Air Conditioning Start-Up Checklist

A great many air conditioning failures take place at start-up or early in the cooling season because of inoperative controls or safety devices. Most of these accidents could have been prevented if a little more attention had been paid to readying the equipment for service. We, therefore, recommend that the following measures be taken to ensure a trouble-free cooling season and reduce the likelihood of equipment malfunction.

This convenient checklist has been designed to help maximize reliability, economy, and fuel conservation in the operation of air conditioning equipment.


  • Energize the crankcase heaters for at least eight hours before the start-up. Crankcase heaters should be left energized for the rest of the season so that whenever the compressor is idle, the heater will prevent refrigerant “migration” to the crankcase.
  • Test the lubricating oil for color and acidity, and check the crankcase oil level.


  • Check the air passages of open motors for cleanliness and obstructions.
  • Check the condition of and lubricate bearings.
  • Take insulation resistance readings. If the readings indicate less than one megohm resistance, don’t start the motor. Check for the cause of the low resistance.

Motor controls

  • Inspect starter contacts for deterioration from short cycling, arcing, or corrosion.
  • Check terminal connections for tightness.
  • Examine the overload protection for the proper size.
  • Check mechanical linkages for binding and excessive looseness.
  • Check timing devices for the correct operating sequence.

Operating and safety controls

  • Determine that the controls are properly calibrated and in working order particularly thermostatic controls, oil pressure safety switches, and flow switches.

Refrigerant circuits

  • Be sure the circuit is equipped with a moisture indicator and if moisture is indicated, install new liquid line filter/drier cores.
  • Determine and correct the source of the moisture.
  • Check the expansion valve for proper operation and superheat settings over the full range of operation.

Condensers and evaporators

  • Ensure that proper cleaning of heat transfer surfaces for the type of unit in use has been completed prior to operation.
  • Cooling towers: Check the baffles for tightness and soundness.
  • Clean the baffles, sump, and the spray nozzles.
  • Check the make-up water valve for proper operation.


  • Check the bearings, packings, shaft couplings, and seals.
  • Lubricate bearings.


  • Check for broken, cracked, bent, or loose blades.
  • Check hubs, fan shaft, and bearings.
  • Check the belt condition and belt tension.
  • Replace air filters.


  • Check all piping supports for signs of distress.
  • Check for external damage and excessive vibration.

The tips offered here are intended to complement and not replace the recommendation of the equipment manufacturer. For more information on loss prevention and preventative maintenance CLICK HERE.

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© 2020 The Hartford Steam Boiler Inspection and Insurance Company. All rights reserved. This article is for informational purposes only and is not intended to convey or constitute legal advice. HSB makes no warranties or representations as to the accuracy or completeness of the content herein. Under no circumstances shall HSB or any party involved in creating or delivering this article be liable to you for any loss or damage that results from the use of the information contained herein. Except as otherwise expressly permitted by HSB in writing, no portion of this article may be reproduced, copied, or distributed in any way. This article does not modify or invalidate any of the provisions, exclusions, terms or conditions of the applicable policy and endorsements. For specific terms and conditions, please refer to the applicable endorsement form.

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