Variable-Speed Motors and Why They Matter w/ Jamie Kitchen (Podcast)

Jamie Kitchen from Danfoss talks all about variable-speed motor technology. He discusses why those motors exist, what they do, and how to think differently about the future of HVAC/R.

Most techs think about variable-speed motors as the X13 and ECM blowers in residential applications. Those motors can adjust their performance based on ambient temperatures and moisture levels. So, variable performance may result in better comfort and efficiency.

ECM motors adjust airflow based on sensor inputs, especially dehumidification calls. The sensors may pick up both sensible and latent heat content. Sensible heat is what we can feel (dry-bulb temperature). Latent heat refers to moisture in the air (humidity, wet-bulb). ECM motors adjust their speed based on data from both, which is highly beneficial for greater comfort in the home. Human comfort is a lot more complex than feeling satisfied with a single number on the thermostat; ECM motors help control humidity and give you more leeway over selecting an acceptable dry-bulb temperature of a space.

Variable-speed motors exist on the commercial side of the HVAC industry as well. Commercial HVAC equipment brings in more fresh air and is overall less restrictive than residential. A variable-speed motor can help manage the latent heat of fresh air and work as a form of air treatment. Variable-speed motors compare indoor and outdoor conditions to treat the fresh air and maintain the indoor conditions. These motors account for sensible and latent heat loads, just like the residential ECM motors, and they adjust themselves constantly.

Jamie and Bryan also discuss:

Capacity and heat profiles
X13 motor controversy
Having multiple variable-speed components in a system (compressor, blower, etc.)
Sensible heat ratio (SHR) and heat load matching
Complex human comfort
Reheat coils
Air treatment requirements

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Author:

Bryan Orr

Company: HVAC School

Position: Founder

Jamie Kitchen

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Chris Hughes and Steve Rogers from The Energy Conservatory discuss TEC’s TrueFlow technology and its crucial role in predicting airflow issues in the sales process, particularly for heat pump retrofits. They explain how the TrueFlow app helps contractors accurately measure both static pressure and airflow in existing systems, enabling them to predict whether proposed equipment changes will work effectively. This is especially vital when considering the growing trend of replacing gas furnaces with heat pumps, as the airflow requirements can differ significantly.

The conversation delves into a detailed example of replacing an 80% efficient 48,000 BTU furnace with a heat pump. They demonstrate how the airflow requirement would nearly double from 652 CFM to 1,200 CFM, potentially causing the static pressure to quadruple due to Fan Law 2 principles. This dramatic increase could lead to significant performance issues if not properly addressed during the system design phase. The experts emphasize that using TrueFlow during the sales process allows contractors to identify potential problems and necessary modifications before installation rather than discovering issues during callbacks.

The discussion also covers the ideal workflow for system assessment and sales, starting with customer comfort evaluation and proper load calculations. It’s important to reduce loads through envelope improvements when possible, particularly in cold climates where heat pump retrofits are becoming more common. Proper system sizing often means going smaller rather than larger, contrary to common industry practices, and the worst HVAC systems are often found in expensive custom homes rather than tract housing.

Key Topics Covered:

TrueFlow technology and its role in system forecasting
Fan Law 2 and its impact on static pressure when changing airflow
Heat pump retrofit challenges and considerations
The importance of accurate load calculations
Dual fuel systems as a solution for cold climates
The relationship between airflow and static pressure
Sales process integration of technical measurements
Common issues with oversized equipment
The importance of envelope assessment
Methods for reducing system loads
Proper duct sizing and modification strategies
The role of proper filter sizing and selection
The benefits of flat-rate pricing for duct modifications
Training resources and support available for TrueFlow users

Check out TEC’s YouTube channel at https://www.youtube.com/@energyconservatory, and you can visit TEC’s website at https://energyconservatory.com/.

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