New construction

[nathan9999]

I am building a new home and the architect has included in his plans some information on HVAC requirements. I will be involved with the general contractor in approving bids. I have three questions.
1. Should I require HVAC contractors to provide a formal load calculation with the bid? Is this the only reliable way to get a correctly sized system?
2. I have two bids so far. The first bid is for a 2 unit York system (one 4-ton unit and one 2.5-ton unit, according to architect's specs). The other bid is from a Trane dealer who has provided a similar bid for 2 Trane units, then he has also provided a bid for a single hi-efficiency Trane (4 ton unit) unit with air handlers. What questions or concerns should I have concerning a single unit being used to heat and cool the entire house?
3. Last question. Is there some way to determine if the higher efficiency units actually make economic sense? I would like to have a higher efficiency unit but not if it has a 20 year payback period. Our climate is quite warm (California central valley) so I was thinking I should be more concerned about a high efficiency a/c unit but not so much about a high efficiency furnace. Is this the correct way to assess this issue.
Thanks very much for any advice.

[cem-bsee]

read lots here.

get | do a load calc!
like buying a truck without knowing how much load it is to haul & what type of load

what does arch state?
did you buy a design? why would you change?

does arch provide space & chases for systems?

sys= plbg, elec, HVAC, CATV, ph, ...

[uktra]

You need to go to http://www.buildingscience.com and check out he Building America section for your climate zone. This site will explain the relationship between the thermal envelope and the proper intigration of the hvac system. I would recommend you find an independant consultant to help you with the room by room heat calc and details of how to build the home properly. It will be money well spent.

[tinner73]

if the archetect DID a load calc you won't need another. i assume he spec'd duct size, cfm, etc. make sure it's put in right. go with a quality 80+ furnace. Don't use builder's grade equip.

[nathan9999]

How would I identify builder's grade equipment? I have been quoted either 12 or 14 SEER York and Trane systems (2 units), as well as a 19 SEER Trane (single unit with air handlers).

[nathan9999]

cem-bsee

I just did not know if I should accept the architect's calculations. I'll look at the plans and see what kind of details he provides.
Thanks