26
FORM CIM 0203
minutes)
5.
If the high side pressure is not at or above 250
psig, block off the condenser inlet air stream
until the pressure is above this threshold. This
will simulate a system performance level close
to the design condition of 95° F ambient.
6.
The hot gas bypass valve setting is 58 psig.
a. If the suction pressure is 58 psig the ther-
mocouple reading should be approximately
120° F or higher. Please note that it may be
necessary to block off some of the evapora-
tor air in order to check this condition.
b. If the suction pressure is above 58 psig the
thermocouple reading should be less than
120° F.
c. If the suction pressure is below 58 psig the
hot gas bypass valve should be adjusted to
raise the pressure.
ADJUSTMENT OF HOT GAS BYPASS
VALVE
The function of the hot gas bypass valve is to pre-
vent the suction pressure from falling below a pre-
determined set point, thereby balancing the system.
The set point is typically 58 psig (R-22).
Refer to the procedure for Checking the Hot Gas
Bypass Valve before proceeding. This will help to
establish where the valve is currently set.
1.
Connect a low pressure refrigerant gauge to
the suction line.
2.
Operate air conditioner in the cooling mode
until system is stabilized. (Approximately 15
minutes)
3.
Remove the seal cap on the top of the hot gas
bypass valve.
4.
Adjust the valve by turning the stem. A
CLOCKWISE turn will increase the pressure
setting. A COUNTERCLOCKWISE turn will
decrease the pressure setting. One complete
turn is equal to approximately a 4 psi change.
Adjustments should be made in small in-
crements, allowing the system to stabilize
after each turn.
5.
Vary the evaporator load to test at various con-
ditions that the suction pressure does not fall
below the set point (58 psig for R-22).
6.
Replace the seal cap on the top of the hot gas
bypass valve.
NOTE:
a. On split system applications the hot gas
bypass line to the evaporator should be in-
sulated to prevent condensation.
b. Use a wet rag around the hot gas bypass
valve when doing any brazing
MARVEL MICROPROCESSOR
CONTROLLER
The microprocessor controller allows you to con-
trol up to 16 separate zones independently from one
location. There are 12 critical alarm sensors per zone
to monitor such things as cooling, heat, humidity;
and there are optional day/night setbacks for mul-
tiple time cycles. User setpoints are easily pro-
grammed at the keypad location. For further infor-
mation, refer to the Installation Instructions for the
Marvel controller which accompanies the unit.
HUMIDIFIER
The optional steam humidifier that comes with the
unit functions on the electrode principle. As water
fills the plastic steam generator, it immerses metal
electrodes which then permits electrical current flow
through the water. This current flow produces heat
which then boils the water into steam. This steam
is then injected on the downstream side of the cool-
ing coil to provide humidification for the area be-
ing served by the unit. Water is replenished through
tubing and the 1/4" flare located on the evaporator
coil panel structure. See Item , Figure 6, page 6.
For further information on operation refer to the
Installation Instruction for air conditioning humidi-
fiers which accompanies the unit.
ELECTRIC HEAT
Electric heat is possible in two options. Option 1 is
integrally built into the unit behind the evaporator
coil, separate power supply is not required.
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