[gatorinmn]

I recently had a new 15 SEER 3-ton Carrier Infinity CAC system installed. In order to qualify for a rebate with my local electric company, the installer filled out a form concerning the A/C's performance. Here's what is listed:

AIRFLOW:

Amps -- Compressor: 29
Amps -- Furnace: 9.0
Return db Temperature: 67.2
Return wb Temperature: 59.1
Supply db Temperature: 54.3
Supply wb Temperature: 48.2
Actual temperature split (return db - supply db): 12.9
Target temperature split: 20
Difference: 6.1

TXV System:

Liquid line pressure: 266
Liquid saturation temperature: 86
Liquid line temperature: 70
Actual subcool (liquid saturation - liquid line): 16
Target subcool: 14
Difference: 2

Now, I've got a couple of concerns with the airflow information:

1. First and foremost, the difference between the actual temperature split and the target temperature split is 7.1 and not 6.1. I don't know if that was an unintended error or was done purposely by the installer on the form.

2. I've read in various sources online that the difference between the actual temperature split and the target temperature split should come out +/- 3, but in my case it's 7.1. What exactly does that mean? (I know little about A/C, I just worry when I see that the actual split is so far off from its target). Does this mean that the system does not have proper airflow? Was something done incorrectly when it was installed? Is the system not functioning within manufacturer's specifications? What can/should be done to remedy this "problem" (if it's even a problem at all)?

Thanks in advance for any thoughts or suggestions.

 

[BaldLoonie]

Something wrong with 12.9° drop with low humidity

 

[gatorinmn]

BaldLoonie, I'm not sure I understand your response. Are you saying that I am wrong for thinking there is a problem, or are you saying that there is actually a problem? Like I said, I know little about A/C. If you're saying that I have nothing to worry about, that's great -- please just say so and tell me why. I appreciate it.

 

[BaldLoonie]

While 20° diff between entering air to the coil and leaving air is a nice goal, it may not always happen. High humidity is the biggest culprit in a lower than desired temp drop. But with a 59° wet bulb, the day your test was taken you had low humidity in the house. So I'm wondering why the drop was so poor. I think you are right to be concerned about that number.

 

[udarrell]

I recently had a new 15 SEER 3-ton Carrier Infinity CAC system installed. In order to qualify for a rebate with my local electric company, the installer filled out a form concerning the A/C's performance. Here's what is listed:

AIRFLOW:
"

For figuring BTUH, Total CFM is a must have figure, was it 350, 400 or 450-CFM per/ton?" - udarrell

Amps -- Compressor: 29
"For one compressor, RLA of 15 to 17-amps would be more like it(?)"
Since there does not appear to be a heavy heatload, an overcharged system can cause high amp draw? - udarrell

Amps -- Furnace: 9.0
"At what ESP & CFM does it pull 9 amps?"
- udarrell

Return db Temperature: 67.2
Return wb Temperature: 59.1
Supply db Temperature: 54.3
Supply wb Temperature: 48.2
Actual temperature split (return db - supply db): 12.9
Target temperature split: 20
Difference: 6.1 (7.1)

TXV System:
"TXV SUPERHEAT SETPOINT? TXV SYSTEM SUPERHEAT?" - udarrell

Liquid line pressure: 266
Liquid saturation temperature: 86
Liquid line temperature: 70
Actual subcool (liquid saturation - liquid line): 16
Target subcool: 14
Difference: 2

Now, I've got a couple of concerns with the airflow information:

1. First and foremost, the difference between the actual temperature split and the target temperature split is 7.1 and not 6.1. I don't know if that was an unintended error or was done purposely by the installer on the form.

2. I've read in various sources online that the difference between the actual temperature split and the target temperature split should come out +/- 3, but in my case it's 7.1. What exactly does that mean? (I know little about A/C, I just worry when I see that the actual split is so far off from its target). Does this mean that the system does not have proper airflow? Was something done incorrectly when it was installed? Is the system not functioning within manufacturer's specifications? What can/should be done to remedy this "problem" (if it's even a problem at all)?

Thanks in advance for any thoughts or suggestions.

There is considerable wrong with what I see.

First, we should all be required to use an anemometer to record the FPM Velocity & the CFM to each room & the total CFM. With that information & the SA/RA db & wb data we & the electric company can ball-park the BTUH output of the system. - udarrell

 

[derbysr]

do you have hot or cold spots in the house?

 

[beenthere]

A. Is your unit a single or 2 stage.
B. Something is wrong with those high amp draws. Seems like he took the info from the data labels. Or fudged them from the data labels.
C. Where these indoor temp readings taken at the grilles, or across the coil like they should have been.

 

[gatorinmn]

do you have hot or cold spots in the house?

Only level by level. The air handler is in the basement; there are two levels above that. The basement level, not surprisingly, stays ice cold. The main level, which is where the thermostat is located, stays very cold. The upstairs level gets cool, but never as cold as the other two levels. Of course, cold air falls, so this doesn't really surprise me.

Within each level, however, the temperature is pretty constant from room to room.

 

[gatorinmn]

A. Is your unit a single or 2 stage.
B. Something is wrong with those high amp draws. Seems like he took the info from the data labels. Or fudged them from the data labels.
C. Where these indoor temp readings taken at the grilles, or across the coil like they should have been.

A. 2-stage.
B. I dunno about the amp draws, although the electrical in this house has always been a little screwy.
C. The indoor temps were taken across the coil.

 

[beenthere]

He may have taken those temp readings in first stage. And if its moving too much air infirst stage you'll get low temp deltas. And its possible the unit could be slightly low on charge which will also cause those low temp deltas.

I think he fudged the amp readings.

 

[21degrees]

More information is needed.

Model number of A/C and size. Same with furnace. I will agree that numbers wether RLA or FLA are high. Delta tee should be close to 20*but can be lower depending on humidy load. Sub cooling seems high for cool day. I would need liquid line temperature and pressure to varify.