How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
Why is the air conditioning temperature split (delta T) fluctuating up and down while the system is running?
Monday, August 1, 2022
The most likely cause is a malfunctioning thermal expansion valve at the evaporator coil unit. If it is opening and closing erratically, that would cause the up-and-down fluctuations in temperature readings when using a temperature probe at the main supply duct. But further evaluation by an HVAC professional is necessary to confirm this diagnosis. See our article What is a TX valve or TXV for an air conditioner or heat pump system? for more on this.
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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
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To learn more about heating and air conditioning systems, see these other blog posts:
• How can I find out the SEER of my air conditioner?
• My air conditioner won't turn on. What's wrong?
• How can I find out the size of my air conditioner?
• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump?
• Where is the air filter for my central air conditioner and furnace? I can’t find it?
• Does an old air conditioner use more electricity as it ages?
• How did homes stay cool in Florida before air conditioning?
• What is wrong with an air conditioner when the air flow out of the vents is low?
• Why has the thermostat screen gone blank?
• Why does it take so long to cool a house when an air conditioner has been off for a while?
• Why is my air conditioner not cooling enough?
• What are the most common problems with wall/window air conditioners?
• Will closing doors reduce my heating and cooling costs?
Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.
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