BGH BMPE36CTL, Руководство пользователя, Страница: 18 / 32

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The air distribution system has the greatest effect on airflow. The duct system is totally
controlled by the contractor. For this reason, the contractor should use only industry-recognized
procedures.
Heat pump systems require a specified airflow. Each ton of cooling requires between 350 and
450 cubic feet of air per minute (CFM), or 400 CFM nominally.
Duct design and construction should be carefully done. System performance can be lowered
dramatically through bad planning or workmanship.
Air supply diffusers must be selected and located carefully. They must be sized and positoined
to deliver treated air along the perimerter of the space. If they are too small for their intended
airflow, they become noisy. If they are not located properly, they cause drafts. Reture air grilles
must be properly sized to carry air back to the blower.If they are too small, they also cause noise.
The installers should balance the air distribution system to ensure proper quiet airflow to all
rooms in the home. This ensures a comfortable living space.
An air velocity meter or airflow hood can give a reading of system CFM.
6. Ductwork
Field ductwork must comply with the National Fire Protection Association NFPA 90A, NFPA 90B
and any applicable local ordinance.
Do not, under any circumstances, connect return ductwork to any other heat producing device
such as fireplace insert, stove, etc. Unauthorized use of such devices may result in fire, carbon
monoxide poisoning, explosion, personal injury or property damage.
Sheet metal ductwork run in unconditioned spaces must be insulated and covered with a
vapor barrier. Fibrous ductwork may be used if constructed and installed in accordance with
SMACNA Construction Standard on Fibrous Glass Ducts. Ductwork must comply with National
Fire Protection Association as tested by U/L Standard 181for Class I Air Ducts. Check local
codes for requirements on ductwork and insulation.
• Duct system must be designed within the range of external static pressure the unit is designed
to operate against. It is important that the system airflow be adequate.
Make sure supply and return ductwork, grills, special filters, accessories, etc. are accounted
for in total resistance. See airflow performance tables in this manual.