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Randal's

"Tech Blog" 

March 13, 2019

Can Your  Duct Designs Pass Testing 

While building our new Duct Design Class I read an article that jumped out at me titled "Do Your Duct Designs Work?" Many would answer that with a resounding yes, even though they have not tested the ductwork airflow to verify its correct. Would you be that confident if the ductwork was going to be tested right after you answered the question?

There is whole lot more to sizing ductwork then setting your duct calculator to .10 friction rate and looking for an airflow number and its corresponding rectangular duct or round pipe size. Do you know the two things in your ducts that can be reduced but not eliminated that cause your blower to push harder against a higher resistance, decreasing the amount of airflow to the rooms if they are not considered in your duct sizing?

Their names are Friction--the resistance to airflow created when the air rubs against the sides of the duct and Turbulence--a kind of a friction created when air rubs against itself. The main cause of turbulence in ducts is when the airflow is turned. They both result in creating pressure drop that has to be accounted for with other pressure drops which would bring us to Effective length, Equivalent length, longest supply run, longest return run, calculating the friction rate, etc., etc.

 

If you would like to read more about what is involved with doing an accurate duct design, please follow the link for some food for thought about Duct Design . 

 

Randal's Multi-Media Educational  Presentation

March 13, 2019

"The Easiest Way I Know to Remove a Furnace Control Board"   

Check out our latest training video demonstrating the easiest way I know of to remove a furnace control board without destroying the clips that hold it in the unit.

The video is titled "Removing a Furnace Board" and is less than three minutes in length.

Because I see so many destroyed clips on furnaces in my travels from technicians using needle nose pliers or wire cutters to squeeze the end of the clip with, I thought it was time to repost this video.

 Watch Video Now


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 I thought they were supposed to be for a two year term but if you read the procedures for license renewal you will see this is not so. See 3.02 below.

 

 

 
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