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dphens 08-18-2009 07:32 PM

Splitting HVAC flex duct
Hello all,

I am new on this forum and need help with a HVAC issue.

I am converting my garage into a workshop and want to run AC into it. Fortunately, my home was a model home so the garage is already finished. The only thing I need to do is reconnect the duct work for that space. The duct work is still in the attic space, it's just been disconnected and tied off.

So, I need to know what components I need to split the current duct. I don't have a clue about the correct terminology, but I hope my explanation is clear enough.

Thanks for any help!


Plumber101 08-18-2009 07:34 PM

Any way to get a pic of the ends that need to be reconnected?

To may varibles

dphens 08-18-2009 07:56 PM


Here's a few images. Do these help?

Plumber101 08-18-2009 08:01 PM

Holly crap what an install.

But to your question. You have 12" flex duct. So if you take a 2" piece of 12" single wall pipe and insert it into each end 12" and use the zip tie straps that should take care of reconnecting. Where the two end met on the pipe wrap with duct tape.

dphens 08-18-2009 08:11 PM

Actually I need to connect both pieces of flex into the other flex that you see attached to the wall. The two pieces of disconnected flex you see in the pics are the return and feed duct (if that's what they're called. They disconnected the return and feed lines from the unit before the house went up for sale. I suspect they had some type of T split if that's possible.

That make sense?

Reread my original post and I don't think I did a good job of explaining the situation.

Plumber101 08-18-2009 08:16 PM

Perfect sence.

However, I don't know any code that allow return air to a garage. Think about it. CO, Ordors and combustables into the house.

How many vents do you have in the garage?

What make you think the two ends just don't go together?

dphens 08-18-2009 08:24 PM

There are three vents and one return. I assume that is why there is two pieces of disconnected flex duct. Keep in mind, my terminology may be off.

hvac122 08-18-2009 08:36 PM

Your garage is 1 hour rated for fire from the rest of the house. That is why when the house was sold the runs had to be disconnected. Code states that you can have no heat runs or returns connected to the house system. Carbon monoxide problems could cause big problems. Also if a fire starts in your garage/shop you want some kind of barrier from the house.

Use a seperate system in the garage.

I'm with plumber, wow what a install. This was a modelhome??????:whistling2:

beenthere 08-18-2009 08:37 PM

Actually, if you have garage doors large enough for a car to enter the garage. Its a code violation. To connect those ducts. Weather you use it for parking a car or not.

Plumber101 08-18-2009 08:37 PM

Take the ties off the to ends in the pic and turn on the blower fan. See if you get air blowing out one of the two. If so connect the two end.

If you have 3 vents in your garage they may be "T" or "Y" somewhere.

For get the term return you only want supply air to a garage

dphens 08-18-2009 08:41 PM

OK, thanks everyone. If it's a code violation, I'll look into something else. I did have an HVAC tech come out and quote me two options.

1. just hooking everything back up for $750
2. create a new zone for $1950

Was hoping to do option 1 myself and save a little.

I'll try what you recommend plumber and see what I get.


beenthere 08-18-2009 08:46 PM

It is a code violation.

Unfortunately, too many techs don't follow code.

dphens 08-18-2009 08:48 PM

OK, glad I found out. Is the violation due to the fact a car can been in that space or are there other issues?

Would a separate zone still violate code or would it have to be a completely separate system?

Thanks again for the help!

beenthere 08-18-2009 08:54 PM

Its because a car in the garage can be left running. An fill the garage, and duct system with CO(caron monoxide), and kill the occupants that are still in the house.

A different system.

Can't have any duct communication with the system that conditions the occupied areas of the house.

dphens 08-18-2009 08:57 PM

OK, I really appreciate the information.

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