Home Improvement Questions? Ask a Handyman for Answers
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Yes a larger duct could help but there are other considerations. You must have adequate return air as well so you can't just increase the size of the supply duct. Also if the thermostat is on the first floor you'll never be able to properly control the tamp on the second floor unless you modify/split the duct work and install zone 2 separate zones with 2 thermostats
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