APRILAIRE
Frequently asked questions
Common questions about APRILAIRE from 3G Electric.
Which Aprilaire humidifier models use the 45 replacement pad?
The Aprilaire 45 pad, supplied under SKU 31TP37, is a Kraft paper replacement pad for duct-mount humidifiers. It is compatible with Aprilaire models 400, 400A, and 400M, and cross-references part numbers 31TP24 and 31TP25. The pad is installed in the humidifier water tray, where it provides a wetted surface for moisture transfer into the supply air of a forced-air HVAC system. Because pad fit is model-specific, confirm the humidifier model number on the unit nameplate before ordering. Pads should be replaced when mineral scale becomes visible or when the pad no longer wets evenly across its surface.
What is the daily humidification output of the Aprilaire 500M bypass humidifier?
The Aprilaire 500M bypass in-duct humidifier is rated for up to 12 gallons of humidification output per day. It mounts on the supply duct of a forced-air heating system and uses a bypass duct to route air through the evaporative pad. Control is via a knob humidistat with a minimum setting of approximately 30% relative humidity. The 500M is one of several models in the 500 series, which also includes the 500, 500A, 500K, 500MK, 500MZ, and 500Z. Replacement pads for this series are supplied under part numbers 4792 and 31TP26/31TP27. Output depends on plenum temperature, airflow, and water supply characteristics.
How do I identify the correct Aprilaire replacement pad for my humidifier?
Aprilaire replacement pads are matched to humidifier model families rather than being universal. The model number is typically printed on a label on the humidifier housing or on the existing pad frame. For example, the 4792 pad fits the 500 series, the 4750 pad fits the 700 and 760 series, and the 4839 pad fits the 600 series. Some pads also cross-reference alternate part numbers such as 31TP24 through 31TP31. If the model label is unreadable, measure the pad height and width and compare against catalog dimensions. 3G Electric lists compatible model numbers and alternate part numbers with each pad SKU to assist with identification.
What does the Aprilaire 4040 solenoid valve do in a humidifier system?
The Aprilaire 4040 solenoid valve controls water flow into the humidifier, opening to admit supply water during a call for humidity and closing to stop flow when the humidistat is satisfied. It is used in residential and light commercial humidification and air-treatment equipment requiring on/off fluid control. The valve is an electrical component, so replacement requires matching the coil voltage and connection type to the original. A failed valve can present as no water in the humidifier tray, continuous water flow, or water overflow. When replacing, isolate the water supply and confirm the valve body orientation matches the installation.
What is the Aprilaire 4231 metering component used for?
The Aprilaire 4231 is a precision metering component used in HVACR humidification systems to control water flow and regulate steam or moisture output. It is installed in the water circuit of humidifiers and supports consistent indoor humidity levels by limiting flow to the rate the humidifier can evaporate. It is suitable for commercial and residential humidification equipment where controlled water delivery is required. Because it is a metering device, the orifice or flow rating must match the humidifier model and water pressure. Replacement is typically indicated when water flow becomes erratic or when the humidifier cannot maintain setpoint despite a functioning valve and pad.
Which Aprilaire humidifier series are covered by the pads stocked at 3G Electric?
3G Electric stocks replacement pads covering several Aprilaire humidifier series, including the 400, 500, 600, 700, 760, and 768 model families. Specific SKUs include the 45 pad for the 400 series, the 4792 pad for the 500 series, the 4839 pad for the 600 series, and the 4750 pad for the 700 and 760 series. Pads are supplied individually. Compatibility is listed by model number and alternate part number on each product page. Because Aprilaire has produced multiple generations within each series, buyers should verify the exact model suffix, such as A, K, M, or Z, against the catalog compatibility list before ordering.
