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Help: Won't get cool; Installer can't help

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hot days
2K views 17 replies 12 participants last post by  gregzoll 
#1 ·
On Sunday night our system stopped cooling like it usual does. The vents seem to put out less air (1/4 the norm?). Set at 69, it holds about 73 in our 9-97 temp days. About 3am it gets back down to 69 until about 2pm the next day.

The installer has been out 3 times but seems confident the system "is doing the best it can" in the high temps. He comes in the morning and vents "seem" to blow harder while he is here.

RGTC-09EZAJS (90,000btu, 95%, 4.5 ton), installed Aug 2012
12x30 return, filter now removed
lines not frozen inside or out (ever)
outside coils were dirty, now super clean by dealer/installer
steady water drip at drain. If fan only for 30 min, drip nearly stops / not unusually high amount (not frozen)
blower running non-stop on high (verified). Amps read 8.3 (rated 9.5)
Refrigerant tested by two different local HVAC techs and said "good"
2000sq ft, 2nd floor (1st floor holds 69 24x7, 10yr old system)
Attic is 117 or so, not vented (no ridge vent), tile roof
Attic is not insulated well (3in?), but walls and ceiling are plaster and lath. We are considering additional insulation.

The only thing we've not done is open coils on the inside unit to check if dirty, since it is all taped and sealed. Being that it doesn't appear to be freezing I didn't suspect that.

Could we be running at the best this unit can do? We remember it running stronger and cooler on hot days in the past. No problems last year and we looked at temp records - they are about the same. The return previously "whistled" and filters were bent in - seemed like it was stronger than it is now.

Thanks for any help.
 
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#2 ·
Have they not done the calculations to determine if the system is sized for the load?

I have noticed that on extremely hot days when the outdoor u it is in direct sun light, the inside air temp isn't as cool as when the unit is shaded. The cooler the condensing unit is, the better the system operates.
 
#4 ·
Thanks...
@InPhase277: The installer is still servicing and I assume he sized correctly to begin with =/ The outdoor units are pretty well located in a ventilated and shaded area.

@rougneck: Greenville, SC! Too hot. And humid. He has not reported pressures or superheat/subcooling. I'm not sure entirely what those are so I will read up and ask him. He and I both checked the duct work quite a bit. No leaks that we've found.

73 right now inside, 91 outside, set for 69. =/
 
#7 ·
Yeah, you are over the design temp and the main floor is good. 69 is way too low. 70-72 or higher is norm and what it is designed for. I suspect something changed in the ductwork to upstairs. Did a damper in a pipe get closed accidentally.

In the morning check the temp difference between the air in the vents on the main floor and subtract it from the house temp at the thermostat. If it is between 16-20F it is fine and you have a airflow problem not unit problem. You should get a steady stream of water when cooling not drip. If it is maxed out then that may explain it. Humidity must drop B4 the temp drops ( thermodynamics/psychrometrics ) so if it is more humid this year than last that may be a issue.
 
#9 ·
69 can lead to frozen coils when you're not careful. Anyways, i would not run that unit without a filter. And i would definitely look at the coil and wash it if needed. It's probably doing the best it can with the airflow across the coil. If 2 different techs have said all is well with the refrigeration side of things, i would lean on their side.

Maybe the blower is dying a slow death? Working half the time. You can find cheaper Anemometers. If you can find a cheap one, it'll help you know if your airflow is fluctuating.

Cheers!
 
#13 ·
Thanks again everyone.

Wondering now if I should insist they open the sealed coils and clean. Will do.

Ordered a CFM meter to get firm numbers from AM to PM at the vents.

The manual indicates 14x20 filter, if I'm reading this right. But what does this "(2)" mean:
https://www.evernote.com/l/ACTnZek7uqNFf5p5DenAKPxQbw3NjwhmPE8

I wonder if the coils are freezing up "some" also. There is no window or way to visual inspect without unsealing. :( Hate that. Hence I used fan only and monitored the drain for 30-60 min.
 
#14 ·
Forgot to add , I recommend you set the tstat to 72F , at least to start out . And open up the " cover " or remove it , so you can visually inspect the A-Coil .

First to look for icing . Second to see if it is dirty .

Once the A-Coil is accessible , I would go ahead and clean it , whether it looks dirty or not . As preventive maintenance .

If I was still in doubt about this , I might even take measurements & buy a piece of Plexiglas and install it instead of your present " cover " , so you can observe it at your leisure . If you continue to have problems . If need be , put some " insulation board " over the Plexiglas , during " normal " observation .

I am a field engineer and problem solver from way back .

God bless
Wyr

PS If the coil is freezing , it may be due to inadequate air flow , you setting the tstat too low or low refrigerant . Perhaps more causes that do not come to mind right now .

God bless
Wyr
 
#15 ·
As a matter of update, we had another technician look at our system today.

* The system is likely performing the best it can for the current weather (high temps) and our home however....

* The suction line is 3/4 and should be 7/8 for our 4 ton system. Left over from the previous system and not replaced or suggested previously.

* As others here said, the return size is too small. He said we should have 800 sq in and suggested a 2nd return be installed.

* The return as it goes in the unit itself is reduced slightly (being picky). When new, the flaps of metal go out and should be connected to a round adapter (?) to the duct work to the vent for return. The metal is pushed into the unit, squaring it off and reducing airflow by 20% or so.

* Minor, but the return as strapped in the attic binds in one place from the load of a single strap. He suggested spreading that over a large surface area with a tin "saddle".

All-in-all, the system is good, but the air flow is restricted some. Improving that, and increasing the line size he said would add a "half ton".

FYI for those who are interested. Thank you again for the initial feedback.
 
#17 ·
If your 3/4" suction line is only 50 foot long, and your A/C is R22, then you have a capacity loss of 2300 BTUs, if its r410A, and 50 foot, then you have a capacity loss of 1035 BTUs.
 
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