Yes, in general the supplier wants it through them. At least that's how we do it at Knoxville Heating Service & Repair. You will find that some suppliers will send you back to the engineer.
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I agree with DavidNJ, a VRF system is can be more efficient regardless of cooling, and in some cases far more efficient.
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MintJulep is right. Generally speaking, less resistance often does increase both air flow and fan amps, but it does seem a bit counter-intuitive.
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