High velocity systems are designed where homes do not have duct work. These systems allow you to install an Air Handler in a crawl space or attic and run mini duct work to rooms. The blower on the system is designed to push hard to circulate air, unlike traditional HVAC equipment.
We have done our share of installations of these systems, however, we no longer install them due to the complications of the industry moving to an ECM motor.
What did the ECM Motor change?
To start, we want to say that we like the ECM motor and we encourage them on all furnaces. Where it gives us problems though is in a high velocity situation. Prior to the new efficient ECM motor mandate, high velocity used PSC motors. They are traditional AC powered motors much like you would find in other appliances and tools.
The ECM motor mandate took place on July 3rd 2019. After that date air handlers and furnaces had to have ECM motors instead of traditional PSC options.
The benefit of the PSC in high velocity is that it just marches through whatever you feed to it. Working with high pressure air circulation it would do as expected. It could handle the abuse that high static environments cause. ECM motors do not.
ECM motors are not designed for high resistant (high static) environments. The manufacturers from our experience also built in protections on this. Because of this, units require significantly more duct work runs to lessen the static pressure load on the system, which is a pain when we are upgrading a system you cannot just change it out.
The manufacturers know that putting an ECM motor under stress for a long period of time will also cause the power head to fail or even the motor. Because of that the brand we worked with designed the blower to only push up to a certain amount of resistance. In other words, there is a safety that limits it.
If a system is not set up exactly right, the system will limit the CFM (cubic feet per minute) of air flow it’s pushing to stay under the limit. Heating & Cooling systems absolutely hate that. Furnaces will go off on high temp limit with poor air flow, and Air Conditioners will freeze up with poor air flow.
Manufacturer support wasn’t there.
We sell equipment here that we have support on. Our team cannot know everything, and the brands we carry are with us because of local representation. If there are unique issues we have someone in the area that supplies it and a team of people who can help us on unique situations.
On the tail end of our installations of high velocity systems we found that the support was not up to our standards, and that makes the manufacturer look bad, as well as us because getting support is much more difficult.
What if I want high velocity?
We should state clearly that high velocity is a valid solution to adding cooling to a house with a boiler or baseboard heat. We simply stay away from new installations due to the complications, the finicky operation of some of the brands, and our lack of support that we need to deliver to you the best service.
If you have a system, take care of it every early spring or fall. We don’t like to be in attics in the summer if we can help it. Make sure you change out the filter regularly, and that someone makes sure the drains are operating like they should.