modulating or on/off control.

• With coils arranged for series airflow, use a separate control on each bank or coil in the direction of airflow.

Valves

• Do not use modulating steam valves on high pressure systems.

• Properly size modulating valves. Do not undersize.

• Avoid freezing conditions (entering air temperatures below

35°F).

• McQuay strongly recommends 5JA, 8JA, 5RA and 8RA coils.

• Supply 5 psi steam to coils at all times.

• Do not use modulating valves. Provide control by face and

bypass dampers.

• Consider using two or three coils in series with two position steam control valves on the coil or coils that handle 35°F or colder air. Use a modulating valve on the downstream coil to provide the desired degree of control.

• Thoroughly mix fresh air and return air before it enters the coil. Also, to obtain true air mixture temperatures, properly locate temperature control elements.

• As additional protection against freeze-up, install the trap sufficiently below the coil to provide an adequate hydrostatic head to remove condensate during an interruption in the steam pressure. Estimate three feet for each 1 psi of trap differential required.

• On startup, admit steam to coil ten minutes before admitting outdoor air.

• Close fresh air dampers if steam supply pressure falls below the minimum specified.

McQuay IM 777-4 11

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