Multi F Outdoor Unit Engineering Manual

Common Indoor Unit Drainage System
It is usual work practice to connect individual indoor unit drain pipes to one common indoor unit drainage system. The diameter of the com-
mon vertical drain pipe should be as large as necessary. (For systems with <80,000 Btu/h total capacity of all connected indoor units, the
standard size for the common vertical drain pipe is 0.98 ID, in. and 1.26 OD, in.) The diameter of the horizontal pipe should be the same
or larger than the vertical drain pipe. To avoid property damage in the event of the primary drain becoming clogged, and to optimize drain
system performance, it may be prudent to install a secondary drain line. Design the drain system to plan for winter operation (condensate line
may freeze up if condensate does not properly drain away). Drain all generated condensate from the external condensate pan to an appropri-
ate area. Install a trap in the condensate lines as near to the indoor unit coil as possible; to prevent overflow the outlet of each trap should be
positioned below its connection to the condensate pan. All traps should be primed, insulated, and leak tested if located above an inhabited
space.
Common horizontal drain pipe
1/50 to 1/100 Slope
≤27-1/2 in.
Include trap
at the end.
45° to 60° Angle
Position the vent
down to prevent
debris from entering
the system
45° to 60° Angle
45° to 60° Angle
45° to 60° angle for protection against overflow
Common
vertical
drain pipe
• It is recommended that a dedicated drain pipe be installed for the air conditioning sys-
tem. If the indoor unit drainage system is shared with a rainwater drain, waste water,
or any other type of building drain system, back flow, leaks, ice may form, or noxious
odors may be present.
• Install a trap if the drain access to the outside faces an undesirable location (i.e., sew-
er), otherwise, noxious odors may infiltrate the air conditioning system.
Figure 86: Example of a Common Indoor Unit Drainage System.
Drain Leak Test
A leak test should be performed 24 hours after the drainage system
has been installed. Only use water for the test; other liquids are
unacceptable.
Drain Pipe Insulation
To prevent condensate from forming on the drain piping, install field-
supplied 0.4 inch thick polyethylene. The insulation should be securely
fastened with all connected joints and ends properly covered.
Condensate Drain Piping
INSTALLATION & LAYOUT BEST PRACTICES
Insulation
Requir ed
Insulation
Not Required
Properly Fitting Insulation
Figure 87: Properly Insulating the Drainage Piping.
Due to our policy of continuous product innovation, some specications may change without notication.
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216 | DESIGN & PRACTICES
Multi F and Multi F MAX Heat Pump System Engineering Manual
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