Insufficient cooling upstairs, what can I do?


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Old 07-21-08, 12:57 PM
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Insufficient cooling upstairs, what can I do?

I have two units outside of my home, one to handle the upstairs and the other downstairs. We have a bonus room upstairs which is over the garage. We live in SC so it gets into the 90s. The units are 10 years old. FYI: I had both units maintenanced about 6 months ago. When I turned on AC in June upstairs unit was not cooling. Hot air was blowing out of the vents. I had the same person that did the maintenance come over. He added Freon and mentioned something about the compressor or condensor being close to needing replacement.


Problems:
(1) I can feel a difference on my hand in the temperature coming out of the vents upstairs and the vents downstairs. (Air is not as cool upstairs) The upstairs will climb into the mid 80's even when I have the temp set for 76 from early in the morning.


(2) The upstairs bonus room has wooden blinds which I keep closed to help with the temperature. In fact, I keep most of the upstairs windows covered during the day. I also purchased a portable cooling unit which is rated to handle 400 sq ft and put that in the bonus room. Bonus room is about that size maybe a bit more. Airflow from the central A/C vents seems to be less in this room. Even with the portable unit running along with the central air, it is still hard to get the temp down during the hot part of the day. FYI: I run a couple of ceiling fans upstairs as well to help with this.

The upstairs unit basically runs all day and still is not able to keep the temperature from rising several degrees above the set temperature. I am looking to see what others may think.

- Do I need some tech to come in and check my ductwork?
- Do I need a larger unit for upstairs?
- Is freon low again which is causing air not to cool as much?
- Some other issue?

All feedback is appreciated!!
 
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Old 07-21-08, 01:12 PM
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- Do I need some tech to come in and check my ductwork?
Or you could check it yourself. Look for any joints that have come apart and any missing insulation. If you feel any airflow from the ducts you need to seal that area. See if there are balancing dampers in the branch ducts where they connect to the main duct. If there are dampers see if they are loose.

- Do I need a larger unit for upstairs?
Possibly. Have you lived in this house for several cooling seasons and if yes, has the system performed adequately in the past?
- Is freon low again which is causing air not to cool as much?
Maybe. If it is low then it would mean a leak that should be repaired.

- Some other issue?
Perhaps. This "portable cooling unit". Does it have one hose or two? If two, how do you have these hoses connected to the great outdoors? Are the hoses insulated? If it is a single hose unit then it may be doing more harm than good.

Have you tried setting the blowers in the central units (both upstairs and downstairs) for manual continuous operation?
 
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Old 07-21-08, 01:32 PM
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- Do I need some tech to come in and check my ductwork?

Or you could check it yourself. Look for any joints that have come apart and any missing insulation. If you feel any airflow from the ducts you need to seal that area. See if there are balancing dampers in the branch ducts where they connect to the main duct. If there are dampers see if they are loose.


** Most of that terminology was Greek to me but I get the idea of what you are telling me to check **


Quote:
- Do I need a larger unit for upstairs?

Possibly. Have you lived in this house for several cooling seasons and if yes, has the system performed adequately in the past?

** I have been here for 10 years. I bought the portable unit about 2 years ago because the cooling in the room over the garage was horrible. **

Quote:
- Is freon low again which is causing air not to cool as much?

Maybe. If it is low then it would mean a leak that should be repaired.


Quote:
- Some other issue?

Perhaps. This "portable cooling unit". Does it have one hose or two? If two, how do you have these hoses connected to the great outdoors? Are the hoses insulated? If it is a single hose unit then it may be doing more harm than good.

** Single big hose that goes to window. Window comes down about 3/4 of the way and then there is an insert that the window close on. **

Have you tried setting the blowers in the central units (both upstairs and downstairs) for manual continuous operation?

** No, I have tried adjusting the temperature downstairs lower than I want it to try and reduce the amount of heat rising to the upstairs. **
 
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Old 07-21-08, 01:59 PM
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If the room over the garage was added after the air conditioning system for the upper floor was installed it is quite possible that the entire upper floor system is too small for the job. If the room was in place when the A/C was installed it is possible the system was inadequate from the start.

In my opinion one-hose portable air conditioners should be outlawed. In order to work they have to move conditioned room air over their internal components and exhaust that now heated air outside. They cannot exhaust that air without an equal amount of air coming into the room from somewhere and that somewhere is the great outdoors. If your house is tightly sealed to prevent outside air entering then the portable unit cannot properly exhaust the heat. If your house is "leaky" and allows a sufficient amount of air in to balance the air being blown out then it is also letting in a fair amount of heat from the outdoors. The net result is that your portable may be rated at 12,000 BTUs per hour cooling capacity but in the real world you may be getting only a third or half of that.

There are some tests that you can do to make a more informed guess as to the operation of your system. You will need to have a thermometer that has pretty close gradations in the range of about 40 to 80 degrees. If you have one of those electronic (digital readout) units that has a ten-foot wire and an outside probe for measuring both indoor and outdoor temperatures it will do nicely.

You want to measure the temperature differential across the cooling coil. Ideally you would measure this right at the coil itself but that is probably not a practical matter for you so instead I want you to measure the temperature at the return air grille and also at the supply (outlet) register closest to the air handler unit. The temperature at the supply register should be from ten to twenty degrees lower than the temperature at the return air grille. This will be dependent on the relative humidity level in the house so don't get too excited if it is in the lower part of this range.

You also want to check to be sure the filter in the return air system is clean. The filter may be at the air handler unit or it may be behind the return air grille.

Check for noise in the system. There should be some air rushing noise but not an excessive amount of noise. If it is extremely quiet it indicates that the blower speed is too low, that there are disconnected ducts, the ducts are plugged with foreign matter or that the ductwork is too large. If the noise level is really high then it probably means the ductwork is too small.
 
 

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