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New Construction HVAC Question

Posted by dhuston (My Page) on
Thu, Nov 10, 11 at 12:59

Building a new house in NW FL and I have some questions regarding the install and what I am being told from different companies. Situation is kind of hard to explain but I will do my best.

Was told by two different installers that we would need to build a soffit from where the air handler will be to the main ac chase because the floor joist above are to close together to get a duct big enough to have sufficient air flow. The floor joist are 16in deep and spaced 16in apart.

Third installer states the they can put in a 16in flex duct between the floor joists and run that to the main ac chase. Main chase would be made out of duct board with flex duct branches for the registers.

I would definitely prefer to not have a soffit in my closet but I want to make sure the house is cooled and heated correctly.

The unit is going to be 3ton, not sure what brand yet, thinking about doing a two stage heat pump. The square footage for the floor is 2100 sqft.

Here is floorplan if it helps. There will be a second three ton unit upstairs.


Follow-Up Postings:

RE: New Construction HVAC Question

What are your floor structures? Are they open web and what size? There are probably too many things to know to be able to answer on a forum.

I am building a house with ductwork in the floor structure of a 2 story house. The situation is not too different than what you are doing except that you are probably putting ductwork for 2 floors on the same floor structure. That is challenging without soffits.

Our current house had to have a soffit built in one area for the basement ductwork although the house we copied did not. But the house we copied did have a closet with a lowered ceiling (basically the equivalent of a soffit).

Anyway -- hard to answer. Hard to have 2 systems in the same floor system without any soffits. Possible but hard.

RE: New Construction HVAC Question

Second floor doctor work will be in attic. The ducts in question are only for the first floor as there will be two units. Floor system in enginered floor trusses.

RE: New Construction HVAC Question

OK, after doing some more research I think I may have answered my own question! Would like some confirmation from the experts here though.

Read that each ton is about 400cfm and that a 16in flex duct is only rated for 850cfm. So that would make the third companies solution a bad idea!

Please tell me if I am understanding this right?

Also, I am looking at buying a Goodman two stage 16 SEER 3 ton unit.

The model numbers are:

Condenser Model No. DSZC160361
Air Handler Model No. AVPTC313714

I have read opinions of Goodman and I would buy a different brand but at this point money is a big factor. Anyway, is it worth it to get the Comfortnet thermostat or would a White Rodgers model # 1f95-1291 work just as well? Also, is there a performance benefit to the remote outdoor sensor or is it just to display the outdoor temp?

Thanks for all the help!

RE: New Construction HVAC Question

Sorry - I assumed since the air handler was in conditioned space that the ductwork would be. Sounds like you could do 2 16 inch flex ducts. That is one way to handle it. But if you are talking about the downstairs unit, then a soffit is probably your best choice.

I don't think you will find anyone here willing to condone a Goodman purchase. Find somewhere else to save the money. If I had to save money, I'd go to single stage.

RE: New Construction HVAC Question

Second floor doctor work will be in attic. The ducts in question are only for the first floor as there will be two units. Floor system in enginered floor trusses.

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