Aprilaire 700A wiring problem

HI Everyone,

I am coming here for help with my newly installed Aprilaire 700A Humidifier.
My Furnace is Lennox ML296UHV, and paired with a Heat Pump. I am using Nest Thermostat E.

I have hooked up the wire according to the wire diagram provided. However, the current set has a trouble with the Continuous Blower Operation function, or Fan Only mode on Nest E. Even I switched to "Fan Only Mode", the blower of the furnace is not running.

I would like to have the air circulated sometime during the day without running the AC or furnace. Can someone provide me some suggestions or solutions?

Thank you!

 

Welcome to the forums.

Sorry for the delay.
You are using a Nest E for dual fuel ?
The Nest E has six terminals.... correct ?
That would not be a good choice for dual fuel.... heat pump / furnace combo.

 

HI Pjmax,

Thank you for your suggestion.

Yes, Nest E has only six terminals, so here is the wiring on my Nest: this is based on your Picture that is ignore the G and Gf on Aprilaire 700A.
R is connected to R on the furnace,
G is now connected direct to G on furnace,
Y is connected to Y1 on furnace, which is also connected to Y on heat pump
W1 is connected to W1 on furnace,
*O/B is connected to B on heat pump.
With this configuration, the furnace blower alone can now be controlled by Nest E, only issue is that if the humidity level is not as expected, the humidifier may work even without the blower is running.

However, if I wires the G and Gf based on the Aprilaire 700A, the furnace blower then cannot be operated and controlled alone.


I am thinking either replace the Nest E with a Nest 3rd Gen, since I have 3 sensors with my Nest E, or replace it with Ecobee 3 Lite, which I have handy, the only downside is I have to purchase few sensors to pair with the Ecobee...

 

Ok.... I was mistaken. You can use your stat for dual fuel but not to ideal parameters.
The stat will only turn the blower on based on programming.

You can only wire the humidifier to the HUM terminals on the furnace or in the G line for heat pump.
To operate with both fuels you'd need ma relay.

With a thermostat like the Ecobee 3 you can use the stat to control the humidifier directly with or without a call for heat. You can program heat stage 1 as heat pump and heat stage 2 as furnace only.
You cannot allow the heat pump and the furnace to both heat at the same time.


pj note: furnace has 120v HUM terminal.

 

Thank You Pjmax,

I just purchased a Nest Learning Thermostat (3rd Gen) this morning which has 10 terminals, to replace my current Nest E, which has only 6 terminals.

I will follow the Nest Pro Guide. I would like to use the Nest Thermostat to control the humidifier completely, instead of using the humidifier controller. Would you mind give some hints on this? I have read some articles that the * terminal will only be needed to connect to humidifier's C terminal, since Rh is connected to furnace already.

by the way, my furnace's HUM terminal support up to 1.0 amp.

 

Problem solved.

Just connect the C terminal from furnace to one end of the solenoid valve, * terminal from thermostat to the other end of the solenoid valve.
All the transformer and humidistat provided by Aprilaire 700A can be eliminated.

 

That's it. Good job. You can program for humidity with or without heat too.