Aprilaire 600 ByPass Flow-Thru Humidifier

Aprilaire 600A ByPass Flow-Thru Humidifier

Aprilaire RP-600A

ByPass Flow Thru Humidifer
17 Gallons Per Day

Price: $168.00

Replaced by Model 600

Manufacturer: Aprilaire

Please Order the NEW Model 600.
In 2009 Aprilaire replaced the Model 600A and Model 600M with the Model 600. We have sold out of the 600A and Aprilaire is now shipping us the Model 600. More Info ...

Aprilaire 600A flow-thru bypass whole-house humidifier. The Model 600A humidifier is designed for use in large to mid-size homes. If room permits we recommend using a larger humidifier, the 600A and 500A have the same water flow rate. The 600 would be more effiecent with its larger water panel.

The Model 600A is a complete system and includes the humidifier with a built-in bypass damper, two water panels (#35), digital automatic humidistat (Model 58) with outdoor temperature sensor, self-piercing saddle valve, and 24vac transformer (#4010). Our photos (click View More Images above) for a view of all the items included. Items not included is 6" bypass duct, copper tubing, drain tubing, and thermostat wire.

Evaporative Capacity 0.7 gph. Unit Size 15-3/8"W x 15¾"H x 10¼"D Plenum Opening 9-7/8"W x 12-5/8"H Electrical data 24 Vac, 60 Hz, 1/2A. When operating the water feed rate is 3 gph.

In 2009 Aprilaire consolidated the Models 600M and 600A to the Model 600. The new Model 600 is identical to the earlier 600A, except the new 600 does not include a 2nd (#35) Water Panel and a DVD Video.

The difference between the 600A (automatic) and 600M (manual) was the 600M included a low cost manual humidistat (#4655) instead of the Automatic Digital humidistat (#58) that was included with the 600A.

The new 600 also includes the humidistat (#58) that can be operated as a Manual or Automatic humidistat.

Previous to the 600A & 600M was the Model 600 Series One. This early Model 600 was Cream in color whereas since the 600A & 600M (2008) the color has been a light Slate.

Our Aprilaire 600A includes a warranty registration card where you mail the card to Aprilaire and they will ship you a free weather station.

Displays fahrenheit or celcius and can be wall mounted or placed on the desktop.


	The Aprilaire 600A can be mounted on the return or supply duct. The air flow can run in either direction, in to the 6" bypass opening or out of the bypass opening. The 600 can be configured with the 6" bypass duct connection on the right or left side.

The Aprilaire 600A operates best when the furnace is producing hot air.

The new Aprilaire 58 humidistat connects to the furnace thermostat terminals. This allows the Model 58 to sense when the furnace is providing hot air. Or the humidistat can be wired to sense when the blower is running with or without hot air. See the Model 58 Installation.

The Model 50 current sensing relay is no longer necessary.

The term Flow-Thru refers to water trickling through the water panel and out a drain. The advantages of a flow-thru design is reduced maintenance and no standing water. Scale from calcium and lime gets flushed out of the water panel and down the drain. The water panel is an aluminum mesh with a porous pumice-like coating that inhibits growth of slime and is easy to change (once a year).

The disadvantage of the Flow-Thru is water usage. When in operation water flows in to the 600 water panel 3 gph. We are in the northeast where this is not an issue. We get a flat rate water bill unless there is excessive usage then the rate goes up. The Flow-Thru humidifier does not cause excessive usage.

The Flow-Thru is an evaporative humidifier and requires hot air. If not using hot air then hot water should be used. We see little humidity gain if our Flow-Thru humidifier is operating with cold air (and cold water). We run our blower on constant to best utilize our electronic air cleaner, but our humidifier is wired to only operate only when there is hot air and works very well.

The term By-Pass or Power refers to the driving force behind the air flow. The Power humidifier (aka Fan Power) uses a fan to draw the air thru the humidifier. The ByPass humidifier uses a 6" diameter duct that connects the supply to the return duct.

In the ByPass configuration the air leaving the furnace is routed back to the supply. The warm air leaving the furnace takes this short-cut of least resistance and bypasses the long trip down the duct work, in to the house, and back through the return. The ByPass is the 6" round duct work shown below. During the the hot humid A/C season the ByPass duct should be closed with the butterfly valve since the air flow through the humidifier would not be needed.

The Power humidifier uses a fan to draw air in from the duct and through the humidifier and exhausts back out in to the duct. The air is drawn in through duct at the center of the humidifier and back out in to the duct at the sides. The power humidifier should be mounted in vertical warm air flow.

The Model 400A, 500A, and 600A are ByPass humidifiers. The 700A is fan powered.

The indoor humidity level needs to be set based on the outside temperature. This is to prevent water from running down the windows. The cool air near the windows can not hold the humidity and water will condense on the glass. To prevent this condensation, the indoor humidity level is sacrificed by lowering the humidistat.

A manual humidistat needs to be set back as the season gets colder. An automatic humidistat (such as the Aprilaire 58) adjusts the humidity by using an outside temperature sensor.

The Honeywell automatic humidistat (H1008A) determines the outside temperature based on the furnace duty cycle or with an optional outdoor sensor. Below the Honeywell owners manual discusses this feature they call HumidiCalc.

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