Thread: Return Air

I've been running into electric air handlers/evap coils being installed in return chases of very small condo units. HVAC contractos says this is proper installation. I say that mechanical equipment can not be located within a return chase.

What do you all say?

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Originally Posted by brianmiller

I've been running into electric air handlers/evap coils being installed in return chases of very small condo units. HVAC contractos says this is proper installation. I say that mechanical equipment can not be located within a return chase.

What do you all say?

I say that they are not being installed in the return chase ... that they are being installed in the mechanical closet, typically with a water heater below the AHU, and the air in that mechanical closet is considered "environmental air", and the closet is not considered a "return chase".

Further information may cause me to change my mind from the above, but let's try this typical installation: There is a closet, typically drywalled, which has a return air grille in a door or a louvered door which opens to a hallway ... how close is that to what you have?

Boy, wish I had my camera today!

Let's see if I can make this clearer:

- 480 sq ft condo.

- Return air intake (12" X 24" ) is located in bedroom at top of the wall with a duct board chase into the attic.

- The duct board return air chase then enters a larger duct boarded space in the attic, which encorporates the AHU/Evap coil.

- I could only view this from the access panel in the living space (bathroom),
which is not sealed to prevent communication into the return chase. (No secondary drain pan, either)

I hope this is clearer????? Probably not....

I always thought that you could not have within a return chase mechanical equipment/ electrical components.

Originally Posted by brianmiller

Boy, wish I had my camera today!

Let's see if I can make this clearer:

- 480 sq ft condo.

- Return air intake (12" X 24" ) is located in bedroom at top of the wall with a duct board chase into the attic.

- The duct board return air chase then enters a larger duct boarded space in the attic, which encorporates the AHU/Evap coil.

- I could only view this from the access panel in the living space (bathroom),
which is not sealed to prevent communication into the return chase. (No secondary drain pan, either)

I hope this is clearer????? Probably not....

I always thought that you could not have within a return chase mechanical equipment/ electrical components.

First, this: "I always thought that you could not have within a return chase mechanical equipment/ electrical components." not in the return air plenum, the term return chase is not specific.

Your description almost defines another installation type I have seen a lot of, not new or built within the last 20 years, but many older installation were done this way, and when done correctly, they are okay:
- Condo has the ceiling furred down and the space is used as a return air plenum, however, where the air handler is located, the return air plenum is sealed off and the AHU is located in the sealed off area where there is a large return air grille, those air handlers almost always made by 'First Company' out of Texas. That sealed off space in the return air plenum is sealed off from the plenum and become similar to the previous AHU closet I described, the AHU unit is located in the space which has environmental air and not return air plenum air.

There is a fine-line difference, but could you put an AHU in the middle of the living room with that return air all around it? Sure, it would look UGLY ... but it could be done so it was code compliant.

Now move that to a drywalled closet as I described previously ... any difference than it being in the middle of the living room? No, I just built a closet around it and installed a louvered door.

Now move that to the sealed area above the return air grille in the ceiling (I took the closet down and moved it up into the ceiling after building a sealed 'chamber' for the AHU) and now you don't see the AHU, any difference from it being in the closet or in the middle of the living room? Hmmm, uuuuh, welllll, er, not really if it is sealed off. Some AHJ may not allow this, however, to my knowledge, most AHJ do allow this, but only when it is sealed off from the return air plenum.

Now, if I just shoved the AHU up into the ceiling being used as a return air plenum and did not seal it off from the plenum, yes, there is a difference and it should not be allowed.

Jerry
That is a good description.

thanks,

so in itself, there is no problem having the AHU enclosed inside the return chase so long at the return chase is properly sealed, correct? What about the electrical , NM cables?

Originally Posted by brianmiller

thanks,

so in itself, there is no problem having the AHU enclosed inside the return chase so long at the return chase is properly sealed, correct? What about the electrical , NM cables?

You keep saying "return chase" and I don't know what a "return chase". Either it is in the return air plenum (not allowed) or it is in the environmental air as described (allowed).

JP: A man with your experience should know that the term "chase" is often used interchangeably (and incorrectly) with the term "plenum" in the trades. Why beat this guy up over it?

Originally Posted by Aaron Miller

JP: A man with your experience should know that the term "chase" is often used interchangeably (and incorrectly) with the term "plenum" in the trades. Why beat this guy up over it?

Aaron, a "chase" would be more like a "shaft" through which other things run, such as return air duct, and if the AHU was in a "chase" and had return air duct connecting to the AHU, then there would not be a problem.

A return air plenum is what the return air moves through when there is no duct, such as with condo's where the ceiling is dropped and the space between the ceiling and whatever is above it (such as a concrete floor) is used as the return air plenum.

Not beating him up over it, just wanting to make sure that what I am envisioning is what he is describing, otherwise what I am thinking may not be applicable to what he is describing ... it is called 'accuracy' and trying to be 'accurate' so the information is not only 'applicable' but is also 'accurate'.

Originally Posted by Jerry Peck

Aaron, a "chase" would be more like a "shaft" through which other things run, such as return air duct, and if the AHU was in a "chase" and had return air duct connecting to the AHU, then there would not be a problem.

A return air plenum is what the return air moves through when there is no duct, such as with condo's where the ceiling is dropped and the space between the ceiling and whatever is above it (such as a concrete floor) is used as the return air plenum.

Not beating him up over it, just wanting to make sure that what I am envisioning is what he is describing, otherwise what I am thinking may not be applicable to what he is describing ... it is called 'accuracy' and trying to be 'accurate' so the information is not only 'applicable' but is also 'accurate'.

JP: Did you even read my post? I know the difference between a chase and a plenum. I'm all for accuracy, but if you already know what he's talking about, it's sometimes not painful to just answer the question and not belabor the point.

[QUOTE=Aaron Miller;209481]JP: Did you even read my post?[/qutoe]

Did YOU even read your post?

You asked "why" ... I provided the answer to the question YOU asked.

I know the difference between a chase and a plenum. I'm all for accuracy,

I know that, that is not being questioned ... unless you are questioning it ...

but if you already know what he's talking about,

That's the point - I don't *KNOW* for absolutely sure that he is referring to a return air plenum, thus my descriptions of the different ways it may be installed and having him pick one ... okay, I did not actually do it that way - Here are the different ways it could likely be installed, pick one: A); B); or C) - maybe I should have? Is that what you are saying I should have done?

JP: You are hard core.

At the risk of stating the obvious, there are regional differences in terminology. I started construction in Lubbock, Texas which is not far from Santa Rosa, NM. We too' interchanged the words "chase" and "plenum".

After moving to Colorado, I had to adapt to the regional differences in terms. Not to mention, the framers in Denver were using tomahawks to drive nails.

Not to mention, the framers in Denver were using tomahawks to drive nails.

Yes, and in my framing days they were called rig axes. I haven't seen a carpenter in 20 years man enough to handle one. Thirty six ounces of bone-jarring steel attached to a very long handle. Makes short work of 16d nails.

Originally Posted by Aaron Miller

Thirty six ounces of bone-jarring steel attached to a very long handle. Makes short work of 16d nails.

And I thought my 32 oz framing hammer was a 'heavy hitter' ...

Cooper Hand Tools Plumb 11554 Broad Head Hatchet With Hickory Handle - Toolfetch.com

Before someone chides me for my terminology, I called them "tomahawks" when I first saw one, but locally they are called "framing axes". After a while, I traded in my 32 oz, hammer for one too.

Sure glad that I no longer have to swing one of those things............

Originally Posted by Lon Henderson

Before someone chides me for my terminology, I called them "tomahawks" when I first saw one, but locally they are called "framing axes". After a while, I traded in my 32 oz, hammer for one too.

Sure glad that I no longer have to swing one of those things............

Based on some of the work I have seen ...

... I think some trim carpenters use those for miter joints.

Originally Posted by Lon Henderson

At the risk of stating the obvious, there are regional differences in terminology. I started construction in Lubbock, Texas which is not far from Santa Rosa, NM. We too' interchanged the words "chase" and "plenum".

After moving to Colorado, I had to adapt to the regional differences in terms. Not to mention, the framers in Denver were using tomahawks to drive nails.

Originally Posted by Aaron Miller

Yes, and in my framing days they were called rig axes.

The store clerk looked it up and called it a 'Rigster's hammer' back in '73 when I bought this one. I used it for heavy handsplit shakes and pounded hundreds of pounds of galvanized shingle nails with it. Flattened a finger once or twice, too.

Around here, the chase is the box around the duct, not the duct itself.

Originally Posted by John Kogel

Flattened a finger once or twice, too.

I think the only reason I never spattulated a finger was that in Texas we mostly used air guns and I only worked construction here for a couple of years. Most of my carpenter work here was finish and punch out work, where I didn't have to use a framing axe except to make things fit......no, not really. But like Jerry, I have seen a lot of trim work that was done with an axe or trained beavers.

However, in Texas I did manage to shoot myself several times with a framing nail gun and saw a buddy shoot his foot down to a roof deck. Ahhhh, the perils of youthful recklessness.