What is typically used to measure electrical current in HVAC systems?

An ammeter is the appropriate instrument for measuring electrical current in HVAC systems. This tool is specifically designed to measure the flow of electric charge, expressed in amperes (A). In an HVAC system, it's crucial to monitor current to ensure components, such as compressors, fans, and pumps, are operating efficiently and within their specified electrical ratings. If the current is too high, it can indicate an overload condition, which may lead to equipment failure or damage.

Voltmeters, on the other hand, measure voltage, not current, which is a different aspect of electrical measurement. Thermometers are used for measuring temperature and would not provide any information regarding electrical currents. Circuit breakers are protective devices that interrupt the flow of electricity in case of an overload or short circuit, but they do not measure current. Hence, the correct choice highlights the importance of using the right tool for monitoring electrical current in HVAC applications.