| 2010-08-10 11:14:58 | MECHANICAL APPROVED WITH EXCEPTION! |
| | THIS PLAN HAS BEEN APPROVED PROVISIONALLY. FAILURE TO |
| | CORRECT THE LISTED DEFICIENCIES IN THIS PLAN PRIOR TO |
| | INSPECTION WILL RESULT IN FAILED INSPECTION(S) AND THE |
| | ASSESSMENT OF RE-INSPECTION FEE(S). REVISIONS REQUIRE |
| | ADDITIONAL REVIEWS WITH ASSOCIATED FEES. |
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| | M1602.4 BALANCED RETURN AIR. RESTRICTED RETURN AIR |
| | OCCURS IN BUILDINGS WHEN RETURNS ARE LOCATED IN CENTRAL |
| | ZONES AND CLOSED INTERIOR DOORS IMPEDE AIR FLOW TO THE |
| | RETURN GRILL OR WHEN CEILING SPACES ARE USED AS RETURN |
| | PLENUMS AND FIRE WALLS RESTRICT AIR MOVEMENT FROM ONE |
| | PORTION OF THE RETURN PLENUM TO ANOTHER. PROVISIONS |
| | SHALL BE MADE IN RESIDENTIAL BUILDINGS TO AVOID |
| | UNBALANCED AIR FLOWS AND PRESSURE DIFFERENTIALS CAUSED |
| | BY RESTRICTED RETURN AIR. PRESSURE DIFFERENTIALS ACROSS |
| | CLOSED DOORS WHERE RETURNS ARE CENTRALLY LOCATED SHALL |
| | BE LIMITED TO 0.01 INCH WC (2.5 PA) OR LESS. PRESSURE |
| | DIFFERENTIALS ACROSS FIRE WALLS IN CEILING SPACE |
| | PLENUMS SHALL BE LIMITED TO 0.01 INCH WC (2.5 PA) BY |
| | PROVIDING AIR DUCT PATHWAYS OR AIR TRANSFER PATHWAYS |
| | FROM THE HIGH PRESSURE ZONE TO THE LOW ZONE. |
| | |
| | EXCEPTIONS: |
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| | 1. TRANSFER DUCTS MAY ACHIEVE THIS BY INCREASING THE |
| | RETURN TRANSFER ONE AND ONE HALF TIMES THE CROSS |
| | SECTIONAL AREA (SQUARE INCHES) OF THE SUPPLY DUCT |
| | ENTERING THE ROOM OR SPACE IT'S SERVING AND THE DOOR |
| | HAVING AT LEAST AN UNRESTRICTED 1 INCH (25 MM) UNDERCUT |
| | TO ACHIEVE PROPER RETURN AIR BALANCE. |
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