Hi Guys! Kind of late to this party as I only recently joined the forum but I’ve had a great time reading all the posts (lots of quality information and debate here, which I really appreciate). HVAC in cultivation facilities happens to be a subject about which I’m pretty well educated so I thought I’d chime in on this one instead of just thread-stalking like I’ve been doing everywhere else.
I love how educated this forum is and you guys are absolutely right–mini-splits are a great option for comfort spaces and very small cultivation spaces, especially when there are budget limitations. But the SEER rating can be deceptive, because a) as you guys mentioned, they’re terrible dehumidifiers, and dehumidification isn’t considered in the efficiency rating, and b) in many cases that high rating is based on the use of an inverter for the system to be able to run at partial load, when your load in most cultivation spaces is constant (or very close to constant). This means that you don’t end up getting to capitalize on that energy rating in most cultivation environments–meaning that their real benefit is that they’re cheap and easy for small applications.
When you migrate to larger scale commercial applications, chilled water systems with heat recovery/reheat for dehu and/or packaged units with hot gas reheat for dehu are a substantially more energy efficient option, with the flexibility you need for dehumidification and maintaining tighter tolerances. Chilled water will typically get you better redundancy and lower connected loads on electrical as you can install fewer, larger chillers to supply cooling and dehumidification to an unlimited number of rooms without mixing air between rooms, and you have more air handling options with chilled water (ducted, ductless, custom, etc). To your point about multiple small rooms, Nick, chilled water would allow you to run a large compressor bank and fill your small rooms with ductless fan coils in whatever size is needed, so you can still independently control temp and humidity in small spaces but with a lower electrical infrastructure (especially if you’re operating on a flip) than with a bunch of 3 and 5 ton compressors. The HGRH units will typically have some integrated controls, and in either case, a good controls system is an absolute must.
Desiccant, as you guys mentioned, is probably the single most energy efficient means of stand alone dehumidification when properly deployed (it can also get you down to superlow humidity and can dehumidify at low temps for those of you who like very cold, very dry drying rooms), but it’s expensive and if you’re using a cooling system you’re getting dehumidification as a byproduct anyway so you won’t always need it as your first line of defense. With the right cooling system, the need for external dehumidification can be minimized or eliminated altogether.
I’m really happy to see you guys talking about maintenance and cleaning of the system, as people really don’t pay enough attention to taking care of the mechanical systems in their facilities in general. The mechanical (HVAC) in cultivation facilities is SO important, both because of temp and humidity but also exposure to fungus and pathogens. That starts with design of course, but proper cleaning and maintenance will a) make sure the system performs to the best of its ability (for decades if it’s the right design) and b) reduce your exposure to contaminants that can cause failed crops.