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Old 08-03-2020, 08:45 PM   #16
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Re: Need new 4 Ton 14/16 SEER unit


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Well, it kicks on and kicks off periodically. I donít know how long but it was taking time to cool down the house , like 4hours to go down 4 degrees F. But could be due to lowe Freon as well I guess?

Doesnít run 24/7 but it does run often , itís like 100 out and always warm in Ft Lauderdale.

It froze up when I put it down to 72 other night. I change filters monthly and also put drain line cleaner as well.


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If while maintaining temp. it runs for 40 to 45 minutes on the hottest/hotter days. Dropping 1/2 ton in size will most likely not be able to hold temp on those days.


Don't know if anyone told you. But it actually gets hot in Florida. lol
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Old 08-03-2020, 08:49 PM   #17
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Re: Need new 4 Ton 14/16 SEER unit


A good number of years ago. A good number of houses in Florida were used in a study for proper sizing. Some of the old systems removed were 1/2 ton, 1 ton and even 1.5 tons over sized.



On the homes that were 1 or 1.5 tons over sized. When the correct size was put in. The humidity rose, so that the people had to set their thermostats lower to get the RH down. Hopefully they bought whole house dehumidifiers down the road.


Don't have the link to that study anymore, or I would post it.
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Old 08-03-2020, 08:55 PM   #18
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Re: Need new 4 Ton 14/16 SEER unit


^Did they measure cfm per ton before and after as well as compare efficiency ratings? Low flow with oversized units and the new ones having worse latent capacity must explain that.
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Old 08-03-2020, 09:03 PM   #19
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Re: Need new 4 Ton 14/16 SEER unit


So... anything in particular I should look for or ask the companies about for the models? Any new things , new types of Freon? New types of alloys to prevent corrosion? New technology that makes it transform into a Decepticon?


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Old 08-03-2020, 09:04 PM   #20
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Re: Need new 4 Ton 14/16 SEER unit


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^Did they measure cfm per ton before and after as well as compare efficiency ratings? Low flow with oversized units and the new ones having worse latent capacity must explain that.



Yep, they measured before and after. Efficiency played no real part in it.


Problem was with the now low friction rate of the duct system. That even on low blower speed, they couldn't drop air flow enough. So they had too high of an air flow for the latent capacity the homes needed.


The cost of redoing the duct savings, would erase any energy savings that the size reduction would give.


While dampers could have been installed in all of the supply runs, and the return/returns. For a fair price. The duct work, would then have not been insulated well enough for the greatly reduced velocity/volume, and would have gained too much heat in the homes with attic insulation. And cost a good fortune to relocate them into conditioned space.


Low velocity ducts in an attic need R8 insulation. Many older homes only have R4.2, or R6, neither is enough.
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Old 08-03-2020, 09:05 PM   #21
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Re: Need new 4 Ton 14/16 SEER unit


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So... anything in particular I should look for or ask the companies about for the models? Any new things , new types of Freon? New types of alloys to prevent corrosion? New technology that makes it transform into a Decepticon?


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How close are you too the ocean. If the coil is leaking because of salt corrosion. You would want a coated coil.
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Old 08-03-2020, 09:10 PM   #22
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Re: Need new 4 Ton 14/16 SEER unit


Update on the Cycling. Itís currently 81F outside. Temp inside is set to 76 degrees, the time from when it clicked off, to now running (clicked on) is 28 minutes.

I will now time how long it runs from on to off.


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Old 08-03-2020, 09:11 PM   #23
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Re: Need new 4 Ton 14/16 SEER unit


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How close are you too the ocean. If the coil is leaking because of salt corrosion. You would want a coated coil.

20 miles inland, so no saltwater factor. Rain is acidic here though.


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Old 08-03-2020, 09:45 PM   #24
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Re: Need new 4 Ton 14/16 SEER unit


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Update on the Cycling. Itís currently 81F outside. Temp inside is set to 76 degrees, the time from when it clicked off, to now running (clicked on) is 28 minutes.

I will now time how long it runs from on to off.


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Ok it took 31 mins from when it was off to click back on again to maintain 76 (81 outside now)


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Old 08-03-2020, 10:09 PM   #25
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Re: Need new 4 Ton 14/16 SEER unit


Considering that your unit froze up when set to 72, it's probably low on gas and running at reduced capacity.

Timing cycles when the charge is off won't help you.

Try https://www.loadcalc.net/.

Knowledge of how your house was built required.

The duct system will have to be checked too as downsizing can cause issues, some of which beenthere brought up. (low velocity causing increased duct loss, making sure air handler can deliver proper airflow on your duct system)

This is a science.
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Old 08-03-2020, 10:20 PM   #26
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Re: Need new 4 Ton 14/16 SEER unit


So here is more info, I am getting the details from the home inspection report (bought the house 7 months ago)

A/C: Split system. 1 Zone

Ductwork: Flex Duct

Insulation: R-30 ; Batts; Loose Insulation

Condensing Unit : Trane 21.8A 10 years old 4 Ton T.D. n/a

Air Handler : Trane 10 years old. 4 ton T.D. 19.6

SF calculation : 4 Tons x 500 SF per ton = 2;000 SF Capacity

Return Air [79.5] - Supply Air [59.9] = Temp. Differential [19.6]


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Old 08-03-2020, 10:22 PM   #27
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Re: Need new 4 Ton 14/16 SEER unit


That SF calculation shouldn’t be used. It’s an antiquated rule of thumb that went out with disco.
Not sure what the home inspector is doing writing up such nonsense.
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Old 08-03-2020, 10:23 PM   #28
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Re: Need new 4 Ton 14/16 SEER unit


Not sure... but he was listening to the BeeGeeís when in my house


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Old 08-04-2020, 03:38 AM   #29
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Re: Need new 4 Ton 14/16 SEER unit


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Ok it took 31 mins from when it was off to click back on again to maintain 76 (81 outside now)


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A nice long run time.
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Old 08-04-2020, 05:33 AM   #30
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Re: Need new 4 Ton 14/16 SEER unit


You are getting some good advice and I grew up in FL so I know how the year round heat and humidity there beats up air conditioning units. One thing I would add is to forget a "smart" thermostat, especially like Nest. You will never know what they are doing and why and the system will often be doing something you don't want. There are just too many variables. Plus they seem to be very problematic but how will you know if they are malfunctioning when you don't even know what they are supposed to be doing when they are working correctly?

But get a wifi stat if you want remote access to monitor the place and/or control remotely. Those are cheap and reliable. Make it a programmable one if you want to have different temps for different times and days... but I am not sure programming makes a lot of sense in a place like Ft Lauderdale with a fairly constant hot and humid environment. Good luck.

Oh, one thing you might consider since this is a DIY forum is to replace the indoor coil yourself if you have some mechanical skills, and have the time to learn the details. I did that on my Bryant system here about 8 years ago and it is still going strong.
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