#magnehelic

Tech Tips:

Static Pressure, Manometers, and Magnehelics

When you start talking airflow, it can get pretty in-depth pretty quickly. There is a big gap between what is useful for the average tech to apply every day and the whole story, so let's start with the simplest part to understand: static pressure. Static pressure is simply the force exerted in all directions within […]

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In this short podcast episode, Bryan talks about crankcase heaters, including their different types, what they do, and when we need to use them.

Crankcase heaters usually come in belly band varieties, but some can be inserted into the sump of the compressor. As their name suggests, crankcase heaters heat the crankcase when the compressor is off. They prevent flooded starts since the heat keeps refrigerant from condensing to a liquid in the compressor when the system isn’t running.

Long off times, long line sets, and cold temperatures all increase a system’s risk of flooded starts. Hard shutoff TXVs, liquid line solenoid valves, and crankcase heaters are all ways to reduce these risks; the valves hold liquid refrigerant back, and crankcase heaters merely prevent refrigerant from condensing.

Crankcase heaters have to be wired to the line side of the contactor or starter. They’re often wired around one of the contacts (with a single-pole contactor). When the contact opens, there is a circuit from one leg, through the crankcase heater and compressor windings, to the other leg. This method does NOT use the compressor winding itself as a crankcase heater. When you use a crankcase heater on a compressor with a seam, you want the part of the heater that does the tensioning near the seam. Crankcase heaters should be installed at the base of the compressor, and you’ll usually use OEM crankcase heaters.

“Crankcase Heaters and Single-Pole Contactors” tech tip: https://www.hvacrschool.com/crankcase-heaters-and-single-pole-contactors/

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