I have several quotes from contactors who all claim the heating proposed will work in my house. I'm skeptical. Here's what I have. A 2 story contemporary with a one story family room at one end of the house. Aprox 2300 sq ft. The A/C unit is in the attic along with the ducting. Heating is baseboard resistance electric. I believe the cooling capabilities will be fine. My concern is that blowing the heat into the A/C ducts in the attic will not provide a comfortable even heat in all rooms. All the duct vents are in the ceilings with a large central return vent at the top of the stairs in the second floor ceiling. I like to be warm and set the stat at 72*, or higher. I don't want settings of 68* and a sweatshirt or jacket needed. We see winter temps here in Pa down to single digits and below 0* on occasion. Will a central air ducting work for a heating system. Maybe some of you contractors have some experience with this. Comments please. Thanks
Ron: You need help. You need to either learn more or find a good contractor. When I take on a retro-fit, I need to be at one with the owner as to what he wants and what I can do to get him there. You are well on your way as you state what your comfort levels are, but you dis-allow for advanced delivery systems, calm down and restate your goals. You want this to be a geothermal system? Mark
There are plus and minuses to all delivery systems. I heat my home in MI top down. Lake proximity has us on a crawl which had to be rebuilt which required relocation of ducts to attic. Convienience was the plus side of this delivery, but even with a low central return, I'm not sure it is as comfortable along the floor as before. Might be my imagination, I haven't measured. I'm looking forward to new unit with variable speed motor see if it mixes it up more. j
I think it preferable to place the ductwork to favor dominant mode. In other words we cool 8 months per year in FL so high wall / ceiling ductwork is favored. In cold climates it would seem preferable to have floor supplies. Will it work the other way? Of course. The bigger issue is likely duct sizing / airflow. Ducts that are adequate fo a PA cooling load may not cut it for geothermal heating...airflows of 2-3x may be required. A complete Man J and Man D calculation is needed to know for sure.
Thanks, Curt. Two to three times of air flow for heat vs cooling has not been mentioned to me before. That seems like a tremendous difference. What is a 'Man J' and 'Man D' calculation?
ACCA Manual J whole house heating and cooling load calculation. Man D handles duct sizing. Ducts sized for cooling use air cooled by 20*F to cool a house to, say, 75* when it is 90-95 outside. For a typical bedroom that might mean 100 CFM of air is needed In heating mode a geo system uses air heated by 25-30* to heat a house to, say 72* when it is 0 outside. The same typical bedroom might need 200 CFM of air for heat. Ducts designed to meet a cooling load up north likely won't be able to flow the required air if geo is used for heating.
