Defrost in Commercial Refrigeration w/ Dick Wirz

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 1 February 2018

⏱️ 36 minutes

🔗️ Recording | iTunes | RSS

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Summary

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.

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Transcript

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0:00.0	This episode of the HVAC School podcast is made possible because of the generous support of our sponsors,
0:09.0	Rector Seal, carrier, and Mitsubishi Comfort.
0:13.0	And I just want to mention real quick for those of you who are contractors or technicians
0:19.0	that one thing you may not realize,
0:21.0	and this is certainly true with Carrier Enterprise, Florida, which is the supply house that we use to get our carrier products and a lot of our other supplies. There's one right around the corner from us.
0:31.0	Is that when you interact with your local supplier you can
0:34.4	often get products that they don't have on the shelf and sometimes as long as you can show
0:39.7	that you buy a decent amount of them you can get them to stock products that maybe they weren't planning on having and I found that to be very true with our local carrier enterprise.
0:49.2	Our territory manager is a really great guy by the name of Greg Schmidbauer and his leadership team has been really great at working on getting the products that we need.
0:58.0	And one of those products is the Rector Seal UV wrap, which is the wrap that we use for line sets. It's a non-adhesive
1:04.7	wrap which we like because it's easier to get on and off. It doesn't make a mess and
1:07.8	it does a really good job of protecting line sets from deterioration from UV the tubing insulation. So a little plug there
1:15.3	for both of those organizations, Rector sale on their app and then also carrier enterprise
1:19.5	for working with us to get products that maybe didn't have on the shelf in the first place and I would just
1:23.4	encourage you if there's something that you see out there in the industry that you would use,
1:27.6	talk to your local supply house. If you have CE in your area, talk to them and see if they would be interested in carrying those products,
1:35.4	and you may find that it's a win-win for both you and them.
1:38.6	Meet Zoomlock, the 10 second flame-free refrigerant fitting from Parker.
1:42.8	Reduce labor costs by 60% with no braising, no flame,
1:46.5	and no fire spotter.
1:47.8	Discover how Zoomlock can help you be more efficient and productive.
1:51.6	Visit Zoomlock.com for more information.
	...

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