Carrier 38AN-009 User Manual download pdf (Page 46)

Application data

Unit selection

Select equipment to either match or be slightly less than

anticipated peak load. This provides better humidity con-

trol, fewer unit cycles, and less part-load operation.

For units used in spaces with high sensible loads, base

equipment selection on unit sensible load, not on total an-

ticipated load. Adjust for anticipated room wet bulb tem-

perature to avoid undersizing equipment.

When selecting equipment which has outdoor air intro-

duced into the unit, determine the mix conditions of room

air and outdoor air at design conditions. The cooling ca-

pacity tables in this literature are based on 80 F edb. Adjust

for actual dry-bulb and wet-bulb conditions with the required

outdoor air to select the proper equipment.

Unit combinations and coil mixed matches

The 38AN and 38HDC units are the only units approved

for use with the Carrier 40QNB, 40QAB, and 40QKB duct-

free split systems. The 38AN and 38HDC units can also be

used with other fan coil units.

Mixed matches of indoor-fan coil capacity more than one

size larger than the outdoor condensing unit capacity may

result in inadequate indoor comfort. Do not select mixed

matches where the indoor-fan coil capacity is more than

one size larger than the outdoor condensing unit capacity

unless speciﬁcally indicated in this data. Heat pump fan coils

can be used with cooling-only condensing units to provide

electric heat capability.

Unit mounting (outdoor)

Unit leveling — For reliable operation, units should be

level in all planes.

Clearance — Adequate clearance must be provided for

airﬂow. See dimensional drawings for proper clearances.

The condensing units are designed for free-blow applica-

tion. Air inlets and outlets should not be restricted. Outdoor

fan external static pressure available is less than

0.1 in. wg.

Unit location — Cooling units may be stacked 2 high.

Units may be wall mounted, pad mounted at ground level,

roof mounted, or mounted on or under a deck or patio. Be

sure water from roof does not drain directly onto the unit.

See your Carrier representative for drawings to construct

stacking rails or wall mounting brackets.

If 38HDC condensing units are being mounted near a

wall, the condenser air should discharge toward the wall.

This will provide inherent coil protection and the best pos-

siblesound and airﬂow performance. The 38AN units should

be mounted with fan discharge pointing away from the wall.

Unit mounting (indoor)

Unit leveling — For reliable operation, units should be

level in all planes. The 40QAB ceiling-suspended fan coils

may have a slight pitch, but only toward the drain

connection.

Clearance — Provide adequate clearance for airﬂow. The

unit return and discharge should not be obstructed by fur-

niture, curtains, or anything which may cause unit short cy-

cling or air recirculation. See base unit dimensional draw-

ings on pages 18-24 for required clearances.

Unit location — When selecting unit location, select a lo-

cationwhich will provide the best air circulation for the room.

40QNB HIGH WALL UNITS — These units should be po-

sitioned as high as possible on the wall for best air circula-

tion. Allow adequate clearances above the unit for servicing

(removing unit covers). Place the unit in the middle of the

wall selected (if possible). Select an outside wall if available

to make piping easier, and place the unit so it faces the

normal location of room occupants.

40QABCEILING-SUSPENDEDUNITS—These unitsshould

be mounted near the ceiling and against a wall. The unit

should be centered in the room for best performance. Lo-

cating the unit on an outside wall will make piping easier,

but units can also be mounted away from a wall if desired.

(If the unit is mounted away from a wall, the rear panel of

the unit may need a ﬁeld-supplied trim strip for improved

appearance.) Locate the fan coil return over an area which

isnot normally occupied for quietest operation. Do not block

air discharge for a minimum of 15 ft to prevent dumping of

cold air and drafts.

40QKB IN-CEILING CASSETTE UNITS — These units

should be mounted in the ceiling, preferably near the cen-

ter of the room. If the unit must be mounted near a wall,

close the air discharge on the blocked side(s). (Up to 2 sides

may be blocked.) Locate the control box away from the

blocked side(s).

Mounting template

The 40QAB and QNB fan coil units are furnished with

mounting templates or mounting plates to mark the loca-

tion of the mounting brackets, wiring, and refrigeration line

hole locations. In addition, the 40QAB units indicate the

location of ventilation-air connections.

Support

Adequate support must be provided to support the weight

of all fan coils. Refer to the Physical Data section on

page 11 for fan coil weights, and the base unit dimensional

drawings on pages 18-24 for the location of mounting

brackets.

System operating conditions

Operating limits:

OUTDOOR CONDENSING UNITS

CONDITION 38AN 38HDC

Maximum Cooling Ambient (F) 125 125

Minimum Cooling Ambient (F) (without

accessory low-ambient kit)

55 55

Minimum Cooling Ambient (F) (with

accessory low-ambient kit)

–20 –20

Minimum Cooling Return-Air Temperature (F) 55 55

Maximum Cooling Return-Air Temperature (F) 95 95

Saturated Suction Temperature Range

Minimum (F) –15 –15

Maximum (F) 55 55

Saturated Condensing Temperature Range

Minimum (F) 85 80

Maximum (F) 150 150

Maximum Compressor Discharge

Temperature (F)

275 275

Minimum Discharge Superheat (F) 60 60

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Carrier 38AN-009 User Manual Page 46

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