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4.0 INSTALLATION
Tubing
4.6 Initial Leak testing
WARNING:
DO NOT
use oxygen
to purge lines or pressurize system for leak test.
Oxygen reacts violently with oil, which can cause an
explosion resulting in severe personal injury or death.
The variable speed inverter driven condensing units
must be matched to indoor coils or air-handlers that
are equipped with EXVs. During shipment, vibration
has been found to move the EXV stem valve to a near
closed position despite being set to a fully open position
in the factory. Prior to leak testing it is recommended to
apply power to the indoor unit, making sure there is no
call for operation by disconnecting the EcoNet™ control
center or thermostat. By doing this, the controls will im
-
mediately close the EXV followed immediately by open
-
ing it to the wide open position, permitting free flow of
nitrogen through the system during the brazing process.
Indoor coils have only a holding charge of dry
nitrogen. Keep all tube ends sealed until connections are
to be made.
ST-A1226-07-00
•
Pressurize line set and coil through service fit
-
tings with dry nitrogen to 150 PSIG (maximum).
Close nitrogen tank valve, let system sit for at least
15 minutes, and check to see if the pressure has
dropped. If the pressure has dropped, check for
leaks at the line set braze joints with soap bubbles
and repair leak as necessary. Repeat pressure test.
If line set and coil hold pressure, proceed with line
set and coil evacuation (see Sections 4.7 and 4.8 for
evacuation and final leak testing).
ST-A1226-06-00
•
The suction line must be insulated for its entire
length to prevent dripping (sweating) and prevent
performance losses. Closed-cell foam insulation
such as Armaflex and Rubatex
®
are satisfactory
insulations for this purpose. Use 1/2” [12.7 mm]
minimum insulation thickness. Additional
insulation may be required for long runs. The
liquid line must be insulated in any unconditioned
space when long line sets are used and anytime
the liquid line is run through an attic due to hot
temperatures that occur there.
4.7 Evacuation
Evacuation is one of the most important parts of
the entire installation and service procedure. The
life and efficiency of the equipment is dependent
upon the thoroughness exercised by the serviceman
when evacuating air and moisture from the system.
Air or nitrogen in the system increases condensing
temperature and pressure, resulting in increased
power consumption, erratic operation, and reduced
capacity.
Moisture chemically reacts with the refrigerant and oil
to form corrosive acid which attacks the compressor
motor windings and internal parts and which can result
in compressor failure.
•
After the system has been leak-checked and
proven sealed, connect the vacuum pump and
evacuate system to 500 microns and hold 500
microns or less for at least 15 minutes. The vacuum
pump must be connected to both the high and low
sides of the system by connecting to the two
pressure ports. Use the largest size connections
available since restrictive service connections may
lead to false readings because of pressure drop
through the fittings.
