Bryant 549B - Manual (Page 36)

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E. Defrost
When the temperature of the outdoor coil drops below 28 F as
sensed by the defrost thermostat (DFT2) and the defrost
timer is at the end of the timed period (adjustable at 30, 50, or
90 minutes), the reversing valve solenoids (RVS1 and RVS2)
are energized and the OFC is deenergized. This switches the
position of the reversing valves and shuts off the outdoor fans.
The electric heaters (if installed) will be energized.
The unit continues to defrost until the coil temperature as
measured by DFT2 reaches 65 F, or the defrost cycle com-
pletes a 10-minute period.
During the Defrost mode, if circuit 1 defrosts first, RVS1 will
oscillate between Heating and Cooling modes (depending on
DFT1 switch position) until the Defrost mode is complete.
At the end of the defrost cycle, the electric heaters (if
installed) will be deenergized; the reversing valves deener-
gize and the outdoor-fan motors will be energized. The unit
will now operate in the Heating mode.
If the space thermostat is satisfied during a defrost cycle, the
unit will continue in the Defrost mode until the time or tem-
perature constraints are satisfied.
SERVICE
I. CLEANING
Inspect the unit interior at the beginning of each heating
and cooling season or as operating conditions require.
A. Indoor Coil
1. Turn the unit power off and install lockout tag on dis-
connect. Remove the filter access panel and indoor
coil access panel.
2. If the economizer or accessory two-position damper is
installed, remove the economizer/two-position damper
by disconnecting the economizer plug and removing
mounting screws. Refer to Accessory Economizer or
Two-Position Damper Installation Instructions for
more details.
3. Slide filters out of unit.
4. Clean the coil using a commercial coil cleaner or dish-
washer detergent in a pressurized spray canister.
Wash both sides of the coil and flush with clean
water. For best results, backflush toward the return-
air section to remove foreign material.
5. Flush the condensate pan after completion.
6. Reinstall the economizer/two-position damper and
filters.
7. Reconnect wiring.
8. Replace the access panels.
B. Outdoor Coil
Inspect the coil monthly. Clean the outdoor coil annually, and
as required by location and outdoor-air conditions.
Clean 2-row coils as follows:
1. Turn off the unit power and install lockout tag on
disconnect.
2. Remove the top panel screws on the outdoor end of
the unit.
3. Remove the outdoor coil corner post. See Fig. 34. To
hold the top panel open, place the coil corner post
between the top panel and center post. See Fig. 35.
4. Remove the device holding the coil sections together
at the return end of the outdoor coil. Carefully sepa-
rate the outer coil section 3 to 4 in. from the inner coil
section. See Fig. 36.
5. Use a water hose or other suitable equipment to flush
down between the 2 coil sections to remove dirt and
debris. Clean the outer surfaces with a stiff brush in
the normal manner.
6. Secure the sections together. Reposition the coil sec-
tions, and remove the coil corner post from between
the top panel and center post. Install the coil corner
post and coil center post, and replace all screws.
CAUTION: When servicing the unit, shut off all
electrical power to the unit and tag to avoid shock haz-
ard or injury from rotating parts.
Fig. 34 — Cleaning Outdoor Coil
Fig. 35 — Propping Up Top Panel