HVAC Procedure and Performance Guide

Replace gas orifice

Training for this procedure can be found in these courses:

                         131 – Oil Heat l  and  161 – Boilers l


Gas orifice must be installed according to manufacturer’s specifications.  Orifice must be specified size for application and burner must operate at rated capacity.  Applicable safety procedures must be followed.


  1. Review job order and manufacturer’s specifications.
  2. Determine type of gas used, gas pressure, burner rating and orifice size required.
  3. Collect tools, equipment and materials.
  4. Put on safety and protective equipment and apparel.
  5. Turn off gas and let furnace cool.
  6. Remove orifice fitting from manifold.
  7. Verify that new orifice is suitable replacement.
  8. Install new orifice fitting on manifold.
  9. Turn on gas and fire furnace.
  10. Adjust primary and secondary air, check furnace performance and determine if furnace is over-firing or under-firing.
  11. If furnace is over-firing or under-firing, recheck specifications, determine corrections that are needed and make necessary adjustments.
  12. Leave equipment in required operating status.
  13. Remove safety and protective equipment and apparel.
  14. Gather tools, equipment and leftover materials, and leave work site clean.