Evaporation is a heat transfer from the conversion of a liquid to a gas. This evaporation process cools down the human body.
How to Connect & Setup a Nest Thermostat to Function as a Humidistat - OHMefficient
If the human body has no other heat transfer processes occurring, overheating will occur. Refer to the heat index tables below: Everything in orange feels like the actual temperature. Everything in red feels warmer to the human body compared to the actual temperature. A flow-through humidifier uses water that drips onto a pad which evaporates while your furnace is running and warm air passes through it. If there is excess water that does not evaporate, the water flows out a drain line.
A saddle valve connected to your homes water line connects to the humidifier solenoid valve via tubing. When the Nest thermostat calls for heat and humidity, a voltage is applied to the humidifiers solenoid valve.
How the Human Body Reacts to Relative Humidity
When voltage is applied to the solenoid valve it opens allowing water to flow through. The saddle valve can be closed a little to prevent too much water from flowing down the drain line. The saddle valve does need to be open enough to maintain the desired humidity levels. It should be noted that warm air is required for these types of humidifiers. If you install these humidifiers and operate it with only the furnace fan running, minimal evaporation will take place.
If you do this, the humidifiers solenoid valve will open and essentially pour water down the drain the entire time the fan is running. A bypass flow-through humidifier is typically installed on the cold air return duct work. This flexible duct allows for some warm air to bypass your homes duct work and supply the humidifier with warm air required for evaporation. During the winter season, the damper blade on the bypass duct or on the humidifier housing should be open to allow for warm air to bypass through the humidifier. During the summer season, the damper blade should be closed since humidification is not required or effective without warm air.
The numbers in the picture refer to the wiring connections from the wiring diagram below. If you plan on installing a bypass flow through humidifier , read the instruction manual before proceeding. A powered flow-through humidifier needs to be installed above the furnace on the supply side of the forced air duct work. Instead it has a fan that turns on at the same time the solenoid valve is opened.
The fan draws warm air from the supply duct through the humidifier pad and returns it back to the supply duct.
How to Connect & Setup a Nest Thermostat to Function as a Humidistat
This type of humidifier is also an evaporative type humidifier and requires warm air to operate effectively. This humidifier will need to be plugged into a V outlet. If you plan on installing a powered flow through humidifier , read the instruction manual before proceeding.
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- Why Humidification is Required in Cold Climates.
Before proceeding with any wiring modifications, use a multi-meter and set it to V AC. Measure the voltage across the R and C terminals of the furnace terminal board. It should be approximately 24V AC.
Most furnaces have an interlock switch that opens when you access this area of the furnace. This switch may need to be momentarily pressed in to measure the 24V AC. If yours only uses 1 wire, good news, you can easily and quickly hook it up to the Nest. But most utilize 2 wires, much like a light switch, where a low voltage signal travels up one wire, the humidistat acts as a switch, closing the circuit for the voltage to travel down the second wire back to the humidifier to signal it should turn on.
So in order to use the Nest, which only has 1 wire to control the humidifier, you must install a relay circuit, which, if done wrong, can damage your HVAC main board, your Nest and your humidifier — so Nest asks that you have a professional do the work. However, I am comfortable doing that kind of wiring and was able to install the relay and get the Nest hooked up on my own.
My understand, which is confirmed by this eHow Guide and this Thermostat Wiring Explained article, the terminals are:. I used a 6AZU2 relay , which seems to be a commonly used relay for people doing exactly this see the comments on the Amazon page.
I used crimp-on spade connectors on the end of the wires to connect them to the relay terminals. You can see someone else describe the same scenario, with a wiring diagram, on this site. Posted on Oct 21, But, after much mental consternation, I've decided to provide some detail, but with this really big disclaimer: Based on my research, I'm planning to use this wiring diagram for my setup and have purchased a 6AZU2 relay: The question I have at this point relates to how the wires from the furnace board wire in.
Here is a picture of the board: Here are the things I'd like to confirm before proceeding: Is this the right diagram to use? Do I need to use the optional common wire from the nest to the board? Right now i'm not using that Common wire on the nest. Find all posts by mustangman Welcome to the forums. The diagram looks like one of mine is showing a second completely independent 24vac transformer to run the humidifier.
Is that what you are doing You will be using a connection to the C terminal on the board. Find all posts by PJmax. Thanks for the reply PJmax!