Fire Protection

Pre-action dry pipe sprinkler systems are sloped in order to allow drainage in the event of discharge:

2"ø and larger: 1/2" per 10'-0"
Less than 2"ø: 1/4" per 10'-0"

Formulas & Calculations

• Cooling coil GPM = Total capacity (Btu/hr) / 500 / Delta T

• Electric Heat (kW) = ((CFM x 1.085 x Detla T) / 3.413) / 1000

• Mixed Air Temperature = ((RA cfm/SA cfm) x RA Temp) + ((OA cfm/SA cfm) x OA Temp)

• Room air changes (per hour) = (Room volume x Number of required changes) / 60

• Btuh = cfm x 1.085 x Delta T

• Watts = btuh/3.413

• kW = watts/1000

• 2.31 psi per 1ft. head

Plumbing Design

• Place shut-off valves in locations to avoid shutting down entire systems if one branch goes down.

• Avoid locating equipment and valves above gyp ceilings if possible.

• No piping over electrical rooms or data rooms/closets.

• Indicate routing and slope of condensate lines.

• When you are showing floor drains under ice makers or any other equipment, verify clearance underneath equipment. Verify that there is at least 3” clearance.

• Minimum 2”ø waste or vent under slab.

Mechanical Design Considerations

• First thing: Check architectural plans for walls that go to structure.

• Loads: Call architect to verify that glass shop drawings match that of installed.

• Loads: Verify lighting watts/ft2

• Verify fan terminal unit placement and type for noise consideration. Think about heating contactors. Magnetic contactors are louder than mercury type. Verify boxes are not over return air grilles or offices.

• Verify fan terminal unit placement and type for accessibility. Even if walls are indicated as not going to deck, the studs may go do deck and gyp may stop at 6” above ceiling. Fan terminal units typically require bottom access as well as side electrical service clearance.

• If possible, put balancing damper for gyp mounted diffusers in adjacent lay-in or other accessible areas. Neck mounted blade volume dampers can be noisy. Consider cable operated dampers if necessary.

• On multi-floor buildings, tag equipment by floor (i.e. VAV 7-1, VAV, 8-1)

• Locate return air transfer openings towards RA source.

• Space O/A intakes and exhaust/vents 15 feet apart. 10 feet is required, but use 15 feet to be safe.

Design Checks & Guidelines

• 400 CFM/Ton (Typical)

• Sensible capacity is typically 80% of Total capacity.

• For local projects (Kansas City), design outdoor equipment at 105°F.

Fuel Gas

• Low pressure fuel gas systems are less than 1.5 psi.

• High pressure fuel gas systems are more than 1.5 psi

• Natural gas heating value: 1,000-1,100 Btu/ft3

• Liquid petroleum heating value: 2,500 Btu/ft3

Gas Heat

• (For an outdoor air unit) specify catalogued MBH capacity instead of actual design capacity. If you specify 252 MBH and the units are only available in 250 or 300, the equipment rep will go with the larger size to cover his ass. The larger unit will be over sized and hard to control to design conditions.