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APPLICATION DATA
Min operating ambient temp (cooling):
In mechanical cooling mode, your Bryant rooftop can
safely operate down to an outdoor ambient temperature of
25_F(--4_C). It is possible to provide cooling at lower
outdoor ambient temperatures by using less outside air,
economizers, and/or accessory low ambient kits.
Max operating ambient temp (cooling):
The maximum operating ambient temperature for cooling
mode is 115_F(46_C). While cooling operation above
115_F(46_C) may be possible, it could cause either a
reduction in performance, reliability, or a protective action
by the unit’s internal safety devices.
Min and max airflow (cooling mode):
To maintain safe and relia ble operati on of your rooftop,
operate within the cooling airflow limits. Operating above
the max may cause blow--off, undesired airflow noise, or
airflow related problems with the rooftop unit. Operating
below the min may cause problems with coil freeze--up.
Airflow:
All units are draw--t hough in cooling mode.
Outdoor air application strategies:
Economizers reduce operating expenses and compressor
run time by providing a free source of cooling and a
means of ventilation to match application changing needs.
In fact, they should be considere d for most applications.
Also, consider the various economizer control methods
and their benefits, as well as sensors re quired to
accomplish your application goals. Please contact your
local Bryant representative for assistance.
Motor limits, break horsepower (BHP):
Due to Bryant’s internal unit design, air path, and
specially designed motors, the full horsepower (maximum
continuous BHP) ba nd, as listed in this ma nual, can be
used with the utmost confidence. There is no need for
extra safety factors, as Bryant’s motors are designed and
rigorously tested to use the entire, listed BHP range
without either nuisance tripping or premature motor
failure.
Sizing a rooftop
Bigger isn’t ne cessarily better. While an air conditi oner
needs to have enough capacity to meet the load, it doesn’t
need excess capacity. In fact, having excess capacity
typically results in very poor part load performance and
humidity control.
Using higher design t emperatures than ASHRAE
recom mends for your locat ion, adding “safety factors” to
the calculated load, and rounding up to the next largest
unit, are a ll signs of oversizing air conditioners.
Oversizing can cause short--cycling, and short cycling
leads to poor humidity control, reduced efficiency, highe r
utility bills, drastic indoor temperature swings, excessive
noise, and increased wear and tear on the air conditioner.
Rathe r than oversizing an air conditione r, wise contractors
and engineers “right--size” or even slightly undersize air
conditioners. Correctly sizing an ai r conditioner controls
humidity better; promotes efficiency; reduces utility bills;
extends equipment life, and maintains even, comfortable
temperatures.
Low ambient applications
When equipped with a Bryant economizer, your rooftop
unit can cool your space by bringing in fresh, cool outside
air. In fact, when so equipped, accessory low--ambient kit
may not be necessary. In low ambient conditions, unless
the outdoor air is excessively humid or contaminated,
economizer--based “free cooling” is the preferred less
costly and energy conscious method.
In low ambi ent applications where outside air might not
be desired (such as contaminated or excessively humid
outdoor environments), your Bryant rooftop can operate to
ambient tempe ratures down to --20_F(--29_C) using the
recommended accessory Motor master low ambient
controller.
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