Dick Wirz's guest appearances

Dick Wirz

HVAC School - For Techs, By Techs

Kevin Hart

Bill Johnson

Ruth King

Chris Stephens

Dan Holohan

John Ellis

Bill Spohn

Jack Rise

Andy Holt

Jerry Eavenson

Nate Adams

David Richardson

Jim Bergmann

Jim Loring

Jamie Kitchen

OwlTail

Dick Wirz, author of Commercial Refrigeration for Air Conditioning Technicians, talks to us about refrigerator and freezer defrost strategies. Check out Dick's book  HERE. In commercial refrigeration, we deal with much lower evaporator temperatures than residential HVAC. Although an evaporator temperature of 40°F may be commonplace in residential HVAC, you can expect evaporator temperatures from 25-30°F in refrigeration. Even though having ice on the coil is a negative thing in residential HVAC, it is perfectly normal in refrigeration. The purpose of defrosting is to bring the evaporator temperature above freezing to melt off the frost. We can defrost a coil in a few different ways, including a mere off-cycle defrost in medium-temperature refrigeration. When the system shuts off, the evaporator coil can start defrosting. However, if too much heat is introduced to the system, more frost can accumulate on the evaporator coil. As such, a planned defrost may be in order. These defrosts occur on a timer and turn the system off overnight. Alternatively, these defrosts may use electricity or hot gas to remove ice from the coil more rapidly, especially in low-temperature applications. Electric and hot gas defrost are common defrost types. The hot gas method generally reverses refrigerant as a heat pump does; hot discharge gas runs through the evaporator coil and melts the ice off the coil. However, hot gas is an expensive method and can negatively impact system longevity if used improperly. The electric method is cheaper than the hot gas method; this method relies on electric heat outside the coil to melt the frost from the outside. Dick also talks about:  Warm air infiltration Coil-sensing thermostat controls Defrost failsafe Defrost termination "Snowing" in the box and fan delays Drain pan heaters and drain complications Paragon timers Demand defrost setups/clocks Check out RefTech HERE. If you have an iPhone, subscribe to the podcast  HERE, and if you have an Android phone, subscribe  HERE.

Dick Wirz, author of Commercial Refrigeration for Air Conditioning Technicians, talks to us about refrigerator and freezer defrost strategies. Check out Dick's book <a href="https://www.amazon.com/Commercial-Refrigeration-Air-Conditioning-Technicians/dp/130550643X" rel="nofollow" target="_blank"> HERE</a>. In commercial refrigeration, we deal with much lower evaporator temperatures than residential HVAC. Although an evaporator temperature of 40°F may be commonplace in residential HVAC, you can expect evaporator temperatures from 25-30°F in refrigeration. Even though having ice on the coil is a negative thing in residential HVAC, it is perfectly normal in refrigeration. The purpose of defrosting is to bring the evaporator temperature above freezing to melt off the frost. We can defrost a coil in a few different ways, including a mere off-cycle defrost in medium-temperature refrigeration. When the system shuts off, the evaporator coil can start defrosting. However, if too much heat is introduced to the system, more frost can accumulate on the evaporator coil. As such, a planned defrost may be in order. These defrosts occur on a timer and turn the system off overnight. Alternatively, these defrosts may use electricity or hot gas to remove ice from the coil more rapidly, especially in low-temperature applications. Electric and hot gas defrost are common defrost types. The hot gas method generally reverses refrigerant as a heat pump does; hot discharge gas runs through the evaporator coil and melts the ice off the coil. However, hot gas is an expensive method and can negatively impact system longevity if used improperly. The electric method is cheaper than the hot gas method; this method relies on electric heat outside the coil to melt the frost from the outside. Dick also talks about: <ul> <li>Warm air infiltration</li> <li>Coil-sensing thermostat controls</li> <li>Defrost failsafe</li> <li>Defrost termination</li> <li>"Snowing" in the box and fan delays</li> <li>Drain pan heaters and drain complications</li> <li>Paragon timers</li> <li>Demand defrost setups/clocks</li> </ul>Check out RefTech <a href="http://reftechapp.com/" rel="nofollow" target="_blank">HERE</a>. If you have an iPhone, subscribe to the podcast <a href="https://itunes.apple.com/us/podcast/hvac-school-for-techs-by-techs/id1155660740?mt=2" rel="nofollow" target="_blank"> HERE</a>, and if you have an Android phone, subscribe <a href="http://www.stitcher.com/podcast/bryan-orr-3/hvac-school" rel="nofollow" target="_blank"> HERE</a>.

Defrost in Commercial Refrigeration w/ Dick Wirz

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 thumb are less likely to overwhelm technicians than the exact technicalities of certain readings and measurements. Some prime examples of using rules of thumb in air conditioning are condenser split, evaporator split/TD, subcooling, and superheat. Those all have relatively neat "rules of thumb" that don't vary too much. (30-degree condenser split, 35-degree evaporator TD, 10-degree subcooling, and 10-degree superheat.) On medium-temperature refrigerators, a common rule of thumb is a 10-degree TD for a 35-degree box with an evaporator running at 25 degrees (35 - 10 = 25). On low-temperature applications, the box temperature is -10 degrees. You still have the 10-degree TD, so the design conditions for the evaporator would be -20 degrees (-10 - 10 = -20). The pressures will vary across refrigerants, but the temperatures WILL REMAIN the same as the rule of thumb. Ice is an alarming sight for residential technicians. However, commercial refrigeration technicians will occasionally see frost or ice under perfectly normal circumstances. Frost merely indicates that the temperature of a pipe is below freezing. Ice alone does NOT indicate floodback. In commercial refrigeration, the fans run all of the time to defrost the system (even during the off cycle). However, in freezers (low-temperature refrigerators), hot gas or electric defrost is required. Dick also talks about:  Subcooling vs superheat in diagnosis R-410a pressure confusion Reach-in and walk-in refrigerators Medium and low-temperature refrigerators Defrost controls Common issues in commercial refrigeration    If you have an iPhone, subscribe to the podcast  HERE, and if you have an Android phone, subscribe HERE.

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 thumb are less likely to overwhelm technicians than the exact technicalities of certain readings and measurements. Some prime examples of using rules of thumb in air conditioning are condenser split, evaporator split/TD, subcooling, and superheat. Those all have relatively neat "rules of thumb" that don't vary too much. (30-degree condenser split, 35-degree evaporator TD, 10-degree subcooling, and 10-degree superheat.) On medium-temperature refrigerators, a common rule of thumb is a 10-degree TD for a 35-degree box with an evaporator running at 25 degrees (35 - 10 = 25). On low-temperature applications, the box temperature is -10 degrees. You still have the 10-degree TD, so the design conditions for the evaporator would be -20 degrees (-10 - 10 = -20). The pressures will vary across refrigerants, but the temperatures WILL REMAIN the same as the rule of thumb. Ice is an alarming sight for residential technicians. However, commercial refrigeration technicians will occasionally see frost or ice under perfectly normal circumstances. Frost merely indicates that the temperature of a pipe is below freezing. Ice alone does NOT indicate floodback. In commercial refrigeration, the fans run all of the time to defrost the system (even during the off cycle). However, in freezers (low-temperature refrigerators), hot gas or electric defrost is required. Dick also talks about: <ul> <li>Subcooling vs superheat in diagnosis</li> <li>R-410a pressure confusion</li> <li>Reach-in and walk-in refrigerators</li> <li>Medium and low-temperature refrigerators</li> <li>Defrost controls</li> <li>Common issues in commercial refrigeration</li> </ul> If you have an iPhone, subscribe to the podcast <a href="https://itunes.apple.com/us/podcast/hvac-school-for-techs-by-techs/id1155660740?mt=2" rel="nofollow" target="_blank"> HERE</a>, and if you have an Android phone, subscribe <a href="http://www.stitcher.com/podcast/bryan-orr-3/hvac-school" rel="nofollow" target="_blank">HERE</a>.

Commercial Refrigeration for A/C Techs w/ Dick Wirz