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How to Repair a Frozen Air Conditioner _ Ask This Old House

WEBVTT
Kind: captions
Language: en

00:00:06.140
so Richard this is the air conditioning
00:00:08.450 00:00:08.460 unit all righty let's see what you got
00:00:10.490 00:00:10.500 gas fired furnace for heating right here
00:00:14.440 00:00:14.450 you've got the returned comes back from
00:00:17.450 00:00:17.460 the building right here comes up through
00:00:20.660 00:00:20.670 the furnace is a blower that's going to
00:00:22.250 00:00:22.260 push it through the first to be heated
00:00:23.720 00:00:23.730 but the air can also come across this
00:00:25.880 00:00:25.890 box right here for cooling there's a
00:00:28.429 00:00:28.439 cooling coil here the air goes up into
00:00:30.650 00:00:30.660 this box at the top called a plenum and
00:00:32.659 00:00:32.669 right here are the supply ducts that go
00:00:35.420 00:00:35.430 out to all the individual registers
00:00:36.889 00:00:36.899 that's how it's supposed to work what's
00:00:38.600 00:00:38.610 going on with yours well during the
00:00:40.760 00:00:40.770 summertime I turn it on and the system
00:00:42.740 00:00:42.750 runs for about an hour okay and then it
00:00:45.680 00:00:45.690 stops working so I come down here to
00:00:47.450 00:00:47.460 check it out yeah and I notice that this
00:00:49.310 00:00:49.320 is all frozen up okay that's actually
00:00:51.290 00:00:51.300 starting to form ice right now so that's
00:00:53.600 00:00:53.610 on the line sets that go to outside and
00:00:55.400 00:00:55.410 I imagine on the coil - all right so
00:00:57.830 00:00:57.840 what do you do anything I actually turn
00:00:59.450 00:00:59.460 on the heat for about five minutes you
00:01:01.099 00:01:01.109 turn on the heat to get air-conditioner
00:01:02.569 00:01:02.579 what happens in well it melts the coil
00:01:04.759 00:01:04.769 inside of here but the problem with that
00:01:06.740 00:01:06.750 is like a water all over my basement
00:01:08.090 00:01:08.100 floor and when you get another hour
00:01:09.380 00:01:09.390 cooling and then you're freezing again
00:01:10.789 00:01:10.799 yep all right so any time I hear about
00:01:13.700 00:01:13.710 this condition a frozen coil first and
00:01:16.789 00:01:16.799 foremost I think about a lack of air
00:01:18.590 00:01:18.600 flow through the unit so here's a return
00:01:21.170 00:01:21.180 air and on anybody's furnace or AC unit
00:01:24.590 00:01:24.600 there's got to be some sort of filter
00:01:26.120 00:01:26.130 like this
00:01:26.690 00:01:26.700 so this is a return air filter and this
00:01:29.359 00:01:29.369 thing is relatively simple but it's got
00:01:31.160 00:01:31.170 to be clean now that doesn't perfectly
00:01:32.899 00:01:32.909 clean but it's not terrible you change
00:01:34.609 00:01:34.619 this all the time okay so if it's not
00:01:37.190 00:01:37.200 something simple like the return air
00:01:38.990 00:01:39.000 filter clog you got to look at some
00:01:41.120 00:01:41.130 other things and do a deeper evaluation
00:01:42.710 00:01:42.720 I want to check the ducts the size and
00:01:45.410 00:01:45.420 number of these ducts and also what you
00:01:47.359 00:01:47.369 have for equipment
00:02:06.330 00:02:06.340 all right let me show you what I found
00:02:08.520 00:02:08.530 wow you were not kidding about a frozen
00:02:10.499 00:02:10.509 coil this is just a big block of ice
00:02:12.480 00:02:12.490 this is called an evaporator coil they
00:02:14.910 00:02:14.920 also called it an a core cause of its
00:02:16.440 00:02:16.450 shape so air is blown across and through
00:02:20.490 00:02:20.500 this coil of this you can see the coils
00:02:22.230 00:02:22.240 right here there's also fins in here the
00:02:24.750 00:02:24.760 air blows across the coils are filled
00:02:26.910 00:02:26.920 with refrigerant so now when the warm
00:02:28.949 00:02:28.959 air goes across any heat that's in the
00:02:31.229 00:02:31.239 air gets absorbed in the refrigerant
00:02:32.699 00:02:32.709 that's inside of these coils right here
00:02:34.800 00:02:34.810 and it gets transferred through this
00:02:37.530 00:02:37.540 line right here to outside it goes
00:02:40.199 00:02:40.209 through the compressor outside and
00:02:41.699 00:02:41.709 through the outdoor condenser and now it
00:02:43.800 00:02:43.810 comes back really cold right here in
00:02:45.690 00:02:45.700 your case it's way too cold and now it's
00:02:47.910 00:02:47.920 freezing this whole coil once this thing
00:02:50.370 00:02:50.380 freezes no longer can that air even get
00:02:52.770 00:02:52.780 through those fins
00:02:53.940 00:02:53.950 exactly what happened to you will happen
00:02:55.680 00:02:55.690 so what would cause this well I think I
00:02:57.750 00:02:57.760 know what the answer is but let's check
00:02:58.890 00:02:58.900 one more thing outside so the other part
00:03:02.640 00:03:02.650 of your air conditioning system is out
00:03:03.990 00:03:04.000 here the condenser now you remember
00:03:05.940 00:03:05.950 there was those refrigerant line since
00:03:07.259 00:03:07.269 we capture the heat bring it out to here
00:03:09.900 00:03:09.910 and then with this fan we dump the heat
00:03:12.690 00:03:12.700 to outside now we always measure air
00:03:15.180 00:03:15.190 conditioning equipment terms of tunz
00:03:16.830 00:03:16.840 tunz that sounds heavy well it's not
00:03:19.229 00:03:19.239 actually a unit of weight it's that unit
00:03:21.479 00:03:21.489 of energy now it goes back a long time
00:03:23.400 00:03:23.410 there was a time in this country that
00:03:25.740 00:03:25.750 the way we conditioned a building or
00:03:27.539 00:03:27.549 stored food safely was with ice every
00:03:31.680 00:03:31.690 local town would had an ice house that
00:03:33.300 00:03:33.310 stored ice all through the year and what
00:03:35.640 00:03:35.650 it was was a measure of how much cooling
00:03:37.410 00:03:37.420 power could you get out of what 2,000
00:03:40.020 00:03:40.030 pounds a ton of ice now the modern
00:03:42.300 00:03:42.310 refrigeration industry borrowed that
00:03:44.130 00:03:44.140 term and nowadays we think in terms of a
00:03:46.979 00:03:46.989 12,000 BTUs is a ton of cooling all
00:03:50.640 00:03:50.650 right so let's see what you got here you
00:03:52.380 00:03:52.390 have a 4 ton system 4 tons is that a lot
00:03:55.470 00:03:55.480 well the amount of cooling power you
00:03:57.090 00:03:57.100 need is a function of the load of the
00:03:58.979 00:03:58.989 building and there's some variables how
00:04:00.930 00:04:00.940 much insulation is inside the walls
00:04:02.729 00:04:02.739 what type of windows are the storm
00:04:04.530 00:04:04.540 windows how big is the building and
00:04:06.690 00:04:06.700 where's the building how hot does it get
00:04:08.550 00:04:08.560 on the hottest day of the year I will
00:04:10.110 00:04:10.120 tell you a rule of thumb for me around
00:04:11.280 00:04:11.290 here with a building like this I would
00:04:13.620 00:04:13.630 expect to see a ton of cooling needed
00:04:16.020 00:04:16.030 for every 500 to 600 square feet how big
00:04:19.259 00:04:19.269 is this house
00:04:20.039 00:04:20.049 mine's only 1300 so 1300 there's a
00:04:22.260 00:04:22.270 chance we needed only like a two and a
00:04:23.909 00:04:23.919 half ton and this is a four now you
00:04:25.649 00:04:25.659 ordered the system urgency right yeah
00:04:27.330 00:04:27.340 the guy that put it in said it would be
00:04:28.860 00:04:28.870 plenty big plenty big we hear this all
00:04:30.719 00:04:30.729 the time over sizing is one of the
00:04:32.700 00:04:32.710 biggest issues in air conditioning
00:04:34.230 00:04:34.240 because if you're too big it just
00:04:35.969 00:04:35.979 doesn't work it'll freeze up like yours
00:04:37.439 00:04:37.449 did we want to make sure the size of
00:04:39.600 00:04:39.610 this unit is just right for the hottest
00:04:41.850 00:04:41.860 data and no more in this case we're way
00:04:44.999 00:04:45.009 too big well then what should we do well
00:04:47.899 00:04:47.909 we could put an addition on about 59
00:04:50.339 00:04:50.349 square foot addition on the back think
00:04:51.779 00:04:51.789 the whites would like that we got to
00:04:53.700 00:04:53.710 think what we can do today and I think
00:04:55.260 00:04:55.270 today what we're going to do is make
00:04:56.580 00:04:56.590 this equipment go away put the right
00:04:58.529 00:04:58.539 size stuff in that's a pretty big job
00:05:03.260 00:05:03.270 when you're working with air
00:05:04.800 00:05:04.810 conditioning you have to deal with
00:05:06.029 00:05:06.039 refrigerant the refrigerant is sometimes
00:05:07.950 00:05:07.960 a liquid sometimes it's a gas what you
00:05:10.110 00:05:10.120 never want to do though is to release it
00:05:11.580 00:05:11.590 to atmosphere so you always have to be a
00:05:13.529 00:05:13.539 licensed refrigeration technician to
00:05:15.450 00:05:15.460 work with it
00:05:16.110 00:05:16.120 that's what Keith is hey Keith hey don't
00:05:17.850 00:05:17.860 rush thanks for helping us so what have
00:05:19.619 00:05:19.629 you done so far so far what we're doing
00:05:21.689 00:05:21.699 is we're covering all this refrigerant
00:05:23.159 00:05:23.169 out of this particular unit using a
00:05:25.920 00:05:25.930 recovery machine so sort of a giant
00:05:27.749 00:05:27.759 vacuum pump
00:05:28.589 00:05:28.599 exactly and then afterwards it gets
00:05:31.260 00:05:31.270 stored into this recovery cylinder how
00:05:33.659 00:05:33.669 long will it take to suck all the
00:05:35.370 00:05:35.380 refrigerant out of this condenser into
00:05:36.719 00:05:36.729 that canister out of this particular
00:05:38.100 00:05:38.110 unit twenty minutes to a half hour or
00:05:40.350 00:05:40.360 until both of these gauges are at zero
00:05:42.959 00:05:42.969 pressure gauges all right you ready to
00:05:44.309 00:05:44.319 go yes I am
00:05:52.379 00:05:52.389 with all the refrigerant gone we can now
00:05:54.940 00:05:54.950 remove the old unit Keith will cut the
00:05:57.340 00:05:57.350 copper line sets disconnect the
00:06:00.909 00:06:00.919 electrical and remove the old unit here
00:06:10.000 00:06:10.010 is our new three ton condenser good down
00:06:13.020 00:06:13.030 alright let's just slide this on all
00:06:18.879 00:06:18.889 right with that in place now we just
00:06:20.590 00:06:20.600 have to remake our connections all right
00:06:27.310 00:06:27.320 we got the connections made on your new
00:06:28.990 00:06:29.000 condenser outside now we have to think
00:06:30.550 00:06:30.560 about inside and we got to get rid of
00:06:32.080 00:06:32.090 this old coil and put a new one in and
00:06:34.450 00:06:34.460 the important thing is that this has to
00:06:35.860 00:06:35.870 be the same size tonnage as the outdoor
00:06:38.320 00:06:38.330 310 310
00:06:39.610 00:06:39.620 this is your new evaporator coil right
00:06:41.290 00:06:41.300 here and it's going to start by getting
00:06:43.390 00:06:43.400 the old lines cut away so we get rid of
00:06:46.690 00:06:46.700 the old coil good all right so now with
00:07:05.080 00:07:05.090 the lines cut we just got to do whatever
00:07:06.909 00:07:06.919 we got to do to get rid of this
00:07:09.010 00:07:09.020 connection right here all right good
00:07:25.150 00:07:25.160 once you come right to here let's see if
00:07:26.380 00:07:26.390 we can muscle this out of the way be
00:07:28.150 00:07:28.160 careful there sharp edges on this metal
00:07:30.010 00:07:30.020 okay
00:07:31.290 00:07:31.300 wait careful what didn't work with me
00:07:38.869 00:07:38.879 okay I got it
00:07:40.589 00:07:40.599 you stay clear it's sharp I'll drop it
00:07:42.629 00:07:42.639 right down high by four ton all right so
00:07:47.669 00:07:47.679 let's get this one into position all
00:07:50.129 00:07:50.139 right
00:07:50.309 00:07:50.319 also come here so now we're gonna
00:07:54.089 00:07:54.099 actually turn this thing whoops good
00:08:10.669 00:08:10.679 okay let me just check that all right
00:08:14.279 00:08:14.289 I'm gonna lift this up a little bit and
00:08:16.049 00:08:16.059 I just want to come just a little bit
00:08:18.589 00:08:18.599 push good there we go
00:08:22.879 00:08:22.889 that awesome all right now we just got
00:08:26.609 00:08:26.619 to reconnect the ductwork sharp edges
00:08:31.189 00:08:31.199 and we come
00:08:33.829 00:08:33.839 let me just pry this out a little tiny
00:08:36.179 00:08:36.189 bit now we just need to cut a nice
00:08:42.569 00:08:42.579 little piece of sheet metal to seal it
00:08:44.009 00:08:44.019 up tight you'll be good
00:08:54.090 00:08:54.100 keith is braising the copper connections
00:08:56.860 00:08:56.870 to the line sets brazing is a lot like
00:08:59.170 00:08:59.180 soldering but it can take the
00:09:00.430 00:09:00.440 extraordinary pressures that come with
00:09:02.050 00:09:02.060 refrigeration
00:09:07.980 00:09:07.990 attend we've been busy down here we've
00:09:10.480 00:09:10.490 got a new coil secured to the furnace
00:09:12.970 00:09:12.980 with sheet metal screws at the bottom
00:09:14.350 00:09:14.360 and at the top all the way around we've
00:09:17.259 00:09:17.269 sealed it really well with this foil
00:09:19.030 00:09:19.040 tape with the sealant on the back we
00:09:20.620 00:09:20.630 want to make sure there's no air that
00:09:21.940 00:09:21.950 leaks out into the room nice okay here's
00:09:25.090 00:09:25.100 the line sets the new lines that's
00:09:26.500 00:09:26.510 connected they've been braised and then
00:09:28.090 00:09:28.100 the suction line the line that gets
00:09:30.190 00:09:30.200 colder has actually been insulated so it
00:09:32.110 00:09:32.120 doesn't drip anything on the floor right
00:09:34.389 00:09:34.399 here you can see the PVC connection to
00:09:36.519 00:09:36.529 the condensate drain which is right down
00:09:38.259 00:09:38.269 at the bog anytime we air-conditioned
00:09:41.019 00:09:41.029 the air comes by that coil and we make
00:09:43.210 00:09:43.220 the air cold but one of the byproducts
00:09:45.220 00:09:45.230 is all the humidity has to have a place
00:09:47.680 00:09:47.690 to go and it turns into what they call
00:09:48.910 00:09:48.920 condensate okay it comes down through
00:09:50.800 00:09:50.810 here through a trap down into this
00:09:53.530 00:09:53.540 reservoir right here this little float
00:09:55.990 00:09:56.000 in there when the float the water level
00:09:57.819 00:09:57.829 rises the float comes on brings on a
00:10:00.220 00:10:00.230 pump and sends that water out to the
00:10:02.800 00:10:02.810 drain over there now it runs on 110
00:10:05.530 00:10:05.540 volts and Keith you working on that
00:10:07.060 00:10:07.070 right yeah everything's all tied in over
00:10:09.069 00:10:09.079 here good so how do we get the right
00:10:11.290 00:10:11.300 amount of refrigerant into this new
00:10:12.759 00:10:12.769 system well the new conductors that we
00:10:15.100 00:10:15.110 install now they all come pre charged up
00:10:17.259 00:10:17.269 the 25 feet of line set that's about
00:10:19.810 00:10:19.820 what we have so there's enough
00:10:20.829 00:10:20.839 refrigerant in to cover our system
00:10:22.449 00:10:22.459 perfectly Wow dad anymore that's exactly
00:10:24.430 00:10:24.440 00:10:24.610 00:10:24.620 what I had to do I had to evacuate the
00:10:26.889 00:10:26.899 lines then after they're evacuated all I
00:10:29.230 00:10:29.240 have to do is just open up the lines on
00:10:31.389 00:10:31.399 the condenser and it's pre charge right
00:10:33.160 00:10:33.170 so we're good to go
00:10:34.030 00:10:34.040 that's it all right ready Oh got up on
00:10:35.470 00:10:35.480 the switch here we go that's some good
00:10:39.189 00:10:39.199 sound in there it sounds good so let me
00:10:40.689 00:10:40.699 out

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