Mixed Air Temperature w/ David Richardson

HVAC School - For Techs, By Techs

Bryan Orr

Careers, Business, Self-improvement, Education

4.9 • 1K Ratings

🗓️ 19 December 2019

⏱️ 34 minutes

🔗️ Recording | iTunes | RSS

🧾️ Download transcript

Summary

David Richardson with NCI, author of Duct Dynasty, joins us on the podcast to talk about mixed air temperature and more topics of interest.

When you bring outside air into the home, you introduce positive pressure into the home. That way, you can offset air lost via mechanical ventilation or through cracks, improving air quality. We often assume that the building will "breathe," but tighter constructions make it difficult for the home to bring in enough fresh air to offset harmful chemicals and VOCs.

We need to measure two different kinds of airflow: fan airflow and outside air. When we have these numbers, we must figure out how much air is coming through the outside air intake. The fan airflow represents 100% of the air content after mixing has taken place. You can perform a duct traverse to get the airflow measurement; when you plot the fan airflow, subtract the two to know how much return air you're getting BEFORE mixing with the outside air.

Once you have your airflow measurements, you must break those into percentages. You must determine the percentage that matches up with the temperature you want to use for the mixed air. Subtract the outside air from the fan airflow to get the CFM from your baseline. You could get 95% of your airflow from the return and 5% from the outside. Once you know the outside air temperature and the percentage of outside air, you will know how much the outdoor temperature will affect the return air and space temperatures.

David and Bryan also discuss:

How David got into writing
Blown-in cellulose insulation
Designed and undesigned leakage
Duct traverse tools and procedure
Dry-bulb vs. wet-bulb measurement applications
SEER vs. AFUE
Duct leakage

Learn more about NCI at nationalcomfortinstitute.com.

Learn more about Refrigeration Technologies HERE.

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Transcript

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0:00.0	This episode of the HVAC School Podcast is made possible by our sponsors.
0:10.0	It really is, I'm not joking, it really is made possible by our sponsors in there.
0:13.1	Carrier and carrier.com speed clean and speed clean.com
0:16.9	speed clean makes a lot of cleaning products both the chemicals and
0:21.5	the delivery method and the delivery method of choice
0:24.8	for me during maintenance season in our like commercial division is the
0:29.3	coil jet. We've used coil jet for many years when we were having issues with
0:34.4	getting water where we needed it in order to clean conenser coils that were
0:37.9	kind of all over the place nowhere near hoses. Sometimes you can stretch a 200 foot
0:42.2	hose out and do the job, but sometimes it's even further than that.
0:44.7	You just don't get the pressure you need.
0:46.8	And with coiljet, it solves that problem.
0:49.1	You can find coiljet by going to truetech tools.com use the offer code get schooled at
0:54.0	check out for a great discount also navac and navac global
0:57.3	com navac makes many many good quality tools including a lot of vacuum pumps and several recovery machines
1:05.2	you're gonna like them all so take a look at navag global.com or take a look at navac products at truetech tools
1:11.6	refrigeration technologies at refrigidect., I got to hang out a little bit with Mike
1:15.5	Pasterello from Refrigeration Technologies recently at the Hardy Conference and I'm reminded
1:21.4	why I'm so proud to be able to talk about their products because they're just all great people.
1:26.0	They're great people who stay connected to the trade and who make chemicals that are safe for technicians to use and are effective at the jobs that
1:35.0	they're designed to do. Things like Viper Cleaner and the aerosol can or Viper Cleaner
1:39.5	concentrate that you can use for washing condensric oils and evaporators all of it really great stuff
	...

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