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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Phil. We have a new Lennox 13ACX 2.5 ton unit to cool off

Customer Question

Hi Phil. We have a new Lennox 13ACX 2.5 ton unit to cool off a 1300 sq. ft. home. Temperatures here in Colorado right now are about 85 to 90 degrees. It is taking about an hour for every one degree drop in temperature. That doesn't right to me. Please advise.
Submitted: 2 years ago.
Category: HVAC
Customer: replied 2 years ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Phil replied 2 years ago.
Hello, The unit may be slightly over charged with refrigerant.Feel the largest copper tube attached to the unit that sits outside. its insulated, tell me if it it is sweating or not. Next, inside the unit, is a big black roundish thing, that is the compressor... if that is sweating the system is over charged with refrigerant. Next using the same thermometer tell me the difference in temperature between the air at a supply register and the house inside, if its lower than 15F differential the system that would confirm the over charges (IF the suction line is sweating)It is common for new techs to over charge a system. Look that over and get back to me. we can go from there. Please hold your rating until we get your system sorted out.
Customer: replied 2 years ago.
When you say "supply register," are you talking about any of the registers around the house, or are you talking about the main return with the filter in it?
Expert:  Phil replied 2 years ago.
I am talking about the registers where the cool air comes out around the house. pick one that is closest to the air handler with the best air flow.
The return with the filter in it is a good place to check the room temperature. be sure to use the same thermometer.
We can go from there.
Customer: replied 2 years ago.
Okay, here are the findings:
1. there is NO sweating around the largest copper tube attached to the unit outside.
2. There is NO sweating around the compressor.
3. The temperature on one of the supply registers is 52 degrees and the temperature inside the house is 72 degrees right now.
Expert:  Phil replied 2 years ago.
Thanks, this means you have 20F differential across the cooling coil and the system is not over charged. 20F is very good *if there is sufficient air flow.... that needs to measured with instruments, You can alsoLook the wiring diagram glued to the inside of the blower section of the air handler over notice the blower speed options, make sure the blower motor is wired for high speed in cooling mode. And you can ask the installer to give you the duct supply and return sizes they used, and I can determine from that if the problem is under sized ducts. Tell me about how old the home is and as much as you can about the insulation and windows facing south and west, and if they are dual pane or single pane glass. We can go from there.
Customer: replied 2 years ago.
Ducts are standard size, insulation and windows are not an issue. I don't know how to check if wiring is correct. I don't think my issue can be diagnosed this way.
Expert:  Phil replied 2 years ago.
Hello again,Did the installer tell you that ducts are 'standard size'. That would be an evasion of the issue, and a huge red flag...there is no such thing as standard size, the duct diameter varies on each job depending on the length of the duct work. Undersized return air ducts are about 50% common in this business. Flexible duct work hung with thin straps are also very common, that kinks the duct work and restricts flow. You can visually inspect for that. From that I can see so far, it IS a duct sizing problem, 90% chance of that, and 20% or so a possible slight over charge of refrigerant... that is very common as well. ______________We have some absolutely superb field techs in this business... a good solid 5 or 10%, 5% or so are superb. Those figures are common for most trades and professions. When you have a system that fails to cool you are not dealing with anyone in the top ranges.A total of 20% or so will not mess your system up and will do an accurate diagnosis most of the time before selling you a part... same goes for new installations.The other 80% are shades of gray as you see in your own business,depending on the nature and complexity of the repair needed.The bottom 30% of outfits will just make guesses, save money and labor expense by under sizing your duct work. Those are detected by noticing that the equipment they install does not work.. followed by bogus explanations such as 'the duct sizing is standard', while still not being able to get your system working properly. I can stay with you on this and point out the range of remedies (contractors license and bond issues) or I can opt out. Let me know your wishes, we can go from there. .
Customer: replied 2 years ago.
Thanks for trying to help. Sorry it didn't work out.