Natch, I am getting conflicting advice from ## folks, bidders. Such is life.
One load calc done, but another outfit wants to do its own. Since some aspects of a load calculation are not so precise as SF I understand that there would be some modest difference between two able folks doing such on the same house. But it appears that the overall load is 4.5 tons.
As folks on this thread know better than I, duct work is at least as important as the equipment. In my case, I need to replace dead AC + furnace (propane) in a very moderate climate (45-85 max temp range over the year) but also do some correction of a house that was sized incorrectly. I will be adding some ducts to an area that has lots of glass and ridiculously small vents now. I have to live with the single 18 inch return--not as bad as it seems since the house is very open and vertical.
The house was originally sized (with respect to duct work and equipment) for a 4 ton.
I should have some boost just by the new AC/furnace equipment (AC unit is 20 years old and likely 8 SEER; "old" furnace is 90+ efficiency, so I will not get much more with with the new furnace). And I will be adding a large vent and dampers to move more air from one level to the other (presently under-ducted) area, and putting in all new vents where they are accessible (mostly the same size, but tighter etc)
(I am leaning toward 13 SEER on the AC--again, moderate climate)
2 issues:
1) 4 ton vs 5 ton system. Some folks say, "for a house this size and the amount of sun coming in, it should have been 5 ton--go with a 5 ton".
Other folks say, "the 18 inch return would not be enough for a 5 ton unit. A 4 ton is enough, given that you will have much better air flow and better equipment, and less loss through leaky ducts."
(And one guy says "4.5 tons is the load, so downsize the conventional AC_ furnace to 3 tons, and add a 1.5 ton mini-split to the presently "under-ducted" area of the house." Given that this added equipment would add at least $$$ to the cost, and the house is not split into separate areas, this alternative seems like the one to avoid).
4 or 5 tons?
----------------------
2) furnaces from a single company now come in as many as 4 grades, ranging from single stage up to units with furnace "communication" with sensors in the ducts.
Again, conflicting advice (from some able contractors, not bozos). One intelligent and honest guy (it seemed to me) said that some hard lessons were learned when the multi-variable stage models came out. He said that a plain ol' single stage unit might be best, and that multi-stage units are better for situations when the equipment is plenty big for the house.
Other folks say a 2500 sq ft house needs at least a two stage unit, and others suggest a unit with 2 stages on the propane and variable speeds on the fan.
Jeez..........
-------------------------------
thanks in advance for advice
One load calc done, but another outfit wants to do its own. Since some aspects of a load calculation are not so precise as SF I understand that there would be some modest difference between two able folks doing such on the same house. But it appears that the overall load is 4.5 tons.
As folks on this thread know better than I, duct work is at least as important as the equipment. In my case, I need to replace dead AC + furnace (propane) in a very moderate climate (45-85 max temp range over the year) but also do some correction of a house that was sized incorrectly. I will be adding some ducts to an area that has lots of glass and ridiculously small vents now. I have to live with the single 18 inch return--not as bad as it seems since the house is very open and vertical.
The house was originally sized (with respect to duct work and equipment) for a 4 ton.
I should have some boost just by the new AC/furnace equipment (AC unit is 20 years old and likely 8 SEER; "old" furnace is 90+ efficiency, so I will not get much more with with the new furnace). And I will be adding a large vent and dampers to move more air from one level to the other (presently under-ducted) area, and putting in all new vents where they are accessible (mostly the same size, but tighter etc)
(I am leaning toward 13 SEER on the AC--again, moderate climate)
2 issues:
1) 4 ton vs 5 ton system. Some folks say, "for a house this size and the amount of sun coming in, it should have been 5 ton--go with a 5 ton".
Other folks say, "the 18 inch return would not be enough for a 5 ton unit. A 4 ton is enough, given that you will have much better air flow and better equipment, and less loss through leaky ducts."
(And one guy says "4.5 tons is the load, so downsize the conventional AC_ furnace to 3 tons, and add a 1.5 ton mini-split to the presently "under-ducted" area of the house." Given that this added equipment would add at least $$$ to the cost, and the house is not split into separate areas, this alternative seems like the one to avoid).
4 or 5 tons?
----------------------
2) furnaces from a single company now come in as many as 4 grades, ranging from single stage up to units with furnace "communication" with sensors in the ducts.
Again, conflicting advice (from some able contractors, not bozos). One intelligent and honest guy (it seemed to me) said that some hard lessons were learned when the multi-variable stage models came out. He said that a plain ol' single stage unit might be best, and that multi-stage units are better for situations when the equipment is plenty big for the house.
Other folks say a 2500 sq ft house needs at least a two stage unit, and others suggest a unit with 2 stages on the propane and variable speeds on the fan.
Jeez..........
-------------------------------
thanks in advance for advice
