Brain overloaded

[wayne soper]

I am at a loss at how to describe what this heating duct does in the attic, Damper opened when heat is on and pours hot air into the attic. Condensation was noted at air handler and zone damper controls.
Little help please, thanks

[Billy Stephens]

I am at a loss at how to describe what this heating duct does in the attic, Damper opened when heat is on and pours hot air into the attic. Condensation was noted at air handler and zone damper controls.
Little help please, thanks

Improperly terminated supply duct in unconditioned attic space is opening during the heating cycle. Contact a competent licensed HVAC for repair, connection to conditioned space or replacement.

[Nick Ostrowski]

I'd also include a mention about wasted heat, increased heating costs, the potential for infiltration of airborne attic insulation dust and debris and rodents into the ducts and air handler.

[wayne soper]

This is done at every air handler, 4 of them, 2 in the attic and 2 in the crawl space.

[Markus Keller]

- Some bizarre attempt at turning the attic into 'conditioned' space in order to avoid having to meet requirements for an unconditioned space?
- Unfinished line that got forgotten about
- some weird heat purge set-up that doesn't make sense

[Doug Baughman]

The furnace appears to be a universal flow. Is this a cooling only unit? I don't see a flu pipe. I don't actually see the supply trunk run. The flex duct running on top of the unit is either laying down or is attached to some type of register. A flex duct run should be no more than 10'. I don't see a return air duct. The opened end duct that you are concerned about is too close to the cabinet take off to be a supply ( where is the rest of the supply duct) and the air flow that you are experiencing could be system back pressure . The damper, does it modulate or does it go open and shut? It looks like it is controlled by grey temp. switch? At any rate nothing should be vented into the attic space and should be vented directly out side. Each space that is supplied by the AHU should have its own return back to the unit. See if you can obtain the installation manual from the owner. Call a licensed HVAC contractor and request duct static pressure check for proper air flow requirements for rated efficiency.
I am at a loss at how to describe what this heating duct does in the attic, Damper opened when heat is on and pours hot air into the attic. Condensation was noted at air handler and zone damper controls.
Little help please, thanks

[Lon Henderson]

You guys! That duct keeps the tech warm and toasty when he works on the unit.

[Brad Rodgers]

From what I see in the picture you have an air handler with a hot water coil. The grey temp switch appears to be an aqua-stat attached to one of the hot water pipes for the coil. This controls a relay in the air handler to turn the blower on when hot water is present.

Regarding the damper, that is called a dump damper. It is used to maintain the proper static in a forced air zoning system. The purpose is to relieve pressure when some of the zone dampers are closed to keep proper air flow moving through the system. This is one method of maintaining proper static. Another method is to put in a bypass damper connecting the supply into the return.

Both ways of maintaining proper static have drawbacks. As demonstrated in this picture, the dump damper "dumps" conditioned air into unconditioned spaces (like a basement). With a bypass damper, you're short cycling the air back into the air handler and run the risk of overheating the heat exchanger or freezing the A/C coils.


The furnace appears to be a universal flow. Is this a cooling only unit? I don't see a flu pipe. I don't actually see the supply trunk run. The flex duct running on top of the unit is either laying down or is attached to some type of register. A flex duct run should be no more than 10'. I don't see a return air duct. The opened end duct that you are concerned about is too close to the cabinet take off to be a supply ( where is the rest of the supply duct) and the air flow that you are experiencing could be system back pressure . The damper, does it modulate or does it go open and shut? It looks like it is controlled by grey temp. switch? At any rate nothing should be vented into the attic space and should be vented directly out side. Each space that is supplied by the AHU should have its own return back to the unit. See if you can obtain the installation manual from the owner. Call a licensed HVAC contractor and request duct static pressure check for proper air flow requirements for rated efficiency.

[Billy Stephens]

From what I see in the picture you have an air handler with a hot water coil. The grey temp switch appears to be an aqua-stat attached to one of the hot water pipes for the coil. This controls a relay in the air handler to turn the blower on when hot water is present.

Regarding the damper, that is called a dump damper. It is used to maintain the proper static in a forced air zoning system. The purpose is to relieve pressure when some of the zone dampers are closed to keep proper air flow moving through the system. This is one method of maintaining proper static. Another method is to put in a bypass damper connecting the supply into the return.

Both ways of maintaining proper static have drawbacks. As demonstrated in this picture, the dump damper "dumps" conditioned air into unconditioned spaces (like a basement). With a bypass damper, you're short cycling the air back into the air handler and run the risk of overheating the heat exchanger or freezing the A/C coils.

From what I can see it's a Gas Fired Furnace with a bypass damper that is deadened and should be connected to the return air side or removed. Could you point out this hot water line?

[wayne soper]

It's hydro air and it is a dump damper, I think this house was spec'd out by the owner who oversized everything thinking it would be better.
Now we have huge ammounts of hot or cold air being dumped into the attic and crawl spaces.
Wood floors at 1st level are cupped in areas and attic shows moisture evidence.
I whacked it! I just wasn't able to pull the wording out of my cluttered brain at time of post.
Thanks for all the comments.
now stop bickering, the report is probably already in the trash :D

[Rich Goeken]

.....The flex duct running on top of the unit is either laying down or is attached to some type of register. A flex duct run should be no more than 10'. .....

I am just curious, as I have seen a lot of HVAC systems installed completely with flex ducts, except for the short rigid plenum to the attic, can you provide backup for your statement of a 10' limitation?

[Brad Rodgers]

From what I can see it's a Gas Fired Furnace with a bypass damper that is deadened and should be connected to the return air side or removed. Could you point out this hot water line?

The hot water lines are circled in the picture. Please point out evidence that this is a gas furnace.

[Lon Henderson]

The hot water lines are circled in the picture. Please point out evidence that this is a gas furnace.
Do those rust circles on the pan indicate a problem?

I think I've only seen one of these and it didn't have the dump damper.

[Billy Stephens]

It's hydro air and it is a dump damper,

I think this house was spec'd out by the owner who over-sized everything thinking it would be better.

Now we have huge amounts of hot or cold air being dumped into the attic and crawl spaces.

Dang, Is you saying a Yankee done out smarted his self?

Do he work for the Gub-Mint ?

If we dump something around here it's not conditioned air. :)
* what are the side by side metallic vents in the top left connected to?

[Mark Reinmiller]

I am at a loss at how to describe what this heating duct does in the attic, Damper opened when heat is on and pours hot air into the attic. Condensation was noted at air handler and zone damper controls.
Little help please, thanks

I agree with the dump damper. I'm assuming it is a zoned system since there appears to be a zone controlled above the system. however, a dump damper should not sent heat or ac to an unconditioned space. Likely to have problems with condensation or ice damming. A bypass damper would be better, but zoned systems can be a hassle to get right.

[Mike Garber]

Is the flex duct to the left that is pointing down into the plywood going thru the plywood decking? It looks as if that may have cut off the open valve and is just sitting on the plywood.

[Billy Stephens]

The hot water lines are circled in the picture. Please point out evidence that this is a gas furnace.
.......

[Jerry Peck]

Billy,

Those things you drew a rounded corner rectangle around look like exhaust fans for bathrooms with remote mounted fans.

[Tom Rees]

I saw this on a house I did Friday. It was also a zoned system. Let me see if I understand this, I hope some HVAC guy will set me straight. The furnace is designed to heat or cool the whole house, when only one zone calls for heat or cooling you have the same amount of air that used to go to whole house now going to half the house. To make up for this and not have too much air going through ducts you dump some of it. The one I saw dumped to exterior. This seems like a real waste of energy. I think someone said you can also dump this back into the return air (bypass damper), is this less wasteful?

[Rod Butler]

I saw this on a house I did Friday. It was also a zoned system. Let me see if I understand this, I hope some HVAC guy will set me straight. The furnace is designed to heat or cool the whole house, when only one zone calls for heat or cooling you have the same amount of air that used to go to whole house now going to half the house. To make up for this and not have too much air going through ducts you dump some of it. The one I saw dumped to exterior. This seems like a real waste of energy. I think someone said you can also dump this back into the return air (bypass damper), is this less wasteful?

I agree mostly Tom. The dump should be going back to the return. If it's going outside there is a major problem in many ways. That air has to be made up somewhere on the return side of the fan or it won't provide the proper flow across the coil. The energy issue is a whole nasty cow in that case.

Relieving or dumping to the return is not overly energy efficient but it offers the luxury of better zone control. I actually like it on small residential systems.

I wonder if the attic or crawl space in the OP's post were meant to be return plenums.