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.

 

[Brandon_oma#692]

So unfortunately life got in the way and I just spent the last week working on this. outdoor unit is damaged. what are my options besides dumpster and buying another?

edit. just pissed at myself for not catching this and making time to get it in right away.

I looked everything over really well I thought. Never thought to look at the inside...

 

[pcmeiners]

40x100x12 walls are insulated ceiling is not.

Un-insulated? do you have a nuke reactor or do you enjoy burning money?

Insulate the ceiling at least, then think about mini splits. Single zone mini splits are very efficient compared to multi zone units. aside from providing redundancy.

Have garage which is 1/3 of yours, fully insulated, with a 12k Fujitsu low temp unit (very efficient/expensive) which is sufficient for my use, I do not have the machinery you have. Even with insulation you are going to need more then 3 single zone units to cool the entire area.

 

[JD291]

So unfortunately life got in the way and I just spent the last week working on this. outdoor unit is damaged. what are my options besides dumpster and buying another?

edit. just pissed at myself for not catching this and making time to get it in right away.

I looked everything over really well I thought. Never thought to look at the inside...

Looks minor to me. Run it.

 

[llaht]

you've a challenge, those CNC machines will give off heat, and the coolant used for machining will mist off raising humidity.
not so sure you have 'enough' but certainly insulation is your friend.

 

[dscheidt]

I have mostly given up trying to use manual J load calculators for mini-splits, they really don't seem accurate for inverter technology.

Heat load is entirely independent of the technology used to manage it. If a contractor gave me that line, I’d show him the door before he started the next sentence, because he’s clearly a hack who wants to sell more expensive equipment than required.

I will believe that the assumptions in a manual S calculation are wrong for mini splits, but that’s a different discussion.

 

[pcmeiners]

what are my options besides dumpster and buying another?

What is damaged ?, if only the fins, it is considered cosmetic, also fins can be straightened with a coil comb.

Another point with multiple mini splits, assuming they are the same make, it would pay to pickup spare parts from auction or Ebay. Further down the rode Ebay or FB will have cheap duplicates of your installed units if you install a popular series, at roughly <1/3 the original cost. Aside from the redundancy of installing multiple unit, a failure of a unit is not an "emergency repair", the other units give you time to shop around for either a repair or new unit.

 

[WildBill]

Heat load is entirely independent of the technology used to manage it. If a contractor gave me that line, I’d show him the door before he started the next sentence, because he’s clearly a hack who wants to sell more expensive equipment than required.

I will believe that the assumptions in a manual S calculation are wrong for mini splits, but that’s a different discussion.

So I'm a hack you would fire but you also agree with what I said? And what does selling more expensive equipment have to do with anything I said, where I actually listed a really inexpensive option that OP bought a year ago? Do you always just look for stuff to complain about? Do you need a hug or something?

 

[dscheidt]

So I'm a hack you would fire but you also agree with what I said? And what does selling more expensive equipment have to do with anything I said, where I actually listed a really inexpensive option that OP bought a year ago? Do you always just look for stuff to complain about? Do you need a hug or something?

No, you said you don’t believe in manual J. Manual J is heat loss/ gain. Manual S is sizing, based on manual J, some building considerations, and equipment type. Manual D is ductwork. If you don’t know that, then clearly you’re not a professional, and any who held themselves out as one would be a hack, at best.

Done properly, manual J gives an accurate indication of the required BTU of heat or cooling required. “Not believing “ in manual J exactly the sort of thing I hear from hcac contractors that are too stupid, too lazy, or too set on scamming to do it properly. I would, and have, not hire someone just because of that.

The manual S numbers are a little more complicated, and doing it properly is much harder, and because it includes equipment behavior, it is entirely possible that it’s wrong, especially for high efficiency and high turndown ratio equipment.

 

[Brandon_oma#692]

Looks minor to me. Run it.

Heat load is entirely independent of the technology used to manage it. If a contractor gave me that line, I’d show him the door before he started the next sentence, because he’s clearly a hack who wants to sell more expensive equipment than required.

I will believe that the assumptions in a manual S calculation are wrong for mini splits, but that’s a different discussion.

No refrigerant in the unit because it all leaked out. Add nitrogen and at less than 50 psi it starts leaking out in that location.

 

[Brandon_oma#692]

Un-insulated? do you have a nuke reactor or do you enjoy burning money?

Insulate the ceiling at least, then think about mini splits. Single zone mini splits are very efficient compared to multi zone units. aside from providing redundancy.

Have garage which is 1/3 of yours, fully insulated, with a 12k Fujitsu low temp unit (very efficient/expensive) which is sufficient for my use, I do not have the machinery you have. Even with insulation you are going to need more then 3 single zone units to cool the entire area.

you've a challenge, those CNC machines will give off heat, and the coolant used for machining will mist off raising humidity.
not so sure you have 'enough' but certainly insulation is your friend.

Have a couple roof leaks. Found a couple small ones but have not found the worst one. Can't insulate before that, not sure if I can after. Building is an old machine shed. Trusses about every 10 feet. Was probably never intended to hold a ceiling or insulation. Building had the ceiling when I moved in. it was built in the 60's or 70's with no info on it.

I can open the doors and run a bunch of fans or try this. I would think standing in front of an ac unit will feel better than standing in front of a fan. If I can have it dryer and a cool breeze I am happy. currently 80 degrees and 84% rh inside. Nothing has ran this week. Getting ready to start for the weekend.

 

[Notgrownup]

I just spoke to a HVAC guy the other day about a 50x100x16 storage unit for work. We need to Keep the temps under 85 and humidity at bay some. He said 2 ministers would help with 2 dehumidifier but we would benefit from like 5 10’ fans

 

[pcmeiners]

Have a couple roof leaks. Found a couple small ones but have not found the worst one. Can't insulate before that, not sure if I can after. Building is an old machine shed. Trusses about every 10 feet. Was probably never intended to hold a ceiling or insulation. Building had the ceiling when I moved in. it was built in the 60's or 70's with no info on it.

Unlikely you could not suspend a ceiling with a high R value insulation or the building would not be standing today due to it's first heavy snow decades ago. Please take a couple pictures of the interior of roof and post. Drop ceiling with insulation are very light compared to a normal ceiling and a relatively cheap/fast to install verses a standard drop ceiling .

"I just spoke to a HVAC guy the other day about a 50x100x16 storage unit for work. We need to Keep the temps under 85 and humidity at bay some. He said 2 ministers would help with 2 dehumidifier but we would benefit from like 5 10’ fans"

NotGrownUP.....
Ministers as in mini splits? Religious folks will not help cool your place down.
Assuming mini splits, (2) fair sized one will cool you down but do not expect to get to normal AC temps. Two units would also remove considerable humidity, no need for dehumidifiers . Aside from that dehumidifiers create more heat.
Without insulation at the ceiling level, even with normal sized mini splits it will be hotter than hell with fans circulating interior air. You will be cooler without fans, letting cool air sink and stratify closer to the floor. If you had an insulated ceiling then fans would be good.

Suggest you find a new HVAC guy, he needs training, as what he states is BS. What your likely getting is........

"If you can't dazzle them with brilliance, baffle them with ********"​

 

[Brandon_oma#692]

Unlikely you could not suspend a ceiling with a high R value insulation or the building would not be standing today due to it's first heavy snow decades ago. Please take a couple pictures of the interior of roof and post. Drop ceiling with insulation are very light compared to a normal ceiling and a relatively cheap/fast to install verses a standard drop ceiling .

"I just spoke to a HVAC guy the other day about a 50x100x16 storage unit for work. We need to Keep the temps under 85 and humidity at bay some. He said 2 ministers would help with 2 dehumidifier but we would benefit from like 5 10’ fans"

NotGrownUP.....
Ministers as in mini splits? Religious folks will not help cool your place down.
Assuming mini splits, (2) fair sized one will cool you down but do not expect to get to normal AC temps. Two units would also remove considerable humidity, no need for dehumidifiers . Aside from that dehumidifiers create more heat.
Without insulation at the ceiling level, even with normal sized mini splits it will be hotter than hell with fans circulating interior air. You will be cooler without fans, letting cool air sink and stratify closer to the floor. If you had an insulated ceiling then fans would be good.

Suggest you find a new HVAC guy, he needs training, as what he states is BS. What your likely getting is........

"If you can't dazzle them with brilliance, baffle them with ********"​

I already have a ceiling. I don't understand what you mean by suspending a drop ceiling. Current ceiling is at 12 ft and I would not want it any lower. Trusses are actually about 8 ft apart not 10.

Pictures are poor. It is what I have from before. Gives you an idea.





I would need to put insulation above it and I currently have a few roof leaks so whenever I put up there is going to be wet. I tried sealing up the area last year where I thought the biggest leak was and it's better but I still get some drips during a heavy rain.

 

[Brandon_oma#692]

It is the old tin and nailed on. Doubt the nails would pull very well so you probably just got to reseal them. Otherwise find somebody to pull them all one at a time and replace with screws. Roughly 60 by 100 so it's a lot.

Tried hiring somebody a couple years ago to come out and give me a solution to improve it. Only thing they would do is put a whole new roof on.

Area where the lean to meets doesn't overlap enough.


Area where the solar is that is not the area with the bad leak. The area with the bad leak I need to get up there and watch next time. It rains bad

 

[Brandon_oma#692]

83° 81% RH inside. 86° and 75% outside currently. Guess I might as well open it back up

 

[Brandon_oma#692]

Just climbed up to take a look and get some pictures. I taped the seam where it was leaking a few years ago and that's a lot better. Looking around. I just realized that part of the roof were the biggest leak is has some type of ridge vent. Pretty sure if the wind's blowing hard enough it's leaking in that vent. The rest of the ridge is not vented. Might rip that off and stick a gable vent in

 

[pcmeiners]

Did not pay to the machine shop pictures, sorry...

Temporarily you could blow fiberglass insulation up in the ceiling, so what if it gets wet as long as you get to the leaks in a reasonable time, water will travel through fiberglass, not adding much weight, when wet it will dry out in a few days of heat . Once the leaks are sealed and you do not expect more leaks (?) you could add a layer of cellulose to stop air flow through the fiberglass ( >5"); cellulose has a weight issue once wet, takes much longer to dry. Fiberglass allow air movement through it, and loses R value the colder it gets, thus the idea of capping it with cellulose later on .