Wiring help: Aprilaire Model 700a to Lennox Elite 650UH

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Old 12-28-11, 11:32 AM
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Wiring help: Aprilaire Model 700a to Lennox Elite 650UH

Hi,

Great forum! Happy I found it. I am trying to wire an Aprilaire 700A to a Lennox Elite 650UH as follows:

* Humidifier works with heat call only
* No outdoor sensor

2 questions please:

(1) the furnace thermostat-control box R/C/W/G seems straightforward. I am not sure about the 24V though. The furnace has a single 24V Hum terminal, but I am not sure where to connect the other wire for 24V? Do I connect it to the 120V/Neutral (see attached diagram)?



(2) if I am not interested in the outdoor sensor do I just not connect anything?

Thanks!
 
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Old 12-28-11, 07:19 PM
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OK - it does not make sense to connect to the 120v Neutral. Would the following work?

Humidistat ------- Fur
R----------------------R
C---------------------C
W-----------------W
G - not needed ?????
H-------------HUM 24 V
H------------------ yellow wire to humidifier ---- other yellow wire to C on humidistat/fur

I am still not sure about the outdoor sensor. I plan not to connect it. I live in the Philly area and temperatures do not vary that much. I want to keep things simple. Thanks for your help!
 
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Old 12-28-11, 07:25 PM
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If you are not using an outdoor sensor then you must use the manual mode kit which is a sticker and a resistor.

The other wire goes to C on control board.
 
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Old 12-29-11, 09:43 PM
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The unit is working. MANY thanks to this forum.

It seems that in manual mode you do not need a resistor - I just switched the little switch on the control box to "manual" mode and everything seems to be working.

I might try changing the wiring to let the humidistat control the fan, but I am a little concerned about adding another potential failure point (humidifier control box failure = no furnace or AC). Any advice? Adding humidity even when the heat is off makes some sense to me.
 
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Old 12-30-11, 03:36 AM
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you have to be careful when doing that. The humidifier needs to have an off cycle so that the water panel will dry out. If it doesn't dry out from time to time it will slime up and start leaking. This is the reason why I like them to only run with a call for heat.
 
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Old 12-30-11, 08:54 AM
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I tried the "Run with forced fan" mode, on mine, and I saw no gain on it.. Matter of fact more run time since there is no heat to help evaporate water off the pad, so I switched it back to heat only run.
 
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Old 01-03-12, 12:46 PM
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The reason that I am thinking about it is that I get 33% humidity on 30F days, which is a little too low. The humidistat is set on Manual mode/dial setting 7.

Jay - are you connected to hot water?
 
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Old 01-03-12, 02:12 PM
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Yes, I am tied to hot water..

Also, if the furnace is oversized, or the t-stat isn't set up right, the short cycle don't help much. What is your avg run time on your furnace?
 
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Old 01-03-12, 02:56 PM
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I actually have 2 furnaces and I am trying to provide enough humidity to the house with 1 humidifier... If all things fail, I guess I can install another unit on the second furnace, but for now I would like to try the fan approach. What is the recommended wiring?
 
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Old 01-03-12, 09:14 PM
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What unit are you planning on putting this on? (What zone, main or upper floor?)

What runs more/longer?
 
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Old 01-04-12, 07:08 AM
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It is a strange config. I have a split-level house with a basement.

Unit 1 - bigger - has the humidifier installed. Serves basement, main level (kitchen and living room) and upper level (master bedroom).
Unit 2 - smaller - lower level (family room) and mid level (kids' bedrooms).

One of the issues is that the smaller unit runs a lot because of the cold temperatures in the lower level family room (sits on a concrete slab).

For the fan-control config: I understand that the HUM terminal is energized only when there is a heat call. If this is true, then I need 24v from a transformer or use R and C, correct?
 
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Old 01-05-12, 07:30 AM
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Do you run your fan all the time?

What model of humidistat control do you have?
 
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Old 01-05-12, 08:03 AM
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I have Model 60 digital control and my fan is set to auto at the thermostat.

I wired the humidifier as recommended by the manufacturer (with a transformer) and it is running on manual mode. Humidity reached 40% after hours of continuous fan operation. So - it does work, but it runs A LOT.

I will give it a few days, but it might be wiser to purchase another humidifier for the second furnace, as opposed to paying for electricity (fan), water (6 GPH!) and gas (boiler for hot water) for the single humidifier.
 
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Old 01-05-12, 08:20 AM
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Yeah, it runs a lot when you use just fan to run it, so that's why I use it only when call for heat.
 
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Old 01-17-12, 12:22 PM
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I just wanted to thank this forum again! I saved over a $1,000, had a lot of fun and the house feels great right now.

The end of my story was that I installed a second unit for my second furnace (I have 2 furnaces in my 3,800 sq ft home). Both humidifiers are wired for heat call only, manual mode. I might add the outdoor sensor later, but I am really not sure it is needed and I am a big opponent of the "keep it simple approach".

Wiring:

Humidistat ------- Fur
R----------------------R
C---------------------C
W-----------------W
G - not connected
first H-------------HUM 24 V

Humidistat -- Humidifier:
second H------------------ yellow wire to humidifier
C ---------------------------other yellow wire to humidifier

Thanks again!
 
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Old 01-17-12, 02:18 PM
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I'd suggest the outdoor sensor. That way you don't have to turn up/down the settings with the outdoor temps all the time.
 
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Old 01-24-12, 12:39 PM
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Yes, I am planning on adding it in the next week or so. I did notice condensation on the windows on colder days.
 
 

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