[Foozgrind]

Hi everyone! I am writting from South Florida. Hope you all could provide some information that would help me. I just moved into a new 2 story home that's about 2225sq. It has a single 4ton Trane unit that is from 2008. The handler inside is spotless looks brand new and the unit outside has been maintained very well also. My issue is that during the day I seem to be only able to get my house to cool to about 76degrees. During the day if I try anything below that the unit runs forever.... The vents are blowing cold about 62degrees? Right now it's set a 75 since 530pm it's about 730pm and has gone nonstop with the vent temp at 62ish. I had a ac person come by he side the inside handler looked great blower was great and the coils looked fine. He did suggest I replace the capacitor which I did but he did not check the freon from what I could tell I asked he said it was fine but never saw that tool with the two meters and cords. I noticed the big pipe outside is missing the top foaming cover and it's cool with some sweating on it not sure if needs to be colder? So any ideas as to why this unit is running non stop? Also I have the nest thermostat I turned off all the features so it just acts like a normal device and the thermostat before this same issue so it's not that piece. Wanted to add that I have all impact windows from 2012 my thermostat is upstairs and it's in the hallway with one ac vent. My doorway when u walk in go straight to the ceiling so it's a lot of dead space and I have two large windows at the top I was thinking about putting some light tint on them...

Thanks!
Michael

 

[dan sw fl]

dT =76'F - 62'F = 14'F

Cool Supply Air needs to be 56'F.
dT = 20'F

It appears that your residence is losing 30% of the 4-ton cooling capacity.

Either a poor refrigerant set-up/ charge
… … or the ducts are losing A LOT OF TEMPERATURE (6'F).

Send your home address to my gmail, racingdan11.
I would likely be able to confirm that a 4-ton unit is close to an appropriate size A/C system.

Residence was built in 20_ _. ??
Something like … House Perimeter is 136' / 40' x 28'.

~ 1,120 Square Feet / Floor

How many windows in each direction ?
North ___ South ___
East ___ West ___

What is the air temperature at the diffusers { vents } at 7am ?
……….
You DO NOT need to talk to the previous technician
who did not perform a reasonably comprehensive evaluation.

In South Florida, one may anticipate that
the A/C will run on the average of ~ 14 hours per day.

 

[Foozgrind]

Don't feel comfortable giving my address to anyone. But I can tell you the house is from 1993 I had FPL come to a survey he said the attic had good insulation and he didn't feel any drafts... I have a new ac guy coming tomorrow different company. I was gonna have him check the refrigerant and not sure if it matters but that big cool pipe is not covered sun exposed...windows. I get plenty of east and west light. The master bedroom faces west and is a very wide large window impact window and downstairs is a 10foot sliding glass door that gets plenty of light. The front window has to two large front windows in the foyer for second floor light which faces the thermometer. I was gonna see about tinting those.

 

[bhenry1013]

Do you keep the thermostat set at the same temp all day, or do you have it set higher and drop lower later on in the day?

 

[Foozgrind]

At my old house we just moved from I kept it at 76 during the day we have dogs and 73 at 530pm then 72 at 10pm till 730am when it gets set back to 76. I tried doing that here and it was nope not happening. I set it at 76 during the day and I can watch it on the nest app it keeps it at 76 and seems to run fine. 5pm it is suppose to start cooling to 74 and I get home at 530 and it will be running to get to 74 for like 3 hours I think it shuts off on a delay to not break the unit for 4 mins. On Wensdays I work from home and like to keep it at 73 but I couldn't so I tried 74 and let me tell you this past Wes the nest app reported 16hours of total runtime. In fact at 1030pm I went to check the vents cause it felt hot and the temp was 78degrees and like 80 degrees coming out of the vents I turned it off for 30 mins and back on and it's been fine since. I don't get it... It's like the ac just can't push the house lower then 76 during the day. I have never seen a unit run so long before. Again I do feel cold air coming from the vent I stuck my temp guage at the vents and they are pushing about 64ish

 

[bhenry1013]

Keeping a consistent temp might help you maintain your desired temp for when you get home. It takes a lot more work to bring your house down from 76 to 74 than it does to keep it at 74 all day. Especially at 5:30 in the afternoon which is pretty much the hottest part of the day. In these Hot months your unit will often run all day in Florida, as long as it is able to maintain the temp if you leave it alone at 74, I wouldn't worry to much about it. Except that you say it stopped cooling all together, which isn't a good sign. Set your temp to 74 and leave it alone, see if it maintains this temp.


If for whatever reason the unit shuts down again and isn't cooling you need to call a different tech to check the equipment. How did your current tech know it was fine? What measurements if any did he provide you? What was the SC/SH?, what DT did he get from the unit? If he can't answer these questions he can't say the unit is running fine because he doesn't know.

 

[dan sw fl]

South FL Operating Hours Perspective

76'F - 64'F = 12'F = dT actual

dT Actual / dT required = 60%

A/C system is providing about half of it's design capacity.
One would not expect to be able to cool a house < 83'F
when it is > 91'F outside.
______

With a t-stat to 72'F, a perfectly maintained and designed unit
will Run CONSTANT from 11 am to at least 10 pm for > ~130 days / year in South Florida.

CONSTANT = NO DOWNTIME for even 3 seconds

My thermostat is set to 78'F after 11 AM.
My new, well maintained system runs about 8 hours straight everyday that is > 84'F
__ AS IT IS INTENDED TO DO __.

My A/C system will probably only last for ~15 to 20 years with
my Annual Maintenance Contract / twice per year service.
Capacitor replacements might be about every 3 years.

___ ~ 2,800 to 3,500 operating hours / year
[ … Service Life of my ' builder grade ' Armstrong Air unit was 15 years. ]

Luckily, the FPL Residential rate is only $0.0994 / kw-hr
& my highest bill is $109.

1,760 Sq Ft Ranch - 2001 Built
Standard Walls in FL =~ R-5
Four new impact, insulated windows.
Two original windows.
9' x 12' sliding glass doors.

 

[dan sw fl]

BALL PARK
- - - - - - - - 1993 BUILT 2,222 SQ FT
- - - - - - - - 2 STORY

_________ MANUAL J CALC

 

[Foozgrind]

I can't really see those pics! Phone won't zoom in on it. But I did have my service contract company come out I just started 2 days ago with them. He said I need freon my unit took about 3pounds. Vents are blowing in the 50s now. Said I probably have a small leak but to wait it out a month so I am fully covered then call back and they will do a line test and if I need replacement parts all covered. If he does it now it's gonna cost money. Said I should be fine waiting!

 

[teddy bear]

If your attic is hot and your insulation on the ducts is mimimal, 62^F supply may be normal. What is the supply temp/%RH at the s? From this information we can tell the real coil temperature.
If you are happy with the %RH in the home, you may have near ideal condition. Adding insulation and eliminating solar gain through windows can help.
Tell us your supply temp/%RH and space temp/%RH.
Keep us posted.
Regards Teddy Bear

 

[Foozgrind]

Let's change gears here now... The ac company put in 3 pounds of freon. They removed the nest and put in a regular digital non programble tstat. So now the ac turns on and off and it's not running for hours the problem is its turning on for about 13 minutes and off for about 9 minutes. Is that a short cycle? It's 4ton it's sized right. Thing that is curious to me is right now the tstat is set to 76 when it shut off it was at 76 isn't it suppose to register 77 before turning on again? It's turning on when it still says 76. Maybe it's just me...

 

[bhenry1013]

Let's change gears here now... The ac company put in 3 pounds of freon. They removed the nest and put in a regular digital non programble tstat. So now the ac turns on and off and it's not running for hours the problem is its turning on for about 13 minutes and off for about 9 minutes. Is that a short cycle? It's 4ton it's sized right. Thing that is curious to me is right now the tstat is set to 76 when it shut off it was at 76 isn't it suppose to register 77 before turning on again? It's turning on when it still says 76. Maybe it's just me...

Most digital Thermostats are +/- 1° saying that they do read in tenths of a degree, so if its 76.6° it will turn on, it just doesn't show you the tenths place. I wouldn't worry about it, and a 13 minute cycle time, with 9 minute downtime doesn't sound bad. The more important question to ask is are you comfortable?

 

[teddy bear]

Why did they change the stat?
Low on refrigerant??
Go figure.
On/off cycle in mins. at 4:00 PM verses 8:00 AM?
Regards Teddy Bear