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Performing Preventative Maintenance on the Cambridge S-Series

Performing Preventative Maintenance on the Cambridge S-Series

by HVAC Distributors

Proper maintenance is key to keeping your Cambridge S-Series heating unit running efficiently. Scheduling preventative maintenance can prevent repair costs for your customers over time. Checking air filters, greasing bearings, or inspecting belts can increase the life span of an S-Series unit.

Cambridge Air Solutions  S-SeriesHow Often Should a Unit be Inspected?

  • Units without filter sections: 2 times per year.
  • Units with filter sections: 4 times per year.

Checking the Air Filters:

Clean or change out the air filter if they are dirty. Dirty air filters will reduce the CFM (Cubic Feet Per Minute) and can lead to damage in the discharge air sensor.

  • Service filters as needed.
  • Clean filters start out with a pressure drop cross the filters between 0.15 and 0.25” WC, says Cambridge Air Solutions (2024).
  • Cleaning or replacing the filter is general practice for pressure drop below the increased factor of four times the initial clean value.

What Should be Greased:

Blower bearings and motor bearings should both be greased when performing a maintenance check.

  • Blower bearings, evenly grease and distribute around the race.
  • Motor bearings, do not use standard bearing grease in the Baldor motor. Motors are normally pre-greased. Follow the schedule for grease motor intervals.

Inspect the Belt for Wear and Tension:

  • A belt can wear out from being too tight. This can cause wear to the bearings as well, not only to the belt.
  • Check to see if a belt is too loose. If the belt is loose, it may cause squealing or slipping causing damage to the belt and bearings.
  • Consider periodic belt adjustments if needed.
  • A Browning Belt Tension Checker can be used, along with a straight edge to verify proper belt tension. Verify proper belt tension during maintenance checks.

Examine Other Preventative Maintenance Actions:

  • Check the blower wheel, making sure the surfaces of the blades stay clean.
  • Cycle the unit on and off through all modes. Making sure all modes on the unit are running correctly.
  • Cleaning the burner may be needed, although it is self cleaning. If the burner becomes dirty and dusty, a burner cleaning is needed. Cambridge provides resources on burner cleaning. Refer to page 82.
  • Inspect the flame sensor for a steady reading between 2.0 and 6.0 µA.
  • Inspect the hot surface ignitor.
  • Check the discharge temperature.
  • Look for any loose wires and make sure connections are secure within the control panel.
  • Perform a gas value leak test.
  • Test the manifold differential gas pressure, making sure it matches the nameplate.
  • Check digital thermostat calibrations.

Following a preventative maintenance schedule on your Cambridge S-Series unit can improve it’s life span., revamping the quality of the unit’s performance, reducing energy cost, and decreasing downtime. Checking air filters, greasing bearings, or inspecting belts can help prevent costly repairs overtime. Introducing preventative maintenance schedules to your clients can give them peace of mind, knowing their unit is running efficiently and properly after each maintenance check.


Cambridge. (2024). Cambridge S-Series Preventative Maintenance Schedule.