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Too little / too much air

What is going on

Possible causes and checks for: too little / too much air.

Likely causes

  • ESP too high / too low vs blower table

Check in this order

  1. Compute ASP = ESP − DPL, FR, resize or reduce fittings
  2. Cfm/ton check
  3. 1.08 × cfm × ΔT output check

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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.