OK, I'm going to show my naivete here and ask a stupid question. I recently moved from a fairly academic setting to a utility and am beginning to have to deal with the real world. One thing I’ve noticed, for instance, that I hadn't really before, is that, pretty consistently, smaller equipment tends to be more efficient than larger equipment. It’s even built into our codes. HVAC equipment is allowed to be less efficient in the larger size categories. This is somewhat counterintuitive. I would have assumed there was an economy of scale and that larger equipment, with bigger motors and more ways to control things, etc., you would be able to get some savings with larger systems. Apparently not. So maybe it’s cost? Wrong again. I am looking at a bid that is over $900,000 for a 40-ton VRF system. This is over $20,000/ton! I can buy small ductless heat pumps for $4,000/ton all day long. How can it make sense to spend 5 times as much for a system whose components are less efficient, and arguably little if any more efficient as a system.
I’m wondering, in this case, a 26,000 sf office bldg., if it would make sense to install, rather than a large VRF system, a “farm” of 8-12 5-ton multi-zone ductless heat pumps. You wouldn’t have building-level control, and there may well be times where one unit is in cooling and another is in heating, but if they are hooked to “connected” T-stats (BPA’s current term for web-enabled T-stats), they would be controllable remotely. If you zone it correctly, you should seldom need simultaneous heating and cooling from a single outdoor unit, and you should be able to do this for under $200K, right? What am I missing? Why does no one do this, or do they? I understand they do do this in Japan. Why don't we? Wouldn't this be cheaper and much more efficient than a bunch of standard rooftop units? We have pretty much eliminated ducts from homes. Is it time to start doing that with commercial, too? What am I missing? I'd love to hear thoughts from you smart people out there who have been dealing with HVAC longer than I have.