6. AHRI Data
• Region IV
• 80°F indoor cooling test temperature
• 67°F indoor wet bulb temperature
• 90°F outdoor test temperature
• 47°F outdoor heating test temperature
• 17°F outdoor heating test temperature
7. System Concept Manual RS
Load Calculation Manual J
Air Distribution Manual T
Equipment Manual S
Selection
Duct Size Calculation Manual D
Adjust, Test & Balance
8. Heating Cooling
T-stat setpoint 70°F 75°F
RH 25% 40%
Temp @ T-stat 68°F - 72°F 72°F - 78°F
Room-Room or Level-
+ 4°F + 6°F
Level ∆ T
Temp in any room + 2°F of set point + 3°F of set point
Floor temp over slab or
> 65°F, 4” above floor
unconditioned space
Filtration > MERV 8 > MERV 8
7.5 cfm/person + 1 cfm/ 7.5 cfm/person + 1
Ventilation
100 ft2 cfm/100 ft2
Duct Leakage < 6% < 6%
Sources: ACCA Manual RS, ENERGY STAR, ASHRAE Standard 62.2
9. ACCA Manual J
• Every home is required to have a Manual J, 8th
edition, load calculation
–Using the 99% winter design temperature
–Using the 1% summer design temperature
IRC Section M1401.3
10.
11. Oversized Furnaces
Furnaces that are sized > 40%
over the calculated load:
• furnace & vent can cool, causing
condensation and rust
• airflow across exchanger can be
too much, causing corrosion from
condensation
12. Oversized Air
Conditioners
Air conditioners that are sized >
15% over the calculated load:
• duct leakage increases
• latent cooling capacity decreases
•Blower motor uses more energy
• equipment life is shortened
13. Oversized Heat Pumps
Heat pumps that are sized > 15%
over the calculated load:
• duct leakage increases
• latent cooling capacity decreases
•blower motor uses more energy
• equipment life is shortened
• register temperatures are low
during heating season
14. Undersized Furnaces
Furnaces that are sized under the
calculated load:
• may not have enough airflow
across the heat exchanger,
leading to deformation or cracking
15. Undersized Air Conditioners & Heat
Pumps
Air conditioners & heat pumps that
are sized under the calculated load:
• may not have enough capacity
• latent cooling capacity increases,
decreasing the sensible capacity
21. Manual S
Sensible Supply Temperature
Room Air
Heat Ratio Air Difference
< 80% 54 75 21
80% to 85% 56 75 19
> 85% 58 75 17
22.
23. Manual D
• Required under IRC M1601.1
• Implies room-by-room load calculation must be
performed
• CFM
• SHR
• ΔT supply-return
• Sensible load
• Friction rate
• Pressure drop x 100 / total effective length
25. Cooling Size
• Friction Rate = Pressure drop x 100 / total
effective length
• Pressure drop = 0.10 i.w.c.
• TEL = straight flex duct + fittings
• 90° elbow = 30’
• 90° supply air boot fitting = 80’
• Straight duct = 20’
Friction Rate = (0.10 x 100) / (20’+30’+80”)
FR = 10 / 130
FR = 0.077
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36. ENERGY STAR
• All cooling equipment must be sized
according to latest editions of Manuals J &
S, ASHRAE Handbook of Fundamentals,
or equivalent procedure
• Maximum oversizing is 15%
• Outdoor design temps 99% & 1%
• Indoor cooling temp = 75°F
• Infiltration rate = Tight or equivalent
37.
38.
39. Responsibilities
• Verify matched coils
• Enter data into rating software tool
• Review (verify)
• Approved tool
• Design values
• Infiltration
• Selected to meet MJ & MS
40. Contact
Brett Dillon
bdillon@ibsadvisorsllc.com
www.ibsadvisorsllc.com
Design support by Backyard Studios
www.backyardstudios.net
