Jimt1000
Member
I am replacing a 3 ton and a 2 ton split AC system serving two zones with a single 5 ton AC with motorized supply dampers to serve the two zones. All good. I have a two story home and the furnaces are located in the upper attic and the condensing units are located at the ground level (21 feet of rise from ground to the attic). The new AC is going to be a Trane 5 ton model 4TTV8060A. The existing vapor line sizes running up into the attic are 3/4" and they run inside my exterior brick wall (behind the sheetrock in a 2x6 stud space) from the ground level to the attic space. The existing old AC condensers being removed are not next to each other (i.e., they are on opposite sides of the house). So, unless I am willing to have 21' of insulated refrigerant line exposed on the exterior brick of my home, which I'm not willing to do else I fear a divorce forthcoming, I must make use of the existing 3/4" vapor line inside the exterior brick wall as described. My AC technician has recommended brazing a 7/8" line where immediately accessible to the 3/4" line running in the brick wall in both the attic and at the ground level where the condenser will be. So, I would have a 7/8" line transitioning immediately off the condenser to a 3/4" line which would then run 21' up in the exterior brick wall into the attic where it would then transition back to a 7/8" line to the furnace.
As a civil engineer who knows enough mechanical engineering to get myself into trouble, this makes sense (i.e., bigger line less friction loss albeit with less velocity). Looking at the Trane installation manual seems to verify this is OK, but it also adds confusion. See below insert picture from the Trane installation manual. Table 3 calls for the vapor line size to be 1-1/8" and as footnoted, a max. length of 80' and a max. length of vertical rise of 25'. Yet, in Table 4, "Alternate Line Sizes" are provided whereby for the 4TTV8060A it is stated that the vapor line can be 3/4" or 7/8" and as footnoted, a max. length of 150' and a max. length of vertical rise of 50'. The footnoting as stated above seems counterintuitive given the line sizes provided; however, regardless, I am OK in my application no matter what the line size configuration (i.e., I only have 21' of vertical rise and I'm less than 80' in total length).
So, my questions are herewith:
1. Given the "Alternate Line Sizes" in Table 4, I'm assuming the usage of a short reach of 3/4" vapor line is OK and the idea of transitioning to 7/8" where possible is a good idea to improve efficiency (i.e., reduce losses in the line). Does this sound reasonable?
2. If Table 3 says 1-1/8" is the "Rated Size" and Table 4 says 3/4" and 7/8" are "Alternate Sizes", then are we dealing with just the degradation of efficiency in the system in terms of reductions in line size? In other words, would it be proper to interpret these tables to say, "... 1-1/8" is preferred, but 7/8" and 3/4" are acceptable"? And the difference would be the slight loss of efficiency which probably wouldn't be noticeable?
Any answers and insight would be appreciated. Regards, jft
As a civil engineer who knows enough mechanical engineering to get myself into trouble, this makes sense (i.e., bigger line less friction loss albeit with less velocity). Looking at the Trane installation manual seems to verify this is OK, but it also adds confusion. See below insert picture from the Trane installation manual. Table 3 calls for the vapor line size to be 1-1/8" and as footnoted, a max. length of 80' and a max. length of vertical rise of 25'. Yet, in Table 4, "Alternate Line Sizes" are provided whereby for the 4TTV8060A it is stated that the vapor line can be 3/4" or 7/8" and as footnoted, a max. length of 150' and a max. length of vertical rise of 50'. The footnoting as stated above seems counterintuitive given the line sizes provided; however, regardless, I am OK in my application no matter what the line size configuration (i.e., I only have 21' of vertical rise and I'm less than 80' in total length).
So, my questions are herewith:
1. Given the "Alternate Line Sizes" in Table 4, I'm assuming the usage of a short reach of 3/4" vapor line is OK and the idea of transitioning to 7/8" where possible is a good idea to improve efficiency (i.e., reduce losses in the line). Does this sound reasonable?
2. If Table 3 says 1-1/8" is the "Rated Size" and Table 4 says 3/4" and 7/8" are "Alternate Sizes", then are we dealing with just the degradation of efficiency in the system in terms of reductions in line size? In other words, would it be proper to interpret these tables to say, "... 1-1/8" is preferred, but 7/8" and 3/4" are acceptable"? And the difference would be the slight loss of efficiency which probably wouldn't be noticeable?
Any answers and insight would be appreciated. Regards, jft
I had cut out those expensive fittings, take piece of tubing, bend it using my knee and fit to unit (Engineers) Unit I took out had more fittings plus what was in attic. Oh well he was customer.