Aprilaire 600 Installation Photos

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This following installation is on a Trane gas furnace using the Aprilaire 600 By Pass type Humidifier. If after reading this page you don't want to run the ductwork which is involved for the 600 Model then you should call us and ask about the Aprilaire 700 Series which does not use ductwork. It uses a small 3" fan to move air through the pad. It however, has to be supplied with a 120 Volt power source and has it's own power supply cord installed from the factory. We feel the 600 works better because it uses your own furnace blower to move air through a 6" duct rather than the small 3" fan on the 700 Series.

Aprilaire has recently changed their humidistat and the wiring is slightly different than what is shown below. We will discuss some important wiring information as well as the need for the A50 Relay further on.

Below are most of the tools needed to install this humidifier. The meter is helpful and should be used if you have one, but we have included a simple way to be sure the power is off further on. The 1/4" nut driver, a small pocket flat head screwdriver, adjustable wrench, pliers, 1/4" tubing cutters and sheet metal cutters are a MUST. A hammer will come in handy for starting a hole in the sheet metal with the edge of a screwdriver.

In the following photos we installed the A50 relay in this Trane furnace even though it wasn't needed on this particular furnace. We did it just to show how it should be done. You can't go wrong installing the A50 relay with ANY furnace, so if you are unsure about your skills or are just confused, just order the A50 relay and install it as in the photos. Many companies selling humidifiers on the Internet don't spell out the need for the A50 relay so we will try to clear it up here. The use of the relay insures your ductwork and bottom of your furnace isn't being saturated with moisture without the blower running.

1. Most of the newer furnaces have a Printed Circuit board in them at the blower compartment area. If you see terminals marked Humidifier you have to then find out if those terminals are 24 Volt or 120 Volt? The documentation that came with the furnace may spell this out but usually you need a Volt Meter to find out. This may be out of your realm of expertise so just install the A50 relay as in the photos. If you are sure those terminals are supplying 24 Volts then simply run a 2 conductor thermostat wire from them to the 24 Volt terminals (also marked R & C on the newest Aprilaire Humidistats.) If you are sure you have this arrangement, you won't need the transformer that comes with the Aprilaire 600 at all! You also won't need the A50 relay either because the furnace circuit board will be sending (24 volt) power only when the fan comes on. You must be certain of this however since sending 120 Volts to the Humidistat or Humidifier will ruin the unit and will void the warranty from the manufacturer!

2. Some furnaces, including the Trane in the photos, don't have terminals on the circuit board marked Humidifier. Instead, Trane and others use a third wire in the junction box where the main 120 volt wiring comes into the furnace. Trane marks this third wire Hum #3. ( See your furnace documentation ). It sends 120 volts of power only when the blower comes on. You then tie the black wire on the transformer that comes with the Aprilaire 600 to this Hum # 3 wire and the white wire to the white wires in the junction box. Then run the 2 conductor thermostat wires from the small terminals on the other side of the transformer directly to the Humidistat terminal marker 24 volts or R & C in the new Aprilaire Humidistat. This arrangement does not need the A50 relay either. Again, if this confuses you, just wire it as in the photos but use the A50 relay.

So let's continue with the installation using the A50 relay. We are including the A50 relay on our web ordering page but if you are sure you don't need it, please give us a call and we will deduct it's cost from the price.

Step # 1 is to shut the main power off to the furnace or air handler. We always use a test meter to be sure it is off. As you see our meter reads 125 volts. On an air handler for a heat pump, or an electric furnace, it would be reading about 220- 240 volts. This is where you can get hurt seriously or even killed! Since we don't know how much testing equipment you have or if you know how to use such equipment, we have an alternate plan to be reasonably sure you have the power off before beginning the installation.

Turn the thermostat up to 90 degrees and put the selector on heat if so equipped. All we are trying to do is to get the furnace or air handler to turn on. Now go to your main electrical panel and find the circuit breaker which controls the furnace or air handler and switch it to the off position. The furnace or air handler should now be shut off. In the case of our meter below, it would be reading zero volts.

Now that the main power has been shut off, we can safely mount the transformer within the furnace cabinet. Remember however that this is a 120/24 volt transformer. What this means is that 120 volts powers the transformer and it reduces that 120 volts down to 24 volts. The Aprilaire 600 Humidifier operates on 24 volts NOT 120 volts!

If you have an Air Handler it will be a 240 volt system. You will need to find another 120 volt source such as an electric duplex receptacle in your basement near the air handler. If you aren't comfortable about doing this you should talk to an electrician. This should only be a problem for a heat pump or electric furnace normally. If you have a normal gas furnace continue below.

Your gas furnace should have a junction box which is where the main power is brought into the furnace from the main electrical panel. In our case the power is brought in on the left side. Our junction box cover had a 1/2" knockout available to install the transformer on, your furnace could be different, but you will need to mount the transformer in some manner and route the black and white wires from the transformer safely into the junction box. Remove the junction box cover. Inside the box you will find a black and a white wire coming from the power source. The black wire is supplying 120 volts to the furnace and the white wire is the neutral wire. The 2 wires on the transformer are also black and white. Simply remove the wire nut (our wire nut is orange, yours may be a different color) from the black wires and join our transformer black wire to them and re install the wire nut. Do the same with the white wire to the white wires in the junction box. Pretty simple - black goes to black, white goes to white! Just be sure the wire nuts are tight and making good contact and that there are no copper strands from any wires hanging out of the wire nuts that can touch metal. Under no circumstances should the transformer be wired into the blower motor leads - you will ruin the motor! Wire the transformer only as shown! Re install the junction box cover.

Pictured below is our transformer which has been wired into the furnace junction box. We have re installed the junction box cover. The brown jacketed wire is a 2 conductor thermostat wire which can be purchased at Home Depot or other supply house. How much you will need will depend on your particular installation. Our installation took 3 pieces of (2) conductor thermostat wire each being 10 feet long, or in other words 30 total feet of wire. Plan your layout before you buy wire so you don't run short, remembering to take bends into the equation. The red and white wires in the picture are hooked to the 24 volt terminals which are then run to the humidistat terminals marked as 24 vac or R & C on the newest Aprilaire Humidistat, which we will show you later.

Below is the A50 Relay installed on the white wire that goes to the blower motor. The white wire to the motor is the " Common " wire. Some motor manufacturers use purple for the " Common " wire but this is very rare. Simply remove the screw from the metal clip, remove the clip from the relay, insert the white motor wire in the metal clip, re install the clip and the screw. Now the humidifier will only run if the blower motor is running. This is to keep the humidifier from soaking the return duct and bottom of the furnace or air handler which will lead to rust on the equipment and damage to the motor from moisture! One of the yellow wires that come out of the relay will go to the humidistat and the other will go to the solenoid of the humidifier. The wiring details are spelled out in a simple diagram that comes with the humidifier and the A50 Relay. Just take your time and double check the wiring to the diagram. Relax - it's easy!

Next we have to mount the Humidifier to the cold air return duct. Pictured below is the Aprilaire 600 with it's evaporative pad removed. The sheet metal has been cut to allow the Humidifier to sit LEVEL. A template comes with the instructions to help you cut the hole to the exact size and level. Simply level the paper template and draw around the edge of it as shown below. Be sure to wear gloves and wear safety glasses! 6 sheet metal screws hold the humidifier to the duct. Note the adjustable damper on the left of the humidifier, it stays closed for summer operation and open in winter. The humidifier is marked winter and summer, most humidifiers make you fabricate a damper in the duct! Worth Noting: If you have Duct Board plenums we suggest you use sheet metal and reinforce the hole you cut out with about a 3" metal frame which you will have to build. If you build a "U" type of frame it will fit over the duct board giving support on the outside and inside of the duct board. It would also be a good idea to take the weight off of the duct board by supporting the Humidifier itself with metal straps such as plumbers strap or at least mechanics wire.

Once you have marked the return drop with the marker, hold a flat head screwdriver at about a 30 degree angle and strike with the hammer to start a hole for the sheet metal cutters. You'll need a slit about 2" long. See shot below.

Once you start cutting the sheet metal be sure to wear gloves. As you cut with one hand use the other hand to gently pull out on the metal - the cutting will go much easier! See below.

Below, we have mounted the shell of the humidifier with 1/4" x 3/4" sheet metal screws. A cordless drill with a 1/4" hex head bit will come in handy, but you can use a screwdriver instead.

The Humidistat mounted in the cold air return duct is pictured below. Note: The Humidistat shown is the older type, the newest Aprilaire Humidistat looks different but the principle is the same, just read the instructions that comes with it. Be sure to mount it at least a foot upstream from the humidifier so that the humidistat doesn't sense humidity from the running humidifier! Some people prefer having the humidistat mounted in their living area near the thermostat. To do this with a finished basement ceiling may be impossible however. If you mount it upstairs you will need much more thermostat wire! There will be 3 thermostat wires hooked to the humidistat, running down into the bottom of the furnace which in our case have been taped to the duct out of harms way.
If you have mounted the transformer in another place than in the furnace of course your thermostat wire will be a different distance than ours. The hole that has to be cut in the duct for the humidistat to sit in is " about " 3"x4". Wear gloves and safety glasses.

Next start running 6" sheet metal elbows and duct to the SUPPLY trunk. Remember this humidifier is a by pass type which by passes return air to the supply air.

A 6" hole will need to be cut in the SUPPLY duct. A 6" elbow is then connected to complete the duct installation ( SEE BELOW ). Our installer has already run the humidifier duct and taped any air leaks which is pictured to his right in the picture. We are only showing him cutting another 6" hole that he is running some extra supply ducts to a room in the basement that our customer also wanted installed.

Below is the Saddle Valve that comes with the humidifier which we have installed to the cold water line. The saddle valve is self piercing once the line is connected, simply screw it all the way in and then back it out all the way. Check for leaks around the small nuts. It humidifies better if installed on the hot water line but will plug with minerals quicker. Be sure the black seal is installed correctly and sandpaper the copper or there will be a water leak! These saddle valves will not work on any tubing except copper! Now connect the 1/4" copper water line and ferrule fittings and run the line to the humidifier solenoid on the side of the humidifier. Cut the copper line square with a tube cutter which can be purchased at Home Depot.

Below we are tightening up the other end of the water line to the humidifier and leak checking for water leaks.

Below we are running a 3/4" P.V.C. drain line which goes to the black fitting at the bottom of the humidifier. This drain then runs to a floor drain or a condensate pump if you don't have a floor drain. Alternately, you can run a 1/2" inside diameter clear plastic tube available at a hardware store or Home Depot.

Below we have finished the secondary wiring and have installed the manual jumper. ( There will be a total of (3) thermostat wires coming out of the humidistat and going to the furnace bottom, and back to the humidifier itself. This humidifier can be installed in either computer controlled automatic mode or manual.

We prefer the manual mode since it puts the control of the humidifier in the customers hands rather than the computer. There is a small black jumper pin in the humidistat which you must be sure to set for the model humidifier you have purchased. Read the instructions as the newest Aprilaire Humidistat has a switch rather than a jumper pin! There is also a way to set the newest Humidistat for un usually cold or mild climates, again read the instructions that comes with the humidifier. Usually it is already set for use with the 600 series but double check it! The manual mode resistor that you see in the photo is only used for the manual mode, all this is spelled out VERY clearly in the instructions.

Re install the pad, black water feed tube and install the front cover. Turn the water on and open the damper (winter). Turn the circuit breaker back on, start the furnace and turn the humidistat to test to be sure it is working. Recheck for water leaks. Set the humidifier to 35% as a starting point. Read the operating instructions.

Our furnace and humidifier are running! Annual maintenance should include being sure the pad has been changed and that water flows through the solenoid and out the drain line. Usually 35% should humidify quite well, but follow the instructions in the owners manual that comes with your unit and you will have a trouble free system for years to come!

The pictures below will show another Humidifier installation on another 90% furnace which we want to show other ways of sealing air leaks you may encounter. In the shot below we are sealing small air leaks with Duct Mastic which is available at Home Depot if you choose to use it. Aluminum duct tape works but doesn't have the long lasting quality of the mastic.

Below is the completed installation on this on the installation job.
NOTE: Notice the purple material on the pipes. This is a primer which is applied to the pipe and fittings first, then P.V.C. glue is applied. A twisting motion is used to seat them together. They are then held tightly together for about 30 seconds, as a hydraulic action will try to push them apart otherwise.

Here are some comments from a client who bought an Aprilaire 600 from us and installed it himself.

Early this winter I purchased an Aprilaire Humidifier from Sheridan HVAC after checking many types of humidifiers and vendors on the Web. The price was excellent and the installation information was very complete on their web site and I felt comfortable with the purchase.

I am 69 years old and my wife and I bought an 1800 sq ft condominium two years ago. For the first year we used a floor model humidifier but the daily process of filling with water, poor performance and general inconvenience prompted me to search for a more automatic process. I am quite handy with tools and have more than an adequate tool compliment.

The unit arrived within several days of ordering. Everything was in order so I immediately laid out the opening cuts. Within a day I was prepared to install the outside sensor, the humidifier body and return and the water supply. Because of the spacing between supply and return vents, I purchased an adjustable 6" elbow which, with just a bit of trimming, fit the job perfectly. When the humidistat was installed and the fan relay installed the unit was fired up .... and worked perfectly.

Within a day the household humidity had jumped nearly 20%. It has held between 32% and 40% all through a particularly cold winter here in the Northeast.

I am very pleased with the product and although I did not need any support from Sheridan, I am sure it would be available if needed. I now understand why you say that this model is your most popular seller.