#Defrost

My goal in this tech tip is to help those who struggle to understand heat pumps get their heads around them as quickly as possible and understand some of the things a tech needs to know about them. The basic idea of a heat pump is to use the compression refrigeration cycle to move heat […]

We’ve entered that season of service calls for “smoking heat pumps,” and I figured now is as good a time as any to share a few quick tips for troubleshooting defrost. Of course, the “smoking heat pump” calls can be solved over the phone with a quick explanation of normal defrost conditions—as can the service […]

If you are used to simple, straight-cool split systems, you know that the low voltage to the outdoor unit is usually VERY simple. In many cases, there's just a Y (contactor power) and a C (common) connected to the outdoor unit. When the condensing unit controls are strictly two-wire low voltage, there is no continuous […]

As an A/C tech, I can sometimes get the terms “defrost termination” and “defrost fail-safe” mixed up because they sound pretty similar. Before we cover these terms, let's set the basic defrost groundwork for refrigeration (coolers and freezers). Defrost is accomplished in one of a few ways; these first two only apply to “coolers” where […]

Why Defrost? Let's start with the basics and move on from there. Defrost is necessary when the coil temperature drops below 32°F. Defrost can be as simple as turning the compressor off for a period of time or as elaborate as reversing the flow of refrigerant for the whole system or just parts of the […]

Let's take a deeper dive into the magic that is gas defrost. Most techs who are familiar with heat pumps understand the basics of a gas defrost. When we apply this strategy to a larger system where we're only reversing a small part of the system, we need to add some controls and valves to […]

When you work on a heat pump system and want to test defrost, you can follow many different test procedures to test the board and sensors. Most involve “forcing” a defrost by shorting out pins on the board or advancing the time of the defrost initiation and installing a factory-provided pin jumper. Lots of pins […]

The most common method to defrost appropriately in refrigeration involves both time for initiation and a combination of time and temperature for defrost termination (ending defrost). But why can't we just use temperature or time alone? (You may wonder.) Imagine a common freezer with a designed box temperature of -10°F and a coil temperature of […]

This article is a quick, real-life diagnosis/find by Kalos Services senior commercial HVAC/R tech Eric Mele. Improper Defrost Timer installation While servicing this display cooler for an unrelated problem, I noticed the defrost timer installed in a way that will almost certainly cause early compressor failure. Because this is a cooler (not a freezer), it […]

Dick Wirz, author of Commercial Refrigeration for Air Conditioning Technicians, talks about making the switch from A/C to refrigeration. Dick Wirz is an advocate for using rules of thumb, which is a controversial position. However, rules of thumb are an excellent way for A/C techs to dip their toes into the refrigeration world. Rules of […]

In this episode of HVAC School, Bryan covers the basics of heat pumps. Heat pumps are common technologies in Florida. They reverse the sequence of the typical refrigerant circuit: the indoor coil can become the condenser, and the outdoor coil can become the evaporator. Heat pumps can achieve that transition via a reversing valve, which […]

In this episode of the HVAC School Podcast, Bryan talks with Jeremy Smith about refrigeration tips, terms and processes. They also cover the similarities and differences between A/C and refrigeration. Being on-call as an A/C tech is not all that different from being on-call as a refrigeration tech. Similarly, the principles of heat transfer don't […]