#overload

Tech Tips:

Why Many Techs Confuse Overload, Short, & Ground Fault

The point of this article is to give you a full understanding of the role fuses, overloads, and circuit breakers play in the protection of HVAC/R equipment. If you skim-read or jump to conclusions, you will be tempted to argue. Be patient; if you want to understand, you will need to read all the way […]

Control Voltage Overamp – The Less Usual Cause

In many cases when a low-voltage or control circuit blows a fuse, it's because one of the circuits is shorted to ground or common. That may happen because of rubbed-out wires, shorted components or boards, etc. Routing wires sensibly and using proper grommets to avoid rubouts and shorts will help prevent those problems. Less commonly, […]

Hot Pull Down and What it Means

If you work in refrigeration, you may have heard the term “hot pull down.” This phrase describes a condition where the load on the evaporator is above design due to the box temperature or the temperature of the product in the box being higher than it would normally be. My grandpa called me a few […]

Careful With That 40VA Transformer

A 40VA transformer is rated for 40 VA or volt-amps on the secondary. For a typical 24 volt secondary, this is simply using Watt's law to calculate amperage. (For more information on Watt's or Ohm's laws, please check out this article HERE.) 40 ÷ 24 = 1.666666 ∞ (round up to 1.67 already) So, you […]

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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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