basics
DESCRIPTION
Basics. Airflow. Basics. Air Flow Basics. -Air is invisible -Everyone assumes adequate airflow -Frequently airflow is 30%-50% low -Cooling – 400 CFM per ton -Heating – 100 to 500 CFM /10,000 BTU -Duct leakage or high static pressure -Air properties must be measured. Basics. - PowerPoint PPT PresentationTRANSCRIPT
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Basics
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Air Flow Basics
-Air is invisible-Everyone assumes adequate airflow-Frequently airflow is 30%-50% low-Cooling – 400 CFM per ton-Heating – 100 to 500 CFM /10,000 BTU-Duct leakage or high static pressure-Air properties must be measured
Basics
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•Low airflow can cause temperature stratification•More fan power is not always the answer•Select equipment based on available airflow – 400 CFM•Inadequate air flow can waste 10% in energy•400 CFM per ton wet coil needed•Select equipment with reserve CFM•Freeze-up occurs at 200 CFM per ton
Air Flow Basics
Basics
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The Equipment Or The System?
-If the problem is with the equipment, the solution is up to you.
-If the problem is with the air distribution system, the primary responsibility for the solution lies elsewhere, and/or possibly you.
Basics
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Correct Air Flow
•You cannot get the performance from an air conditioner without it•You cannot accurately charge orifice or capillary tube systems without it.•So, how do we determine it?
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Correct Air Flow• Total Static Pressure
• Temperature Rise
• Evaporator Pressure Drop
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System Static Pressure
Measurement
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System Static Pressure
(See Handout)
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Static Pressure Measurement
-The key to system airflow diagnostics-A companion to airflow measurement
-It takes less than 5 minutes to measure-Similar to blood pressure diagnostics
Total External Static Pressure+.65” (Supply side reading) -.45” (Return side reading)
1.10” Total External Static Pressure
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System Static Pressure
(See Handout)
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CFMBy
TemperatureRise Method
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Airflow Measurement(Temperature Rise Method)
(Red Book, Pg. 33)
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CFM By Temperature Rise
BTUH OUTPUTT X 1.08*
= CFM
*1.08 = constant number for std air. It’s a combination of a number of values that are in the complete equation. Std air is 70F, sea level
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CFM By Temperature Rise•425 CFM Per Ton (Wisc.-Dry Coil)•Humidifier bypass closed•Switch Heating and Cooling Speed Tap!!!•Relocate Heating Speed tap to proper speed!
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Blower should always be on high speed? •2 TON – 800 CFM
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CFM By Evaporator Pressure Drop
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