Airflow / cold air return

[billygoat22]

I met up with an engineer a few weeks ago that subscribed to the "high" school of thought. I ran a pitot tube check at the return duct and reset the airflow for the required cfm by units chart( Trane has the required cfm on the charging chart).
He gets bent out of shape because the airflow is less (much more correct than before) and that his other unit blows a lot, and this unit was on high before, and HE DON"T CARE WHAT TRANE SAYS to set the airflow at. Because hes an engineer and knows it should be on hi.

If the airflowe is right at the unit, and you don't have duct leakage, you won't neccessarily feel airflow x distance from the registers. If you cranked up the flow just to be doing it, it would throw off the system from proper operation

Bryancorfu-The idea of not feeling/sensing the a/c operate is aslo called "transparency".

[dash]

Do you have the Infinity Control?


What model #'s,furnace ,coil ,outdoor unit?

Size of the home?

Newer homes are often better insulated,have better windows,etc..This will reduce the size of the system and air flow required,so their can be a lot less air movement then in your previous home.

[robroy]

Originally posted by dash
Do you have the Infinity Control?
What model #'s,furnace ,coil ,outdoor unit?
Size of the home?

Yes, I have Infinity Control.
Furnace: 58MVP080
A/C: 38TDB037
Coil: ??
Also have a separately-ducted ERV: Venmar AVS Duo 1.9

Home is 2400 sq.ft. with 9' ceiling in bsmt & main floor. Basement is cold, main floor is comfortable, 2nd flr. is warm.

To cut down on heat, I was actually thinking of applying a tinting film to windows (says it cuts down ~60% of heat, as well as provides UV protection). This I would think would help with cooling my 2nd flr, and lower my energy costs.

[dash]

Your second floor has all or most of the attic,so the cfm required per sq ft there is likely higher then the other two floors.




Your best bet would be a zoning system,Infinity as weel ,if the duct work can easily be adapted.

Manual dampers,one per floor adjust by the season,can also be effective,again if the duct system can easily be adapted.


With the Infinity control system,you can be certain it's moving the correct amount of air thru the equipment,if not it should have a fault history,in the controoler.

How many ACH were you looking for and how many cubic feetof space?

[docholiday]

[QUOTE]Originally posted by robroy

the Infinity 96 is quiet for the most part -- better be since it's supposed to be the quietest furnace on the planet!

The furnace has nothing to do with the sound of air coming out of the registers, thats a duct design issue. Each register has a designed velocity and volume intended, the ducts (provided the furnace is proper) provide volume and velocity. Poor ductwork can make any system noisy or ineffective.

Originally posted by robroy
One thing I do notice is that the original installer definitely uses a lot of the joist work to channel the return air flow -- I thought this was not allowed i.e. building code does not allow use of building structure (???) since it is not intended to provide a proper air seal.

Nothing wrong with that for the most part as long as it doesnt leak. Return static and velocity always need to be considered.

[robroy]

Originally posted by docholiday
The furnace has nothing to do with the sound of air coming out of the registers, thats a duct design issue. Each register has a designed velocity and volume intended, the ducts (provided the furnace is proper) provide volume and velocity. Poor ductwork can make any system noisy or ineffective.

Doc...my point was that I shouldn't be able to hear any furnace operations through the registers for my particular furnace. However, with less "quiet" furnaces, of course you should be able to hear this as the nature of duct work being like a primitive phone line, will transmit sound quite effectively. I used to play a game with my kids where I would speak into a gap in one of my supply ducts in the basement (opened to run some cables), and they could hear me clear as a bell from a 2nd floor register. This is of course in addition to duct-induced noises.

[docholiday]

[QUOTE]Originally posted by robroy

I used to play a game with my kids where I would speak into a gap in one of my supply ducts in the basement (opened to run some cables), and they could hear me clear as a bell from a 2nd floor register.

I used to play a similar game with mine.... It was "go outside and play, can't you see Dad's busy bleeding down here?"

[coco]

i would start by figuring out wht the return airflow is so weak