# Manual J question

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• 06-17-2005, 11:50 PM
sean88
Don't you also need to know where the OP lives, what design temperatures he desires, and the orientation of the various windows and doors? How about the number of fireplaces and the number of people living in the house?

In central VA - richmond - tidewater area design is 95 F 76 wb.

Fireplaces are negliable since they would not be used for heating purposes. They do contribute to infiltration due to stack effect if the damper is not closed.

For a family of 4 thats 450x4=1800 mbh total or .15 tons.

Hopefully the sketch would have a north arrow, but you're right need the orientation of walls too.
• 06-18-2005, 05:28 AM
dan sw fl
Quote:

Originally posted by lit'l cat
Should the outside or inside of a house be used to figure load calc. 1 contractor measured inside (sd 2.5 ton a/c) the other measured outside & sd (3 ton a/c)
1,800 Sq.Ft., 300 Sq.Ft total Window area with Low E,
_____ Use 2.5 Ton ____

Low E ( S.H.G.C. ~ 0.46) requires 0.5+ ton less than CLEAR Glass ( SHGC 0.75). Room Temperature desired 75'F

S.H.G.C. Solar Heat Gain Coefficient
S.H.G.C. = 7/8 * Shading Coefficient

100 Sq.Ft. difference in floor + ceiling area may make Cooling load difference of << 0.2 ton
I use close to the Inside Area.
• 06-18-2005, 12:44 PM
lit'l cat
Designer Dan,

Your post sd 1800sq ft use 2.5 Ton. My house is ~ 1600sq ft. In theory, that would make the tonnage even less, then wouldnt I have an airflow problem?

Before you answer, this is more a general question since I realize you have no detailed info abour my house
• 06-18-2005, 07:45 PM
dan sw fl
Quote:

Originally posted by lit'l cat
Your post sd 1800sq ft use 2.5 Ton. My house is ~ 1600sq ft. In theory, that would make the tonnage even less, then wouldnt I have an airflow problem?

It ALL Depends on ...

Blower + Blower Settings + Condenser +
+ Duct + Duct Transitions + Outlets + dT + %RH
+ Time of Day + Day + Month + ... +

+ Sunny + Cloudy + use of Ceiling Fans +
whether you have several visitors +

+ How it ALL Works together AS A SYSTEM! ? ______
• 06-20-2005, 03:02 PM
dash