Aprilaire 700M + Lennox G40Uh + Nest 3

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Old 03-06-18, 02:14 PM
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Aprilaire 700M + Lennox G40Uh + Nest 3

Hello - Iím novice and after reading through countless forms and threads still unsure what to do, so thank you in advance for any assistance. I currently have a Nest 3.0 thermostat connected and working properly with a Lennox G40UH 36B-090-10 furnace (furnace board has HUM-N and HUM- H terminals) and Lennox 10HPB30-14P outside AC unit. Iím getting hardwood flooring and would like to DIY install an Aprilaire 700M Whole House Humidifer without humidistat to be controlled by the Nest 3.0. I live in the Missouri with temperture and weather swings, so I would like to have the Aprilaire 700M provide humidity as needed, when needed to maintain humidity level set on Nest 3.0. Pjmax can you help me with a wiring diagram and step by step explanation for proper install of humidifier to Nest 3.0 and furnace board?
 
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Old 03-06-18, 02:39 PM
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Current Set Up

Pjmax....the following are photos of my Nest 3.0 wiring, Lennox furnace board and HUM terminals on board.

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Last edited by PJmax; 03-06-18 at 03:53 PM. Reason: cropped/enlarged pics
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Old 03-06-18, 02:42 PM
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Welcome to the forums.

A very easy connection. One brown solenoid wire goes to C on the furnace board and the other brown solenoid wires goes to the * on the nest.

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Old 03-06-18, 02:46 PM
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That's great. From review the other forums i thought that might be the case, but doubted it was that simple. So i won't need a relay or to connect to the HUM terminals on the board?

Thanks
 
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Old 03-06-18, 03:52 PM
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No.... the Nest takes the place of the HUM supply.
 
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Old 03-07-18, 09:15 AM
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PjMax.....Understood. Last night, I traced the wiring from Nest 3.0 to furnace and noticed that wiring goes from Nest 3.0 to terminals on a FuelMaster 21 board (photo below) and from there to terminals on the furnace board and outside heat pump Lennox HPB30-14P unit. Does it matter if i connect the brown solenoid wire to C at the furnace board or the FuelMaster 21 Board? Also, I plan to use a Sharkbite push to connect reducing tee instead of the saddle valve off Pix water heater line. Does it matter if I tap into the hot or cold line? Is one better then the other for humidifier setup on supply side?

Thanks again,
 
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Old 03-07-18, 10:31 AM
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You can connect to that C terminal where the black wire connects or at the C on the furnace board. That black wire should actually be going to the furnace along with the red, green, yellow and white wires in the same cable.

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You can use the hot or cold supply line. The hot supply may give a little more increased humidity.
 
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Old 03-07-18, 11:29 AM
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Thx, Yes, the P3 terminals are the ones that go to the furnace and there is extra unused wire terminating at that board location that leads back to Nest 3.0 location. So I can wire humidifier to "C" terminal at that board and one of the 3 unused wires at that location for other humidifier wire to Nest 3.0 "*" terminal. The Aprilaire 700M is arriving Friday and installing it this weekend. Thx for all the help, will let you know how it goes..
 
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Old 03-15-18, 12:15 PM
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So, I was able to get the Apriliaire 700M installed this past Friday night and wired per diagram from Humidifier brown wire to furnace "C" terminal and from Humidifier's other brown wire to Nest "*" terminal. I used 7' of 18/3 thermostat cable i got from Lowes to run from Humidifier brown wires to furnace terminal, connected one to "C" terminal at that location, connected the other brown line from that location onto grey spare wire on 18/10 thermostat cable going from furnace to FuelMaster 21 board and from there direct connect to grey wire on 18/10 thermostat cable going up to Nest and "*" terminal. Well the 700m without the humidistat started working when heat or fan/blower ran, that is until 2 days later on Sunday afternoon when solenoid, fan and water flow stopped.

So far the following trouble shoot checks have been made:
- I checked water inlet and outlet to ensure water flow and no blockage. Verified water coming from sharkbite valve on cold water line and through soleniod.
- Checked for 25VAC at all terminals for Nest, furnace and FuelMaster 21. Had 25VAC on all but "*" wire.
- Connected 25VAC from furnace "C" and "R" terminals directly to humidifier's two yellow wires without 110 cord plugin and then to Humidifier's two brown wires while cord was plugin. Both checks provided open soleniod with water running out drain plug and second option produced same, plus turned humidifier fan on. This direct 24VAC wiring was done with 18/3 thermostat cable from Lowes.
- Tried using one of the other 4 spare wires on the existing thermostat cables from furnace to Nest for the "*" wiring connection, but Humidifier would still not turn on and could not get 24VAC reading.

Don't know what else to check other than buying another thermostat cable for connection from humidifier to furnace terminals? I'm I missing something? Pjmax, any help would be appreciated.

Thanks
 
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Old 03-15-18, 12:29 PM
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Just to clarify..... there should be absolutely nothing in line from the humidifier to the C and * connection. No humidistat.

With one wire on Common.... touch the wire that would go to the * to the R terminal. The humidifier should operate. Remove it from R and put back to *.

Go to the thermostat, remove the wire from * and touch to the R wire/terminal. Verify the humidifier works correctly.

Did you program the nest for humidifier active with heat only ?
 
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Old 03-15-18, 01:16 PM
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Pjmax...that is correct, there is nothing in line from humidifier's two brown wires, one to "C" terminal on furnace board and the other brown wire to "*" terminal on Nest. Nest is programed under pro setting for "humidifier+heat" (only other option is "humidifier only") and i set minimum humidity to about 40% (or 5 water droplet turn clicks).

Thanks, when i get home tonight I'll try what you suggested with touching the "*" to "R" terminal at furnace board and then at Nest.

 
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Old 03-16-18, 08:38 AM
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I ran your suggested test last night and it worked, with one humidifier wire on "C" common and the other humidifier wire for "*" to the "R" terminal at furnace board, the humidifier started up and worked. It also worked, when I connected the "*" wire to the "Rc" wire at the Nest. I then checked all the wiring connections per your diagram again for humidifier's brown wires, one to "C" on furnace board and the other to "*" Nest. That when i discovered the problem was a broken wire at one of my "*" connections, which i must have caused from over twisting the wire connection ( i have tendency to over tighten). As of this morning with an out side temperature of 40, I have 37 percent humidity reading on the Nest and the humidifier is also showing up on my phone's app (which was not the case before). I still have to call Nest to help me fine tune the settings as it took a long time for heat to switch from the outside heat pump to gas furnace heat mode.

Thanks so much for all the help. One last question Pjmax...Can you confirm that my Lennox G40UH-36B-090-10 furnace with a Lennox 10HPB30-14P is dual fuel system with Stage 1 electric outside heat/cooling pump and Alt. 1 gas furnace unit? I always get confused about the AC/heat pump outside unit and how it works.

Thanks again,
 
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Old 03-16-18, 11:29 AM
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You have a dual fuel setup. Your heat pump is primary heat. Your furnace is AUX/E heat. With this type of setup.... the AUX heat mode and the E heat mode must shut down the heat pump. Both cannot run at the same time.

In PRO setup.... the nest will ask you if system is single or dual fuel. You need to select dual.
I believe even in dual fuel mode you will need to use the W2/AUX terminal for the furnace.
The pro setup should ask what source and you choose gas.
It should also ask delivery method which is forced air.

I believe you also need to set the temperature where the heat pump will stop working and the furnace will take over. That may be a setting you can change.
 
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