Basic Refrigerant Circuit Course May 13, 2025, 3:22 pm - HVAC School

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Basic Refrigerant Circuit Course May 13, 2025, 3:22 pm

May 13, 2025

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Understanding Voltage Drop – Short #251

HVAC School – For Techs, By Techs

Understanding Voltage Drop – Short #251

In this short podcast episode, Bryan drops some knowledge to help with understanding voltage drop, a few different causes of it, and NEC recommendations.Voltage is[...]

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Understanding Voltage Drop – Short #251

byBryan Orr

In this short podcast episode, Bryan drops some knowledge to help with understanding voltage drop, a few different causes of it, and NEC recommendations.

Voltage is electrical potential or “pressure,” and voltage drop is the reduction in electrical potential energy. We often think of it happening across conductors (which add resistance), but it also happens across loads (like contactor coils). Voltage drop across loads is usually designed, but voltage drop across conductors is usually undesigned and undesirable.

Several factors contribute to conductor resistance. Length is a major one; long runs of wire introduce more resistance to the circuit than shorter runs. Size/gauge also matters; smaller-gauge wire has more resistance than larger-gauge wire. Copper is the most common material for wiring, but we use other materials (including steel or aluminum), and those have different resistance values. Temperature also affects resistance, as they both increase and decrease as the other one does.

When we measure voltage drop, we want to make sure we’re doing it under load, NOT on startup. Voltage drops that happen on startup can be mitigated with more suitable infrastructure (including larger wires) or soft starts.

Undersized conductors don’t have sufficient cross-sectional area for the applied load. To avoid voltage drop due to undersized conductors, we should size conductors based on minimum circuit ampacity (MCA), not breaker size (MOCP). Poor connections can also cause resistance to jump, which reduces voltage; we need to pay attention to the connection design (including torque specs and proper lugging) to avoid making mistakes. Long wires don’t cause overheating by themselves, but they still contribute to voltage drop and cause reduced performance (including drawing higher current on startup).

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Nylog Blue Gasket -Thread Sealant for AC/R Systems One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

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Nylog Blue Gasket -Thread Sealant for AC/R Systems

Nylog Blue Gasket -Thread Sealant for AC/R Systems One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER

VENOM PACK CONDENSER PURE CONCENTRATE COIL CLEANER Venom Pack Condenser Cleaner is a high foaming pure concentrate liquid designed to tackle the toughest soils. The proprietary blend of specialty detergents will liquify heavily embedded grease and grime to restore heat transfer and increase the efficiency of the coil.

Viper Condensate Pan and Drain Treatment

Viper Condensate Pan and Drain Treatment Viper Condensate Pan and Drain Treatment is a sprayable gel. It coats the pan, p-trap and drain piping with a lubricative film to improve flow and prevent future soil adhesion. The slow dissolving enzyme gel will outperform and outlast conventional tablets and strips.

Nylog Blue Gasket -Thread Sealant for AC/R Systems

Nylog Blue Gasket -Thread Sealant for AC/R Systems One drop of Nylog on your rubber hose gaskets prior to attaching your core tools, hoses or vacuum gauge will assure that things do not bind or leak during evacuation. Derived from refrigeration grade lubricants. Non-hardening, non-drying fluid which bonds tenaciously to many different substrates. Typically, one drop of Nylog can be stretched about three feet before breaking.

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