Mechanical acceptance testing

For property developers, architects, mechanical subcontractors, and general contractors, mechanical acceptance testing (MAT) should now be on your radar. MAT applies to almost all new and modified mechanical systems, regardless of their size or capacity.

For example, if you install new controls, coils, or economizers, you will need to have them tested by an MAT technician and present these results to your building inspector prior to occupancy. To avoid critical delays in earning a certificate of occupancy, this article will highlight some key points for you to consider prior to performing MAT testing.

First off, what exactly is Mechanical Acceptance Testing?

MAT is a mandatory process that ensures your mechanical systems, such as heating, ventilation and air conditioning (HVAC), meet the energy efficiency standards set by the California Energy Commission (CEC). MAT has been required since 2005, but since 2022, only certified Mechanical Acceptance Test Technicians (MATTs) can perform the scope.

Different tests are required depending on the types of systems to be installed. Two common tests for most HVAC systems are MCH-02a (Outdoor Air Acceptance) and MCH-03a (Constant Volume Single Zone HVAC). These tests check the performance of your outdoor air (OSA) intakes and zone thermostat controls, which are essential for providing adequate ventilation, and comfort in your building. You should expect to complete these tests for any project with new or upgraded HVAC systems or controls.

Based on recent experience, we’ve highlighted three key points to consider during the design phase should this common mechanical acceptance testing be required for your project.

Each thermostat must be able to demonstrate connectivity to a local internet connection.

The ability for each thermostat to connect via Wi-Fi (or Wi-Fi Hotspot), ZigBee, BACnet, Ethernet, or a hard-wired connection must be established at the time of testing. This would normally be expected for a building automation system, but now it is even required for simple single-zone standalone systems (e.g., a clubroom in a multifamily development, a stand-alone conference room in a maintenance building, etc.).

No exemption is given if the IT infrastructure has not been set up completely (as with core and shell projects). This is a firm requirement regardless of the state of the rest of the electrical and/or IT infrastructure.

Thermostats must support occupancy-based fan behavior.

Supply fans are required to only operate intermittently when in unoccupied mode (to save energy) and continuously when in occupied mode (to meet ventilation requirements). Most single-zone thermostats, even “smart” thermostats, only support manual selection of “Auto,” “On,” and “Off” modes. These are usually not automatically triggered by simply the system’s scheduled mode (e.g., “Home” or “Away” schedule).

This means thermostats usually used in residential applications (e.g., a Nest or Honeywell Home thermostat) may not comply depending on the specific model selected. They must not only be JA-5 compliant but also at a minimum support an independent fan schedule to fully comply with MCH-03a.

For property developers, architects, mechanical subcontractors, and general contractors, mechanical acceptance testing (MAT) should now be on your radar.

Typical RTUs showing mechanical OSA damper

Manual OSA dampers are no longer compliant.

Dampers must automatically reset to minimum OSA/closed position during unoccupied heating/cooling, at minimum during occupied heating/cooling and closed during unoccupied heating. If the damper position is found to be incorrect at any step during mechanical acceptance testing, then the system is considered not to be code compliant.

The OSA cfm must also be within 10% of what is documented in the schedule. This means that each piece of HVAC equipment with an OSA requirement will need to have been through the TAB process prior to MAT so the damper position is set to control the OSA cfm.

Additionally, the thermostat needs to communicate to an actuator to close or open the damper depending on the occupancy setting. Therefore, this could be a potentially costly retrofit for direct ducted fan coils for buildings with a multitude of RTUs. This should be a consideration during any value engineering exercise used in conjunction when selecting HVAC systems.

Benefits of Mechanical Acceptance Testing

MAT is not a simple or easy process. It requires a lot of preparation, coordination, and attention to detail. It is also more rigorous and demanding than a typical HVAC start up or even a Title 24 system commissioning.

However, MAT is also a valuable opportunity to ensure that your mechanical systems are operating efficiently and effectively, saving you energy and money in the long run. For building owners, this translates into a greater level of confidence in, and a higher level of reliability for, their building’s HVAC systems. Benefits include:

– A higher chance of passing functional performance testing the first time (when commissioning, or Cx, is required by code), reducing the need for costly re-visits by installers and Cx agents to have issues fixed and then retested.
– A greater likelihood that manufacturer defects that would normally be missed by a rudimentary start-up procedure get caught early, while the equipment is under warranty for both parts and labor. This is especially true in cases where Cx was not a code requirement.
– Mechanical installers and controls technicians are aware their work will be scrutinized rigorously, which should lead to an overall higher level of installation and initial performance of the installed equipment.
– Catching potential equipment installation issues while the trades involved are still on site. Installers with a mechanical acceptance testing technician on staff can certify their own work, however there is an understanding that a certain number of their projects will be audited at random.

This testing will also benefit the building’s tenants:

– The building’s thermostats will have been completely programmed with settings that maximize both energy savings and ventilation providing them with both lower energy bills and a building with good indoor air quality.
– Tenants won’t be burdened with having to figure out how to program the various complicated schedules themselves since this will have been completed as part of the process. They would just need to select their desired temperatures.
– Building tenants will also be able to benefit from any discounts that utilities offer for participating in DR programs having demonstrated their ability upfront would avoid any costs that would be incurred while trying to upgrade their HVAC controls to the technical level required to participate in the future.

MAT is not a simple or easy process and additional consideration will be required for what equipment is selected for a typical HVAC design going forward. Even after selecting the right equipment, the testing itself requires additional preparation, coordination, and attention to detail. Though this is a new and challenging process, VCA Green has the know-how to provide project teams with the assistance needed to navigate this rigorous and demanding code requirement.

Moe Fakih, Principal

Robyn Vettraino, Principal