Hello everyone,
I've been tasked with helping a seniors complex (3 storey/wood frame/Calgary, Canada) swap out their old Nordyne G5RA060C-12 80% furnaces with new 96% furnaces.
I did a basic heat loss calculation by doing an R-value calculation of the exterior walls and ceiling as I performed this calculation for the largest (1367 ft2) top floor unit in the wing where the furnace replacements will take place. Currently, the furnace in this unit has an input/output of 54,000/43,200 respectively. Note that the smallest unit in this condo wing is only 603 ft2 and it had a input/out of 45,000/36,000 respectively. The average unit size in the wing is about 990 ft2.
The walls were found to have a u-value of 0.064 and the ceiling a u-value of 0.027.
I also took the smallest window in the unit to find the worst case scenario u-value and found the u-value using WINDOW7.7 from LBNL. These windows are fairly old so I only achieved a U-value of 0.456.
The exposed envelope area was found to be 529.86 ft2
The ceiling area was 1367 ft2
The window area area was found to be 219.34 ft2
The environmental conditions I used were based on the climatic data in my province's building code taken at a January design temperature at 2.5%. This was -30C or -22F.
Interior temperatures were estimated to be at 23C or 73.4F as this is a seniors condo.
Therefore,
Walls
0.064(529.86)[73.4-(-22)] = 3,235 btu/hr
Ceiling
0.027(1367)[73.4-(-22)] = 3,521 btu/r
Windows
0.456(219.34)[73.4-(-22)] = 9,541.82 btu/hr
Total = 16,298 btu/hr.
I added 10% for margin or error - 16,298x 1.10 = 17,927.60
Then I added 15% for infiltration as this building doesn't have the greatest construction.
17,927.60 x 1.15 = 20,616.73.
So I'm looking at about 20,616.73 btu/hr using some basic calculations.
Remember that the furnace in this unit has an input/output of 54,000/43,200 respectively.
For your reference, I have attached information regarding the unit floor plan with exposed walls highlighted pink. I have also included information regarding the furnace in the unit. Note that the furnace units are enclosed in a semi-conditioned room only accessed by the balcony and are separate from the unit.
Currently I have been offered estimates for:
Single Stage:
Goodman GMES96 40k (ECM Motor/DC?)
Lennox ML196E 44k (Constant Torque Motor/DC)
Lennox EL196E (As above)
Two Stage
Lennox ML296V 44k/29k (Variable)
Lennox EL296V 44k/29k (Variable)
Lennox EL296E 44k/29k (Multi-Speed DC?)
Daikin DM96VE 40k/28k (Multi-Speed)
Amana AMVC 40k/28k (Variable)
If you're still with me to this point, thank you.
Now this is a cash-strapped seniors condo that needs a furnace that works for them, is reliable (assuming the installation is proper), and isn't equipped with capabilities that they likely won't realize. Since the lowest BTU furnace with 40k at high fire and the low stage significantly below the 20,600 btu/hr I calculated, then how likely would it that if they installed a two stage furnace that they would regularly use the high fire mode. I don't want them paying for a two stage furnace when they will only use the low fire mode. I still have to confirm if the wiring in the units can accept a two stage thermostat.
Furthermore, from some research, single stages are less complex which should therefore mean cheaper to maintain and repair. I don't know if this is true or not, but if so, those potential long term savings would be another benefit to the condo.
Since this is a seniors condo, comfort and minor temperature swings are also important. I've been told that variable is good for this, but temperature swings could also be mitigated with a single stage by running the fan to circulate area, but this comes with a caveat that a Hoyme damper would be installed to block out the cold winter air from being taken up when the fan is running.
What do you all think given the conditions at the condo? Do you think they would be better served with a single stage for cost efficiencies and with modern DC ECM motors, that temperature swings won't be as significant as on a PSC motor, which I believe they have now?
I'm trying to set the Condo Board on the correct path as they will likely want to commit to a single type of furnace for the entire wing. They likely won't change the BTU's of the furnace either based on unit size as 40k seems to be the lowest unless we go for the Goodman GMEC96 two-stage multi-speed at 30k high fire and 21 low. Therefore, even the 603 ft2 unit would get a 40/44k btu furnace.
Thanks for sticking with me to this point everyone!
I've been tasked with helping a seniors complex (3 storey/wood frame/Calgary, Canada) swap out their old Nordyne G5RA060C-12 80% furnaces with new 96% furnaces.
I did a basic heat loss calculation by doing an R-value calculation of the exterior walls and ceiling as I performed this calculation for the largest (1367 ft2) top floor unit in the wing where the furnace replacements will take place. Currently, the furnace in this unit has an input/output of 54,000/43,200 respectively. Note that the smallest unit in this condo wing is only 603 ft2 and it had a input/out of 45,000/36,000 respectively. The average unit size in the wing is about 990 ft2.
The walls were found to have a u-value of 0.064 and the ceiling a u-value of 0.027.
I also took the smallest window in the unit to find the worst case scenario u-value and found the u-value using WINDOW7.7 from LBNL. These windows are fairly old so I only achieved a U-value of 0.456.
The exposed envelope area was found to be 529.86 ft2
The ceiling area was 1367 ft2
The window area area was found to be 219.34 ft2
The environmental conditions I used were based on the climatic data in my province's building code taken at a January design temperature at 2.5%. This was -30C or -22F.
Interior temperatures were estimated to be at 23C or 73.4F as this is a seniors condo.
Therefore,
Walls
0.064(529.86)[73.4-(-22)] = 3,235 btu/hr
Ceiling
0.027(1367)[73.4-(-22)] = 3,521 btu/r
Windows
0.456(219.34)[73.4-(-22)] = 9,541.82 btu/hr
Total = 16,298 btu/hr.
I added 10% for margin or error - 16,298x 1.10 = 17,927.60
Then I added 15% for infiltration as this building doesn't have the greatest construction.
17,927.60 x 1.15 = 20,616.73.
So I'm looking at about 20,616.73 btu/hr using some basic calculations.
Remember that the furnace in this unit has an input/output of 54,000/43,200 respectively.
For your reference, I have attached information regarding the unit floor plan with exposed walls highlighted pink. I have also included information regarding the furnace in the unit. Note that the furnace units are enclosed in a semi-conditioned room only accessed by the balcony and are separate from the unit.
Currently I have been offered estimates for:
Single Stage:
Goodman GMES96 40k (ECM Motor/DC?)
Lennox ML196E 44k (Constant Torque Motor/DC)
Lennox EL196E (As above)
Two Stage
Lennox ML296V 44k/29k (Variable)
Lennox EL296V 44k/29k (Variable)
Lennox EL296E 44k/29k (Multi-Speed DC?)
Daikin DM96VE 40k/28k (Multi-Speed)
Amana AMVC 40k/28k (Variable)
If you're still with me to this point, thank you.
Now this is a cash-strapped seniors condo that needs a furnace that works for them, is reliable (assuming the installation is proper), and isn't equipped with capabilities that they likely won't realize. Since the lowest BTU furnace with 40k at high fire and the low stage significantly below the 20,600 btu/hr I calculated, then how likely would it that if they installed a two stage furnace that they would regularly use the high fire mode. I don't want them paying for a two stage furnace when they will only use the low fire mode. I still have to confirm if the wiring in the units can accept a two stage thermostat.
Furthermore, from some research, single stages are less complex which should therefore mean cheaper to maintain and repair. I don't know if this is true or not, but if so, those potential long term savings would be another benefit to the condo.
Since this is a seniors condo, comfort and minor temperature swings are also important. I've been told that variable is good for this, but temperature swings could also be mitigated with a single stage by running the fan to circulate area, but this comes with a caveat that a Hoyme damper would be installed to block out the cold winter air from being taken up when the fan is running.
What do you all think given the conditions at the condo? Do you think they would be better served with a single stage for cost efficiencies and with modern DC ECM motors, that temperature swings won't be as significant as on a PSC motor, which I believe they have now?
I'm trying to set the Condo Board on the correct path as they will likely want to commit to a single type of furnace for the entire wing. They likely won't change the BTU's of the furnace either based on unit size as 40k seems to be the lowest unless we go for the Goodman GMEC96 two-stage multi-speed at 30k high fire and 21 low. Therefore, even the 603 ft2 unit would get a 40/44k btu furnace.
Thanks for sticking with me to this point everyone!
source https://hvac-talk.com/vbb/showthread.php?2226155-Seniors-Condo-Furnace-Selection-With-Basic-Heat-Loss-Calculations&goto=newpost
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