We are in the process of building a log home.

1. Size of the home is 1796 sq ft. second floor is 534 sq ft. catheral ceiling, home will be on full basement.

2. planning to use propeane for heat. And will have central air.

3. What would to the best size propane heat unit and central air units?

4. Bedroon area will be carpeted and pine flooring in the other areas.

Any suggestion apppreciated.

I think you really need to do a detailed heat loss calculation to figure out how large a furnace you'll need. It will have to take into account the insulating qualities of the walls and roof, window sizes, number of doors, and all kinds of other things as well. Similarly, a Manual J (is that right?) is the calculation done to determine what size air conditioner is appropriate. Neither undertaking is trivial, but if you want to do things right.. .

I am by no means a heating and cooling expert, just quite good at DIY. Yesterday I had my BBQ propane tank filled, and was amazed at the $15.80 cost for about 4.5 gal. I don't know how cold the winters get in Maryland, but you might ask the local HVAC dealers if a Heat Pump would work to provide both A/C and heat. They make Heat Pumps with auxiliary heat strips when it is too cold outside. Here in sunny Phoenix it gets hot enough to boil your brain. My home which is about 1800 sq ft has a 4 ton unit and my garage addition of about 1200 sq ft has a 3 1/2 ton unit. They provide all the heating and cooling that I need. If feasible, that might reduce your total install cost, and might be cheaper to run. I hope that I am not in left field on this one.

My Daughter recently built a log home(1500 Sq. Ft.) in Colorado. They opted for electric heat(25 KW) and are extremely happy with it as far as comfort and economy. You might consider 2 units(Small one for the second floor) or a zoned system to make the home more comfortable and efficient... You will need a furnace that will supply at least 80,000 BTU's of heating or at minimum, 20-25KW electric heat. Best would be sized 10-15% over what you need. Some recommend 20-25%, but I feel that's overkill. If it were me, I would install a 60,000 BTU unit for the main area and a 40,000 BTU unit for upstairs...

I am still stuck in my Heat Pump mode. In today's newspaper supplement (USA Weekend), they had an article on energy saving. In it they mentioned a Geothermal Heat Pump which uses the Earth's ground temperature instead of outside air to heat and cool your home. This is obviously much more expensive than a traditional HVAC system, but can cut heating and cooling costs by 50 %. I have a friend who just built a home in Maryland with such a system.

I have a 1850 sq ft home and wanting to get new air conditioner unit. What size you recommend?