47
The net effect of the rooftop when in hot gas reheat mode is
to provide nearly all latent capacity removal from the space
when sensible loads diminish (when outdoor temperature con-
ditions are moderate). When in hot gas reheat mode, the unit
will operate to provide mostly latent capacity and extremely
low sensible heat ratio capability.
Similar to the subcooling mode of operation, hot gas reheat
mode operates only when the outside air temperature is warmer
than 40 F. Below this temperature, a factory installed outside
air temperature switch will lock out this mode of operation.
See Table 30 for the Humidi-MiZer adaptive dehumidifica-
tion system sequence of operation.
SERVICE
Cleaning —
Inspect unit interior at the beginning of each
heating and cooling season or as operating conditions require.
EVAPORATOR COIL
1. Turn unit power off and install lockout tag. Remove
evaporator coil access panel.
2. If Economizer or accessory two-position damper is
installed, remove economizer or two-position damper by
disconnecting Economizer plug and removing mounting
screws.
3. Slide filters out of unit.
4. Clean coil using a commercial coil cleaner or dishwasher
detergent in a pressurized spray canister. Wash both
sides of coil and flush with clean water. For best results,
back-flush toward return-air section to remove foreign
material.
5. Flush condensate pan after completion.
6. Reinstall economizer or two-position damper and filters.
7. Reconnect wiring.
8. Replace access panels.
CONDENSER COILS — Inspect coils monthly. Clean con-
denser coils annually, and as required by location and outdoor-
air conditions.
Clean 2-row coils as follows:
1. Turn off unit power and install lockout tag.
2. Remove top panel screws on condenser end of unit.
3. Remove condenser coil corner post. See Fig. 52. To hold
top panel open, place coil corner post between top panel
and center post. See Fig. 53.
4. Remove device holding coil sections together at return
end of condenser coil. Carefully separate the outer coil
section 3 to 4 in. from the inner coil section. See Fig. 54.
5. Use a water hose or other suitable equipment to flush
down between the 2 coil sections to remove dirt and de-
bris. Clean the outer surfaces with a stiff brush in the nor-
mal manner.
6. Secure the sections together. Reposition the coil sections,
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.
CONDENSATE DRAIN — Check and clean each year at
start of cooling season. In winter, protect against freeze-up.
FILTERS — Clean or replace at start of each heating and cool-
ing season, or more often if operating conditions require it. Re-
placement filters must be same dimensions as original filters.
OUTDOOR-AIR INLET SCREEN — Clean
screen
with
steam or hot water and a mild detergent. Do not use throwaway
filters in place of screens.
Table 30 — Humidi-MiZer Adaptive Dehumidification System Sequence of Operation
and System Response — Dual Compressor Units (50HJ008-14)
LEGEND
NOTE: On a thermostat call for W1, all cooling and dehumidification
will be off.
When servicing unit, shut off all electrical power to unit to
avoid shock hazard or injury from rotating parts.
THERMOSTAT INPUT
ECONOMIZER FUNCTION
50HJ UNIT OPERATION
First Stage
Second Stage
H
Y1
Y2
OAT <
Economizer
Set Point
Economizer
Compressor
1
Subcooling
Mode
Hot Gas
Reheat
Mode
Compressor
2
Subcooling
Mode
Hot Gas
Reheat
Mode
Off
—
—
Unit Operates Under Normal Sequence of Operation
On
On
On
No
Off
On
Yes
No
On
Yes
No
On
On
Off
No
Off
On
Yes
No
On
No
Yes
On
On
On
Yes
On
On
Yes
No
On
No
Yes
On
On
Off
Yes
On
On
No
Yes
On
No
Yes
On
Off
Off
No
Off
On
No
Yes
On
No
Yes
OAT
—
Outdoor Air Temperature
Fig. 51 — Humidi-MiZer™ Hot Gas
Reheat Mode Operation
