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Basics

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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 ... – PowerPoint PPT presentation

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Title: Basics


1
Basics
Airflow...
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Air Flow Basics
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

4
Basics
Air Flow Basics
  • 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

5
The Equipment Or The System?
Basics
  • -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.

6
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?

7
Correct Air Flow
  • Total Static Pressure
  • Temperature Rise
  • Evaporator Pressure Drop

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System Static PressureMeasurement
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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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  • CFM
  • By
  • Temperature
  • Rise Method

15
Airflow Measurement(Temperature Rise Method)
(Red Book, Pg. 33)
16
CFM By Temperature Rise
BTUH OUTPUT ?T X 1.08
CFM
1.08 constant number for std air. Its a
combination of a number of values that are in the
complete equation. Std air is 70F, sea level
17
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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