Aprilaire 700 Application Manual page 9

HeAT PuMP – AIR HAndlInG unIT
WITH ACCeSSIBle SuPPly And ReTuRn PlenuMS
Recommended Series: 400, 500, 600, 700, 800
Plenum Temperature
Heat pumps typically have plenum temperatures between 90 and 100°F which require HOT water to aid in the evaporation process. Using
Blower Activation will help maintain humidity levels in the home. Series 400 Humidifiers will perform at reduced capacity due to lower plenum
temperatures.
Inlet Water Temperature
To maximize evaporative performance plumb to HOT Water (140°F Max) and use Blower Activation.
The Model 700 series Fan Powered Humidifier must be plumbed to HOT water when installed on a return duct.
Model 400 Water Saving Humidifier can be plumbed to Hot water but the benefit is minimal.
Model 800 Steam humidifier MUST be plumbed to COLD water only.
Variable Speed Blowers
The more HOT air delivered to the humidifier, the more humidity is delivered 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 evaporative 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 evaporative 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 evaporative 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 evaporative 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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