Overview

Honeywell HE280C2010/U Higher Capacity Whole House Bypass Humidifier

Parts

Humidifier Pad - HC26A

Wiring with a Nest Thermostat 

In order to have the humidifier work effectively with the nest thermostat, we will need to make some changes.

• disconnect our humidistat.
• bypass flow check in the humidifier controller
• wire the humidifier to the thermostat 
• configure the thermostat to use the humidifier

Disconnect the furnace mounted thermostat.

Remove the wire to the furnace mount thermistat at the solenoid controller.

Remove the cap to the controller and cut the wires for the flow check switch and marret the connections together. The other 2 wires go to the solenoid valve.

The end result should be resemble the following:

Wiring the Thermostat

In my zone control cabinet, I connected both *(HUM) wires from the thermostats to the HOT line of the humidifier.

Wiring with a Humidistat

Google stopped supporting its 1st and 2nd generation thermostat and we no longer have control over our humidity settings. Based on this, we will be wiring up our old humidistat to control our humidifier. Prior to this, we had disabled flow check in the humidifier controller.

Our furnace control board has a HUM(Humidifier) connection point that we will use to trigger our humidifier on and off.

Furnace Control Board

Humidifier Controller

Controller Images

Schematic

Here is the schematic that I put together based on some testing.

You would think that the GND pin on the 555 would go to ground via a pullup and that would be that.

Other thoughts:

• D2 is a zener diode which acts as a voltage regulator for the 555 chip.

555 Timer Reference Diagram

Fixing the Humidifier Controller - No Water

Since the solenoid was no longer activating, it seemed like a replacing it was in order. The replacement solenoid that I purchased was rated 24 VDC but didn't activate when connected. Perhaps the transistor Q1 does support the amount of current required by the new solenoid. 

I opted to bypass the 555 timer circuitry by connecting pin 4 of the internal connector (under cap) to ground. The 555 timer is not required. 

New Parts

Finished Product

Here is a picture of the finished fix. Should be more maintainable now that these changes have been made. The new solenoid valve will allow a lot of water to pass so I have ball valve (not shown) limiting the flow to a trickle.

Future Updates

• Replace solenoid output connector with barbed connector

Issues

Cracked Tubing

We seem to get cracks in our water lines.
Could this be because we are running with hot water?

References