Fan Cycle Switch; Hot Start Sensor; Refrigerant Charging; Method Of Charging - Friedrich WallMaster PE07K Service Manual

Fan Cycle Switch

NOTE: It is recommended that this switch be set in the continuous position for maximum comfort and
temperature control.

Hot Start Sensor

(Heat Pump Models Only)
Under cold room conditions, the Hot Start Sensor brings
on the heater strips with a call for heat. This is to dis-
tribute warm air at the beginning of the heat cycle. Once
the return air has warmed sufficiently, the heat pump
mode will begin.

Refrigerant Charging

NOTE: Because The Ptac System Is A Sealed System,
Service Process Tubes Will Have To Be Installed.
First Install A Line Tap And Remove Refrigerant From
System. Make Necessary Sealed System Repairs And
Vacuum System. Crimp Process Tube Line And Solder
End Shut. Do Not Leave A Service Valve In The Sealed
System.
Proper refrigerant charge is essential to proper unit
operation. Operating a unit with an improper refrigerant
charge will result in reduced performance (capacity) and/or
efficiency. Accordingly, the use of proper charging methods
during servicing will insure that the unit is functioning as
designed and that its compressor will not be damaged.
Too much refrigerant (overcharge) in the system is just as
bad (if not worse) than not enough refrigerant (undercharge).
They both can be the source of certain compressor failures if
they remain uncorrected for any period of time. Quite often,
other problems (such as low air flow across evaporator,
etc.) are misdiagnosed as refrigerant charge problems. The
refrigerant circuit diagnosis chart will assist you in properly
diagnosing these systems.
An overcharged unit will at times return liquid refrigerant
(slugging) back to the suction side of the compressor
eventually causing a mechanical failure within the
compressor. This mechanical failure can manifest itself
as valve failure, bearing failure, and/or other mechanical
failure. The specific type of failure will be influenced by the
amount of liquid being returned, and the length of time the
slugging continues.
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The fan cycle switch is located behind the decorative front
cover below the control box. It is designed to operate the fan
either continuously or intermittently with the compressor or
heating elements. When the switch is in the CONTINUOUS
position, the fan will run continuously when the unit is turned
on. With the fan cycle switch in the CYCLE position, the
fan will run only when the compressor or heating elements
cycle on.
Not enough refrigerant (undercharge) on the other hand,
will cause the temperature of the suction gas to increase to
the point where it does not provide sufficient cooling for the
compressor motor. When this occurs, the motor winding
temperature will increase causing the motor to overheat
and possibly cycle open the compressor overload protector.
Continued overheating of the motor windings and/or cycling
of the overload will eventually lead to compressor motor
or
overload failure.

Method Of Charging

The acceptable method for charging the PTAC system is
the Weighed in Charge Method. The weighed in charge
method is applicable to all units. It is the preferred method
to use, as it is the most accurate.
The weighed in method should always be used whenever
a charge is removed from a unit such as for a leak repair,
compressor replacement, or when there is no refrigerant
charge left in the unit. To charge by this method, requires
the following steps:
1. Install a piercing valve to remove refrigerant from the
sealed system. (Piercing valve must be removed from
the system before recharging.)
2. Recover Refrigerant in accordance with EPA
regulations.
3. Install a process tube to sealed system.
4. Make necessary repairs to system.
5. Evacuate system to 300 microns or less.
6. Weigh in refrigerant with the property quantity of R-22
refrigerant.
7. Start unit, and verify performance.
8. Crimp the process tube and solder the end shut.