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vent spacing
- Thread starter MARC
- Start date
Dr. J
Silver Member
I assume you are talking about the supply and return grilles. There is no specific requirement in the IMC, but there is a "backdoor" angle.
2006 IMC 403.1 states " Ventilation supply systems shall be designed to deliver the required rate of supply air to the occupied zone within an occupied space. The occupied zone shall have boundaries measured at 3 inches (76 mm) and 72 inches (1829 mm) above the floor and 24 inches (610 mm) from the enclosing walls." If the supply and returns are right next to each other, the supply will short circuit directly to the return without mixing with the room. Thus, the air is not being delivered to the occupied space. While it is not a hard and fast prescriptive requirement, if you saw an obvious short-circuiting arrangement, you could use this section to question the designer.
2009 has a little more meat. 403.3.1.2 has a table for "ZONE AIR DISTRIBUTION EFFECTIVENESS", where a factor is used to determine if good mixing can be expected. Poor mixing situations are penalized by requiring more outside air than good mixing situations.
2006 IMC 403.1 states " Ventilation supply systems shall be designed to deliver the required rate of supply air to the occupied zone within an occupied space. The occupied zone shall have boundaries measured at 3 inches (76 mm) and 72 inches (1829 mm) above the floor and 24 inches (610 mm) from the enclosing walls." If the supply and returns are right next to each other, the supply will short circuit directly to the return without mixing with the room. Thus, the air is not being delivered to the occupied space. While it is not a hard and fast prescriptive requirement, if you saw an obvious short-circuiting arrangement, you could use this section to question the designer.
2009 has a little more meat. 403.3.1.2 has a table for "ZONE AIR DISTRIBUTION EFFECTIVENESS", where a factor is used to determine if good mixing can be expected. Poor mixing situations are penalized by requiring more outside air than good mixing situations.
JBI
Registered User
ASHRAE anyone?
Dr. J
Silver Member
The 2009 IMC Ch 4 is based on 2004 ASHRAE 62.1, particularly regarding the Zone Air Distribution Effectiveness, and getting the outside air to the breathing (occupied) zone.