Aprilaire 700 Application Manual page 16

AIR HAndlInG unIT
WITH An InACCeSSIBle SuPPly oR ReTuRn PlenuM
Recommended Series: 700, 800
Plenum Temperature
Plenum temperatures between 120 and 140°F will maximize evaporation or steam absorption, plenum temperatures less than 120°F require a
supply mounted Series 700 humidifier to be plumbed HOT water to aid in the evaporation process. Return duct mounted Series 700 must be
plumbed to HOT water.
Inlet Water Temperature
Hot or cold water can be used with Series 700 humidifiers. However to maximize evaporative performance plumb to HOT Water (140°F Max).
The Model 700 series Fan Powered Humidifier must be plumbed to HOT water when installed on a return duct.
Model 800 Steam Humidifier MUST be plumbed to COLD water only.
Variable Speed Blowers
The more HOT air delivered to the humidifier, the more water is absorbed into the air stream. Systems with low continuous fan speeds will
have reduced evaporation or absorption unless the fan speed setting is increased. Set the continuous fan speed to approximately the same
speed as a heat call setting.
Plumbing Series 700 humidifiers to HOT water can increase evaporation at low fan speeds.
Blower Activation
The Blower Activation feature on Model 60 and 62 humidifier controls will sample the household air if the HVAC system has been idle for
one hour and will energize the HVAC fan to allow the humidifier to run for two hours or until the desired humidity level is reached, whichever
comes first. If humidity levels are not reached during a normal heating call, the Blower Activation feature will extend the blower call for two
hours or until the humidity call is satisfied, whichever comes first.
When using Blower Activation plumb Series 700 humidifier to HOT water; the Model 800 Steam Humidifier must be plumbed to COLD water
only, in order to temper drain water.
The Blower Activation Relay (Model 4851) will activate the HVAC blower on a call for humidity when used in conjunction with a manual
humidistat; plumb Series 700 humidifiers to HOT water.
Third Party Controls
All current Aprilaire controls use a dry contact to switch 24VAC on and off. Ensure that third party controls are applied in the same manner. If a
third party control provides 24VAC (10VA minimum) do not use the included 10VA transformer when installing Series 700 humidifiers.
The Model 800 supplies 24VAC internally. If a third party control that supplies 24VAC is used with the Model 800, use an isolation relay to
switch power. DO NOT apply 24 VAC to the HUMIDISTAT terminals.
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