by Donald Prather
The definition of a Catch-22 is: a circumstance that has rules with conflicting conditions. Example: being required to tie yourself off for safety before going up a ladder in a location where you can’t reach the tie-off point without a ladder. Contractors need to know about conflicting conditions during the planning stages of a project in order to make adjustments early so they can avoid becoming trapped with no good solutions available.
Recently, a design-related Catch-22 came to my attention when an HVAC contractor called into ACCA. He had just completed a multi-family new homes project that had been approved and certified by ENERGY STAR (ES). Unfortunately, the homes did not qualify for the local utility rebate program. The contractor had two questions. The 1st question was, could ACCA send a letter stating that the installation met the Manual S requirements so he could get the utility rebate on the numerous units installed? The 2nd question was, how can an approved ES new home project based on ANSI/ACCA 5 QI-2015 HVAC Quality Installation Specification (ACCA 5 QI Standard) requirements fail to qualify for an energy rebate?
The answer to the 1st question was sad, but fairly easy: No, ACCA would not send a letter contradicting Manual S requirements to the utility.
The second question’s answer takes up a little more space:
Scenario 1: The ACCA 5 QI Standard does not specify minimum energy efficiency requirements. Thus, meeting all of the ACCA 5 QI Standard’s requirements does not guarantee that a utility’s energy efficiency program’s requirements will be met. For example, if a program called for a Seasonal Energy Efficiency Ratio (SEER) higher than 13 for a heat pump, the requirement would exceed the minimum requirements in the ACCA 5 QI Standard. The heat pump example above could be expanded to include rating values for the Heating Season Performance Factor (HSPF); Energy Efficiency Ratio (EER); Coefficient of Performance (COP); and the Annual Fuel Utilization Efficiency (AFUE) for combustion appliances. So be warned, an HVAC system that was properly installed following the QI-Standard’s design, installation, and documentation requirements might not meet the utility’s energy efficiency requirements even though it will work properly, and perform at the original equipment manufacturer’s design SEER, HSPF,EER, COP and/or AFUE.
Scenario 2: In an earlier version of ES (3.0), the requirements listed on the HVAC contractor’s checklist mirrored Manual J, D, and S requirements. In the current version (3.10, Rev. 08), ES made subtle changes in the equipment sizing “Allowed” that may have big implications for HVAC contractors in jurisdictions where Manual S sizing requirements are called for in the codes. Jurisdictions that specify the International Residential Code (IRC) or the International Energy Conservation Code (IECC) will require the designer to size HVAC Equipment in accordance with Manual S requirements.
What are the EPA’s current sizing requirements one might ask? Conflicting conditions become obvious when we take a look at the new EPA equipment sizing chart in Figure 1 (extracted from ES: Contractor Checklist). ES “Recommended” sizing ranges align with those of Manual S. Unfortunately, higher values are listed as “Allowed” on the chart. For example, an HVAC contractor who selected a two-speed heat pump that was 140% of the Manual J design value would be accepted as within an ES qualifying range and would be eligible to receive an ES label. The Catch-22 is, the installed system may not meet a local utility program’s rebate requirements. Worse yet, the installed system may not meet local code requirements.
Figure 1: HVAC Design Report Table from ES Version 3/3.1 (Rev. 08)
Let’s give the Scenario 2 sizing Catch-22 a closer look. For increased savings, the utility’s program specifically required the 2015 version of the IECC’s sizing requirement, and a system rated at 16 SEER or higher. The contractor did not use the ES “Recommended” values that aligned with Manual S. Instead the contractor opted for the ES sizing “Allowed” range. The two-speed (two-stage) equipment installed exceeded both Utility and ES efficiency requirements with a 16.5 SEER and a 13.0 EER, but failed to meet the Manual S maximum sizing requirements when operating in stage 2, even though it met the ES “Allowed” range. The calculated Manual J load for the units was 15,452 sensible and 3,902 latent with a total cooling load of 19,354 BTU/H. For the two-stage equipment selected, the size listed by the original equipment manufacturer (OEM) was as follows:
Stage 1, 16,300 sensible BTU/H and 4,100 latent BTU/H for a total of 20,400 BTU/H (105% of design); Stage 2, 18,300 sensible BTU/H and 6,500 latent BTU/H for a total of 24,800 BTU/H (128% of design). Thus, the equipment met the ES “Allowed” requirement. Unfortunately, the high-speed value did not meet the Manual S two-speed maximum requirement of 1.2 or 120% (Note: In the caller’s calculations, the expanded OEM data was used to determine OEM sizing).
The sizing Catch-22 above could have been much worse: if the local code authority required the contractor to meet the current IECC requirements, the equipment might have failed the mechanical inspection. Fortunately, for the contractor, the local codes had not yet been updated and the requirements were met using the ES “Allowed” sizing values.
The plan was to offset the added cost per unit by qualifying for the utilities rebates did not materialize. Thus, after upgrading to two-stage equipment with a higher SEER/EER rating than ES required, the contractor did not qualify for the anticipated utility rebate for the multifamily project (ouch).
To avoid conflicts in equipment sizing, a safe approach for all contractors is to know the local code requirements, and to always design using Manuals J, D, and S. Additionally, read the fine print in utility rebate programs. As a final note: always install the equipment to the ACCA 5 QI Standard requirements will cover the installation and documentation bases.
Author's Note: Don Prather is technical services manager with ACCA. Reach him at firstname.lastname@example.org or 703-824-8867.