Air flow

Supply air plenum should be 7x length of barrel fan diameter before first spigot to avoid turbulence
Return air plenum should be 2x length of fan barrel diameter before first spigot to avoid turbulence
Large duct = high volume, low velocity, low static pressure, short throw, low noise
Small duct = low volume, high velocity, high static pressure, long throw, high noise
Surface area of return air filter should be no less than the surface area of the indoor coil ideally filter should be
no less than 1.8x indoor coil surface area
Return air flex duct cross sectional area should be the same size as the indoor coil surface area or larger
Air speed across indoor coil should be no lower than 1.3m/s and no higher than 2.8m/s
The colder the air the higher the relative humidity (supply air can be close to 100% RH)
For maximum throw on side blow diffusers angle all blades horizontally except for the bottom blade. Turn the front edge of bottom blade up on a 45° angle
To overcome stratification on heating increase air velocity
Decrease noise by changing duct direction 3 times (this can be flex or hard duct)
Toilet exhausts require 10L/s of exhaust per stall

Electrical

Running amps of a motor are generally 7x less than locked rotor amps
Star connection = low speed, high torque
Delta connection = high speed low torque
Capacitors connected in series decrease capacitance (C1 x C2 / (C1 + C2))
Capacitors connected in parallel increase capacitance (C1 + C2)
Fan amp draw decreases due to a resistance in air flow (e.g., blocked filter) on centrifugal fans (unless speed controlled on air flow)
Fan amp draw increases due to a resistance in air flow (e.g., blocked condenser coil) on propeller fans.

Five changes in direction before between fixing points reduces vibration without the need for vibration eliminators
Suction lines should tilt downhill towards the compressor 10mm for every horizontal meter of suction pipe
The longer the suction line and the more bends the bigger the reduction in unit capacity
Suction line must be trapped at the very first vertical rise after indoor unit regardless of total vertical height.
Traps should be as short as possible horizontally as to only hold the minimum amount of oil before flushed out (prevention of oil logging)

Drain trap exit should be half the height of entry.
Use a deeper drain trap to overcome large negative static on the return air chamber
Drain lines should slope down a minimum of 10mm per 1m
Water pressure increases 10pa with every 1m of vertical rise
Pumps at ground level are larger and consume more power than pumps on roof level due to water level (gravity) not increasing the head required to create flow
Ideal condensing water temperature supplied from cooling towers is 28-32 degrees
Ideal condensing temperature on water cooled equipment is 32-34 degrees
Swapping inlet and outlet hoses on water cooled equipment can clear condenser blockages, just remember to swap them back after its cleared!
Wind thread tape in the opposite direction to thread

General home sizing is approximately 130 W/m
1 computer is approximately 100W
Heat load of a passive person is 150 -200W
Sensible load performs the change of air temperature
Latent load removes humidity and does not change air temperature
High humidity can make rooms ‘feel’ excessively hot. This is common is oversized air-conditioned spaces during low load
Glass is an architect’s best friend and the HVAC designer’s enemy. Reduce impacts of sun on glass wherever possible

Economic lifespan of packages and split ducted units is 10 years full use (10 hrs day 5 days a week)

Keywords: Air Flow, Electrical, Piping, Water, Heat Load estimation,