Answers, details about ASHRAE 90.1 Addendum ch

Several questions were addressed by the presenters after the ‘HVAC: New chiller requirements’ webcast.

By J. Patrick Banse, PE, LEED AP, Smith Seckman Reid; and Jason Gerke, PE, LEED AP September 16, 2014

Though J. Patrick Banse from Smith Seckman Reid in Houston and Jason Gerke from GRAEF in Milwaukee tackled several questions during the live webcast ‘HVAC: New chiller requirements,’ several audience members had additional questions. A selection of these answers is included below.

Question: Are air cooled chillers also rated in kW/Ton?

  • J. Patrick Banse: Air cooled chillers have ratings expressed in energy efficiency ratio (EER), which is determined by BTU/W.

Question: Can energy efficiency values be exceeded and still meet ASHRAE Standard 90.1?

  • J. Patrick Banse: If by exceeded you mean be more efficient (lower values)-then, yes. If by exceeded you mean less efficient (higher values)-then, no.

Question: It’s all very well selecting an efficient chiller (and all the other equipment that ASHRAE 90.1 covers), but if they’re not put together "properly," the system may not be efficient. Does ASHRAE 90.1 stipulate the overall efficiency of the system? If so, where does it stipulate this?

  • Jason Gerke: ASHRAE 90.1 allows for multiple compliance paths for HVAC systems. These paths include the "simplified approach" or "mandatory approach." The simplified approach provides a list of required compliance items. The mandatory approach compliance may be accomplished through either selection of equipment meeting minimum efficiencies in the tables and other criteria or the energy may complete an "energy cost budget" calculation to prove compliance.

Question: Can air cooled systems beat the system efficiency of water cooled considering all loads, fans, pumps, etc.? Or in other words, is a big centrifugal chiller always the best?

  • Jason Gerke: This answer will depend on the building type, location, and use of the space. A small air cooled chiller can easy beat the efficiency of a water cooled machine, but the equipment selection criteria may only allow an air cooled machine to be used because of the capacity. The total system efficiency greatly depends on how the whole system is put together, controlled, and maintained. Each system needs to be judged on the specific goals for every project.

Question: What is an owner to do if only one manufacturer can provide the chiller that can meet the requirement, in accordance with the local authority having jurisdiction’s (AHJ) adoption of Addendum ch?

  • J. Patrick Banse: Either accept or negotiate with the one manufacturer, or redesign the project chiller requirements for more competition.

Question: Must chiller manufacturers label their products as to how they comply with ASHRAE 90.1-2010?

  • J. Patrick Banse: Yes. Paragraph of 90.1-2010 requires an equipment manufacturer to label the equipment stating compliance with ASHRAE Standard 90.1

Question: Do you have the option in ASHRAE 90.1-2010 to use ratings for standard or non-standard AHRI conditions? Or are you required to show compliance at actual design conditions?

  • J. Patrick Banse: You must show compliance with either the listed values in Table 6.8.1C for standard conditions or provide calculations for nonstandard conditions. The design conditions would be either at standard conditions (no calculations) or at nonstandard conditions requiring calculations.

Question: Which COMcheck edition applies for Addendum ch?

  • Jason Gerke: AHJs typically require the latest version of the program to be used. The best way to accomplish this is to use the online version of COMcheck which can be found at

Question: Do the requirements of ASHRAE 90.1 Addendum ch apply to process chillers as well as HVAC chillers?

  • Jason Gerke: Process equipment is exempt from the requirements of ASHRAE Standard 90.1. The standard only addresses the requirements for "mechanical equipment and systems serving the heating, cooling, ventilating, or refrigeration needs….".

Question: How are chiller efficiencies impacted by ASHRAE Standard 90.1-2013?

  • J. Patrick Banse: When Standard 90.1-2013 is adopted by the AHJ either directly or by reference, the chiller efficiencies in Table 6.8.1C are in effect and must be followed.

Question: Are heat recovery chillers are outside the scope of the AHRI certification program?

  • Jason Gerke: Heat recovery chillers are excluded from the AHRI 550 certification program. These chiller efficiencies are calculated by the equipment manufacturers following their own internal guidelines. Comparison of these chillers at AHRI standard conditions would provide little benefit to the engineer. This equipment should always be selected on a project system by system basis.