Replace furnace and new A/C

[ashatara78]

Hi

We are in the process of getting estimates for replacing our 30 year old furnace and also installing a new a/c. The contractors are giving a free estimate but are not willing to share the Manual-J calculation. We need to be absolutely sure about what we want before we can go ahead with the purchase and installation.

The house is 2070 sq ft, single storey. Windows are double-paned but the insulation in the attic is poor. These are the things we are sure about:

- Most contractors recommended a 3.5 tonne a/c. This matches with our estimate too. Trane has a 3.5 tonne a/c that we will go with.
- We need a 2stage 2 speed furnace with 92% efficiency

However, we are not able to figure this out:
- What is the furnace BTU needed? The current 30-year old furnace is 80,000BTU and it does not work well. Given that we are getting a new one with a high efficiency, should we stick with 80,000 BTU, or can we reduce it?
- One contractor recommended adding another return grill. The furnace is in a closet with a return grill on the wall under the closet. What should I measure and calculate to see if another return grille is needed for appropriate CFMs?

Thanks in advance for your help.
Asha

[dash]

You could give us current model numbers,duct sizes,detaled descriptions,post pictures ,etc..We could probably make some valid recomendations,but you'll still need someoen onsite,that can see it and test it.


So,call your contractor and the others if they can't do a Manual J,S,and D,to size ,select equipment,and design(or redesign )the ducts an grilles.These are the industry standards,from http://www.acca.org Be upfront let them know,this is what you want and won't settle for "rules of thumb" or "based on my X years of experience".

Keep dialing until some can be found,that has the knowledge needed to do it right the first time.