Sizing question

[fatcat]

2200 SQ FT 10FT CEILINGS BROTHER IN LAWS 3 TON CONDENSER CAN ONLY GET TEMP TO 77 WHEN T-STAT CALLS FOR 69 AND COMPRESSOR THERMAL O/LSs After 45 minutes or so kicks on (Compressor).
Again this is only when ambient is 90+. Would a larger condenser and A coil HELP THIS Delima..? wHEN IT COOLING REGISTER AIR IS 64 DEG

CAP. TUBE

AMBIENT 89
LIQUID L PSI 228
TEMP LIQ LINE 90

iNDOOR WB 64

SUCTION PSI 70
SUCTION LINE TEMP 75 AND SWEATING
CALCULATED 10 DEGRES SUPERHEAT + OR -5 DEGREES

GOD BLESS ARE VETERANS Living and Deceased so we can practice our PROFESSION HAVE A PROFITABLE DAY

[tinknocker service tech]

do manul j and see what it calls for

[dan sw fl]

Originally posted by fatcat
2200 SQ FT
10 FT CEILINGS
3 TON CONDENSER, 77'
When it is COOLING REGISTER AIR is 64'

BOTH Undersized and Underperforming:
___Underperforming based on 13'F Delta T air flow.

___Seems significantly __Undersized (needs At Least 4-ton or maybe even a 5-ton) based on my experience performing ACCA Manual J 8th edition analysis on 300+ custom homes.

However, you have not provided:
1. R-values for Walls
2. R-value of Ceiling
3. Window Area
(including Sliding glass doors) on EACH Side of house
4. Windows CLEAR or Tinted
5. House Orientation

MORE Later in Update or Follow-up

[Edited by dan sw fl on 06-26-2005 at 12:54 PM]

[BaldLoonie]

First thing to do is find out why comp won't stay running. Undersized unit working properly can run 24/7 without failing. You say register air only 64. Also take readings of supply & return right at the unit and see if you are picking up considerable duct heat gain.

[Freezeking2000]

I think you had better find out why it is overloading and i think the house will cool better!

[dan sw fl]

Summary of Approx. Loads

.......WINDOWS.. 15,444 BTUh CLEAR GLASS 280 S.F.
.......CEILING.. 6,368 R-19
.........Walls.. 2,292 R-19
.........Floor....... 0
.........DUCT.....6,286 R-6 in 130'F Attic
.INFILTRATION.....2,420
.INTERNAL Gains...2,977
.........People...1,466
_________TOTAL___37,153. BTUh = 4-Ton

[trane]

Dan, I know everything your doing is trying to help but why give these loads without knowing the needed info. There is most likely a contractor that is trying to fix this and you giving incorrect information will only make matters worse. His first problem is getting the unit working like it should and then he can see if there is a size problem.

[beenthere]

I hope that suction line temp of 75° was a type o, error.

70 psi is a saturation temp of 41°, that would give you 34° superheat.

[beenthere]

Originally posted by beenthere
I hope that suction line temp of 75° was a type o, error.

70 psi is a saturation temp of 41°, that would give you 34° superheat.

Which would explain the compressor going out on over load.

[mech890]

Assuming your readings are right it appears overcharge w/ a restriction

[dan sw fl]

Originally posted by trane
His first problem is getting the unit working like it should and then he can see if there is a size problem.

Following PARALLEL SIZING & Performance Paths
is a COMPLETELY ROUTINE Evaluation Process
which requires a couple iterations.

DEVELOP THE WHOLE PICTURE.

If you can't stand the heat, get out of the kitchen.

Fatcat,

It is QUITE OBVIOUS within < 7-minute evaluation that
75'F will never be consistently achieved at Outside Design Temperature with a Good performing 3-ton unit, UNLESS there are < 130 S.F. TOTAL AREA of Tinted windows in this 2,200 S.F. house.

NEARLY ALL (i.e. 97%) U.S. HOUSES
HAVE > 10% RATIO OF GLASS-TO-FLOOR AREA.

I'd say __< 1% chance__ of this 3-ton being the most appropriately sized unit in this case.

[trane]

Originally posted by dan sw fl

Originally posted by trane
His first problem is getting the unit working like it should and then he can see if there is a size problem.

Following PARALLEL SIZING & Performance Paths
is a COMPLETELY ROUTINE Evaluation Process
which requires a couple iterations.

DEVELOP THE WHOLE PICTURE.

If you can't stand the heat, get out of the kitchen.

Fatcat,

It is QUITE OBVIOUS within < 7-minute evaluation that
75'F will never be consistently achieved at Outside Design Temperature with a Good performing 3-ton unit, UNLESS there are < 130 S.F. TOTAL AREA of Tinted windows in this 2,200 S.F. house.

NEARLY ALL (i.e. 97%) U.S. HOUSES
HAVE > 10% RATIO OF GLASS-TO-FLOOR AREA.

I'd say __< 1% chance__ of this 3-ton being the most appropriately sized unit in this case.

Or the 2200 sq. ft. includes a basement, earth contact home, foam and concrete walls, foam insulation, the list goes on. If it was a home that I had sized I wouldn't want someone guessing on the internet and telling the homeowner I had installed the wrong size. I hope you see my point.