The news this month has multiple stories about Heating and Air Companies being very busy with units not cooling or not cooling enough. Driving around town, I see most of these contractors have a sign out front looking for help. The wait time is up to two weeks. In the 7 homes I’ve been in this week. One had no working AC, one home was on it’s last legs, and two other homeowners were very concerned. For the 1st time in 7 years, I’m getting calls from my website asking if I can fix their AC unit.
This morning I found a report on HVAC Problems, Problem Identification and Repair. I have scanned this 27 page report and these are the things that jumped out.
Background: California has some of the toughest energy requirements for buildings, both new and remodeling of existing buildings. These is a direct result of the problems they had 15 years ago, with not enough electricity. They resulted to black outs, (Utilitys were allowed to shut off electricity to various geographic areas). and brown outs, (Utilities were allowed to provide only part of the electricity needed to a geographic area). Both are not good.
These energy codes are generally referred to as Title 24. A large part of the work in California the last few years has been testing and measuring how well the requirements are being met. This report is just one small piece of that process.
Title 24 refers to the problems, their identification and repair as “Fault Detection and Diagnosis” or “FDD”
The Report was working on the answers to these questions
- Is FDD worth the investment, and what is the savings potential?
- How effective are available FDD methods and what do they cost to implement?
- What training is needed for effective FDD and is it being provided?
- Are codes and standards working?
- What are the major gaps and how can they be addressed?
This particular session and reporting was limited to:
- System Types–new and existing residential only
- Air conditioners
- Heat pumps
- Furnaces and air handlers
- Fault Types
- Low airflow
- Refrigerant system charge, restrictions, and contaminants
- Mechanical and electrical faults and faulty installation
- Repair vs. Replacement Issues
- Cost-effectiveness of FDD
- Replacement refrigerants for R-22
- Human Factors
- Training and quality of maintenance
- Homeowner knowledge and expectations.
The reporting included tests applied with standard AHRI methods. The tests were designed to determine the impacts on efficiency and capacity of a variety of conditions, including:
- Airflow of 250 cfm/ton reduced energy efficiency ratio (EER) by 12% and has the potential to produce a false overcharge diagnostic due to freezing of the coil (the asterisk denotes an unofficial EER)
- Liquid line restrictions (e.g. due to clogged filter-dryer or metering devices) reduced EER by 30% to 36% for non-TXV and TXV systems respectively
- Only 0.3% Nitrogen in the refrigerant reduced the EER by 18% with no TXV and 12% for the TXV-equipped system
Discussion pointed out that California Title 24 charge verification methods, which only measure superheat (for non-TXV) and sub-cooling (for TXV) systems, and ACCA Standard 4, for which only 3% of the procedures are related to energy performance. Also covered were how improperly maintained vacuum pumps, test instrument error, and poor service practices such as use of rules of thumb contribute to the introduction of non-condensables, improper charge, and other faults.
John Proctor, PE presented a case for making improvements to California’s Title 24 standards, John worked with a team to inspect a large number of recently built homes to identify HVAC installation and performance issues. He began his presentation by defining an “incremental effectiveness ratio” that divides benefits of maintenance by the incremental cost to diagnose, repair, and ensure quality, which is fundamental to the question of the value of HVAC service. He proceeded to show a series of graphs from his experience and other studies that illustrate the deviations from the ideal for airflow, charge, duct leakage and efficiency, and non-condensables, as well as the incidence of occurrence of these defects.
For example, his graphs show:
- 50% reduction in airflow reduces EER by 25%.
- A refrigerant charge that is 70% of the recommended charge reduces EER by about 55%.
- Leaving Nitrogen in the line set and coil at 20 psig before charging with refrigerant reduces the sensible EER by about 45%.
- From his 2003 survey, more than 60% of the houses checked failed on refrigerant charge, airflow, and duct leakage, and more than 95% failed overall.
Many of these issues result from a lack of training and a lack of follow up by supervisors.
They had some specific things that could be done by builders, HVAC Contractors and home owners to ensure these items do not get missed.
I will read the report in more detail and have further comments.