Third-party troubleshooting review of problematic HVAC installations can be a profitable business if done correctly. Similar to third-party peer review, this is a niche business requiring a special kind of HVAC engineer with years of technical and hands-on experience. It also requires someone that can be cost-effective in their approach while being sensitive to those who design and/or built the project. The added benefit for the troubleshooting engineer (TSE) versus the third-party peer design review is that most (if not all) the problems have been experienced (not necessarily identified) via occupant complaints and unexpected system shutdowns due to safeties and alarms.
Also similar to peer review, the first thing the TSE must recognize is that she has been hired to identify the problems and make recommendations (TSE Step 1).