01What are the different alternatives to CFC-12 (R-12)?

02What are the disadvantages of using HFCs?

03What care should be exercised while servicing HFCs appliances ?

04What are the advantages of using HCs?

05What are the major issues with regards to HCs?

06In what state must blends be removed from a cylinder and why?

07Does HC600a require a bigger or smaller compressor than CFC12?

08What is the most common HC blend used and why?

09Does HC blend require a bigger or smaller compressor than CFC12?

10What are the advantages of using HC blends?

11Which refrigerant appears to be most desirable from the point of View of both GWP and ODP? Why?

12Why is global warming harmful to human life?

13Which element in CFCs triggers the formation of ozone hole? How?

14How does the use of more energy efficient refrigerators help in reduced global warming?

15What are safety issues with HFCs?

16How should HFC cylinders be stored?

17What are the precautions to be taken in handling of POE oil?

18What are the steps to be followed in the servicing of HFC based appliances?

19Why the HFC refrigerants are to be recovered?

20What are the advantages of using Nitrogen for flushing and pressure testing?

21Which is the chemical to be used for cleaning in place of CTC?

22Part details for various cold chain equipment (Dansfoss Component)

23State the Refrigerant charge in following ILR/FREEZERS.

01	What are the different alternatives to CFC-12 (R-12)?
Ans	Alternative to CFC are HFCs  which contain Fluorine, Hydrogen and Carbon for example HFC134a, HFC32. HCs contain Hydrogen and Carbon such as HC290, HC600a.
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02	What are the disadvantages of using HFCs?
Ans	The disadvantages are that HFCs have relatively high GWP and are included in the basket of six gases under the Kyoto Protocol. The greatest disadvantage is that HFCs do not work with mineral oil; there are reliability/compatibility issues with HFCs and lubricating  oil. Therefore, HFCs require major system changes.
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03	What care should be exercised while servicing HFCs appliances ?
Ans	As HFC refrigerant can work only with POE oil we need to pay attention towards properties of POE oil.POE oils are very hygroscopic, and thus easily absorb moisture from the atmospheric air. The servicing procedures therefore need to be improved. To remove moisture, which is very likely to enter during servicing, we need to evacuate properly using a good two stage vacuum pump.The system should not be left open for a long time.
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04	What are the advantages of using HCs?
Ans	HCs are ideal with zero ODP and negligible GWP. It is the safest refrigerant from the environmental point of view. They are miscible   with mineral oil and can be used in existing or new systems, with few changes.The system capacities of HCs(HC blend) are similar to those of CFCs. But, the liquid density of HCs is much lower as compared to CFCs.  Therefore, the charge of HCs required by weight is low as compared to the CFC charge.
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05	What are the major issues with regards to HCs?
Ans	HCs are flammable which puts limit on its use.Due to the flammability of HCs, the electrical components attached in the close vicinity of the system must be non-sparking
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06	In what state must blends be removed from a cylinder and why?
Ans	HC blends are zoetrope in nature, i.e., their compositions change during the phase change like evaporation and condensation. As a result, a zeotropic blend does not behave like a single fluid. A blend should always be removed from the cylinder in liquid form so that its composition will not change while transferring.
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07	Does HC600a require a bigger or smaller compressor than CFC12?
Ans	HC600a require a bigger compressor than CFC12 as HC600a requires almost double the compressor displacement as that of CFC12.
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08	What is the most common HC blend used and why?
Ans	Various blends of HC290 and HC600a are being used as alternative to CFC12 and HFC134a. The most common composition of the blend is about 50/50% mixture of propane and sobutane by weight, e.g.Care-30 and Hychill. HC blends are also fully miscible with mineral oils (MOs) and compatible with the materials used in CFC12 compressors.
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09	Does HC blend require a bigger or smaller compressor than CFC12?
Ans	No. The HC blend produces a similar cooling capacity close to CFC12 with a same size compressor.
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10	What are the advantages of using HC blends?
Ans	The HC blend produces a similar cooling capacity close to CFC12 with a same size compressor.HC blends are also fully miscible with the traditionally used mineral oil. The Coefficient of Performance (COP) of HC blend may be 5-10% higher than that of CFC12.The HC blend can be used to convert both CFC12 and HFC134a systems.It can also be used with both CFC12 and HFC134a compressors, under retrofit conditions, as well as in new systems.
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11	Which refrigerant appears to be most desirable from the point of View of both GWP and ODP? Why?
Ans	HC ,as it has got zero ODP & negligible GWP.
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12	Why is global warming harmful to human life?
Ans	In the last hundred years, the mean global temperaturehas increased by 0.3 to 0.60C. Because of this, the sea water thermally expands and the icecaps melt, leading to rising sea levels. An increase in global sea level of 4 to 10 inches has been observed over the last 100 years. This also affects rainfall pattern on the earth, leads to climate changes and thereby alters the bio-diversity. It also has a negative effect on human  health, a evinced by increase in cases of Malaria, Dengue and Yellow Fever.
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13	Which element in CFCs triggers the formation of ozone hole? How?
Ans	Chlorine is the main element which plays major role in ozone depletion.When a CFC molecule reaches close to the ozone layer, it triggers a chain of reactions which initiate the ozone layer depletion. Firstly, on coming in contact with sun's UV rays, a CFC molecule decomposes and releases a chlorine radical. This chlorine radical reacts with a molecule of ozone, yielding an oxygen molecule and a chloro mono-oxide molecule. The chloro mono-oxide molecule thus formed is unstable and thus breaks and releases a free chlorine radical. This  chlorine radical starts another reaction with an ozone molecule, and once again releases yet another chlorine radical.  Thus, through this chain, the ozone layer gets continually depleted with consumption of CFCs.
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14	How does the use of more energy efficient refrigerators help in reduced global warming?
Ans	If the refrigerators are poorly insulated, they have a higher energy consumption. Use of energy efficient refrigerators results in low energy consumption.This implies less need to produce energy, the process of which essentially emits more and more of carbon dioxide, a source of global warming. Thus, by using energy efficient refrigerators, reduction in global warning can be achieved.
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15	What are safety issues with HFCs?
Ans	HFCs are heavier than air, they displace air and there is no smell HFCs. HFCs get collected in lower portions like at the bottom of the appliances (Chest Coolers), basement of the building trenches etc. HFCs do not support life,  one may suffocate upon breathing in an environment having high concentration of  HFCs.It is advised to work in well ventilated areas.
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16	How should HFC cylinders be stored?
Ans	HFC cylinders should be stored like other gases in dry, well ventilated areas and out of direct sunlight.It is advised not to ever refill disposable cylinders, they are not designed for refilling.
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17	What are the precautions to be taken in handling of POE oil?
Ans	POE oils are used with HFCs. POE oils cause skin problems. It is advised to wear gloves when handling oil/ components. One must take special precautions in handling burnt-out systems,  as burn-out of compressors results in formation of  undesirable gases.
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18	What are the steps to be followed in the servicing of HFC based appliances?
Ans	Recover of HFC refrigerant from the appliance using piercing tool and the recovery machine. Do the necessary repair work in the appliances as required. Ensure that the system should not be open for a longer period otherwise it may absorb moisture. Conduct Pressure testing and leak detection. Evacuation of the appliance Charging of appliance with measured quantity of HFC Sealing of process tube Finally checking for proper operation of the appliance.
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19	Why the HFC refrigerants are to be recovered?
Ans	HFCs (R-134a) are global warming gases. It is advised to recover the gas in a cylinder rather than venting it out in the atmosphere. This gas can be re used after  recycling.
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20	What are the advantages of using Nitrogen for flushing and pressure testing?
Ans	Atmospheric air contains moisture, which is detrimental to the system. Use of  air should be totally avoided specially with HCs & HFCs.Always use dry nitrogen at about 10 bar (150 psig). The Nitrogen cylinder must be fitted with two stages regulator.Dry Nitrogen al Nitrogen also act as a blotter,which absorb the moisture when introduced in the system & thus minimize the load vaccum pump.In other words it helps proper evacuation of system
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21	Which is the chemical to be used for cleaning in place of CTC?
Ans	Use trichloroethylene where chemical cleaning is required. CTC is also an Ozone depleting substance it is to be phased out soon.
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22	Part details for various cold chain equipment (Dansfoss Component)
Ans	A)  Electrolux TCW-1151  ILR/Freezer.       Compressor -   FR8.5 B       Starting device - relay - 117 U 6015       Thermostat -Refrigerator - 077B0030       Freezer       - 077B2008       Starting Capacitor     -      117U5021-80µf, 220V B)  Vestfrost MK-140/142 Icelined Refrigerator       Compressor     -           TFS4AT       Starting device -           Complete - 117U4109       Relay    -           117U2010       O.L.P   -           117U3150       Thermostat       -           077B0030 C)  Vestfrost  SB-140/142  Deep freezer            Compressor   -  TFS SAT       Starting device -           Complete - 117U 4103       Relay               -           117U2028       O.L.P.                          -           117U3197       Thermostat                   -           077B2007                                                 OR       Compressor                 -           FR6B       Relay                           -           103N011 (R.T.C  device)       Thermostat                   -           077B2007. D)  Vestfrost MK-300 Freezer       Compressor                 -           TFSSAT       Starting device - complete -     117U4103       Relay                            -           117U2028       O.L.P.                          -           117U3197       Thermostat                   -           077B0030                                               OR       Compressor              -       FR6B       Starting device          -       103N0011 (PTC dewice)       Thermostat               -        077B0030. E)  Vestfrost  -  SB-300 Freezer       Compressor                 -           FR75B       Relay                            -           103N0011 (PTC device)       Thermostat                   -           077B2007
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23	State the Refrigerant charge in following ILR/FREEZERS.
Ans	1.         MK140/142 :- R12      =          0.160 kg 2.         SB 140/142 :- R12       =          0.150 kg 3.         MK 300       :- R12      =          0.200 kg 4.         SB 300         :- R12      =          0.210 kg 5.         TCW1151     :- R12      =          0.190 kg
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