Coil no cold in middle

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  #1  
Old 07-23-09, 04:47 PM
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Coil no cold in middle

I had my 5 ton Carrier ciol replaced about a year and a half ago. The people doing the work totally destroyed my transition and supply plenum. I called them back and was told "all a/c systems leak like that". I asked them to leave as they were not going to repair this problem. I rebuilt the transition and supply plenum. I noticed that the coil was cold at the top and bottom but was air temp in the middle half. The metering bulb was attached to the suction line inside the case. Was told this needed to be outside the case. Moved it and the suction line stopped sweating. Coil still not cold in center. What is everyones opion. Do I need to have the ciol replaced or it it now undercharged. I need to have an a/c company but the coil is under the 5 year warranty by Aspen. Thanks for any replies.
 
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  #2  
Old 07-24-09, 12:10 AM
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Please don't shoot the messenger. Aspen- there's your problem. Next time use the Carrier coil, even though they aren't much better. The Carrier coils are bad about leaking but Aspen has never learned how to design a coil for proper air/refrigerant flow. It sounds like they put in a cased coil [coil and cabinet] which is why they messed the ductwork. And no, the ducting is not supposed to leak. It would have been much simpler if they had just replaced the leaking coil with another of the same.
 
  #3  
Old 07-24-09, 04:45 AM
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Coil

Thanks for the reply. My biggest problem right now is humidity. I do not have all the right equipment but the humidity gauge that read 50-55% humidity now reads 75-85%. I can not feel cool even at 72. If this does have a restriction in it I will check to see how much a Carrier or Trane coil is. They want about $900 to swap out the coil even thou the coil is a free replacement.
 
  #4  
Old 07-24-09, 06:46 AM
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that's a rip off

It's possible that one of the distrbutor tubes is restricted. Look at the small tubes that go from the TXV outlet to the coil. Are they all sweating?
 
  #5  
Old 07-24-09, 06:57 AM
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Coil

That is what I have been told by the a/c supply that I bought the Plenum and ducts from. I can only do the work to a point. I checked the small tubes from the valve located inside the case and only half are sweating. I was told that since the TVX valve is part of the coil that they will warranty it even if it is a restriction. The center that is not cold seems to be putting humidity back into the house. I thought $900 was a rip-off. I told the a/c company that all I needed was to have them pull down the system (EPA) and replace the coil. I would have the transition and supply plenum removed. I have held a Plumbing lic for years and would disconnect all drains. They would have a bare case and coil. My outside unit I was told can recover the freon. The first company did not even put a dryer / filter in the system when they replaced the coil. My outside unit is a 2001 Trane XB-1000.
 
  #6  
Old 07-24-09, 03:13 PM
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They can't just take the front cover off the case to replace the coil? Why does the ductwork have to come out?
 
  #7  
Old 07-24-09, 04:07 PM
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I was hoping that I could leave the case in place. I have an a/c company coming out on Monday that comes highly recomended. When we spoke today he told me it could be as simple as air or moisture at the valve given it took a total 1.5 hours for the first company to remove the old coil and install the new. His comment was that was not enough time to evacuate the system properly. I do know they did recover the freon to the condenser as I did not pay for freon. I hope this is the problem. If the coil came in the case do you need to exchange with the case? Thanks for your help.
 
  #8  
Old 07-24-09, 06:37 PM
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It would be senseless to have to exchange the case as well, but some of these companies have the stupidest policies, so I guess you would have to ask them.


Case in point- recently my sis had one those Swiffer vacs go South; it was just past the warranty. I called Proctor and Gamble to complain and they sent a coupon to get a new one for free. When I got the new one at Wal-mart, they made me pay the sales tax on it. I was like- it's not a sale, but it was pay the tax or forget the transaction. I'd never heard of anything so stupid.

Let me see if I have this straight. A moisture at the valve problem means the moisture is freezing at the valve and restricting flow. The refrigerant is apprx 45 degrees F at the valve. What cha think?
 
  #9  
Old 07-24-09, 07:14 PM
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Like I said daddyjohn, I can do work up to a point and then I count of folks like yourself for help. I read this forum almost daily just to understand things hoping they do not happen to me. The way he explained it to me was someting to the effect of non-compressable. I have no idea if this could cause the problem. It seems he is trying to cut the cost to me by ruling out all outer possabilities. I'm all for saving money if it fixes the Problem. Running a 5 ton unit for 22 out of 24 hours to maintain a 75 degree temp inside gets $$$$.
 
  #10  
Old 07-25-09, 03:00 AM
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He meant non-condensables , not non-compressables.

Non-condensables is a fancy way of saying the gasses that are in the air we breath. Air is 78% nitrogen, 21% oxygen and 1% so called rare gasses. Rare gasses include Argon, Neon, Helium, Methane, Xeon, Krypton, and some others that I don't remember. All these gasses can be compressed and condensed but not at the pressure levels that refrigeration systems operate at; hence the moniker non-condensables.

Air also contains water vapor [moisture]. When a system is running the moisture combines with the refrigerant to from acids. I'm sure you realize that's not a good thng.

So the purpose of the evacuation process is to remove the non-condensables and moisture. The vacuum pump simply pumps the non-condensables out but the moisture is another story. The deep vacuum converts any water that is in liquid form to vapor and then the pump can remove it. The deep vacuum is measured in microns which necessitates the use of a special guage for that purpose.

I agree with the gentleman you spoke with that they probably didn't do a good evacuation if they even used a vacuum pump at all. That said, a poor evacuation will not cause what you are describing. Aspen coils are crap to start with but it sounds to me like a distributor tube is blocked.

How many tubes come out of the exit of the TXV? How many are sweating and how many are not?
 
  #11  
Old 07-25-09, 05:58 AM
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Thanks for the explanation. I will be back in the attic this evening after it cools below 100. I believe when I checked the sensing bulb there were 6 or 8 tubes. I do know only 3 were sweating. This is what promted the move of the sensing bulb. I will check and report back.
 
  #12  
Old 07-25-09, 07:13 AM
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Moving the sensing bulb would not have any effect on that. Just curious- is the sensing bulb on a vertical or horizantal section of tube? If horizantal- attach it [2 clamps] at 10 o'clock or 2 o'clock. If vertical, orient the sensing bulb so that the little capillary tube comes out the top; in other words upwards, not downwards.

also- is the TXV body itself vertical or horizantal? Focus on the valves orientation and which tubes sweat and which ones don't with respect to the orientation. The device the tubes are brazed into is called the distributor. Also look to see if there is a 1/4' tube emanating from about the middle of the valve body and piped to the suction line. That 1/4" tube is called an external equalizer tube.
 
  #13  
Old 07-25-09, 08:04 AM
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The sensing bulb I moved it to horizontal. It was horizontal inside the case before. It is now at about the 3 o’clock position. I used the copper clamp that was on it. It is about the width of the bulb itself. After I secured it I taped good and used insulation that is about 1.5” thick on all sides to cover. What was strange was when I did move the bulb the suction line did not sweat for about 20 mins. Does it make any difference if the tube that goes to the valve from the sensing bulb on up top or on bottom? The TVX body is vertical with the small tubes come from the bottom. I will have to check on the equalizer tube this evening. I do not remember seeing it. The tubing for the sensing bulb was wrapped all in the tubing that came from the distributor. I was very careful not to kink or damager this tube. What might stop the suction line from sweating after I moved the bulb? Look forward to hearing.
 
  #14  
Old 07-25-09, 02:43 PM
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3 o'clock position for the sensing bulb is acceptable. The orientation of the capillary tube from the sensing bulb is only critical when the bulb is vertical.Ii'm not happy with the capillary tubing for the sensing bulb being intertwined with the distributor tubes. The sweating only stopped for 20 minutes and now has returned? If yes, don't get sidetracked.
 
  #15  
Old 07-25-09, 02:50 PM
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Yes the sweating only stopped for about 20 mins. It returned to sweating and the liquid line is warm to the touch. The only thing is it did take me a little bit to get the insulation around the sensing bulb. I will check the tubes from the distributor to the coil and see how many are warm and how many are sweating. thanks
 
  #16  
Old 07-26-09, 09:34 AM
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Hot Attic Today

Well I pulled the inspection plate and there are 6 tubes coming from the distribtor. 3 are sweatimg 3 are case temp. Suction line sweating, humidity in house going up. stiil have a 19 degree drop thru coil. Checked for leaks on return and supply ducts. Out of things I can do. Service persom that is friend of fried trying to come Monday pm. Any thing I should look for before. thanks
 
  #17  
Old 07-26-09, 09:36 AM
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I forgot to mention, the 3 that are sweating are very cold. You can see this as you look down the coil. It almost looks like frost.
 
  #18  
Old 07-26-09, 02:25 PM
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Not sure what you mean by case temp. The orientation of the tubes is probably the best orientation one could want. All the refrigerant flows straight down to the tubes, no stratification. Think about this- each distributor tube represents apprx 17% [1/6] of the refrigerant flow to the coil. The compressor has a fixed capacity, so if half of the tubes are partially or fully restricted, then the compressor capacity is much greater than the evaporator coil capacity which means the refrigerat operating temperature [in the evaporator coil that is] will be lower, hence the COLD, almost frosty tubes. Is the suction line cold or COLD?
 
  #19  
Old 07-26-09, 02:52 PM
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Just took temp readings:

Outside temp 105
air into compressor outside 104
air flow from fan at top of compressor 117
suction line at outside unit 75
liquid line at outside unit 99
air flow at return air plenum 77
air flow at supply plenum 68
looks as thou the coil operating at half capacity can not keep up with the 105 temp.
 
  #20  
Old 07-26-09, 03:33 PM
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doesn't compute. I would expect the suction line at the outside unit to be in the 40's if some of the distributor tubes were resticted. What is the suction line temp where it exits the evaporator coil? The house is 77 with 105 outside and a partially active evaporator? Not anywhere near what I would expect.
 
  #21  
Old 07-26-09, 03:49 PM
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suction line at coil 66.4
line is now not sweating at coil.
attic 122
could this be a low freon condition. Is it possable moving the bulb worked and now low freon due to working txv?
 
  #22  
Old 07-26-09, 06:46 PM
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I forgot to ask, what about the equalizer tube?
 
  #23  
Old 07-26-09, 06:51 PM
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the eq tube is hooked to the suction manafold. When I went up to take the temps at the coil I checked the tubes that hook into the suction manafold. Only two were cold. The other 4 were the temp of the air flow in the case. When I say case it is the case in which the coil sets. This is a 5 ton slab ciol we are dealing with. It is in the attic in the horz position. thks
 
  #24  
Old 07-26-09, 07:11 PM
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yes, it very well could be a refrigerant shortage or the TXV needs adjusting. Usually, TXV's work fine out of the box without the need for adjusting but who knows what "bozos r us" did? The next step is to get a full st of both refrigerant sdie and air side readings.
 
  #25  
Old 07-26-09, 07:28 PM
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I totally agree with the Bozos r us comment. This experience has been very educational to me. It has taught me how the a/c system really works. Daddyjohn you have made this as enlighting as if you were here. Not just you turn it on and cold air blows. As far as the charge I will know tomorrow as this “friend of a friend” that owns an a/c company is coming by to find out what is going on. I will be here this time to see what he does. I was not here when they did the coil and am paying for it now. I will report back as possibly others with the same or like problem can save some hot days. I owned a fire protection company and all was self-taught. This has almost made me want to learn more and go for my a/c license. Nothing like starting a new career at 58 years old.
 
  #26  
Old 07-26-09, 07:32 PM
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One other thing is there anything I can see that I can post by looking over his shoulder? When he gets here he will think he has two shadows. I will not get in his way, Just learn.
 
  #27  
Old 07-27-09, 04:45 AM
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I got to wondering about something. The TXV body, is it brazed in or is it a threaded type body? Reason I ask is Aspen coils [as well as other brands] can be had with a flowrator orifice or with a TXV. The coils can be converted from flowrator to TXV in the field. One simply takes the flowrator apart, REMOVE THE ORIFICE, and thread on the TXV. I wonder if bozos r us installed the TXV and didn't remove the orifice. The other thing is the weather. is 100+ a normal Summer in your area?

It's imperative that the guy you have coming take superheat and subcooling readings on the system as well as try to get a ballpark airflow.


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  #28  
Old 07-27-09, 05:03 AM
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The TXV is what looks to be threaded in. Once the system is down it has a compression type fitting on the inlet side and screws onto the distr. The eq tube is also threaded into the suction manifold. When I looked at the Aspen mtg site the TXV that I have is listed as obsolete. Yes 100 + with high humidity is the norm here in the Houston area. After the thunderstorms came thru on Sunday I started getting my temp drop in the house. At night it can cool down to 72 inside. Like I mentioned I do not think half or less of 5 tons can keep up with this heat and humidity. Now hopefully today we will find out why we have half. I will check out that site. I will post back with the results this afternoon.
 
  #29  
Old 07-27-09, 05:05 AM
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Originally Posted by daddyjohn View Post
doesn't compute. I would expect the suction line at the outside unit to be in the 40's if some of the distributor tubes were resticted. What is the suction line temp where it exits the evaporator coil? The house is 77 with 105 outside and a partially active evaporator? Not anywhere near what I would expect.

Good info on this thread.

One question. I always thought that a warm suction line like the one he has is indicative of a restriction. Why would you expect his suction line to be in the forties? A suction line in the forties would probably indicate a system that had an air flow problem which does not seem to be the case here. A temperature of say 45 with a gauge reading of say 70 would give you a low superheat which usually isn't a sign of a restriction. I realize we are not getting all the readings seeing that its a home owner doing it.
 
  #30  
Old 07-27-09, 05:24 AM
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He suspects that some of the distributor tubes might be blocked which would lower the saturated suction temperature. However, it now appears the superheat is too high. A full set of readings is needed, both refrigerant side and air side.
 
  #31  
Old 07-27-09, 11:21 AM
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Well as my luck would have it got a call today that the a/c man can not make it today. He will try latter this week if not early next. I know "friend of friend". Need to find good ac comoany to try to fix and not just a sales person looking to make a sale on a complete system.
 
  #32  
Old 07-28-09, 11:53 AM
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After much thought I am getting the original company to correct the problem. I did learn alot doing this but for a one time charge of $60 I will let then fix it. This morning they sent the first of a long list of techs I am sure and he hooked up the high guage and stated "looks to be low on freon" added 2# told me to run it and that should fix it. Well I just placed the 2nd call to come back out as that did not fix it. I will keep everyone up to date as to what they finally find wrong. Thanks
 
  #33  
Old 07-28-09, 01:29 PM
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Thanks. He put on a guage, but no temp readings on the pipes. Back to school for him.
I have never understood this top off the charge mentality. If a system is truely low, where's the leak[s]?
 
  #34  
Old 07-28-09, 04:16 PM
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I could not understand his response. He told me they must have put the coil in the hot afternoon. Never was charged properly. Stated other company did not know what they were doing. I must admit the humidity has dropped to around 62% and the a/c did not let the house get above 76. But then again it was not 102 in the shade. This afternoon I went ahead and cleaned the evaporate coil as it was due. They get cleaned every 2 months. I did not notice the cold spots like before. Just think how it would work if someone took a few more min and charge it correctly. I will keep everyone posted as to the outcome. Maybe it will help someone in the future. Thanks
 
  #35  
Old 07-28-09, 04:38 PM
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Originally Posted by lake81 View Post
Just took temp readings:

Outside temp 105
air into compressor outside 104
air flow from fan at top of compressor 117
suction line at outside unit 75
liquid line at outside unit 99

Reply: The liquid line temp should normally not be below the temp of the air going through the condenser!

117 minus - 104 = 13 Subcooling, That's usually considered okay, but look up equipment's Rated Subcooling.

==============================
air flow at return air plenum 77
air flow at supply plenum 68
Reply: At 105-F outdoors, a 9-F indoor temp/split is unacceptable unless you have over 83% Relative Humidity.

At 105-F outdoors, 50% RH, a 20-F temp/split is normal.
It's important to know the indoor relative humidity.

With normal outdoor temps, Indoor relative humidity has the biggest influence on the outdoor condensing temperature.

========================================
looks as thou the coil operating at half capacity can not keep up with the 105 temp.
Reply: The liquid line temp should normally not be below the temp of the air going through the condenser!
 
  #36  
Old 07-29-09, 02:00 PM
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OK Standings as of this time. Second tech left. Slight adjust of freon charge.
Suction Temp: 63
Liquid Temp: 96
Outside Temp: 94

Stated superheat on the mark. Was not there with tech but spoke with him over the phone. After it cooled down last night I did check the coil and had no cold spots. Even temp across the coil. Inside humidity is now at 62% and not climbing. maybe it is still pulling all the moisture that has accluminated over the past few years. Return air was at 72 with a duct temp 55. This was last night. Now return air at 73 with 52 at the supply plenum. I have my fingers crossed that this was the problem I did notice this unit is drawing more current as the meter has increased in rotations since they added freon yesterday. Unit did start to cycle at 73 around 8:30 last night. Has not done that since I can remember. I will let everyone know with an update.
 
  #37  
Old 07-29-09, 06:58 PM
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Airflow...

Originally Posted by lake81 View Post
OK Standings as of this time. Second tech left. Slight adjust of freon charge.
Suction Temp: 63
Liquid Temp: 96
Outside Temp: 94

Stated superheat on the mark. Was not there with tech but spoke with him over the phone. After it cooled down last night I did check the coil and had no cold spots. Even temp across the coil. Inside humidity is now at 62% and not climbing. maybe it is still pulling all the moisture that has accluminated over the past few years. Return air was at 72 with a duct temp 55. This was last night. Now return air at 73 with 52 at the supply plenum. I have my fingers crossed that this was the problem I did notice this unit is drawing more current as the meter has increased in rotations since they added freon yesterday. Unit did start to cycle at 73 around 8:30 last night. Has not done that since I can remember. I will let everyone know with an update.
The 73 R & 52 SA looks good at a 21-F drop.
Bet indoor humidity was 50% or less.

It is always good to know the amount of airflow CFM that is being delivered through the indoor coil.

A 5-ton system requires a tremendous amount of airflow!

RETURN AIR FILTER RACKS
Typical disposable 1-inch capacity return air filter is 2 cfm per square inch of gross filter area. Recommended filter velocity is 300-350-fpm, lower is better.

Velocities higher than 500 fpm will decrease filter performance. Increase flow resistance, and possibly blow off collections of dirt. Measure Velocity 1” from RA grille face.

Average Free Air area of most Return Air grilles about 75%.

At a required 2-cfm per sq.in., 5-ton requires 2000-cfm /2= 1000-sq.ins., 2 X 144= 288-fpm velocity.

The grille would reduce the free area by 25%, & so would the filter reduce free air area, therefore the air velocity would be much higher than 300 perhaps 350-fpm, before the filters start loading.

You would need (2) 500-sq.in. Return Air filter Rack Grilles.

You may, if lucky, have 350-cfm per ton of cooling, or 1750-cfm; which one can get by with especially in humid climates.
- Darrell
 

Last edited by HVAC RETIRED; 07-29-09 at 07:01 PM. Reason: before filters begin loading
  #38  
Old 07-30-09, 05:04 AM
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Thansk Darrell
My Manual D is packed away and I couldn't remember the cfm/sq. in. #. RA grille free area is a concept very few understand.
 
  #39  
Old 07-30-09, 05:22 AM
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Thanks for the replies on the return air and grills. I have 4 siberians the are like shedding blankets. We change our filters every 2 weeks need it or not. We use the pleated type. I read on on of the other post that the air flow should be on the side of the filter. We have one 20x30 and one 12x24. Our master is about 550 sq ft with 11 ft ceilings. We keep the doors closed most of the time. The man at the supply house recomended a return for this room as I have a great amount of air flow under the door. I know this should as I feel I am pressureizing this room. Given the two I have what size would you recomend. We are redoing the ductwork anyway. What's one more run back to the return air plenum.
 
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