- Outside and indoor temperature can make a big difference on this test. Try to do it on a 80ºF to 85ºF day and room temperature around 75º.
- Also make sure the system runs for at least 15 minutes before you take the measurements.
- This is a simple test for the homeowner. It does not substitute a professional assessment of your system and it’s intended to indicate possible problems. A TD below 15ºF USUALLY indicates a problem or just simple inefficiency and it is recommended you call a professional to check your system.