Read and understand the manufacturer's instructions that accompany the humidifier
Before installing a humidifier turn off the furnace as well as the electrical power to it.
Heat from your furnace warms the air in your house, and dries it out, too. Forced hot-air systems in particular can lower indoor humidity to the point at which people feel uncomfortable. To add moisture to dry winter air and create an indoor environment that's comfortable for you and good for your house as well, you can use a variety of portable or whole house humidifier systems.
The most economical systems connect to the furnace.
These have a moisture control, called a humidistat, and feed moisture directly into the warm airflow.
Portable, or console, humidifiers are concealed in small cabinets. They are helpful if one room is particularly dry or if you have a heating system without an air-distribution system, such as electric baseboards, or hot water boiler system, that isn't suited to a central humidifier system. The drawback is that you have to add water to console storage tanks periodically. Also, they require maintenance much more often than central systems.
Central humidifiers are attached to the home heating system, normally at the warm air plenum, where heated air is distributed to the ducts . The advantage is that the appliance is part of the house; you don't have to plug it in or add water.
Installing a Humidifier
1) Mark the Placement of the Humidifier
In a typical installation, you tape a paper template for the humidifier on the warm air plenum above the furnace. Use a level to make sure the lines of the template are level. Also mark the position of the humidifier duct on the cold air return if needed. Then, using metal cutting snips cut through the template and sheet metal along the lines of the template. To protect yourself, wear work gloves and safety goggles.
2) Install the Humidifier
Position the humidifier in the warm air plenum, making sure it is level. It's
important to level the humidifier for even water distribution; Then fasten the humidifier in place, following the manufacturer's instructions.
3) Cut Hole for bypass Duct (if a bypass type)
Using metal snips, cut through the cold air return to make a hole for the humidifier . some kit's comes with a mounting collar for the bypass.
4) Connect Duct (if a bypass type)
Using flexible duct or a length of standard metal duct and an elbow fitting, connect the humidifier to the cold air return.
5) Installing Water Supply to the Solenoid Valve
A typical humidifier has a solenoid valve to control water flow. This needs a small 1/4" flexible copper pipe or hard plastic tubing that runs from the saddle valve to the humidifier.
6) Install a saddle valve (if permitted by code)
on the hot water supply pipe. Clamp it to the pipe, and turn the handle to pierce the pipe.
7) Provide for Overflow or drain
Whole house humidifiers typically have a catch basin that recirculates water, or a 1/2" drain hose like this one.
8) Install the Humidistat
Following the instructions that accompany the humidifier, install the humidistat on the cold air return or near the existing thermostat. A humidistat allows you to regulate the indoor humidity.