Application Data - Bryant 581J Series Manual

APPLICATION DATA

Minimum and Maximum Airflow (Heating and
Cooling) —
To maintain safe and reliable operation of your
rooftop, operate within the heating airflow limits during heating
mode and cooling airflow limits during cooling mode. Operating
above the max may cause blow-off, undesired airflow noise, or air-
flow related problems with the rooftop unit. Operating below the
min may cause problems with coil freeze-up and unsafe heating
operation. Heating and cooling limitations differ when evaluating
operating CFM, the minimum value is the HIGHER of the cooling
and heating minimum CFM values published on page 5 and the
maximum value is the LOWER of the cooling and heating mini-
mum values published on page 5.
Heating-To-Cooling Changeover —
ically change from heating to cooling mode when using a thermo-
stat with an auto-changeover feature.
Airflow —
All units are draw-though in cooling mode and blow-
through in heating mode.
Outdoor Air Application Strategies —
duce operating expenses and compressor run time by providing a
free source of cooling and a means of ventilation to match applica-
tion changing needs. In fact, they should be considered for most
applications. Also, consider the various economizer control meth-
ods and their benefits, as well as sensors required to accomplish
your application goals. Please contact your local Bryant represen-
tative for assistance.
Motor Limits, Break Horsepower (BHP) —
nal design of Bryant units, the air path, and specially designed mo-
tors, the full horsepower (maximum continuous BHP) band, as
listed in the Fan Performance tables, can be used with the utmost
confidence. There is no need for extra safety factors, as Bryant
motors are designed and rigorously tested to use the entire, listed
BHP range without either nuisance tripping or premature motor
failure.
Propane Heating —
Propane has different physical qualities
than natural gas. As a result, propane requires different fuel to air
mixture. To optimize the fuel/air mixture for propane, Bryant sells
different burner orifices in an easy to install accessory kit. To select
the correct burner orifices or determine the heat capacity for a pro-
pane application, use either the selection software, or the unit's ser-
vice manual.
High Altitude Heating —
which affects the fuel/air mixture in heat exchangers. In order to
maintain a proper fuel/air mixture, heat exchangers operating in al-
titudes above 2000 ft (610 m) require different orifices. To select
the correct burner orifices or determine the heat capacity for a high
altitude application, use either the selection software, or the unit's
service manual.
High altitudes have less oxygen, which means heat exchangers
need less fuel. The new gas orifices in this field-installed kit make
the necessary adjustment for high altitude applications. They re-
store the optimal fuel to air mixture and maintain healthy combus-
tion on altitudes above 2000 ft (610 m).
NOTE: Typical natural gas heating value ranges from 975 to 1050
Btu/ft 3 at sea level nationally. The heating value goes down ap-
proximately 1.7% per every thousand feet elevation. Standard fac-
tory orifices can typically be used up to 2000 ft (610 m) elevation
without any operational issues.
The optional Bryant economizer can adequately cool your space
by bringing in fresh, cool outside air. In fact, when so equipped,
Your unit will automat-
Economizers re-
Due to inter-
High altitudes have less oxygen,
accessory low-ambient kit may not be necessary. In low ambient
conditions, unless the outdoor air is excessively humid or contam-
inated, economizer-based "free cooling" is the preferred less costly
and energy conscious method. In low ambient applications where
outside air might not be desired (such as contaminated or exces-
sively humid outdoor environments), your Bryant rooftop can op-
erate to ambient temperatures down to –20°F (–29°C) using the
recommended accessory Motormaster
Sizing a Rooftop —
Bigger isn't necessarily better. While an
air conditioner needs to have enough capacity to meet the design
loads, it doesn't need excess capacity. In fact, excess capacity
typically results in very poor part load performance and humidity
control.
Using higher design temperatures than ASHRAE recommends for
your location, adding "safety factors" to the calculated load, are all
signs of oversizing air conditioners. Oversizing the air conditioner
leads to poor humidity control, reduced efficiency, higher utility
bills, larger indoor temperature swings, excessive noise, and in-
creased wear and tear on the air conditioner.
Rather than oversizing an air conditioner, engineers should "right-
size" or even slightly undersize air conditioners. Correctly sizing
an air conditioner controls humidity better; promotes efficiency;
reduces utility bills; extends equipment life, and maintains even,
comfortable temperatures. Please contact your local Bryant repre-
sentative for assistance.
Low Ambient Applications —
mizer can adequately 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 out-
door air is excessively humid or contaminated, economizer-based
"free cooling" is the preferred less costly and energy conscious
method. In low ambient applications where outside air might not
be desired (such as contaminated or excessively humid outdoor
environments), your Bryant rooftop can operate to ambient tem-
peratures down to –20°F (–29°C) using the recommended acces-
sory Motormaster low ambient controller.
®
2-Speed Indoor Fan Motor System with Variable Fre-
quency Drive (VFD) —
Bryant's 2-Speed Indoor Fan Motor
System utilizes a Variable Frequency Drive (VFD) to automatical-
ly adjust the indoor fan motor speed in sequence with the units
cooling operation. Per ASHRAE 90.1 2010 standard section
6.4.3.10.b, during the first stage of cooling operation the VFD will
adjust the fan motor to provide
the unit. When a call for the second stage of cooling is required,
the VFD will allow the total cfm for the unit established (100%).
During the heating mode, the VFD will allow total design cfm
(100%) operation and during the ventilation mode the VFD will
allow operation to 2 / of total cfm.
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The VFD used in Bryant's 2-Speed Indoor Fan Motor System has
soft start capabilities to slowly ramp up the speeds, thus eliminat-
ing any high inrush air volume during initial start-up. It also has in-
ternal over current protection for the fan motor and a field installed
display kit that allows adjustment and in depth diagnostics of the
VFD.
This 2-Speed Indoor Fan Motor System is available on models
with 2-stage cooling operation with electrical mechanical or RTU
Open (multi Protocol) controls. Both space sensor and convention-
al thermostats controls can be used to provide accurate control in
any application.
The 2-Speed Indoor Fan Motor System is very flexible for initial
fan performance set up and adjustment. The standard factory
shipped VFD is pre programmed to automatically stage the fan
speed between the first and second stage of cooling. The unit fan
low ambient controller.
®
The optional Bryant econo-
/ of the total cfm established for
2
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