Trying to get Aprilaire 700 to work using Bryant Evolution thermostat

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Old 12-16-14, 12:23 PM
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Trying to get Aprilaire 700 to work using Bryant Evolution thermostat

Hi Everyone, I have just purchased and installed a new Aprilaire 700 fan powered humidifier and I'm having trouble getting it to work using what I've found on previous threads. The furnace is a Bryant plus 80V, manual states it's a model 315AAV/JAV. The instructions in this manual state "connect an accessory 24V VAC 0.5 amp max humidifier (if used) to the 1/4-in male quick connect HUM terminal and Com-24V screw terminal on the control board thermostat strip. The HUM terminal is energized when blower is engaged in heating. " Nowhere does it mention the need for an isolation relay if using a direct blower type humidifier. However, when reading the Bryant Evolution thermostat instructions, it states "Most fan powered humidifiers produce internal 24 vac in order to energize upon a switch or contact closure. For this application, a 24 vac N.O. Isolation Relay (DPST) must be used to prevent mixing the internal humidifier power with the indoor equipment transformer." it goes on to say "do not apply 24vac fan powered humidifier (with internal power supply) direct to indoor unit HUM and COM terminals." Assuming that the Aprilaire 700 has an internal power supply, I went ahead and purchased a honeywell r8222d1014 isolation relay and hooked it up with HUM and COM on the coil side, and wired the two brown wires coming out of the 700 to the top left and right terminals - based on other threads I have read on this site. I have set up the thermostat so that it reads there is a humidifier and I have it currently set on auto but cranked it to max humidity. This setup is not turning on the humidifier. I have confirmed this humidifier is the "2008 and newer" model with a relay requiring 24vac coming into the brown wires. When the furnace is running, I am not getting any voltage coming through the relay the way it is wired. I haven't tested whether or not the thermostat is calling for the humidifier, but it is 21 degrees out and indoor humidity is at about 40%. Do I have the relay wired up correctly and is it supposed to supply 24vac out to the humidifier or just act as a switch? Is the isolation relay needed on the newer model 700's? Any help on wiring this correctly would be greatly appreciated!!!
 
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Old 12-16-14, 12:56 PM
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Welcome to the forums.

I see a lot of confusion here. Your 700 requires 24vac in to operate even though it has a direct 120v plug in connection. Below is the basic diagram and it shows 24vac in.

Name:  700M.jpg
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I'm not totally familiar with the Evolution system. Is there a control board for that ? A separate one from the furnace board ?
 
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Old 12-16-14, 01:11 PM
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Hi Pete, thanks for the quick reply. I don't believe it does, it has the standard 4 wire running directly from the furnace board to the thermostat. Here's a picture of the relay on the 700 model I have. I wouldn't think that it is considered an internal power supplied humidifier if it requires 24vac in, would you? Name:  Capture.jpg
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Size:  51.3 KB Do I still need to worry about humidifier power feeding back into the furnace board if I wire the HUM and 24V COM directly to the 2 brown wires?
 
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Old 12-16-14, 01:58 PM
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Hi Pete, thanks again, I actually called Aprilaire technical support, they said all I need to do is to wire it directly up to the 24vac COM and HUM terminals, no need for the isolation relay as the 700 does not create it's own 24vac. Thanks for the assistance though!
 
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Old 12-16-14, 06:24 PM
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Yes... that is correct but I don't think the thermostat will control the humidity level. The HUM terminal on the board becomes live when the burner lights.

You need a humidistat in the circuit or the humidifier will run every time the burner is in operation.

It's possible for the t'stat to control the humidity but it would need to be a communicating t'stat or require special humidifier wiring.
 
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