Mini split for cooling / dehumidification only

[Brandon_oma#692]

Looking for some dehumidification and cooling in the shop. 40x100x12 walls are insulated ceiling is not. Newer doors but need to seal up the edges better. 1960's machine shed with new steel over top so walls are 10" thick keeping me from making a window for a window unit. Thinking 2 or 3 12k minisplits. How do I see what these use for electricity is constant running. Heat is already covered so I only need the cooling.

Having a cool breze blowing out of it in the area I am using rather than just a fan would be a huge improvement even if I do not keep it cool. I would be happy keeping it 80 and turning it down when I am in the shop all day. I am thinking 2 or 3 cheaper units as being disposable if they fail. Or just 1 for now to try?

Good/Bad/Horrible idea? Other ideas?

 

[chinboys]

Get a Manual J heat load calculation done to size the correct tonnage of cooling required based on your usage style, insulation, location, etc.
Add roof insulation to keep the heat from driving into the space.
A leaky shop, hot and humid air will transfer or diffuse from an area that has higher heat and moisture into an area that has lower amounts, try to fix these leaks.
Look for a multi-zone rated mini-split using its SEER value relative to multiple single zone units and its SEER value.
The SEER value will be an indicator of how much it will cost you to run these units. Usually, the higher SER value means the unit will cost more to buy. So you need to figure out the payback period to buy a higher rated SEER unit realtive to a lower one.
The con of a many single units is running dedicated electrical circuits and cutoffs to each one.
Maintain the cooling temperature even when you aren't using the shop and install ceiling fans as the minium cooling temp can be raised while the fans are circulating the air.

 

[WildBill]

I have mostly given up trying to use manual J load calculators for mini-splits, they really don't seem accurate for inverter technology. If your roof is metal and not insulated trying to keep it cool is going to be tough, but throwing three units down the long side and running them as needed should work well. I would probably start with one cheap 18-24k unit pointed wherever you are most likely to be working and see how it does. My 24k unit can be felt across my 36ft shop when its on high, and about 20ft away when its on normal speed. So if you just wanted to have cold air hitting you while working a mini split definitely would do the job. Keeping the whole place cool would depend on insulation and probably take three as you said. They can spool way down so energy wise it doesn't hurt to go bigger, just makes them cool faster when cranked up. There is no way to use electricity to produce cool air more efficiently, so whatever it costs to run will be less than anything else. If your shop was insulated well three 12k might be Ok, but I would go bigger as the cost isn't much more.

I would also buy separate single units, I have seen way to many expensive multiple head units have one part fail and not be worth the money to fix, and they generally cost more than all the single units combined. Plus you have backup if one fails using multiple singles. Since they are mostly made by a couple of places brand doesn't matter very much, and since they are pretty much disposable I would just look for a good deal. Even the Mitsubishi ones we used to like seem to be the same as everything else now from a reliability standpoint. I went with a Mr.Cool DIY 24k setup because it was, and I think might still be, the only one with sealed lines so you don't need a vacuum pump or anything special to install one. Was super easy to install. Having installed a bunch of different ones since its not really that big of deal, and you can also use the Pioneer purge can to clear the lines if you don't want to mess with a pump and gauges. https://www.pioneerminisplit.com/pr...g-kit-for-mini-split-air-conditioning-systems

Here is a Costway branded 21 seer2 and energy star rated 24k unit for around $900 when you use coupon code XQFP10793.

GreyVolt Series Energy Star Certified 24000 BTU 21 SEER2 208-230V Mini Split Air Conditioner and Heater Gray Wifi Enabled - Costway

Buy Energy Star Certified 24000 BTU 21 SEER2 208-230V Mini Split Air Conditioner and Heater Gray Wifi Enabled at Costway, enjoy great savings and discounts with fast, free shipping on everything.

www.costway.com

 

[Brandon_oma#692]

I guess I should have added my budget spend $1000 maybe up to $1,500 or continue to open the doors and run the big fans.

Currently 75° inside with 86% humidity pouring rain outside. If I could maintain a lower humidity and keep it 80° or less I would be happy. Assuming it wasn't running 24/7 to do that. I currently have excess electricity available. Need to measure how much electric the big fans use. I wouldn't be surprised my electric use running fans would be just as much. If I had a unit installed now, I would bump the thermostat down to make it run for the next couple hours while I'm out here. And a single fan to blow it in my general direction if I'm not in front of it.

Building runs east west with doors on both ends so you get a nice breeze usually. Unfortunately when I'm out here in the evenings that breeze is usually very. Thought about adding a big vent in the gable ends in the attic to let the hot air out.

Shop I was at a month ago was surprisingly nice inside. Running a single portable unit with the vent. Going out a hole in an overhead door and a fan circulating. I was going to go that route before I stumbled across off-brand mini splits for around $500 for a 12k unit. To me it makes much more sense to have that instead of a portable unit.

Insulation will have to wait. I have a few drips that I need to go find and fix. Didn't have the time or ability to get it done myself before doing the solar last year and tried getting quotes on it. All anybody local wanted to do was replace the entire roof on the building which has a 20-ft lean to, so it's actually 60x100 roof.

 

[Brandon_oma#692]

I have mostly given up trying to use manual J load calculators for mini-splits, they really don't seem accurate for inverter technology. If your roof is metal and not insulated trying to keep it cool is going to be tough, but throwing three units down the long side and running them as needed should work well. I would probably start with one cheap 18-24k unit pointed wherever you are most likely to be working and see how it does. My 24k unit can be felt across my 36ft shop when its on high, and about 20ft away when its on normal speed. So if you just wanted to have cold air hitting you while working a mini split definitely would do the job. Keeping the whole place cool would depend on insulation and probably take three as you said. They can spool way down so energy wise it doesn't hurt to go bigger, just makes them cool faster when cranked up. There is no way to use electricity to produce cool air more efficiently, so whatever it costs to run will be less than anything else. If your shop was insulated well three 12k might be Ok, but I would go bigger as the cost isn't much more.

I would also buy separate single units, I have seen way to many expensive multiple head units have one part fail and not be worth the money to fix, and they generally cost more than all the single units combined. Plus you have backup if one fails using multiple singles. Since they are mostly made by a couple of places brand doesn't matter very much, and since they are pretty much disposable I would just look for a good deal. Even the Mitsubishi ones we used to like seem to be the same as everything else now from a reliability standpoint. I went with a Mr.Cool DIY 24k setup because it was, and I think might still be, the only one with sealed lines so you don't need a vacuum pump or anything special to install one. Was super easy to install. Having installed a bunch of different ones since its not really that big of deal, and you can also use the Pioneer purge can to clear the lines if you don't want to mess with a pump and gauges. https://www.pioneerminisplit.com/pr...g-kit-for-mini-split-air-conditioning-systems

Here is a Costway branded 21 seer2 and energy star rated 24k unit for around $900 when you use coupon code XQFP10793.

GreyVolt Series Energy Star Certified 24000 BTU 21 SEER2 208-230V Mini Split Air Conditioner and Heater Gray Wifi Enabled - Costway

Buy Energy Star Certified 24000 BTU 21 SEER2 208-230V Mini Split Air Conditioner and Heater Gray Wifi Enabled at Costway, enjoy great savings and discounts with fast, free shipping on everything.

www.costway.com

Thanks for the info. I have been thinking and going back and forth on this. Just placed an order. It ended up at $998.66 with tax and shipping insurance. I will update once received and installed.

 

[fitter30]

RH moves like heat from higher to lower. The tighter the building especially with a vapor barrier the better chance the RH will get down to the low 40%. 50% and above mold can grow.

 

[Brandon_oma#692]

Looking North in about the middle of the building West to East. Unit will be mounted ion the north wall next to the conduit. Directly behind me taking the picture is my desk.