plenum

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lmchenry

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I have a room (approx 4 x 8) that has a air handler (draws air from the room), a water heater, a washer, and a dryer. What part of this do I consider a plenum and does 300.22b apply to this whole room? If it does how about the cords for the washer and dryer? Must everything be plenum rated?
 
I am not quite visualizing what you have.

Just because an air handler draws air from a room doesn't make the room a plenum. For example a central heating system draws return air from multiple return air vents but the rooms that the vents are in are not plenums.

Chris
 
I see your point. Looking at 300.22c the purpose of this room is air handling along with being a laundry. Do this code apply?
 
Here is what 300.22(C) says:

"(C) Other Space Used for Environmental Air. This section applies to space used for environmental air-handling purposes other than ducts and plenums as specified in 300.22(A) and (B). It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling."

I added the bold to this section to clarify that this section only applys to areas where air handling is the prime purpose.

I guess I would ask if the prime purpose of this room is to convey enviromental air or is it a laundry?

Chris
 
So what is the intent of this code? If I remove the washer and dryer the prime purpose would be air handling. So wouldnt you think they would need protecting just the same? To clarify, if I dont put the W/D in then I need to
protect my conductors (300.22c1), but if I do I dont have to?
 
For a room to be considered to be a "Plenum" the room must play a major part in the distribution of enviromental air.

I don't believe that a room in which an air handler recieves it's return air would be considered a plenum.

Chris
 
Please read 300.22c. This is not refering to a plenum but just enviromental air. Disregard my earlier reference to 300.22b. So now what about that space?
 
lmchenry said:
So what is the intent of this code? If I remove the washer and dryer the prime purpose would be air handling. So wouldnt you think they would need protecting just the same? To clarify, if I dont put the W/D in then I need to
protect my conductors (300.22c1), but if I do I dont have to?
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I think the most common place where this code has application would be where the design of the HVAC system uses space above a ceiling for air handling. This would occur where there are return ducts installed in the ceiling, but no ducts between them and the air handling unit (most commonly a roof top unit). When the system is designed this way, the return air is drawn up through the ceiling and then through the above ceiling space without ducts. The above ceiling space becomes "Other Space Used for Environmental Air"
 
Thanks. What seems to confuse matters is the handbook. It shows a room that has a electrical panel and an air handler. This is what led to my questioning.
 
lmchenry said:
Thanks. What seems to confuse matters is the handbook. It shows a room that has a electrical panel and an air handler. This is what led to my questioning.
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I think I see what you are saying.

plenum.png



Your room is like the room on the right in the drawing except that it has a water heater, washer and dryer in it, right? So, if you remove the w/h, washer and dryer it would be just like the room on the right?

I can see where this room might be considered as being primarily for air handling space since the air handler is located in the room. It's a good question and I'm not sure what the answer would be.:-?
 
lmchenry said:
Thanks! You are correct. Any other input would be greatly appreciated.
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Where is the air being pulled from? The ceiling or under the door. This is an unusual circumstance. The air is just circulating within the room so I do not see that as a plenum
 
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It is not a plenum. It is other space. The air is being pulled from under the door and from a grill cut in the wall.
 
lmchenry said:
It is not a plenum. It is other space. The air is being pulled from under the door and from a grill cut in the wall.
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How is that any different than any other cold air return. The cold air return in my hall pulls from under the door ways, etc. I just don't see this as an issue but I do understand the questioning.

Again I think chris nailed it earlier with the bolded section

(C) Other Space Used for Environmental Air. This section applies to space used for environmental air-handling purposes other than ducts and plenums as specified in 300.22(A) and (B). It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.
FPN: The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies.
Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.
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I am not sure what the handbook is trying to illustrate, a panel board would be allowed in 'other airspace' unless it was plastic.

My gut says your over thinking it as any building with forced air heating / cooling is going to be used for air handling.

I have been in 'Air handling rooms' in large buildings that where large rooms created for the express purpose of air handling. These where large, well lighted rooms with more or less standard doors for entrance.
 
This may be stretching it, but say you have a room that had its prime purpose as air handling. Does that restrict what you can put in that room?

Another situation I have seen is a mechanical room(that was used for air handling) with some PVC conduit and boxes in it. This would appear to be a violation from 300.22c.
 
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