Type 3 Flashcards
A typical setting for the high-pressure cut-out control on a recovery unit used for evacuating refrigerant from a low-pressure chiller is
10psi
A charged low pressure refrigeration system can be efficiently leak-checked by
raising system pressure by heating with circulated hot water or heating blankets
The existence of air in a low pressure system causes
high head pressure.
Which safety precaution should be adhered to for low pressure systems?
All of the above.
Refrigerant-11 (R-11) at 14.7 psia, will boil at about
74.5 F
When there is excessive moisture collecting in the purge unit of a low pressure refrigeration system, this indicates that
the condenser or chiller barrel tubes are leaking.
ASHRAE Standard 15-1994 requires equipment room refrigerant sensors for what safety group classification?
All safety groups
When recharging a refrigeration system with R-11, what vapor pressure is necessary in the shells before charging with liquid?
16.9 inch Hg vacuum
After reaching the required recovery vacuum on a chiller, you should
wait for at least a few minutes to see if the system pressure rises, indicating there is still refrigerant in liquid form or in the oil.
A hydrostatic tube test kit is used to
Determine if the tubes leak
When charging a chiller, refrigerant vapor is introduced into the system before charging with liquid refrigerant. This is because
liquid charged into a deep vacuum will cause the refrigerant to boil and may lower temperatures enough to freeze the water in the tubes.
When evacuating a system, the use of too large a vacuum pump can cause
trapped water to freeze.
On a low pressure chiller with an open-type compressor, the _________ is/are very susceptible to leaks.
Shaft seal
What steps may be taken to prevent air accumulation into an idle low-pressure refrigeration system?
System pressure should be maintained slightly above atmospheric pressure.
Commercial and industrial process refrigeration systems must be repaired when the leak rate exceeds ______ percent of the charge per year.
30%
When recovering vapor from a low pressure refrigeration system,
the system water pumps, the recovery compressor, and the recovery condenser water should all be on.
Where does refrigerant go after it leaves the purge unit of a low pressure centrifugal system?
The evaporator
The purge unit takes its suction from the
Top of the condenser
Which of the following repairs would ALWAYS be considered a “major” repair unde EPA’s regulations?
Replacement of an evaporator coil.
Charging liquid refrigerant into a refrigeration system when it is under a 29-inch Hg vacuum can cause the
system water to freeze.
Charging liquid refrigerant into a refrigeration system when it is under a 29-inch Hg vacuum can cause the
system water to freeze.
According to the EPA there is approximately ________ of refrigerant vapor left in an average 350 ton R-11 chiller at 0 psig pressure once all the R-11 liquid has been removed.
100 lbs
An oil sample should be taken when
there has been a compressor burnout.
Both CFC-11 and HCFC-123 chillers require purge units because
the system operates below atmospheric pressure.
Under EPA regulations, _________ is used to pressurize a low-pressure chiller for the purpose of opening the system for a non-major repair.
warming the refrigerant
