Final Charge Adjustment - Goodman GSX Series Installation & Operation Instructions

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If pressure rises above 2000 microns, a leak is present.
Check for leaks as previously indicated and repair as
necessary then repeat evacuation.
System Start Up
When opening valves with retainers, open each valve only
until the top of the stem is 1/8" from the retainer. To avoid loss
of refrigerant, DO NOT apply pressure to the retainer. When
opening valves without a retainer remove service valve cap
and insert a hex wrench into the valve stem and back out the
stem by turning the hex wrench counterclockwise. Open the
valve until it contacts the rolled lip of the valve body. NOTE:
These are not back-seating valves. It is not necessary to
force the stem tightly against the rolled lip. Open the suction
service valve first! If the liquid service valve is opened first, oil
from the compressor may be drawn into the indoor coil TXV,
restricting refrigerant flow and affecting operation of the
system. After the refrigerant charge has bled into the system,
open the liquid service valve. The service valve cap is the
secondary seal for the valves and must be properly tightened
to prevent leaks. Make sure cap is clean and apply refrigerant
oil to threads and sealing surface on inside of cap. Tighten
cap finger-tight and then tighten additional 1/6 of a turn (1
wrench flat), or to the following specification, to properly seat
the sealing surfaces.
1. 3/8" valve to 5 - 10 in-lbs (0.56-1.30 Nm)
2. 5/8" valve to 5 - 20 in-lbs (0.56-2.26 Nm)
3. 3/4" valve to 5 - 20 in-lbs (0.56-2.26 Nm)
4. 7/8" valve to 5 - 20 in-lbs (0.56-2.26 Nm)
Do not introduce liquid refrigerant from the cylinder into the
crankcase of the compressor as this may damage the com-
pressor.
1. Purge gauge lines after attaching to the service valves.
2. Determine the proper charge from the serial data plate.
Charge includes the evaporator coil and 7.6 m of line set.
Systems having more than 7.6 m of interconnecting tubing
require an additional charge allowance of 6 oz.
3. Break the vacuum by opening the suction and liquid
valves on the gauge set and weighing in the calculated
charge.
4. Set thermostat to call for cooling. Check indoor and
outdoor fan operation and allow system to stabilize for 10
minutes for fixed orifices and 20 minutes for expansion
valves.

FINAL CHARGE ADJUSTMENT

The outdoor temperature must be 60°F (16°C) or higher.
Set the room thermostat to COOL, fan switch to AUTO,
and set the temperature control well below room tempera-
ture. After system has stabilized per startup instructions,
check superheat as detailed in the following section.
GENERAL:
The following information has been developed to assist the
service technician in determining the proper charge for
®
Goodman Heat Pump Systems.
It must be noted that many field variations exist that may
effect the operating temperature and pressure readings of a
heat pump system.
It should also be noted that all Goodman
Systems utilize fixed orifice refrigerant control devices. As such,
the following procedures have been developed for this type of
refrigerant control device.
I. DETERMINATION OF INDOOR AIR FLOW (L/S) AND
HEATING CAPACITY (KW)
Prior to using the methods described below to check the
system's charge it is important to verify that the system is
delivering sufficient air across the indoor coil (L/s, liters per
second), as well as, the operating capacity of the system. The
following procedures are suggested methods for determin-
ing the system air flow (L/s) and its operating capacity (kW).
Airflow Test Instruments - There are a number of readily
available instruments which can be used in the field for airflow
determination such as Barometers, Volume-Aire Air Balanc-
ers, Anemometers, and Velometers. When using these de-
vices it is important to follow the manufacture's instructions
provided with them.
Airflow Determination - Indoor Coil
The heat pump system has been designed for optimum perfor-
mance with the airflow across the indoor coil equaling
approximately 190 L/s per TON.
e.g.
A 2 TON system should have 2 x 190 = 380 L/s.
Temperature Rise Method - Although not as accurate as the
use of test equipment, a method of determining the indoor
airflow in a system employing electric resistance heat as the
backup heat source is by the temperature rise method and is
calculated using the following formula:
828.3 x Input Power (kW)
________________________
Air Flow (L/s) =
Temperature Rise (°C)
where
measured input voltage (Volt) x current (Amp)
________________________
kW =
e.g.
input voltage = 230 Volt, measured current 35 amps
temperature rise = 12°C
air flow = 828.3 * 230 * 35 / 1000 / 12
= 556 (L/s)
NOTE: The compressor circuit (outdoor unit) must be off
to insure that the Temperature Rise measured across
the indoor unit is due only to the electric heat.
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® Heat Pump
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