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Heating, Air Conditioning, Fridge, HVAC/NEW A/C CAN'T KEEP UP WITH STAT
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Question
REPLACED OLD 3TON HP WITH GOODMAN 3.5HP.NEW UNIT WORKS WELL,BUT CAN'T KEEP 1900SQFT 1960s JACKSONVILLE,FL. HOME COOL (78) WHEN OUTSIDE TEMP GOES OVER 90.THE DISCHARGE AIR TEMP IS 56,THE INSULATION AND DUCTWORK ARE ORIGINAL.THE SUPPLY VENTS BLOW OUT 58-64.THE AIRHANDLER IS IN ATTIC. THE CUSTOMER BELIEVES THE CONDENSING UNIT IS BAD, BUT I THINK IT'S THE POOR AMOUNT OF INSULATION.WHAT'S YOUR OPINION?
THANKS SO MUCH
Bruce:
So there was a 3 ton unit and you replaced it with 3-1/2 tons, right?
1,900 SF/ 3.5 Tons = 543 SF/Ton. That should be more than enough to maintain 75 with a degree or two of float during the peak time of day.
I'm thinking you're not delivering anywhere near 1,400 CFM, as evidenced by the low discharge temperature and wide split; what is the actual flow now and what was the actual flow with the old system? Why did you put in a larger unit? Did you perform the Manual J required duct survey to make sure the ducts would deliver the required flow? Did you do anything to increase the capacity of the duct system the required 17%? Do you have any inleakage on the return? Did you put in a sophisticated filter? If so, is it properly sized?
You might check askweldin.com, there's a lot of good stuff on ductwork there.
Fred
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Answers by Expert:
Fred Weldin
Expertise
I can't help you if your whatsis won't work, people (Especially if it's a refrigerator); I have no experience with appliances, and I haven't been involved with H&AC service and repair since March 08, 1996 (Thank the Lord); I always send a "standard" reply to appliance questions and H&AC "Service and Repair" questions (about 20 a month), so if you want to know why your whatsis isn't working like it used to, ask someone else. A lot of my answers aren’t read by the questioners; in that event, I always send reminders to read the answers for a month or more (the word "idiots" comes to mind - actually there's another more appropriate word, but discretion prevents its use here). If you have questions about how big a unit you need, if one room's warmer than the others, if you want an opinion oas to scope of work on bids received, etc. just ask. Do visit www.askweldin.com, there's a lot of good information on sizing, ductwork, efficiency, as well as some techniques accomplished DIY-ers can use to troubleshoot and improve their H&AC. Finally, I want to thank all of the kind, serious people whom I meet here: I enjoy working with you. My wife says I'm "snarky" from time to time; as for you others, please use your imagination as to the responses swirling on the snarky side of my brain when I read your questions.
Experience
53 years in the business. See www.askweldin.com
Organizations
ASHRAE, ICC.
Education/Credentials
B of ME U of D 1965, numerous classes, seminars and a lot of "Hands On" learning since.
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