All,

I live in the midwest and I am getting tired of feeling extra cold due to the lack of humidity plus the static electricity is terrible. To make a long story short, this Lennox furnace originally had a humidifier but it was removed when an air conditioner unit was installed a few years back. The furnace should probably be replaced but there are no funds in the budget at this time. Besides it has been given a clean bill of health from a recent inspection. My thoughts are to purchase a hunidifier now and reuse it when the furnace is replaced.

I am interested in either installing an Aprilaire 500A or 500M humidifier but have a few questions.

1) Can I install the bypass 6" duct opening on the supply which is located on the right side? My main concern is that the cooling coil is located right beneath the old 6" duct opening that was sealed up when the A/C was installed. If I do this the new 6" duct opening would just fit above the old hole under the vertical section of ducting but would be above the cooling coil. Should I be concerned with air flow to the bypass duct?

2) Assuming I am able to install either a 500A or 500M will I need a current sensing relay with either of the two units or just the 500M with my furnace?

3) Does anyone know if the 500A comes with the outside temperature sensor that is referenced or does it need to be purchased separatley? Also, is this ODT optional or required for the 500A to work?

Thanks all!

 

yes, you can put a humidifier back on the furnace.

Is there anything controls or transformer left from the old one? I see the humidistat is still there.

As for the bypass you could put it in the duct that is going towards the right, that way we don't have to worry about the A-Coil being in the way.

 

As far as old hardware is concerned I believe the only thing left is the humidistat. I took a look in the blower motor area and I did not see any type of current sensing relay unless I missed it. Not sure if it is only required for 500M model only.

The duct on the right only goes to one section of the house, wouldn't that be an issue?

 

You are going to need it on either unit. With that old of a furnace, it has nothing in it to wire up to. I would suggest mounting a transformer near by, and let the A50 do the work.

Nope, the air is coming out of that duct into the humidifier, and the moist air is mixed into the air in the return ductwork.

 

Thanks.

With the price difference aside, is there any reason why I would want to choose one unit or the other? That is the 500M vs the 500A?

Will I need to purchase an outside temperature sensor if going with the 500A?

 

I think I like the Automatic one over the manual dial for people in the northern states that has temps up and down pretty much everyday.

The 500A will come with an outdoor sensor and also a manual mode if you wish not to use the outdoor sensor.

I have the outdoor sensor on my Honeywell, and like it alot, I don't have to play with the dial when the temps drops down to -20˚ later this week.

 

Thanks. I think I am getting closer to pulling the trigger. Had a few other questions though?

You said the 500A comes with the outdoor temperature sensor. Will I need any additional wiring so I can connect it from the outside location to the humidifier? I'm also curious to what this thing looks like?

Also, the furnace is nearest to the West side of the house. Assuming I put the sensor on the brick surface outside it would be in my neighbor's gangway. I'm wondering how high I need to mount this thing to avoid the neighbor's kids from playing with it considering when it comes out from the basement wall since it will be well within reach of anyway outside the house. My guess is to mount it up a few feet higher on the wall so that it is out of general reach. Not sure how delicate this thing is.

Additionally, do you have any suggestions on how or what tool I would use to cut the 6" round hole for bypass?

Regarding, current sensing relay. Would I need the 24V (Aprilaire Model # 50) or 120V (Aprilaire Model # 51)? My guess is the 120V one.

thanks

 

Yes, you may need more wire, just need the 18/2 t-stat wire for it.



Do you have anything else on the side of the house? (Deck, meter... ect)

A new/sharp snips, and a... I am drawing a blank on what's called.. has sharp tip on one end, and a pencile on the other end.

You want the 24 volts.

 

No, the back of the house is the yard side which has the A/C unit, electric meter and a porch which is open underneath. The problem (if it is one) is that the back of the house faces south. The porch itself is covered so the deck surface and underneath is shielded from the majority of rain, snow and sun.

 

You can mount the sensor any where you want, just as long you don't get a false reading from the sun.

Rain/snow won't hurt it.

I have mine under my deck railing.

 

Thanks.

I will be draining the 500A into a Little Giant Condensate pump that is being used for the A/C unit. Is there a concern with using this pump with the humidifier?

Little Giant Pump Company - Model VCMA-15ULS

 

Yes, you can use that pump.

Is anything wired to the cut off switch?

 

No, there are two black wires just hanging from the pump.

The thick black cable (main power I believe) is running to a 120V power source I think.

 

The furnace is in the basement, right?

No floor drain near by?

 

No floor drain close by. There is one but not in a convenient location. It is in an area that has a lot of foot traffic.

 

I'll suggest to tie the pump to the humidifier, that way if the pump fails, the humidifier won't run.

We'll get that in our plan when you do get the humidifier.

 

Ok. Btw, I went and checked the 400A as an alternative. It is obviously more expensive but would eliminate the drain issue. The problem is it has a height 15-3/4" vs 13" of the 500A. I only have about 16" of vertical height so the 400A looks like it could fit but it would be real tight.

 

I haven't seen much results with the 400, I'd' stay with the flow though type units.

 

Ok, I placed the order for the 500A and 24V current sensor relay. Until then...

 

Well, I received the humidifier the other day and started installing it yesterday.

It took a lot longer than I expected but I took my time with mounting it and making cuts.

I am almost done with the expection of the following:
- Mounting the temperature sensor (currently running in manual mode)
- Clean up the wiriing with zip ties, etc.
- Position the drain line better with respect to the condensation pump.

I do have a few questions still...

1) I mounted the humidistat controller on the nearest return duct but it is the smallest of the two mains. This one only gets air from one bedroom. Any concerns with leaving it here?

2) I used Tstat wire to power the humidistat. I will also use the same wiring to connect the outside sensor. I did not use this type of wiriing to connect the circuit coming from the H terminals to the water valve, current sensing relay and condensation pump. I used some 16 guage stranded wire to do this instead. I figured I would be wasting a lot of Tstat wire only to be utilizing one wire inside the cable itself since this whole circuit is in serial.
Any concerns with doing this?

3) I am very pleased with the outcome of the installation of the unit itself and the bypass ducting however I am not to thrilled with the messe wiriing. I know I could tact wiriing along joists if necessary but in this case the wires are running up and over the unit so things are just hanging all over the place.
What are my options here? Do I just use zip ties where possible and duct tape where wires are hanging around the humidifier and humidistat?

4) For the drain going to the condensation pump, does this need to be tied into a fixed piece of pvc like that was done by the A/C guys or can I just leave it as is but zip tie it so the hose does not pop out?


Some other general observations...
- The humistat controller always says it is ON regardless of the furnace or fan actually being on. The only way it will go off is if I turn it off, lower the manual setting or the humidity has reached to appropraite level. I believe this is do the wiriing required to support the current sensing relay and the fact that I had to jumper the terminals W/G and Cf to R and C respectively. I believe the only thing the humidstat relies on to turn on and off is its relative humidity readings since the water is being controlled by the current sensing relay regardless. Is that correct?

- I also turned off the water panel indicator by adjusting the dial as suggested in the instructions. Not a big deal but I guess we can not rely on the idiot light for advice on when to do so.

Here are some pictures...

 

On that duct, you are going only get a reading from that room.. I would move it to the back side of the main return if you can, or above the humidifier itself.. (About 5" above the unit)

No not really... But would I do it? No. I'll draw out later on tonight of how I would of wired it..

I usely tuck the wire into the return duct itself.

Yes, you can leave it in place... as long you got a zip tie, it will be fine...

Do get it away from the hot flue pipe.


I would of wired the R and C to R and C on the furnace itself, then wire W/G and Cf to the transformer. use the A50 relay on W/G line.. But you can leave it as it is, and just ignore the light.

 

I am hesitant to move it to the main return (which is on the backside) only cause that will be a finished area of the basement in the future. I can put it above the humidifier near the top of the plenum. There is at least 6 inches above the unit. Since the instructions said to use return I wasn't sure if that was a big NO NO to put it on the plenum itself.

Yes, please do. I would like the wiring job to look as good as the install itself.

Would there be an advantage of going this route? Would the humidifier be off if wired this way when the fan / furnace is not running? I wired it exactly as the manual indicated but would like to do it a better way. I also wonder what the terminals R, C W/G and Cf imply or mean in the heating world.

 

That whole plenum is your return side of the system, so you are safe.

Here is how I'd do it.



Yes, the LED would be off when the equipement is not running, also will shut it off if the pump fails.

R= Hot
C= Common
This is for the display reading.


W/G= power for the water valve.
Cf= Common side of the valve.

H= is hook up for the humidifier.

 

Jay,

Sorry for the delayed post but I have been out of town for business for the past few weeks.

Well I rewired as you suggested and it is no longer working.

The furnace has terminals R, W, Y, G, and T so I wired R and C of humidistat to R and W of the furnace. There is no C on this furnace.

Now the humidifier goes on when the furnace is not running and the display completely turns off when the furnace turns on.

Please advise.

 

Undo the wire now before you burn something up! R and W are both hot!

Do you have A/C?

 

Ok, disconnected. I hope nothing got fried but my luck it probably did.

Yes, I have A/C. Humidistat was not lit up when I went down to disconnect it.

 

Ok, the the A/C wire that comes in from the unit outside, where are the attached to? One should be Y, and I am guessing the other one is on T?

This is an older furnace, and I am not able to pull anything up on it.

 

Yes, A/C is on Y and T terminals.

 

Ok, T is your common. Wire that up to your C from the humidistat.

 

Ok. I did that Jay. Now I have another problem. The humidifier wants to run all the time along with the water valve obviously. I checked the circuit coming from the current sensing relay and it is always hot. Did the current sensing relay get fried?

 

Does it stop when you undo the wire from the Relay, and what wire is the relay wrapped on?

 

Yes it does stop when I disconnect the relay.

It looks identical to your diagram except that the relay is swapped with the pump since it is closest to the transformer. So transformer, relay, pump then humidistat terminals W/G and Cf.

I did a simple test by connecting a A/C volt meter as follows and it is always reading ~30V.

 

30 volts? What's coming out of the transformer itself?

Does it stop when you remove the relay from the blower wire (low voltage still connected)

 

Out of the transformer is the same. About ~30.00 VAC. Btw, I have two transformers available to me. One that came with the unit and one that was already installed on the furnace but not used. Both read within 29.98 VAC to 30.05 VAC. I am using the one supplied with the unit.

No, when I disconnect it from the blower wire, that is leave it hanging on the side it does not stop. Voltage is still seen across terminals W/g and Cf.

 

I'd say the relay is bad if you take it off the blower wire.

 

That was my thought as well.

Am I stuck purchasing one of these online or can I get one locally?

Btw, I noticed that the control unit turns off completely when the lower door if the furnace is removed now. Is that normal?

Also, since the unit is still being controlled by the relay via the blower the idiot light will still be on regardless of whether the furnace is off or on.

 

If this is brand new, I'd go back to the dealer who you got this from. Otherwise, I've never seen them sold at retail stores.

Yes, the blower door switch is killing the power.

[/quote]Also, since the unit is still being controlled by the relay via the blower the idiot light will still be on regardless of whether the furnace is off or on.[/QUOTE]
The light? You mean the display light or call for humidity?

 

Light, meaning, the call for humidity or the "humidifier on" light which is why I believe we tried to re-wire it in the first place. Oh well, I can chalk this up to a learning experience.

When I get the new relay I will go back to the original wiring as suggested by Aprilaire so that the display doesn't go dead when removing the door or changing the filter.