Nortec HP Series - Manual (Page 13)

HP Series Installation Manual | 10
Construction of a Wet Duct Section
General
The section of ductwork that the HP HVAC manifolds are installed to be in needs to be capable
of handling excess water that is not absorbed by the air. Nortec requires that a wet section be
installed in the duct. The wet section should be as long as expected wetting distance. In most
cases Nortec recommends the wet section extend 1.5 feet upstream and 6 feet downstream of
the HP manifolds.
A wet duct section consists of; a double walled plenum, drain pan, and drains. All material used
in the wet section should be made of stainless steel. All seams should be sealed properly with
caulking to prevent leaks.
Double Walled Plenum
A stainless steel liner should be secured to the existing wall. The objective of this is to cover any
exposed insulation, seams, and any existing ducting materials that may not be corrosion
resistant or suited for constant exposure to water. The liner should cover both sides and ceiling
of the plenum. All seams should be caulked and sealed to prevent leakage.
Drain Pan
A stainless steel drain pan should be installed on the floor of the duct. This pan should slope
downwards in the direction of airflow from the HP manifolds to end of the wet section. The
drain pan should terminate with a drain connected to a “P” trap. The “P” trap should be at least
2 inches taller (center to center) that the duct static pressure, and should drain to an open
funnel drain.
For systems up to 750 lb/s per hour a 1” diameter drain should be used. For larger systems a
2” diameter drain, or multiple 1” diameter drains should be used.
HP HVAC systems must NOT drain onto a roof. Building damage could result. Any drain lines
routed outdoors must be insulated and heat traced to protect from freezing.
Ensure that all traps are primed by filling them with water.
Mist Elimination
In some cases, the HP HVAC system will need to be installed in tight spaces or where water
sensitive equipment is present a short distance downstream. In these cases a mist eliminator
is required. The mist eliminator will be located immediately after the drain in the wet section. A
second drain will be then installed immediately after the mist eliminator.
Air Handler Installations
In many cases the HP HVAC system is installed in an air handler upstream of the cooling coil.
Many air handlers include a wet section around the cooling cool as a standard offering. These
cooling coils also function as natural mist eliminators and thus an additional mist eliminator
may not be required. Consult the air handler manufacturer for further information.