Nest 3rd Gen + Aprilaire 500

Old 11-16-17, 10:27 AM
Thread Starter
Join Date: Nov 2017
Location: United States
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Nest 3rd Gen + Aprilaire 500

Long story short the solenoid for my humidifier is not getting enough voltage to open. The way the wiring is set up is the wiring from the thermostat go to my zoning panel, HZ311, then to the furnace.

1. Across my power and common at the circuit board in the furnace I'm getting 28.55v
2. From my *, humidifier signal wire, to the common at the zoning panel I'm at 26.61v. The humidifier wire does not go to the panel. It gets jumped to the wiring that goes to the furnace.
3. Inside the furnace the voltage drops again to 23.5v, * to common
4. Once the fan activates voltage drops again to 22.6v and this is the same reading I get at the solenoid valve.

Do I need another transformer and a relay installed? Another question I have is why is there such a voltage drop across the lines? When the humidifier is "active" I still have 28.55v across the power and common.

Appreciate your input.
Old 11-16-17, 07:01 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 63,130
Received 3,615 Upvotes on 3,241 Posts
Welcome to the forums.

Not completely sure what you have there or how it's wired.

If the R and C power for the nest thermostat comes from a zoning board then one wire from the humidifier goes to C on the zoning board. The other humidifier wire goes to the * terminal. No connections to the furnace.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: