Connect Aprilaire 760 to Bryant 95S

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Old 02-23-15, 08:09 AM
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Question Connect Aprilaire 760 to Bryant 95S

Hi, I am attempting to connect my fan-powered 760 humidifier to my Bryant Evolution 95S gas forced air furnace model 355CAV042060FASA and Bryant Evolution thermostat. Only been in this house 6 months now, so I'm learning about all this equipment still.

The 760 works ok and currently has a basic analog control installed on the return duct. It's not ideal because the analog sensor seems to not be very accurate and I have to fiddle with it a lot to maintain proper humidity levels. Since my furnace has a HUM control, outdoor temp sensor, and the Bryant thermostat can maintain humidity automatically, I'd like to make use of this instead. Ideally I would like to leave the Aprilaire manual control connected to the circuit, but it would be used only as a master "high" cut-off just in case the thermostat gets overzealous. If I can only make the thermostat work by removing the old analog control from the circuit, that's ok.

I've read both here and in the furnace manual that a N.O. isolation relay (DPST) must be used to prevent mixing internal humidifier power with power coming from the 24V furnace HUM/COM contacts.

So my questions are:
1. Do I need a relay, and which one?
2. Is it possible to leave the analog humidity control in the circuit as a "high" emergency cut-off?
3. How to wire it appropriately?

Thanks in advance!
 
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Old 02-23-15, 08:41 AM
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Welcome to the forums.

The 760 is a little confusing as there is an older and newer model. They both plug into AC power. Is yours the one where you short the two wires to the unit and it starts or it needs external 24vac in to start ?

Regardless of which model.... your current humidistat could be still left inline and operational.
 
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Old 02-23-15, 09:01 AM
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Thanks!

I believe it is the older model. It certainly looks very old with that beige plastic...

I'm going by memory here as I'm not at home. It has an AC power plug and then there are two wires with wire nuts on them that go to the 24V relay connected to the water line and the plastic connector inside the housing. I believe these also connect to the brown wires of the analog humidistat.

I'm about 95% sure the only power going to the unit is the 120V AC. I guess it must step down somehow on the control board inside the unit?
 
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Old 02-24-15, 04:46 PM
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I checked the humidifier and it's like I said above. 2 brown humidistat wires connect to two yellow wires next to water relay by wire nuts then head inside the unit.

Any ideas?
 
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Old 02-28-15, 06:12 PM
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Ok..... we're missing something here. Does your humidifier currently work when the blower starts and the humidistat is calling for humidity ?

I'm having a problem envisioning your current wiring. If the humidifier is just plugged in and you have a simple two wire humidistat..... then the receptacle where the humidifier is must be connected to the 120v HUM terminal.
 
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Old 02-28-15, 06:28 PM
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The humidifier is not connected to the furnace in any way whatsoever. That's precisely what I'm trying to achieve. My furnace and thermostat both support controlling a whole house humidifier, so I want to connect them instead of the current setup where the humidifier is completely running on it's own (and doing a poor job of it).

I usually have to leave the humidifier off because the humidistat doesn't work well and it will happily go way past the RH% that I have set.
 
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Old 02-28-15, 07:00 PM
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So then you are telling me that the humidifier can run 24 hours a day regardless of whether or not the blower is running..... is that correct ?
 
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Old 02-28-15, 07:35 PM
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That is correct.

Well ok, I do think it would eventually shut off, but not before the RH% goes well over 40% and the windows are fogged up, etc. Kind of hard to test it because I'm not going to let the humidity hit 50% or higher just to find out at what point it will turn off, if at all.

At the end of the day, I don't think the humidistat is reading properly. It's probably broken. I am basically running it manually, only while I'm home, and only for an hour or 2 and then turning it off again.

But anyway, I would like to connect the humidifier to the furnace as so many others here have done. The thermostat has humidity control built in and it's much more capable than the old and busted aprilaire humidistat that's currently being used. I'm about 70% sure I know what to do based on reading other posts, just looking to confirm that last 30% and make sure I buy the proper 24v relay. Hopefully one that doesn't hum while active...
 
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Old 03-01-15, 07:12 AM
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Two possible relay choices... 90-290.... 6AZU2. Both will work ok. There are many more that will also work. You need a single pole relay..... 24vac SPST.

Here's one place to get one... amazon/Industrial-Grade-6AZU2-Enclosed-Relay/dp/B004ZROX4S

The diagram below will be easy to follow. In reading the tech support information on your system it is highly advisable and recommended to just use the Bryant thermostat only to control the humidifier.

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Old 03-01-15, 07:55 AM
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Perfect. I will report back how it works. Thank you for your help!
 
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