Aprilaire 550 Humidifier

[barlowc]

I have an Aprilaire 550 flow-through humidifier connected to my furnace. I believe it's 20 years old and was installed when the furnace was.

Today I noticed how much water seems to be wasted. A LOT of water drains off the pad, out of the unit, and down the drain. I don't think it's doing anything different, but was just something that I happened to notice.

For those of you that know something about furnace humidifiers, is this normal? Or could the solenoid valve be letting way too much water through?

Other than replacing the pad annually, I haven't done anything to it. Poking around Aprilaire's website, I see a maintenance kit that includes a feed tube with a new oriface. It also includes an in-line strainer which mine doesn't have. I wonder if that just strains large particles out of the water or if it restricts the flow too.

 

[JimPghPA]

Usually the connection for the water is a tap-on set-up. Those have a T handle to turn to make the initial hole in the pipe it taps on to. If you have one of those you can adjust the water flow rate by turning that T while the furnace and humidifier are supplying heat, so you can watch the exit flow rate. There is about a 20 second delay to the exit flow when you change the input water flow. You do want some water to be flowing out. If you had it so almost no water was flowing out, the humidifier pad would clog up faster. The output flow carries with it some of the minerals that eventually clog the humidifier pad.

Also, If you have whole house AC, and you do have the tap-on set-up you should add a T handle inline valve for completely shutting off the water to the humidifier in the summer if you have whole house AC, because it is a big load on the AC to remove extra humidity.

 

[JimPghPA]

So even if you do not have the tap-on set-up, you could add a valve to the water line feeding the humidifier and use that to adjust the water flow rate.

 

[barlowc]

The water flow is controlled by a saddle valve. That valve is closed during seasons when the furnace is not in use. As for using the valve to regulate the flow of water, the manual says to NOT do that. Specifically, it says: "The correct water flow is determined by an orifice equipped with each drain type unit. When the unit is operating, there will be a small, steady stream of water to drain, which flushes away most of the trouble-causing minerals. Do not use the saddle valve to regulate the water flow. It is designed to be completely opened or closed."

 

[Pop_Rivit]

The orifice in the feed tube is missing or damaged. It should keep the amount of water flowing onto the pad just slightly more than a drip. If it's flowing it's time to replace it. They used to sell just the orifice (a packet of 10 or so for $5.99) but I don't think they sell the orifices any longer. At one time there were also different sized orifices, but I don't know if they still have multiple sizes.

Replace the pad and clean the unit annually.

 

[barlowc]

The orifice is still there, in the feed tube right where it connects to the solenoid valve. If it regulates the flow of water, what does the solenoid valve do? Does it just open and close as triggered by the humidistat?

Maybe I should get that maintenance kit that I linked to in my original post? Other than the case and solenoid, it essentially replaces everything else.

"This kit includes everything you need to make your Aprilaire Model 550 Series like new: #10 water panel, #4217 Scale Control Insert (black plastic frame), #4226 feed tube and compression sleeve, #4218 water distribution tray, #4231 orifice, to meter the water flow to the humidifier, 4223 drain spud, 4184 nozzle and #4004 inline strainer."

It appears that I can purchase it on eBay for about $50.

 

[JimPghPA]

Originally Posted By: barlowc
The water flow is controlled by a saddle valve. That valve is closed during seasons when the furnace is not in use. As for using the valve to regulate the flow of water, the manual says to NOT do that. Specifically, it says: "The correct water flow is determined by an orifice equipped with each drain type unit. When the unit is operating, there will be a small, steady stream of water to drain, which flushes away most of the trouble-causing minerals. Do not use the saddle valve to regulate the water flow. It is designed to be completely opened or closed."


Saddle valves are NOT a good way to shut off the water when running whole house AC in the summer. They often leak some water and that water adds significantly to the cooling load of the whole house AC system because it is humidity that the AC must condense. A second valve to completely shut off the flow of water in the summer if you have whole house AC is a very good idea.

As for using the saddle valve or the added shut off valve to regulate the water flow rate, it can be used that way, but if you have a large amount of minerals in your water then the valve doing the regulating can clog up.

Also water pressure varies from house to house. So the standard size orifice will have more or less water flow depending on the water pressure of the house in question. While it would be nice if the house had a good working water pressure regulator, some have them and some don't. And even if the house has a water pressure regulator it may not be working properly.

 

[Pop_Rivit]

Originally Posted By: barlowc
The orifice is still there, in the feed tube right where it connects to the solenoid valve. If it regulates the flow of water, what does the solenoid valve do? Does it just open and close as triggered by the humidistat?


Yes, the solenoid turns it on and off and is controlled by the humidistat. The orifice (a small piece of plastic with a tiny hole in it) controls the amount of water that flows onto the pad. Your problem is solved by the kit with the following sentence:

Quote:
#4231 orifice, to meter the water flow to the humidifier,

 

[Mr_Incredible]

I have a knob on mine that goes from low to high. I don't know whether it is time or flow controlling...never checked.

The flow didn't bother me. I see it as part of the design. Water flows, humidity is picked up. Seems legit to me.

 

[Pop_Rivit]

Originally Posted By: Mr_Incredible
I have a knob on mine that goes from low to high. I don't know whether it is time or flow controlling...never checked.

The flow didn't bother me. I see it as part of the design. Water flows, humidity is picked up. Seems legit to me.


The water in a humidifier should trickle or drip. It should be obvious that if it "flows" you have an issue and you're wasting water. All it needs to do is keep the pad moist, but it does not need to flow out the bottom of the pad.

Chances are the knob to which you refer is the humidistat, and it signals the solenoid when to turn the water on (when the humidity is low) and off when the humidity has reached the appropriate level. When you turn it to "high" it leaves the solenoid running longer to put more humidity in the air. When it's on low it turns the solenoid off sooner so the humidity level is lower. It's the orifice in the flow tube that restricts the amount of water down to a very slight trickle.

See that tiny little hole in the middle? It's what controls the amount of water passing from the flow tube onto the pad. The orifice seats in the end of the tube and it's what keeps you from wasting gallons of water and over saturating the humidifier pad.

It's not a complicated system-in fact it's extremely simple. If you have water trickling out, then you have too much going in. The pad need only be moist, never saturated. Anything more is a waste of water which can add up over the course of a heating season.

 

[barlowc]

Originally Posted By: Pop_Rivit
The water in a humidifier should trickle or drip. It should be obvious that if it "flows" you have an issue and you're wasting water.

Thanks Pop_Rivit! I have enough flowing out that the Furnace Condensate Pump runs nearly every time the furnance does. So it indeeds seems like I have too much going in. I can get a new orifice for $6.50 on eBay, so maybe I'll start with that. I'm just wondering if I should also get the inline strainer since mine is missing that.

 

[Vikas]

I am watching this topic in earnest. I have similar system (560). As far as I can figure out, the solenoid valve is either open or closed. It does have a flat head adjustment with lock nut on the outside. I wonder if that is supposed to control the flow rate.
The valve is turned on and off by the hygrostat which I presume is measuring the humidity in the airflow.

The drip tube is filthy dirty. What is the best way to clean it?

 

[Kestas]

What is it dirty with? Calcium deposits? I found the best way to clean calcium deposits is with muriatic acid. It melts it right off. Of course I do it at work under a fume hood. It's probably too nasty for most homeowners to do - even outside.

I believe the gentler method is to use vinegar or the commercially available CLR.

 

[Vikas]

I was thinking of dumping bleach or something in that tube but sanity prevailed. Would CLR be ok to run through pump?

On the second thought, I should measure the diameter of the vinyl tube and just buy a new one.

 

[Mr_Incredible]

Ahh-so. It appears I do not have the orifice insert for the nozzle. I don't remember ever having seen it. A $3 part, not including shipping and handling.

Thanks for the heads-up.