Quote:
Originally Posted by red-beard
What is different in the duct design for a VSD system versus a single stage?
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Variable speed systems are more sensitive to duct design than single speed systems. If you're going to go variable speed, have the static pressure measured to make sure your duct system is adequate for the variable speed system. It has been a long time since I installed a variable speed system but I seem to recall using a different static pressure to design the duct system. The duct system has a pretty big effect on a variable speed system and its ability to reach maximum efficiency.
fisch,
Not saying you're wrong... but variable speed systems do not overcome an improperly designed duct system. They suffer efficiency loss if the system isn't properly designed. Point being, if you're going to spend money on a variable speed system, why not make sure the duct system is designed properly to achieve the maximum efficiency. As a dealer for Carrier for several years, I can tell you with 100% certainty that Carrier would recommend a full duct system evaluation prior to installing one of their infinity systems. They'd also tell you that an infinity system will not reach maximum efficiency without a properly sized duct system.