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DISTRIBUTION TUBE AND CONTROL DEVICES LOCATION OPTIONS
CHOOSING A DISTRIBUTION TUBE LOCATION
When installing a steam humidifier on a split system, there are three locations that can be used to mount the steam
distribution tube: the supply plenum (Location A), the return duct (Location B), or a supply branch (Location C).
Note: Wherever distribution tube is installed, there must be a minimum of 4.5” between top of tube and the duct
ceiling. Refer to Figures 12 and 13 on page 17.
Location A is the best choice
because:
• The distribution tube is humidifying 100% of the air, and
• The supply air temperature is typically warmer than the return air temperature, allowing for better absorption.
Location B is the second choice because the distribution tube is humidifying 100% of the air, but the cooler
temperature of the return air requires more space for absorption.
Location C should be the last choice because, in most cases, there is more than one branch off the supply air
plenum, and less than 100% of the air would be humidified in such a multi-branch system. However, if there is only
one branch, the Location C would be considered equal to Location A because the same reasons listed under
Location A would apply.
Choosing control device locations
• Install the high humidity limit switch (a recommended optional device) a minimum of 5’ (1.5 m) downstream
of the distribution tube.
• Install the Automatic Steam Humidifier Control in the return air drop a minimum of 6” upstream of the distribution tube.
• Install the airflow proving switch in the supply air plenum.
OM-4016
FIGURE 10 – Recommended Installation Locations, Split System Application
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