00:00:00.030 in this video we're going to be talking 00:00:02.51000:00:02.520 a little bit more about evaporators 00:00:04.30900:00:04.319 because this is such an important 00:00:05.99000:00:06.000 subject 00:00:07.15000:00:07.160 remember vaporators are one of the major 00:00:09.62000:00:09.630 components of your refrigeration system 00:00:11.87000:00:11.880 so it's really important we have an 00:00:13.73000:00:13.740 understanding of the temperatures the 00:00:15.23000:00:15.240 operation and everything having to do 00:00:17.26900:00:17.279 with evaporators so an evaporators 00:00:20.15000:00:20.160 function basically is to absorb heat 00:00:21.95000:00:21.960 from the space okay what we do is we put 00:00:25.09900:00:25.109 we pull warm air through an evaporator 00:00:27.65000:00:27.660 warm air enters the coil the aluminum 00:00:30.74000:00:30.750 fins are wrapped around tubes to 00:00:33.29000:00:33.300 increase the heat transfer area the 00:00:35.47900:00:35.489 refrigerant inside the tubing absorbs 00:00:37.76000:00:37.770 the heat and cool air leaves the coil 00:00:39.61900:00:39.629 because cool air is just a lack of heat 00:00:42.43000:00:42.440 so the evaporator temperature is the 00:00:46.10000:00:46.110 temperature the refrigerant that's 00:00:47.77900:00:47.789 inside the refrigeration tubing inside 00:00:50.93000:00:50.940 the tubing how do you measure evaporator 00:00:53.75000:00:53.760 temperature determine the suction 00:00:55.93900:00:55.949 pressure refer to your pressure or 00:00:58.09900:00:58.109 temperature chart for that refrigerant 00:00:59.84000:00:59.850 choose the temperature of the 00:01:01.63900:01:01.649 refrigerant at that suction pressure 00:01:03.13000:01:03.140 okay so to met it's basic conversion 00:01:06.98000:01:06.990 you're changing your suction pressure 00:01:09.14000:01:09.150 which is your low side pressure to 00:01:12.25000:01:12.260 temperature using the appropriate chart 00:01:15.17000:01:15.180 now temperature difference versus delta 00:01:18.05000:01:18.060 T is pretty important in an evaporator 00:01:20.35900:01:20.369 the temperature difference is the air 00:01:23.35900:01:23.369 temperature entering the evaporator 00:01:25.64000:01:25.650 minus the refrigerant temperature inside 00:01:28.76000:01:28.770 the evaporator okay so temperature 00:01:31.70000:01:31.710 difference is a difference between the 00:01:34.85000:01:34.860 air temperature coming into the 00:01:37.01000:01:37.020 evaporator and the refrigerant 00:01:39.53000:01:39.540 temperature inside the evaporator delta 00:01:43.34000:01:43.350 T is the difference between the air 00:01:46.81900:01:46.829 entering the evaporator and the air 00:01:49.01000:01:49.020 leaving the evaporator don't get the two 00:01:51.49900:01:51.509 confused because technical support and 00:01:53.74900:01:53.759 technical documents will sometimes list 00:01:56.71900:01:56.729 both of these ok delta T is most often 00:02:00.23000:02:00.240 used in air conditioning temperature 00:02:02.74900:02:02.759 difference is most used in commercial 00:02:05.14900:02:05.159 refrigeration so we have a typical AC 00:02:08.71000:02:08.720 evaporator okay the air coming into the 00:02:12.55900:02:12.569 evaporator 00:02:13.85000:02:13.860 is 75 degrees my refrigerant or my 00:02:18.26000:02:18.270 boiling point from my pressures is 40 00:02:21.77000:02:21.780 degrees my temperature difference is 35 00:02:24.83000:02:24.840 degrees the air leaving has been cooled 00:02:28.79000:02:28.800 from 75 degrees to 55 degrees my delta T 00:02:34.13000:02:34.140 is 20 degrees so as you can see if you 00:02:37.64000:02:37.650 get these two confused these the 00:02:39.94900:02:39.959 temperature difference versus the delta 00:02:41.93000:02:41.940 T and if the technical documentation is 00:02:44.78000:02:44.790 telling you one thing and you have 00:02:46.22000:02:46.230 another thing you could end up in some 00:02:48.59000:02:48.600 real issues our humidity is 50% 00:02:52.61000:02:52.620 okay so again one of the things our 00:02:54.89000:02:54.900 evaporator has to do is to remove 00:02:57.65000:02:57.660 humidity so originally evaporators were 00:03:03.08000:03:03.090 just pipes with fins gravity coils or 00:03:05.54000:03:05.550 convection coils fans increased this 00:03:08.00000:03:08.010 heat transfer okay he dubs absorbed 00:03:10.19000:03:10.200 during the boiling process of 00:03:11.75000:03:11.760 refrigerant and that's latent heat then 00:03:14.47900:03:14.489 we increased surface area by in capacity 00:03:17.87000:03:17.880 by folding the coils over using multi 00:03:20.81000:03:20.820 circuit coils and we made the coils 00:03:23.44900:03:23.459 longer and had more surface area without 00:03:25.75900:03:25.769 increasing pressure drop okay now this 00:03:31.61000:03:31.620 is a gravity or convection coil you have 00:03:34.49000:03:34.500 tubes with fins you have drain pans 00:03:36.47000:03:36.480 under them why do we need the drain pans 00:03:38.84000:03:38.850 because the air will actually the 00:03:41.75000:03:41.760 humidity will start accumulating on the 00:03:44.09000:03:44.100 tubes and have to drip someplace okay 00:03:47.15000:03:47.160 and those drain pans have to be kept 00:03:49.46000:03:49.470 clean and they have to take the moisture 00:03:51.53000:03:51.540 out or there's going to be a puddle on 00:03:53.12000:03:53.130 the floor sometimes ice okay the fan 00:03:56.99000:03:57.000 coil unit okay fans he increased the 00:04:01.07000:04:01.080 heat transfer and this is the most 00:04:04.67000:04:04.680 common evaporator construction copper 00:04:07.28000:04:07.290 tubing with aluminum fins okay it's a 00:04:11.18000:04:11.190 block almost and the fan blows air 00:04:13.55000:04:13.560 across of it and you have your where the 00:04:16.13000:04:16.140 black caps are here on the tubing that's 00:04:19.43000:04:19.440 where the connections are made in for my 00:04:21.71000:04:21.720 suction line and my liquid line it's a 00:04:26.71900:04:26.729 single circuit 00:04:27.71000:04:27.720 the operator okay this is a Multi 00:04:30.71000:04:30.720 circuit evaporator notice the 00:04:32.42000:04:32.430 distributor here okay you come in out of 00:04:35.48000:04:35.490 your metering device the refrigerant 00:04:38.39000:04:38.400 vapor or the flash gas gets distributed 00:04:41.24000:04:41.250 it out and then you also have then you 00:04:46.22000:04:46.230 also have a manifold that takes it back 00:04:49.46000:04:49.470 to the suction line of the compressor 00:04:52.03000:04:52.040 okay your TV is their distributor tube 00:04:55.01000:04:55.020 to each circuit and circulator outlets 00:04:57.08000:04:57.090 enter a suction header that come back to 00:04:59.48000:04:59.490 the suction line they a stamped or plate 00:05:02.84000:05:02.850 type evaporator again using distributor 00:05:05.15000:05:05.160 notice it's plates it's not it's not 00:05:08.36000:05:08.370 fins and tubes it's plates and it's 00:05:10.91000:05:10.920 stamped and it the two sections are put 00:05:13.25000:05:13.260 together okay they're used in ice 00:05:16.04000:05:16.050 machines into cool liquids okay to 00:05:21.38000:05:21.390 understand that evaporator temperature 00:05:23.75000:05:23.760 difference we have to know the type of 00:05:25.85000:05:25.860 refrigeration so air conditioning space 00:05:29.09000:05:29.100 temperature 75 degrees evaporator 00:05:32.36000:05:32.370 temperatures forty degrees so my 00:05:34.25000:05:34.260 evaporator temperature is 35 degrees 00:05:38.26000:05:38.270 okay reach-in refrigeration we have a 00:05:41.42000:05:41.430 space temperature forty evaporator 00:05:44.06000:05:44.070 temperature of twenty evaporator 00:05:46.96900:05:46.979 temperature difference of twenty degrees 00:05:50.35000:05:50.360 reach-in freezer zero Degree space 00:05:53.54000:05:53.550 temperature evaporator temperatures 00:05:56.51000:05:56.520 negative twenty degrees so my evaporator 00:05:59.57000:05:59.580 temperatures 20 degrees this is because 00:06:01.82000:06:01.830 the space temperature is what's being 00:06:03.92000:06:03.930 pulled through the evaporator okay it's 00:06:06.44000:06:06.450 the air entering the evaporator versus 00:06:09.23000:06:09.240 the evaporator temperature okay walk-in 00:06:13.04000:06:13.050 refrigerator 35 degrees evaporator 00:06:16.15900:06:16.169 temperature 25 degrees evaporator 00:06:19.15900:06:19.169 temperature difference 10 degrees 00:06:22.21000:06:22.220 walk-in freezer space temperature 00:06:24.74000:06:24.750 negative 10 evaporator temperature 00:06:27.44000:06:27.450 negative 20 evaporator temperature 10 00:06:30.40900:06:30.419 degrees so this is an air handler with 00:06:34.76000:06:34.770 an evaporator coil like you would find 00:06:36.46900:06:36.479 in the in the in an air conditioning 00:06:39.20000:06:39.210 system not in refrigeration 00:06:41.60000:06:41.610 okay we have our fan we have our coil we 00:06:44.83900:06:44.849 have our return air coming in of 75 00:06:47.80900:06:47.819 degrees we have a 40 degree refrigerant 00:06:50.71900:06:50.729 temperature so for air conditioning 00:06:53.08900:06:53.099 units my temperature difference is most 00:06:55.61000:06:55.620 often 35 degrees we don't want our coil 00:06:58.61000:06:58.620 under freezing reach in and a walk-in 00:07:01.99000:07:02.000 okay reaching evaporator temperature 00:07:05.42000:07:05.430 difference of 20 degrees walk-in 00:07:08.20900:07:08.219 evaporator temperature difference of 10 00:07:10.64000:07:10.650 degrees these are numbers that are the 00:07:12.40900:07:12.419 standards okay so you really should know 00:07:14.71900:07:14.729 these low velocity high humidity 00:07:17.65900:07:17.669 evaporator coil temperature different 00:07:20.39000:07:20.400 eight degrees so refrigerate evaporators 00:07:25.07000:07:25.080 dehumidified they remove moisture from 00:07:27.64900:07:27.659 the refrigerated space so what's 00:07:30.20000:07:30.210 affecting our humidity evaporator 00:07:32.54000:07:32.550 temperature difference the lower the 00:07:34.30900:07:34.319 temperature difference the less moisture 00:07:36.86000:07:36.870 removed so humidity is a measurement of 00:07:39.83000:07:39.840 the amount of moisture in the air based 00:07:41.71900:07:41.729 on its temperature okay 00:07:44.77900:07:44.789 so different types of systems need to 00:07:47.80900:07:47.819 have different types of space humidity 00:07:50.58900:07:50.599 okay and that's what this chart is going 00:07:52.87900:07:52.889 to show you so air conditioning 00:07:55.48000:07:55.490 okay coil temperature difference 35 00:07:58.39900:07:58.409 degrees humidity 50% reach-in coil 00:08:03.05000:08:03.060 temperature 20 degrees humidity 65% 00:08:06.86000:08:06.870 walkin coil temperature 10 degrees 00:08:09.86000:08:09.870 humidity 85% okay so for medium 00:08:15.80000:08:15.810 temperature walk-in refrigerator we have 00:08:19.18900:08:19.199 a relatively high humidity of 85 percent 00:08:23.98000:08:23.990 okay for medium temp reach-in 00:08:26.80900:08:26.819 refrigerator I have a lower humidity 00:08:30.12900:08:30.139 okay of 65 percent for air conditioning 00:08:35.54000:08:35.550 which is considered a high temp air kiss 00:08:38.07900:08:38.089 refrigeration system we have a 50 00:08:41.12000:08:41.130 percent humidity notice the difference 00:08:43.75900:08:43.769 based on the temperature difference okay 00:08:47.48000:08:47.490 so the top left has a temperature 00:08:50.21000:08:50.220 difference of 10 degrees I have a pretty 00:08:52.18900:08:52.199 high humidity the next one the medium 00:08:55.55000:08:55.560 Chinn refrigerator has a temperature 00:08:57.17000:08:57.180 difference of 20 degrees slightly lower 00:08:59.33000:08:59.340 humidity coming out of that coil the 00:09:02.12000:09:02.130 bottom one which is air conditioning has 00:09:04.22000:09:04.230 a temperature difference of 35 degrees 00:09:06.26000:09:06.270 we have a very high hue or lower 00:09:09.23000:09:09.240 humidity of 50% why do we want a low 00:09:12.38000:09:12.390 humidity of 50% because mold and mildew 00:09:15.82900:09:15.839 will start growing on sheetrock and 00:09:18.32000:09:18.330 everything else if I had maintained an 00:09:20.12000:09:20.130 85 percent humidity too much heat load 00:09:24.86000:09:24.870 boils the refrigerant away very quickly 00:09:27.25000:09:27.260 refrigerant molecules move faster okay 00:09:32.32900:09:32.339 and it results in higher pressure and 00:09:33.95000:09:33.960 temperature - lil heat load decreases 00:09:36.47000:09:36.480 refrigerant boiling refrigerant 00:09:38.48000:09:38.490 molecules move slower pressure and 00:09:40.55000:09:40.560 temperatures drop okay so superheat as I 00:09:44.54000:09:44.550 said is the difference between the 00:09:45.98000:09:45.990 suction line temperature and the 00:09:47.78000:09:47.790 evaporator superheat - high is starving 00:09:51.17000:09:51.180 an evaporator superheat to low is 00:09:54.59000:09:54.600 flooding an evaporator okay so we want 00:09:58.22000:09:58.230 to take our coil temperatures okay as 00:10:02.36000:10:02.370 close as we can get to that liquid line 00:10:05.48000:10:05.490 okay so again pressures of 49 is 25 00:10:09.29000:10:09.300 degrees 00:10:10.04000:10:10.050 okay liquid line temperature is 35 so 35 00:10:14.09000:10:14.100 minus 25 is 10 degrees superheat okay 00:10:21.26000:10:21.270 when space temperatures above normal 00:10:23.75000:10:23.760 there's a heavy load on the evaporator 00:10:25.31000:10:25.320 that's considered a hot pull down okay 00:10:28.72000:10:28.730 for a cur superheat calculations the 00:10:32.84000:10:32.850 space temperature must be within 5 00:10:35.39000:10:35.400 degrees of design conditions evaporator 00:10:41.30000:10:41.310 troubleshooting basically comes down to 00:10:43.19000:10:43.200 three main problems air flow refrigerant 00:10:46.01000:10:46.020 and load air flow dirty filter dirtier 00:10:48.89000:10:48.900 iced evaporator blower ductwork problems 00:10:51.26000:10:51.270 refrigerant metering device issues 00:10:53.44900:10:53.459 refrigerant charge load too high too low 00:10:59.01900:10:59.029 okay 00:11:00.23000:11:00.240 medium temperature refrigerators will 00:11:02.69000:11:02.700 frost if space temperatures between 36 00:11:05.51000:11:05.520 and 40 and evaporator temperatures are 00:11:07.88000:11:07.890 15 to 25 00:11:09.50000:11:09.510 oyel frosting is normal coil will 00:11:11.81000:11:11.820 defrost during its off cycle because we 00:11:14.63000:11:14.640 still pull air across that coil and that 00:11:16.64000:11:16.650 air is above freezing medium temperature 00:11:19.58000:11:19.590 refrigerators used a thermostat off 00:11:21.62000:11:21.630 cycle to melt frost accumulation 00:11:23.80000:11:23.810 sometimes the time clock is needed to 00:11:26.39000:11:26.400 extend the length of the off cycle okay 00:11:30.23000:11:30.240 so basic wiring of a hundred fifteen 00:11:33.26000:11:33.270 volt evaporator and a walk-in 00:11:34.67000:11:34.680 refrigerator okay we use a pump down 00:11:37.40000:11:37.410 solenoid okay to shut off the flow of 00:11:41.03000:11:41.040 refrigerant to the evaporator okay we 00:11:44.30000:11:44.310 have our evaporator coil okay the common 00:11:48.71000:11:48.720 time clock is used for cycling outdoor 00:11:50.78000:11:50.790 lights heaters etc okay the clock is 00:11:53.69000:11:53.700 eight in our example has one set of 00:11:55.67000:11:55.680 normally closed contacts 00:11:57.14000:11:57.150 it is a refrigeration it cycles the 00:12:00.62000:12:00.630 refrigeration compressor for extended 00:12:02.51000:12:02.520 off cycle okay the time clocks are used 00:12:06.17000:12:06.180 in refrigeration for planned off cycle 00:12:08.66000:12:08.670 defrost it gives the evaporate or extra 00:12:11.00000:12:11.010 time to air defrost the clock shuts off 00:12:13.70000:12:13.710 the compressor while the evaporator fan 00:12:15.44000:12:15.450 continues to run okay fan switch wiring 00:12:21.59000:12:21.600 some customers want to shut off the fan 00:12:24.02000:12:24.030 switch may serve as a service disconnect 00:12:26.66000:12:26.670 fan switch must also turn off the 00:12:28.76000:12:28.770 refrigeration if not your evaporator 00:12:30.77000:12:30.780 freezes and floods the compressor okay 00:12:34.19000:12:34.200 this is just a wiring diagram of our fan 00:12:37.64000:12:37.650 switch wide spacing of fins slows frost 00:12:45.29000:12:45.300 build-up medium temperature evaporators 00:12:47.54000:12:47.550 have about ten fins per inch low 00:12:50.24000:12:50.250 temperature evaporator --zz have seven 00:12:52.46000:12:52.470 fins per inch or less so the lower to 00:12:54.62000:12:54.630 the temperature the wider the fin 00:12:56.30000:12:56.310 spacing okay and you can measure the 00:12:59.30000:12:59.310 evaporator fin spacing to make sure the 00:13:01.31000:13:01.320 correct evaporator is being used in the 00:13:04.16000:13:04.170 system so again we really have to 00:13:07.19000:13:07.200 understand what the evaporators are you 00:13:09.14000:13:09.150 have to know about superheat and you 00:13:10.94000:13:10.950 have to totally understand how the 00:13:13.25000:13:13.260 superheat works in a system and how you 00:13:15.80000:13:15.810 can use it to troubleshoot systems
Office location
Engineering company LOTUS®
Russia, Ekaterinburg, Lunacharskogo street, 240/12