R-134a is a code_____ refrigeration and R-123 is a code ____ refrigerant
when dismantling a centrifugal on site, the technician must
ensure that recovery is made
water should be circulated through the chiller during recovery because it will
prevent water freeze up
water tube leaks in a low pressure chiller are usually found with
a hydrostatic tube kit test
acording to _________ if the pressure in a system rises 1mm Hg to a level above 2.5 mm Hg during a standing vacuum test the system should be tested for leaks
ASHRAE guideline 3-1990
in order to raise the pressure in a chiller so that a minor repair can be made to the system it is best to warm the evaporator(chiller barrel) using
electric heating blanket and controlled hot water
the EPA defines _______ as maintenance service or repair that involves removal of compressor condenser evaporator or auxiliary heat exchanger as
True or False: there are no exceptions to the required evacuation levels established by the EPA
a halide torch should always be used in a well ventilated area because
A. open flames and refrigerants can create poisonous gases
B. refrigerants are heavier than air and displaces the technicians oxygen
C.the technician is in close proximity to the torch
D. all of the above
in refrigeration accidents where the technician dies the cause typically is?
for R-11 or R-123 systems refrigerant removal typically starts first with?
at all times a system should be protected by a
pressure limiting device
in an average 350 ton R-11 low pressure choler at 0 psig after all the liquid has been recovered roughly _________ pounds of refrigerant as vapor remains
when recovering R-11 or R-123 from a chiller what is the setting of the high pressure control on the recovery machine?
the recovery vessel receiving the recovered refrigerant from the recovery machine must have a pressure limiting device that is set for
an average low pressure chiller requires about 3 pounds of refrigerant per ton the large amount of liquid refrigerant involved is removed more quickly by?
a spécial liquide pump from the evaporator into the recovery vessel
all the liquid has been recovered what is the next step in the recovery process?
recover the remaining vapor refrigerant
appliances need not be evacuated to the EPA prescribed level when?
leaks in the appliance makes evacuation to the required level unattainable
increasing the temperature of the system oil to 130°F during recovery does what
maximizes the recovery of refrigerant from the oil
the RPM of a single stage centrifugal compressor is approximately
capacity control for a single stage centrifugal compressor is accomplished by?
the guide vanes
why do low pressure chillers need purge units?
the system operates below atmospheric pressure
what will the evaporator temperature of R-11 be at vapor pressure of 13.1 psig?
pressure relief valves should not be installed in what way
the oil pump for a centrifugal compressor
A. is started before the compressor to prefabricate the high speed shaft
B. us cinokete external assembly with its own motor,pump and heat control
C. is started when the compressor starts
D. A and B
the EPA defines a ________ appliance as equipment that uses a refrigerant with a boiling point above 10°C at atmospheric pressure this definition includes but is not limited to R-11
R-113 and R-123
the evacuation level required by EPA for a low pressure appliance using recovery equipment manufactured before november 15 1993 is?
the evacuation level required by the EPA for a low pressure appliance using recovery equipment after november 15 1993 is
25 mm Hg absolute
what does 25 mm Hg absolute equal?
29 Hg vacuum
high pressure chillers using refrigerants R-12, R-22 and R-134a are
recovery machines for large chillers usually have water cooled condensers where would you get this water from when using portable recovery units?
cooling tower water and condensate
True or False: with type III certification only you can also work on type I and type II systems
the most common refrigerant used by low pressure chillers has been CFC (R-11) the current replacement refrigerant for R-11 is a HCFC which is?
the pressure relief device for a low pressure chiller is
the rupture disk on a low pressure chiller is connected to the
the rupture disk is generally set for
when leak testing a low pressure chiller the maximum test pressure should be
a type II service technicians vacuum pump should be capable of pulling a vacuum of at least
under EPA regulations chillers used for comfort cooling with annual leak rate of ___% must be repaired as per the staute
under EPA regulations chillers used in commercial refrigeration and/or industrial process cooling with a leak rate of ___% must be repaired
almost all of the refrigerants in general use are rated under ASHRAE 34 standard as group A1 which means non toxic and non flammable but_______ is listed as group B1 which means that it is non flammable but is somewhat toxic
machine room safety standards have been established by
the generally accepted current replacement refrigerant for R-11 which is a CFC is
a low pressure chillier using R-11 as a refrigerant has been shut down and has an evaporator pressure of 18.2 Hg what is the corresponding temperature?
because a low pressure chiller operates in a low vacuum a constant problem is non condensible entering the system these are drawn in to the system through?
gaskets and fittings
an automatic purge unit is small condensing unit which
A. removes non condensibles(mostly air) from the system
B. takes its suction from the top of the condenser
C.returns refrigerant to the system and vents the air
D. all the above
all the above
because the air that is vented from a purge unit contains a small amount of refrigerant this loss can be minimized by
a leak and repair chiller
what is considered a major repair under EPA regulations
replacement of an evaporator coil
under EPA regulations what method can be used for the purpose of opening a system for non major repairs
controlled hot water
refrigerant is added to a centrifugal machine through the