Carrier 50EQ - Manual (Page 7)

2. In Fig. 10, locate the percent humidity on the
left-hand scale and the dry-bulb temperature on
the right-hand scale. Example in Fig. 10 uses 60%
RH and 66 F.
3. Draw a straight line connecting the 2 points.
4. Adjust the enthalpy control dial to the setting
indicated on the control setting scale in Fig. 10.
The control setting for the example conditions
is the B range.
Then set mixed air thermostat in unit filter com­
partment to desired temperature of air delivered
to the conditioned space (not less than 50 F or
condensation in unit will result).
HEATING OR COMPRESSOR COOLING
Night Switch Closed — The dampers will assume
and hold the ventilation position whenever indoor
air fan is operating. When indoor air fan shuts off,
the outdoor air damper will close.
Night Switch Open — Outdoor air damper remains
in the closed position. No outdoor air is introduced
into the airstream; unit operation is unaffected.
INTERMEDIATE SEASON (FREE COOLING)
Night Switch Closed (Normal daytime operation) —
If outdoor enthalpy is below enthalpy control
setting, the compressor will remain off when the
room thermostat operates the indoor air fan in the
usual manner. The damper will modulate to main­
tain the mixed air thermostat (MAT.) setting. If the
outdoor enthalpy rises above the enthalpy control
setting, the unit operates as described in Heating
or Compressor Cooling paragraph above.
Night Switch Open — Unit operates as described in
Heating or Compressor Cooling paragraph above.
Power Exhaust Operation (if fitted) — When unit
is on economizer mode, the outdoor air damper is
open providing low-cost cooling. The exhaust fan
(runs only during economizer operation) exhausts
return air to the outdoors.
Crankcase Heater — Keeps oil free of refrigerant.
Main power must remain on for heater operation. In
case of extended unit shutdown (more than 24
hours), energize heaters at least 24 hours before
starting compressor.
#
50-
20-z
V
H-
z>
X
>
i 40“
a:
sss
its
SL.
SO­
TO-
80-
CONTROL
SETTING
SO
'SO
ii.
sz
X
<
0:
ut
j-~70 S
-SO
Fig. 10 — Nomograph for Determining
Enthalpy Control Setting
7