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How to Install a Whole-House Humidifier

Ask This Old House plumbing and heating expert Richard Trethewey shows an efficient, low-maintenance way to humidify the air

In this video, Ask This Old House plumbing and heating expert Richard Trethewey shows an efficient, low-maintenance way to humidify the air.

Steps:

1. Disconnect the flexible supply ducts from the sides of the heat pump.

2. Remove the existing main trunk from the top of the heat pump.

3. Build a new sheet metal trunk.

4. Cut three 4-inch-diameter holes into the top of the new main trunk.

5. Over each hole fasten a take-off fitting with balancing damper.

6. Mount a louvered sheet metal elbow to the top of the heat pump, then attach the new main trunk to the elbow.

7. Attach one 12-inch-diameter take-off fitting onto the side of the main trunk. Fasten a second fitting to the bottom of the trunk.

8. Cut a 2½-inch hole in the back of the trunk, then insert the humidifier wand. Secure the wand to the trunk with sheet metal screws.

9. Run a new copper cold-water supply line from the water heater to the humidifier.

10. Connect a drain line from the humidifier to the existing drainpipe on the heat pump.

11. Have a licensed electrician run a new 220-volt circuit to the humidifier.

12. Control the humidifier with a humidistat set to approximately 35 or 40 percent.