Hanging ductwork questions

[ssathre]

I'm trying to run 10" round ductwork for my exhaust/intake fan. my problem is the vent hoods are placed in a less than favorable spot. (see pics) trying to friction fit ductwork together to get an idea of how to route this stuff is not working out. I am not an hvac guy at and im wondering if anyone could offer some advice or tips on how to make my life a little easier.

here are the vent locations, note the truss support is right in the way. there is enough room to translation around them with 90's.

View media item 10529

here is the fan. Manufacture shows it being mounted lengthwise on one of the truss supports. kind of an awkward angle, maybe I should frame up a support and hang it horizontally?

View media item 10534

 

[Lump]

I was an industrial sheet metal worker for some years, and I can tell you that it is pretty rare that things naturally line up like you want.

First do some careful measuring. How far left/right do you need to go, and how far down do you need to go with each of them?

Once you have carefully measured, keep in mind that elbows are usually made up from "gores", which are wedge-shaped sections. These sections of each elbow can be rotated to change your elbow from a 90 degree on just one plane, to lesser degrees on two planes. In other words, you can take a 90 degree elbow and twist the sections around to help you go BOTH down and sideways, to a certain degree. Additionally, don't forget that today they have some terrific flexible duct available, which can make the job much easier.

When mounting that fan, make sure you place it where vibration won't be a problem for you. Make sure it is near the specific air you wish to exhaust, and has a short distance to the outdoors. Also, place it where it will be easy to clean, if needed.

Have I given you useful answers? I am not TOTALLY sure I completely understood all of your question.

 

[ssathre]

I was an industrial sheet metal worker for some years, and I can tell you that it is pretty rare that things naturally line up like you want.

First do some careful measuring. How far left/right do you need to go, and how far down do you need to go with each of them?

Once you have carefully measured, keep in mind that elbows are usually made up from "gores", which are wedge-shaped sections. These sections of each elbow can be rotated to change your elbow from a 90 degree on just one plane, to lesser degrees on two planes. In other words, you can take a 90 degree elbow and twist the sections around to help you go BOTH down and sideways, to a certain degree. Additionally, don't forget that today they have some terrific flexible duct available, which can make the job much easier.

When mounting that fan, make sure you place it where vibration won't be a problem for you. Make sure it is near the specific air you wish to exhaust, and has a short distance to the outdoors. Also, place it where it will be easy to clean, if needed.

Have I given you useful answers? I am not TOTALLY sure I completely understood all of your question.

thanks for the tips. I had thought about the flex but I didn't know if it would handle 1100 cfm or if it would create too much resistance and kill my cfm rate.

when setting the elbows do you screw them off as you go? I don't have any help right now and it's frustrating trying to fit longer pieces to the elbows without being able to be in two places at once.

 

[ssathre]

No way you are getting 1100 CFM through 12" duct, unless those are high static fans.

Good luck.

it's a 10" fan and duct. I'm only going off the cfm listed in the product specs.

http://www.tamtech.com/store/infinity-balanced-ventilation-postive-negative-ducted-fan,Product.asp

 

[mrobins297aaa]

the max cfm for a 10" duct on a low pressure system is 450 +-

to handle 1100 cfm you need at least a 14" duct.

I'm not quite sure what your trying to do here?, what are these fans for and how long are the runs?

 

[mrobins297aaa]

as far as fastening the duct together get some #7 x 1/2 zip screws with a 1/4" adapter (thats the head size of the screws) to fit in your battery drill. that pipe is probably 30 ga. so those screws will go right in. Home depot has them, get the ones made by malco.

if your trying to run it yourself sometimes on the long pieces you can tie one end up with wire while your making the connection or twine or even a 2x4 on the horizantel across the truss members.

flex is ok but try to keep it as straight as possible, lots of hangers to eliminate all the droops. I think the code in michigan is no more than 14' but we always tried to keep it less that 5'.

 

[ssathre]

the max cfm for a 10" duct on a low pressure system is 450 +-

to handle 1100 cfm you need at least a 14" duct.

I'm not quite sure what your trying to do here?, what are these fans for and how long are the runs?

I'm trying to set this up as a balanced system, one intake and one exhaust, the runs will be short and straight as possible. it's just basically there to get the air moving and get rid of cigar smoke when the guys are over. I don't have any windows in the garage so I thought this would help cycle the air. if it doesn't move enough air set up as balanced I'll run both as an exhaust and put a screen door on the walk in.

The fan is what it is and for better or worse it's what I have to work with. I'm not trying to convince anyone of it's abilities... I'm just the dummy that's reading the spec sheet and trying to get some advice on hanging ductwork.

 

[ssathre]

as far as fastening the duct together get some #7 x 1/2 zip screws with a 1/4" adapter (thats the head size of the screws) to fit in your battery drill. that pipe is probably 30 ga. so those screws will go right in. Home depot has them, get the ones made by malco.

if your trying to run it yourself sometimes on the long pieces you can tie one end up with wire while your making the connection or twine or even a 2x4 on the horizantel across the truss members.

flex is ok but try to keep it as straight as possible, lots of hangers to eliminate all the droops. I think the code in michigan is no more than 14' but we always tried to keep it less that 5'.

awesome info, thanks. what type of flex should I get? metal or the insulated type that has the wire structure in it?

 

[mrobins297aaa]

1100 cfm is at the top of the range for 14", 16" would be better

this is what we used to size runouts on low pressure ductwork.

10" 250-450 cfm
12" 450-750 cfm
14" 750- 1100 cfm
16" 1100- ?.........lol ......I can't remember without looking at a ductalator

 

[mrobins297aaa]

don't get the metal, get the stuff with the wire in it.

does that box with the two fans on it mount in the ceiling?
is there a grille that fits to it?

 

[mrobins297aaa]

I know you don't care about the cfm just remember the more 10" duct you run the less air you will get, so keep that in mind, the shorter the better on the runouts.

 

[ssathre]

don't get the metal, get the stuff with the wire in it.

does that box with the two fans on it mount in the ceiling?
is there a grille that fits to it?

the fan is installed in the attic, it's actually two independent fans in one housing... like those window mount fans. here's an illustration showing how it's mounted and the different configurations.

http://www.tamtech.com/userfiles/Infinity March 2011.pdf

 

[mrobins297aaa]

I see, I'd hang it just the way they show except I would hang it level not on a angle on the rafter like they show. unless that works better for you.

I think your intake and discharge at the wall are plenty far enough apart.

are you going to install a ceiling in there? or is it going to be open?
if your going to use the diffusers that they offer? just make sure they are at least 6'+- apart and I think you'll be ok.

if your not using the diffusers then I would run at least 5' of duct off of at least one fan to create some separation.

 

[ssathre]

I see, I'd hang it just the way they show except I would hang it level not on a angle on the rafter like they show. unless that works better for you.

I think your intake and discharge at the wall are plenty far enough apart.

are you going to install a ceiling in there? or is it going to be open?
if your going to use the diffusers that they offer? just make sure they are at least 6'+- apart and I think you'll be ok.

if your not using the diffusers then I would run at least 5' of duct off of at least one fan to create some separation.

I am drywalling the ceiling but I was just going to use the round vent grills. thanks for all your help, I really appreciate it.

 

[HVAC Phil]

I would run it in hard pipe. Try to swivel the elbows to eliminate 90 bends. Also, insulate the pipe to prevent condensation.

 

[ssathre]

I would run it in hard pipe. Try to swivel the elbows to eliminate 90 bends. Also, insulate the pipe to prevent condensation.

Thanks, Phil.