REF UNITS 8 - 9 Flashcards
(8.2) How do you check for a leak in an evaporator coil?
pressurize system with nitrogen (equalize high and low sides)
position leak detector probe at drain trap
2 positive tests confirm a leak
use spray foam to locate exact leak
(8.2) How do you check for a leak in a condenser coil?
pressurize system with nitrogen
cover unit with tarp
monitor for 10 minutes
(8.3) How do you check for temperature dependent leaks?
partially block condenser’s air intake (this raises system temperature)
(You can pressurize system with warm water)
(8.3) How do you check for combination-dependent leaks?
check for pressure, then vibration, then heat.
(8.3) How do you check for cumulative microleaks?
use a helium mass spectrometer
(8.4) How do you perform a standing pressure test?
pressurize
allow rest for 10 minutes
mark pressures on manifold
come back like the next day or an hour or something, depending on the size of the system.
(8.4) What element do halide leak detectors respond to?
chlorine
(8.7) define degassing
removing air and other non-condensable gasses from a system using a vacuum pump.
(8.7) define dehydration
removing moisture from a sealed system.
(8.7) define evacuation
the removal of any gases not characteristic to a system using a vacuum pump.
(8.7) how many microns are in 1 inch of mercury?
25,400 microns
(8.7) What is the range of a “deep vacuum”?
250 to 500 microns
(8.7) How do you perform a triple evacuation?
- pull vacuum of 1500 microns, then add a bit of nitrogen.
- repeat.
- pull to a deep vacuum, let sit for 10 to 15 minutes.
(9.2) What is the chemical composition of ozone?
O3
(9.2) Where is good ozone located?
the stratosphere (7 to 30 miles above the earth)
(9.2) What type of radiation does the sun protect us from?
ultra-violet radiation (UV-B)
(9.2) Where is bad ozone located?
the troposphere (ground to 7 miles above the earth)
(9.2) What element in refrigerants are ozone depleting?
chlorine
(9.2) What is tropospheric ozone also known as?
smog
(9.2) How many ozone molecules can 1 chlorine atom destroy?
up to 100,000
(9.3) Define GWP
(global warming potential) the scale that measures the global warming impact of a substance’s emissions.
(9.3) How is GWP measured?
as a ratio compared to the GWP of carbon dioxide
(9.3) What gas is the #1 contributor to global warming?
CO2
(9.3) Define TEWI
(total equivalent warming impact) the scale that measures the total impact of refrigerants on global warming.
(9.4) Why do CFC’s have the highest ODP?
because their molecules are not destroyed before reaching the stratosphere.
(9.5) Why is July 1st of 1992 an important date?
it became illegal to intentionally vent CFC and HCFC refrigerants.
(9.5) When were CFC’s phased out?
by the end of 1995.
(9.5) What is the GWP and ODP of CFC’s?
high GWP, high ODP.
(?) What is mass equal to?
volume X density
(9.5) What are some examples of CFC refrigerants?
any of the r-10s (like R-11, R-12).
(9.6) What is the GWP and ODP of HCFC refrigerants?
medium GWP, medium ODP
(9.6) When are HCFC’s scheduled to be phased out?
by 2030
(9.6) what was the Montreal protocol?
An agreement signed in 1987 by the United States and other countries to control the release of ozone-depleting substances. specifically banning R-22.
(9.something) How is ODP scaled?
from 0 to 1
(9.7) What is the GWP and ODP of HFC refrigerants?
medium GWP, no ODP
(9.7) Why is November 15 1995 an important date?
it became illegal to intentionally vent HFC refrigerants.
(9.7) What are some examples of HFC refrigerants?
R-134A, R-410A
(9.8) What refrigerants are known as the 4th generation of refrigerants and why?
HFOs, and because they are pretty cheap and not harmful to the environment.
(9.8) What is an example of an HFO?
HFO-1234yf
(9.8) What oils work well with HFO’s?
POE oil
(9.8) What is the GWP and ODP of HFO refrigerants?
low GWP, no ODP
(9.8) How flammable are HFOs?
slightly
(9.9) How flammable are HC refrigerants?
very flammable
(9.9) what are HC refrigerants also known as?
natural refrigerants
(9.9) What areas are there warnings to technicians of an HC unit?
compressor or condenser, evaporator, exposed piping, exterior.
(9.9) Define terminal venting
when one or more terminal pins blows out of its terminal, allowing a pressurized refrigerant and oil spray to escape into the atmosphere.
(9.9) Define LEL
(lower exposure limit) the lowest concentration of the gas in air capable of producing a flash or fire in the presence of an ignition
(9.9) Define UEL
(upper exposure limit) the highest concentration of a gas in air capable of producing a flash or fire in the presence of an ignition source
(9.10) How are refrigerants numbered?
- # of fluorine atoms
- # of hydrogen atoms + 1
- # of carbon atoms -1
(9.11) which refrigerant is listed first when displaying blend ratio?
the refrigerant with the lowest boiling point.
(9.11) What is the max number of refrigerants in a blend?
5
(9.11) Define azeotropic blend
works as a single refrigerant, no fractionation.
(9.11) Define near-azeotropic blend
a blend that can fractionate.
(9.11) Define zeotropic blend
a refrigerant blend that has a large temperature glide.
(9.13) What are the 3 most used synthetic oils in the industry?
alkylbenzenes, glycols, esters
(9.13) What refrigerants tend to work well with alkylbenzene oils?
HCFCs
(9.13) What refrigerants tend to work well with ester-based oils?
HFCs
(9.14) What did the United States Clean Air Act Amendments of 1990 accomplish?
regulated the use and disposal of CFCs and HCFCs
(9.15) When did de minimus release come into effect?
July 1st, 1992
(9.15) Define recycling
separating oil from refrigerant using filter driers, and returning it back to the system.
(9.15) What machine do you need to recycle refrigerant?
a recycling machine
(9.15) Define reclamation
sending the refrigerant to a reprocessing site
(9.16) What is a type I certification tech able to work on?
small systems with 5 pounds or less of refrigerant in them.
(9.16) What is a type II certification tech able to work on?
high pressure appliances
(9.16) What is a type III certification tech able to work on?
low pressure appliances
(9.16) What is a type IV certification tech able to work on?
all appliances
(10.3) What is the liquid line service valve also known as?
the king valve
(10.7) When do you calculate charging a system with subcooling?
when the system uses a TXV
(10.7) When do you calculate charging a system with superheat?
when the system uses a fixed-bore metering device.
