My A/C is not cold enough


  #1  
Old 04-19-06, 10:36 PM
J
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My A/C is not cold enough

The A/C at my house does not give me cold enough temparature even if I set the thermostat to reach 70F. (I am
in florida, the outdoor temparature during the day is around 85F now)

This A/C was purchased on 2002 brand new. Worked well until today. It is a split system. It was made by Lennox.

I have checked the outdoor unit first by the following steps:
1. removed the cover/fan combo.
2. cleaned the unit inside out, removed all leaves, debris
3. turned A/C on while cover/fan combo is removed
4. the spiral coil become hot immediately
5. reinstalled the cover/fan combo back
6. now fan turned on and cools the spiral coil down immediately
7. checked two pipes connected to the outdoor unit, the thin
pipe is warm and the thick pipe is cold, with water on it.
So, to me, it seems the outdoor unit is working fine

Then I checked the indoor unit located on the roof of my garage.
1. checked the air duct form one end to other end, feel that
the temperature goes from room teperature to cool.
I don't know if that's cold enough.


Then I checked the following items inside my house:
1. replaced a brand new air filter in the utility room
2. checked the vent in other rooms, they seem to blow a strong
wind out, but the temperature is around 76F while my themostat
set it to be 70F.

So my guess currently are:
1. the temperature control circuit is not working fine, making
condenser stop working before it reaches desired low temperature

2. There is a leak of refirigirant somewhere. Probably in condenser or the pipe from outdoor unit to indoor unit

3. I downloaded some repair document from Lennox.com,
basically, those document said there is an air filter inside the
indoor unit. I wonder if that air filter is too dirty and could
decrease the performance. But I can not find this air filter.
I wonder if it actually exist or not because I already have
one air filter in my utility room.


4. the coil (through which refrigirant flows) in the outdoor unit is not functioning well.

Right now, the A/C helped the house to reach tempearture of 77F while the outside temparature is 74F.

Can anyone give me some suggestion on where should I start my repair?

Thanks a lot!
 
  #2  
Old 04-19-06, 10:41 PM
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One more thing:

I noticed the outdoor unit fan is working fine, blowing a strong wind out. But the temperature of the air is warm, it used to be pretty hot.
 
  #3  
Old 04-20-06, 10:58 AM
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Alot depends on heat loss heat gain. What's the temp outside? 70deg is really pushing it. Probably not designed right to get that low of an indoor temp.
 
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Old 04-20-06, 11:25 AM
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Outside temperature is about 85F during the day and 72F at midnight.

Used to set themostat to 72F since 2002 and it worked fine until now.

Set Themostat to 76F, still the same result.

Any suggestion?

Also, do you think the indoor unit has a air filter in it? I am sking this is because I already have an air filter in the vent of the utility room.
 
  #5  
Old 04-20-06, 11:33 AM
DNT1
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If your system has been functioning well up to this point I would hazard a quess that you have developed a refrigerant leak. It sounds as though the condensor fan/compressor and blower fan are operating with good airflow at the vents. On a typical unit with a moderatley low charge the performance will suffer greatly. When you call your favorite local HVAC repair firm mention to them to put on the work order that you want a leak check performed not a gas and go. Not that familiar with lennox but they probably have a coil warranty that will cover the parts you just have to pay the labor cost.
 
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Old 04-20-06, 11:51 AM
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Thanks for your reply

I saw a "5 years warranty" on the outdoor unit, so I will call Lennox to see if they do cover at least the part.

Like picking up a local mechnic shop vs dealer for a car repair job. Should I ask local HVAC repari firm or the Lennox Technician
to fix it? Which way is cheaper usually?
 
  #7  
Old 04-20-06, 12:12 PM
DNT1
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I think lennox may have a program like trane where the contractors have to be company certified to purchase and install the units and that may apply to repairs not a big deal but I would rather have one that is factory certified to perform repairs on the equipment they are repairing. A few phone calls (due diligence) to your local HVAC companies should answer that quickly. Good luck Note: you could just have a leak at a service valve or solder connection that would be fairly inexpensive (compared to coil replacement) to repair, your favorite field technician will be able to diagnose your problem quickly I bet.
 
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Old 04-20-06, 02:11 PM
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DNT1:

thanks a lot for your prompt response.

Beside this almost certain cause of low refirigirant. Is it possible
that thick ice/frost devloped around the coil in the indoor unit (located on the roof of my garage),
making the heat exchange efficiency really really low?

Anothing I am wondering now is that if my indoor unit has
a filter in it? I can not find a filter access panel which hides
the filter. Or the filter does not exist inside the indoor unit.

I am saying that because my utility room has a big vent which
sucks air inside the house through an 8x4 air filter. Which to me
means enough filtering and no need to have additional one in
the indoor unit.

Please give me your opinion.

Thanks a lot!
 
  #9  
Old 04-21-06, 08:03 AM
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8X4 return ?? What size is the unit ?? No way could that return be enough.
 
  #10  
Old 04-22-06, 08:31 PM
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Yes, the vent in utility room uses a 8x4 return air filter.

Does it mean the in door unit still need another air filter?
 
  #11  
Old 04-23-06, 04:50 AM
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So you have more returns in the other rooms rooms and this filtered one just happens to be in a work room.

Then yes you should have a filter for the main unit either just outside of it near where the return enters the airhandler or inside of it.
 
 

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