![]() If you’re replacing or servicing equipment with an ECM, and the TESP exceeds rated capacity, be sure to look up the motor amp draw in the manufacturer’s specifications. ![]() Once you know your TESP and your fan speed setting lookup delivered fan airflow on the manufacturer’s fan table. Other pressure readings will help you diagnose the cause of high statics – but that’s for another article. TESP is calculated by adding the pressures before and after the fan. Once you’ve installed the test ports, use a digital or analog manometer with a static pressure tip (see diagram) to measure pressure at each location. So, what do you measure? The first thing you should do is install test ports on either side of the blower. When you don’t measure, you’re just guessing that it will turn out OK. These issues can be avoided with good pressure and airflow testing, both before and after the equipment is replaced, and on every system you service. This can reduce the system’s dehumidification capability and cause numerous moisture-related indoor air quality issues. High velocities and pressures created by ECMs on systems with dirty evaporator coils can also blow moisture off the coil surfaces into the supply ductwork. Once you’ve installed the test ports, use a digital or analog manometer with a static pressure tip to measure pressure at each location. In very extreme cases filter media can be pulled into the fan, chopped up, and blown through the system causing all sorts of damage. ![]() In extreme cases, filter media can be sucked out of its rack causing filter bypass. Other consequences of high static installations include noise at the registers from higher air velocities. Newer models are designed to drop airflow but time will tell on how well they will hold up. Some older ECM motors will overheat and even fail when constantly running in over-amped conditions. When this happens, some ECMs will ramp down and drop airflow significantly. Systems with TESPs of 1.0 and higher, which are more typical than many non-performance-based contractors are willing to admit, can eat up to eight times the power they should be using. This reduces actual equipment EER, which means your customer won’t get the savings of the higher efficiency matchup. The extra torque often required to overcome the higher statics results in higher electrical consumption. The tradeoff is higher velocities often cause a noisy system and some coil blow-off. TESP system – the motor still may be able to maintain airflow close to design. In marginal systems with higher-than-design static pressures – for example, a 0.5-in. When installed properly, systems with ECMs can improve dehumidification, reduce register noise, save energy, and provide trouble-free operation. These systems can deliver precise airflow to match two-speed condenser designs and multi-stage gas furnace firing rates to deliver quiet, draft-free comfort in virtually any configuration.Īdditional benefits of these brushless DC motors include low electrical consumption when operating within design Total External Static Pressure (TESP). When a furnace or air handler with an ECM is installed on a good duct, coil, and filtration system with static pressures within proper design parameters, it can perform flawlessly. Let’s take a candid look at the good, bad, and ugly of the application of these great gems of technology. There are, however, some serious downsides associated with the improper application of these motors in new and existing HVAC systems. Electronically Commutated Motors (ECMs) manufactured today are the best they’ve ever been and can provide unprecedented airflow delivery to match the required BTUH of a heating and/or cooling system.
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