Installing Lennox humidifier to a Nest

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Old 01-25-15, 08:51 AM
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Installing Lennox humidifier to a Nest

Hi all,
First post here. I posted this question on the Nest forums, and one wonderful person has helped me there, but I was hoping I could get some more opinions here since this seems a bit more active. This post is pic heavy!

I'm setting up my nest to use with my Lennox HCWP3-18 power humidifier: Healthy ClimateŽ Whole-Home Power Humidifier | Lennox Residential . I assume this humidifier is a "Stand Alone" type, since it is a power one, and from my understanding it operates independently of the furnace, since it has it's own fan. I would have gotten the pro to do it when they installed the humidifier, but they only support honeywell.

Anyways, I have everything set up according to diagrams online, in this configuration:

http://support-assets.nest.com/image...Hum-2-wire.png

However, when I turn the system on, the relay just buzzes and heats up, and nothing happens. The solenoid does not activate.

I have the two brown wires from the humidifier hooked into the relay on the switch side, with the C (white) and * (black) on the coil side of the relay. The C wire (from relay), goes to the HVAC control board C terminal, and the black wire goes directly to the * port on the nest.

There is a C wire that goes straight from the terminal on the HVAC controller to the C port on the nest.

Here are some pictures of my setup. White wires are common, the black wire goes to * :



This is the relay switch:



This is the furnace control panel, you can see 3 white wires going in the C terminal (second terminal from left), 1 for air conditioning, 1 goes to the Nest, and 1 goes to the humidifier relay switch:




Ok so I grabbed a multimeter (the one at work was broken, and the local store had them on sale so I bought one for myself).

- The C wire that goes from the C terminal on the furnace control board has 0V... I thought it would have some. Maybe I misunderstand what the Common wire does. Therefore, the C port on the nest also had 0V on it. Is the C wire a ground?

- The R wire at the nest had the voltage on it.

- When I activate the humidifier (through equipment and test), the C wire going to the relay has 0V. However, the * wire going to the relay has 27V. Both of these are on the load side.



- When I touch the multimeter leads to the switch side of the relay it reads 0V.



- If I touch the C wire to one of the humidifier wires, and the * wire to the other humidifier wire, the humidifier solenoid kicks in and water flows through it




The humidifier is plugged into a 120V wall socket. The instructions does make it sound like there is a transformer inside that should kick in when the 2 brown humidifier wires are in a complete circuit. Though touching the 2 browns do not open the solenoid.

I checked the resistance (ohm value) of various things, to learn if the there was a break in the system. I learned this:

- The switch works fine. When the nest has the voltage off, the switch is closed:



- When the voltage goes on, the switch opens, shown by the ohm value:



- Now I would assume the issue is indeed the humidifier, but if I check the ohms of the humidifier wires, it reads fine:




I'm a bit perplexed. I assume the issue is the humidifier, but I figured that the ohm value would be zero on the humidifier wires. I just want to know for certain before I call back the people who installed it.

So that's my pictorial guide of my problem solving. I'm fairly certain I have everything hooked up correctly, and I'm pretty sure the relay is working right. I'm fairly sure I understand the system, and that it is the humidifier that's the problem.

Can anyone provide any tips, or confirmation that I should be contacting the service people who installed the humidifier?

One more question for the Pro Nest Setup: In the option that says "Fan: Active/Deactivate", I assume I want deactivate since the power humidifier has a fan itself, and don't want the furnace fan. Correct?

Thanks for any help anyone can provide!
 
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Old 01-25-15, 08:56 AM
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Welcome to the forums.

Your thread was in moderation due to your new membership status and the quantity of pictures.
I'll look over your post and offer help.

"Fan: Active/Deactivate"
Is referring to the furnace fan..... not the humidifier's internal fan. Basically you want the humidifier to only work when the furnace is heating. You don't want the humidifier to operate with just blower only.
 
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Old 01-25-15, 09:04 AM
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Thanks PJ! I will change my fan setting to Activate then. Will it burn out the blower on the humidifier if I leave it on deactivate? Or it just won't have enough power to get the humid air into my house?
 
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Old 01-25-15, 11:45 AM
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It's more effective to use warm air to carry humidity than cold air.

You've got a lot of "stuff" posted here. Try this for me......

Without the relay connected..... touch the two brown wires from the humidifier together. The humidifier should operate. If that doesn't happen then you have a humidifier problem.

With the C and * connected to the coil (1+3) of the relay..... you should measure around 24vac on the coil if the nest is calling for humidity. If you have 24vac to the coil..... then the relay should close and you should measure a short across the contacts(2+4).
 
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Old 01-25-15, 02:57 PM
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Hi PJ,

Thanks very much for this reply. I really appreciate it!

So if warm air carries humidity better than hot, should I use for Activate "Hum + Heat"? Right now I'm just using "Hum. only", since the Pro Installer Guide said to use Hum. only if you have a stand alone humidifier. Maybe I should have just gotten a bypass humidifier... oh well, too late now.

Touching the two brown wires together, there is no voltage and the humidifier does not operate. You are the third person to suggest this (my father, someone on the nest forums). So I will be popping the installers an email to let them know.

I'm fairly sure that the relay is working as it should. However it is buzzing and heats up, which is a bit odd. When I measure the voltage for the C and *, it measures 27V. I'm wondering if that's too high, and it's overloading the relay? The switch does seem to close when voltage is applied.

Thanks a ton for the response!
 
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