question about adding a ducting run

[fuente]

Hi all,

My current furnace setup is all flex ducting thru the house. The furnace is located in the attic, as is all the ducting. Registers are ceiling mounted. Currently there are 8 branches off the main trunk.

Recently completed an addition, and I'd like to add a ducting run. The truck is relatively close to the addition; I'd need a run of a bout 10 feet to get there.

The installation seems pretty straightforward, but I"m sure there ae some things I need to verify first prior to determining location of the cut-in, flex duct diameter, and anything else I'm missing.

My current furnace setup is all flex ducting thru the house. The furnace is located in the attic, as is all the ducting. Registers are ceiling mounted. Currently there are 8 branches off the main trunk.

Recently completed an addition, and I'd like to add a ducting run. The truck is relatively close to the addition; I'd need a run of a bout 10 feet to get there.

The installation seems pretty straightforward, but I"m sure there ae some things I need to verify first prior to determining location of the cut-in, flex duct diameter, and anything else I'm missing.

The house without the addition is a 3/2, around 1100 sq. ft. The addition is only 1 room, which is approx. 13/20, so let's say 260 sq. ft.

My furnace is new as of last winter. I'm looking at the manual, and forgive me for not being specific but HVAC is new to me. Here is what I see:

Looks like it's a UPG/York Model LY8S, Single Stage 80% Downflow...?

Probably need to look on the unit itself to determine the CFM's??




My original plan is to run the new duct from the furnace, thru the garage, and then into the addition and position the register about 1 ft from the ceiling. The way the addtion is built, there is no floor or ceiling access. The only other option is to run the duct thru a wall, but the only wall available is one that used to be the outside of the house years ago, so it's load bearing (I would assume)



Thanks for any advice, in advance.

[Phelps]

It sounds like each room with the existing duct then would lose about 1 1/2% of the potential air volume (and speed to heat) potential. If the existing 8 ducts are 100% of the potential, that means each duct would represent the number (or percent) of 12.5. By introducing a 9th duct, the 100 potential for all combined ducts would then be down to about 11 (percent) for each duct. I am not into duct sizing, but unless you live in the Yukon, I can't see how this reduction would be that significant. (Unless I goofed up on my math thinking somehow)

Maybe someone else could shed some light on this.

[fuente]

thanks I appreciate the reply. Does the length of run factor into the equation? Also, is there a good link/site that will step me thru the process of adding the new run?

Thanks again.

[HayZee518]

to start the run at the furnace you'll need a "takeoff" fitting at the other end you'll need a register boot. in between you use fiberglass flexi duct. both fittings are made of galvanized sheet stock so you'll have to cut in the takeoff into the trunk line. square hole or round hole depending on your duct.

[fuente]

to start the run at the furnace you'll need a "takeoff" fitting at the other end you'll need a register boot. in between you use fiberglass flexi duct. both fittings are made of galvanized sheet stock so you'll have to cut in the takeoff into the trunk line. square hole or round hole depending on your duct.

thanks for the reply. is it possible to install a 'Y' fitting from and existing takeoff (branch)? Reason I ask is that there is another branch that terminates at a register that is about 3 feet from where I need the new one. It services a guest bathroom that is fairly small, so I suppose I could adjust the dampers on the register to flow most of the air into the addition. Don't know if this is possible?

Also, can i notch the load bearing wall, and if so, I suppose I need a steel oval to run to the register, which will be on the wall (no attic on the addition)?

And when I connect the branch to the trunk (or 'Y' to the trunk), I suppose I need some sort of collar, then tape or clamp?

I am new to HVAC, so please bear with me.

Any DIY sites available for this sort of thing, I'd appreciate it. Thanks !!

[HayZee518]

wall construction

Look at this diagram -

[fuente]

Thanks for the diagram, but is that all really necessary for just a small duct penetrate the top plate? Anyway, I can't reasonably get into the walls to add those studs. I could bring it in thru the garage, but the branch will be much longer. No penetrations of any studs, just a hole in the stucco enterior wall to run the ducting.

Probably should you steel ducting in that case?

Thanks again.