CARNES HBAH Manual Download Page 11

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Humidifiers

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G-11

Humidifiers | System Design Considerations



STEAM DISTRIBUTOR PIPE LOCATION

(Continued)

Steam distributor pipes must be located on a plumb
surface so condensate that forms will run back into the
return line. The pipe should be located in the center
of the duct to insure even distribution of steam into
the airstream. A minimum clearance of 4” must be
maintained between the top of the duct and the distrib-
utor pipe.
The steam distributor pipes are usually located in the
supply duct downstream of the fan. When installed in
packaged units the distributor should be mounted just
downstream of the fan discharge.
It is important to locate the distributor as far upstream as
possible from any obstructions in the ductwork so that
air can absorb moisture before it impinges on a surface
and accumulates. There must be a

minimum

of six (6)

feet between the distributor and any fans, coils, filters,
dampers, elbows or outlets downstream to reduce the
possibility of condensation.
It may be possible to minimize the absorption distance
by using multiple distributor pipes. Duct air temperatures
below 50-60°F may require a condensate drain pan
supplied by others below the steam distributor pipe.
The steam distributor pipe may be located below the
humidifier if the installation is made in accordance with

Figure F.

A trap may be necessary to prevent steam from

flowing back through the condensate return line when
hose goes directly to common drain.

Figure F

It is very important that both the steam hose and con-
densate return line be installed so that sags and dips are
prevented. The steam is at very low pressure and it
cannot overcome resistance caused by water standing in
the steam hose. Water accumulating in sags in the return
line will restrict the flow and may cause water to backup
and enter the duct from the distributor pipe.
If it is difficult to install the steam hose to prevent sags,
it is recommended that copper tube be used as a
substitute. If copper tube is used, a minimum of one
inch of insulation must be applied to prevent excessive
condensation. A short length of steam hose

must be used to connect the cylinder in the humidifier
to the copper tube and another short length to connect
the copper tube to the distributor pipe. Size 3/4” copper
tube can be used with steam cylinders having output
rates up to 30 pounds per hour. Size 1-1/2” copper tube
should be used with steam cylinders over 30 pounds per
hour. Length restrictions shown in Table 5 also apply to
installations where copper tube is used and any 90°
elbows add approximately three feet of equivalent length.
Proper inclines of hard tubing is necessary for good
performance and operation.



WATER SUPPLY REQUIREMENT

Carnes humidifiers will operate at water supply pressure
from 20 to 120 psi and maximum water temperatures of
140°F. Water piping must be sized to allow the minimum
flow rate shown in Table 6. This table does

NOT

indicate

water consumption, only minimum flow rates. Actual
consumption is determined by steam generated and
water drained during the automatic or manual drain cycle.

In certain areas with extreme water conditions it may
not be possible to operate the humidifier at all voltages.
Table 7 shows acceptable water conductivity, measured
in micromhos, in relation to the primary supply voltage.
Water conductivity may be determined by contacting
the local water utility or sending a six ounce sample to
Carnes for a free analysis. Deionized water or water
treated by a reverse osmosis process may have conduc-
tivity too low to operate. It may be possible to use a water
softener to treat the water but contact the factory before
installing the equipment.

ACCEPTABLE CONDUCTIVITY RANGES
(Micromhos)

Table 7

Table 6

Model Minimum

Flow

Rate GPM

H_AH

18 .3-.5

gpm

H_DH

18 .3-.5

gpm