Adding an HVAC unit to your shop, ducting questions

[Roothawg]

I usually don't post here, but lately I have had deals dropping into my lap.

The last deal I just had was I have tenatively purchased a 5 ton Lennox HVAC system, that is still in the box. It has the outside unit and the inside portion.


I would like to add some of the large round ducting to help distribute the air. My question is this. How do you know what size ducting to use?

I don't have all of the specs just yet. This is sort of a wierd deal. I should know more by tomorrow....I just can't get out there to physically see the unit until tomorrow evening.

Just trying to figure this out in my head.

My shop is a 40X50X14, insulated.

Thanks

Root

 

[BoilermakerNate]

There are a couple things you will need to know:

1. The total supply airflow of the furnace. If it is a 5 ton, it should be around 2,000 cfm.

2. General ductwork layout with number of supply diffusers and desired airflow at each diffuser.

With this information, you can determine the amount of airflow passing through each section of ductwork. You generally want to size supply ductwork at 0.1" of static per 100' of ductwork.

For example, a supply branch serving a 200 cfm diffuser would be 8" round.

If you post a sketch of a single line ductwork layout with the above information, I can help you size it.

 

[Tman]

Root, I am doing the same with a wood furnace. 3000cfm need to fuigure out my ducting.

 

[mpraddict]

5 ton seems a bit oversized for your building (although I did not look up your cooling degree days).