Defrost; Quiet Shift-2 - Bryant Base Series Application Manual And Service Manual

Residential Air Conditioners and Heat Pumps Using R-22 and Puron® Refrigerant: Application Guideline and Service Manual
Utility Interface
With Evolution Control
The input labeled UTIL is active only when a communicating Evolution
Control is used. This input allows a power utility device to interrupt
compressor operation during peak load periods. See
connections. When the utility sends a signal to shut the system down,
the User Interface will display "CURTAILMENT ACTIVE".
Fig. 40 – Utility Interface
With Non–Communicating Thermostats
When the utility curtailment interface is used with a non–communicating
thermostat, the utility relay should be wired between R and Y.
Low Ambient Cooling
When this unit is operating below 55_F/12.78_C outdoor temperature,
provisions must be made for low ambient operation.
Evolution Controlled low ambient cooling:
This unit is capable of low ambient cooling without a kit ONLY when
using the Evolution control. A low ambient kit is not required, and the
outdoor fan motor does not need to be replaced for Evolution controlled
low ambient operation. The Evolution Control provides an automatic
evaporator coil freeze protection algorithm that eliminates the need for
an evaporator freeze thermostat. Low ambient cooling must be enabled
in the User Interface set up. Fan may not begin to cycle until about
40_F/4.44_C OAT. Fan will cycle based on coil and outdoor air
temperature.
Evolution controlled low ambient mode operates as follows:
• Fan is OFF when outdoor coil temp is < (outdoor air temperature +
3_F/–16.11_C) or outdoor fan has been ON for 30 minutes. (Fan is
turned off to allow refrigerant system to stabilize.)
• Fan is ON when outdoor coil temp > (outdoor air temperature +
25_F/–3.89_C) or outdoor coil temp > 80_F/26.67_C or if outdoor
fan has been OFF for 30 minutes. (Fan is turned on to allow
refrigerant system to stabilize.)
• Low pressure switch is ignored for first 3 minutes during low
ambient start up. After 3 minutes, if LPS trips, then outdoor fan
motor is turned off for 10 minutes, with the compressor running. If
LPS closes within 10 minutes then cooling continues with the
outdoor fan cycling per the coil temperature routine listed above for
the remainder of the cooling cycle. If the LPS does not close within
10 minutes, then the normal LPS trip response (shut down cooling
operation and generate LPS trip error) will occur.
Standard Thermostat low ambient cooling mode:
A Low Ambient Pressure Switch kit, Evaporator Freeze Thermostat and
Isolation Relay must be installed for low ambient operation in standard
thermostat mode. The fan motor is a ball–bearing type and does not need
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
to be changed. A crankcase heater must be installed. See Product Data
for part numbers on appropriate unit size and series units.

DEFROST

This control offers 4 possible defrost interval times: 30, 60, 90 or 120
Fig. 40 for wiring
minutes. These are selected by dip switches on the unit control board, or
in the Evolution control (if used). The Evolution Control selection
overrides the control board dip switch settings.
Auto defrost is available with Evolution communicating control only
and it must be enabled in the User Interface. Auto defrost adjusts the
defrost interval time based on the last defrost time as follows:
• When defrost time is < 3 minutes, the next defrost
interval = 120 minutes
• When defrost time is 3–5 minutes, the next defrost
interval = 90 minutes
• When defrost time is 5–7 minutes, the next defrost
interval = 60 minutes
• When defrost time is > 7 minutes, the next defrost
interval = 30 minutes
The control board accumulates compressor run time. As the accumulated
run time approaches the selected defrost interval time, the control board
monitors the coil temperature sensor for a defrost demand. If a defrost
demand exists, a defrost cycle will be initiated at the end of the selected
time interval. A defrost demand exists when the coil temperature is at or
below 32_F/0_C for 4 minutes during the interval.
A05410B
The defrost cycle is terminated when the coil temperature reaches
65_F/18.33_C or 10 minutes has passed.
If the coil temperature does not reach 32_F/0_C within the interval, the
interval timer will be reset and start over.
NOTE:
• Upon initial power up the first defrost interval is defaulted to 30
minutes. Remaining intervals are at selected times.
• Defrost is only allowed to occur below 50_F/10_C outdoor ambient
temperature.
Defrost Hold
In a non–communicating system, if the thermostat becomes satisfied
before the defrost cycle is terminated, the control will "hold" in defrost
mode and finish the defrost cycle on the next call for heat. Defrost hold
is not needed in a communicating system because the User Interface will
complete the defrost cycle before shutting down the system.
Forced Defrost
Forced defrost can be initiated manually in a non–communicating
system, or by communicated command from a User Interface. The
board contains a 2–pin header labeled FORCED DEFROST (see
Fig. 11). To initiate a forced defrost:
• Manually, short FORCED DEFROST pins for 5 seconds then
release
• If coil temp is at defrost temp of 32_F/0_C, and outdoor air
temperature is below 50_F/10_C, a full defrost sequence will occur
• If the coil temp or outdoor air temperature do not meet the above
requirements, an abbreviated 30 second defrost will occur
• The Quiet Shift–2 compressor on/off delays, as described below,
will be included in a forced defrost if Quiet Shift–2 is enabled.
QUIET SHIFT–2
Quiet Shift–2 is a field selectable defrost mode which may eliminate
occasional noise that could be heard at the start and finish of the defrost
cycle.
On a non–communicating system, this feature must be enabled by
selecting the 3rd position of the 3–position dip switch on the outdoor
control board. For communicating systems, it must be enabled at the
User Interface. When activated, the following sequence of operation
occurs: Defrost Initiation – the compressor is de–energized for 70
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