Free Shipping on orders over $99 | FREE 365-DAY RETURNS
Filters Fast Logo Header
Free Shipping Item Banner

AprilAire 4851 Humidifier Blower Activation Relay


Retail: $49.99 /ea
You Save: 30%
Buy 1 - 2 for $34.99 ea.
Buy 3+ for $31.99 ea.
As low as
Retail: $49.99
You Save: 30%
Special Order. Ships in 5 to 6 business days.
Home Filter Club

Sign up for the Home Filter Club in checkout. You choose how often you want your filter, and we take care of the rest. Home Filter Club
Purchasing for a Business?

Contact [email protected] to gain access to case quantity discounts, account management and terms! Home Business Services

The AprilAire 4851 Blower Activation Relay is the correct replacement for the following humidifiers:

  • AprilAire 500 Series Humidifiers
  • AprilAire 600 Series Humidifiers
  • AprilAire 700 Series Humidifiers

The AprilAire 4851 Humidifier Blower Activation Relay allows the humidifier to energize the HVAC blower on a call for humidity where the humidifier is no longer dependent on a call for heat. Also known as part number 4851, the AprilAire Blower Activation Relay will deliver the comfort and protection needed for controlled humidification. It is highly recommended to use this AprilAire 4851 Relay if your humidifier is installed on a heat pump or during certain times of the year where there is a need for humidity, but not heat.

AprilAire Blower Activation Relay Specifications:

  • Part 4851
  • Initiates HVAC fan operation
  • Used on humidifiers installed on a heat pump
  • For humidifiers using automatic digital controls
  • Fits AprilAire 500, 600 and 700 series humidifiers

AprilAire advises that you make sure your humidifier is plumbed to hot water when using this blower activation relay. This replacement is recommended for humidifiers that run in conjunction with the heating system in your home, particularly during the winter months. This AprilAire 4851 humidifier relay fits all 500, 600 and 700 series humidifiers that use the automatic digital humidifier controls (#56 and #58). Please note that the AprilAire brand is also known by the following spelling variations: April Aire, April Air and Aprilair.

Product Availability

Please provide your e-mail address below to receive a notification when this product becomes available:


Thanks! We'll send you a notification when this product is available!