Chapter 8 – Maintenance
Page 8-8
TestEquity 115A-EX Temperature Chamber
Refrigeration System Charging Instructions
!
WARNING:
Repair of the refrigeration system must be performed only by a properly
trained mechanic who is experienced in repairing cascade refrigeration
systems. Do NOT substitute any component. Do NOT substitute refrigerants.
Improper repairs will void the warranty.
These instructions are intended as guidelines for repairing TestEquity chambers. Details such as
how to attach a gauge manifold are not covered. These are NOT do-it-yourself instructions!
R-404A High-Stage Charge
1.
Repair any leaks before recharging.
2.
Attach a vacuum pump and manifold gauge to the suction and discharge ports.
3.
Evacuate the system to at least 100 microns. DO NOT GUESS! You must use a micron
gauge.
4.
Use a charging scale to weigh in 7 ounces of R-404A.
5.
Verify the cooling performance as outlined in “How to verify the chamber performance”.
R-508B Low-Stage Charge
1.
Repair any leaks before recharging.
2.
Attach a vacuum pump and manifold gauge to the suction and discharge ports.
3.
Evacuate the system to at least 100 microns. Do NOT guess! You must use a micron gauge.
4.
Do NOT put any additives in the system. Pentane or propane is NOT necessary or desirable.
5.
Charge the system until the standby pressure is 120 PSIG at an ambient temperature of
73°F/23°C. Allow time for the charge to equalize as read on the suction and discharge
gauges. This is 15 PSIG higher than the target amount of 105 PSIG. This corresponds to
approximately 6 ounces. See NOTE below.
6.
Verify the cooling performance as outlined in “How to verify the chamber performance”.
NOTE:
If the low-stage has been evacuated and recharged, the standby pressure should be
rechecked after 24 hours to make sure it is 105 PSIG at an ambient temperature of 73°F/23°C.
This is because the refrigerant mixes with the POE oil in the compressor, causing a lower
standby pressure than was initially observed. Do not mistake this initial loss of pressure with a
leak. After verifying that there is no leak, you may need to top-off the charge if the pressure is
too low. Or, if the pressure is too high, you will need to bleed out some refrigerant to achieve a
standby pressure of 105 psig.
