Aprilaire 700 Humidistat Wiring - Not working

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  #1  
Old 01-20-12, 10:50 AM
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Aprilaire 700 Humidistat Wiring - Not working

Hello all, i've been trying for weeks to make my nifty new Aprilaire 700 work on my furnace. I hooked up the humidistat as instructed in the manual, however here comes the issue.

When the furnance kicks on and it calls for heat the humidistat sometimes turns on, however, when the furnance is NOT calling for heat it completely turns of the humidistat (no power whatsoever). Then when the furnance calls for heat again, the humidistat powers back on and sometimes it kicks on the aprilaire. My guess is this is not suppose to happen.

So working around this issue (furnance kicking off power to the R & C terminals which lead to the Humidstat I figured I would try this:

Scenrio 1:
I connected the R & C connections from the Humidistat right to the 24v transformer. Will this keeps the humistat on, but the aprilaire will not kick on unless i put it in test mode. Humidity reads 32 and I have the humidistat set at 7 (highest).

I have the following connection:

R ---> 24v transformer
C ---> 24v Transformer
W ---> W on Furnance control board
G ---> G on Thermostat upstairs (not sure if this works or not as I cannot turn the FAN ON via the thermostat to circulate air if needed. It nevered worked)
H ---> Humidifiter
H---> 24v Transformer
GF --> G on Furnance control board
ODT1 & ODT2 ---> outdoor temp sensor.

as indicated: Aprilaire works in test mode only
It did work sometimes when R & C were connected to the furnance board instead of the transformer, but each time the furnace called the heat off, but keep the blowers running it would power off the humidistat.

Please help :-)

I feel like i'm so close, but whatever I try is just not working.

Thanks in advance!
 
  #2  
Old 01-21-12, 07:36 AM
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How is the transformer hooked up? Is it plugged into the outlet or wired to the furnace's board?

You can skip the G/Gf hook up. I see no point of "forcing" the fan "ON" on call of humidity.
 
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Old 01-27-12, 10:12 AM
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Transformer is hooked up directly to a outlet box by the furnance (dedicated circuit)
 

Last edited by jwhiteuwc; 01-27-12 at 10:12 AM. Reason: spelling error
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Old 01-27-12, 08:39 PM
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If it's like that, the display shouldn't be turning off.

DO you have a meter? Put the meter on the transformer and see if it still has power when the screen goes blank.
 
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Old 01-28-12, 06:45 AM
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Jay, thanks for the information. The Humidistat doesn't shut off when connecting directly to the transformer. However, if the 24v leads are connected to the control board on the furnance and the furnace is not calling for heat it will turn off the humidistat. Then when the furnance calls for heat again it turns back on. Odd as the humidistat should be on all the time no mater what.

Does wiring the humidistat directly to the transformer stop the humidifier from turning on when called for? Meaning does the R & C HAVE to be wired to the furnance control board?
 
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Old 01-28-12, 10:17 AM
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The unit must have R and C and W wired from the control board on the furnace in order for it to see that Heat is operating.

 
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Old 01-28-12, 03:24 PM
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Thanks! However, when I wire up the R&C to the furance control board i have the issue of the furnance turning off the power to the humidistat when not calling for Heat (fan can be on, but if it's not calling for heat the humidistat is dark and off).

What could be causing that? Shouldn't the R&C always have continues 24volt operation even if the furnace is on, blowing air, or calling for heat?

How can I work around that issue or can't I?
 
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Old 01-28-12, 03:38 PM
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yes it should always have 24V. You need to verify you are losing power from the control board. If you are then there is something wrong with the furnace. R and C on the furnace control board are designed to have power anytime the furnace has power. You need to verify your power with a meter before you can go any further. What make and model of furnace do you have?
 
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Old 01-29-12, 06:50 AM
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Thanks. I will check that out. I do have a meter, but not 100% sure how to use it. Which setting do I set the meter on to test the control board? Sorry, I haven't used a meter in years and don't remember much about them.

Furnance type is a Dayton Fueltrimmer. Never heard of them and the furnace was in the house when I bought it.
 
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Old 01-29-12, 08:25 AM
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Set the meter on AC Voltage side, 120 or 50 if it goes that low. Your reading should give or take around 24 volts on R and C. When you remove the cover there may be a button that needs to be pressed in to power it back up again.
 
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Old 02-12-12, 01:28 PM
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Ok, so there is power coming from the control board on the furnance when the furnance is not on and running. The power will remain on until the furnance cuts off the gas and keeps the blower going. Then there is no power. The power returns when the gas kicks back on / callig for heat and then cuts back off when the gas is cut off (blower still running, just not calling for heat).


The aprilaire does indeed kick on now, however it never shuts off with the furnance when it does :-)

So it looks like I may have to call in a repair main to look at why the 24v cuts off when the furnance is running and just not calling for heat. However, why would the aprilaire turn on when needed, but not shut off?


Thanks for everything.
 
  #12  
Old 12-07-12, 10:43 AM
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I have exactly the same problem with my newly installed Aprilaire 700 and old Comformaker HVAC. Did you figure it out?

TIA.
 
  #13  
Old 12-07-12, 10:51 AM
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I wish I could say I did, but I haven't yet. So far the humidifier is on the furnance just sitting there. I think I migh have to call someone in to see if they can fix it, but it looks like everything is connected correctly.
 
 

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