Mini Split Install Done!

[Jack Frederick]

My experience in DIY jobs of this type, and keeping Brad's position in mind, is that you end up paying one way or the other. If you supply the machinery, the labor bill increases to cover the contractors costs, and they are substantial and that is fair. Perhaps a way to handle this is to ask if the contractor will allow you to mount the condensing unit and the interior mounting bracket only, drill the holes and have the 220v disconnect located. He supplies the equipment, does the secret sauce and gets off the job in one piece. In order for this to work, the contractor has to be able to make it a single call. In and out. If you do this work, take photos and go see the contractor to show what is in place before he shows up. Most hvac contractors are slammed with work. Something like this might work out. Brad?

[Tim M Tuttle]

My experience in DIY jobs of this type, and keeping Brad's position in mind, is that you end up paying one way or the other. If you supply the machinery, the labor bill increases to cover the contractors costs, and they are substantial and that is fair. Perhaps a way to handle this is to ask if the contractor will allow you to mount the condensing unit and the interior mounting bracket only, drill the holes and have the 220v disconnect located. He supplies the equipment, does the secret sauce and gets off the job in one piece. In order for this to work, the contractor has to be able to make it a single call. In and out. If you do this work, take photos and go see the contractor to show what is in place before he shows up. Most hvac contractors are slammed with work. Something like this might work out. Brad?

I was all in for $1500 by doing the majority of the install myself. That wouldn't even cover the unit if I went with Mitsubishi and I was looking at probably another $1000-2000 for installation. I am well aware that I didn't get as good of a unit as a Mitsu but it was either this or nothing. For now at least.

[Bob Bouis]

I'm not sure of the legalities of it where you live, but mini split installs are easy DIY work and the tools for hooking one up (vacuum pump, micron gauge, mini split adapter, hoses or gauges, flare tool, and...uh...wrench...) cost less than hiring someone to do it.

You don't get a warranty but with generics they're not worth anything anyway.

[Tim M Tuttle]

I'm not sure of the legalities of it where you live, but mini split installs are easy DIY work and the tools for hooking one up (vacuum pump, micron gauge, mini split adapter, hoses or gauges, flare tool, and...uh...wrench...) cost less than hiring someone to do it.

You don't get a warranty but with generics they're not worth anything anyway.

The manufacturer of my unit warrants DIY installs.

There's also Mr Cool units which are made specifically for DIY installs. The only problem with those is that you may have excess lineset rolled up next to the outdoor unit.

[Robert Hayward]

mini split installs are easy DIY work and the tools for hooking one up (vacuum pump, micron gauge, mini split adapter, hoses or gauges, flare tool, and...uh...wrench...) cost less than hiring someone to do it.

That was what my calculations for the cost of my self installed mini showed when I was thinking about a mini. I even bought pro grade tools to do the job, just to be safe. An eccentric flaring tool and torque wrench with the proper wrenches to fit my flare nuts. Around here the auto parts stores will give for free the vacuum pump, gauges and hoses with a credit card deposit equal to the value of the stuff you are walking out of their store with. Keep them as long as you need them, return them and they refund the deposit.

The compressors are pre charged with freon and the compressor unit has valves built in to it. After you pump down the lines and evaporator just open the freon valve and you are done.

Please note that I have an extensive construction background ( not A/C though ) so the install may have been easier for me than someone never involved with the trades.

[Steve Catts]

Tim,
I've been looking at the Pioneer units as well - price is great and the warranty is reasonable. I see you got the unit with the high SEER rating at 20.8 which runs almost $300 more than their 17 SEER unit. If the primary difference is energy efficiency, the cost to operate is only a few bucks a year difference. What am I missing that would make the more expensive unit worth the extra cost?

I have a 500 sf +/- garage in Houston. 9' ceiling. Well insulated. Two exterior walls with brick. No windows. Two single doors - pretty well sealed. Most of the 'rule of thumb' tables suggest a 12,000-BTUh unit. The Pioneer 12k unit ranges from 4500BTUh to 16700BTUh. I don't want to come up short but also know that oversizing can be a problem. Can anyone offer some thoughts about if the 12k will do or do I need to upsize to the 18K (7600BTUh to 24800BTUh)?

Thanks! I don't want to get this wrong!
Steve

[Tim M Tuttle]

Tim,
I've been looking at the Pioneer units as well - price is great and the warranty is reasonable. I see you got the unit with the high SEER rating at 20.8 which runs almost $300 more than their 17 SEER unit. If the primary difference is energy efficiency, the cost to operate is only a few bucks a year difference. What am I missing that would make the more expensive unit worth the extra cost?

I have a 500 sf +/- garage in Houston. 9' ceiling. Well insulated. Two exterior walls with brick. No windows. Two single doors - pretty well sealed. Most of the 'rule of thumb' tables suggest a 12,000-BTUh unit. The Pioneer 12k unit ranges from 4500BTUh to 16700BTUh. I don't want to come up short but also know that oversizing can be a problem. Can anyone offer some thoughts about if the 12k will do or do I need to upsize to the 18K (7600BTUh to 24800BTUh)?

Thanks! I don't want to get this wrong!
Steve

Hey Steve,

I went with the higher efficiency unit because it will still heat when the outside temp drops to as low as -13. The other unit only heats down to 5 I think.

As far as sizing goes, I recommend calling Pioneer and giving them the specs of your garage. They will then be able to size the unit appropriately. Load questions are a little out of my wheelhouse.

[Bob Bouis]

Keep in mind that most a/c sizing guides are oriented toward residences that are climate controlled 24/7. It depends on how you're heating and cooling your shop and your personal preferences as to comfort, but you're often better off oversizing a mini split so you can quickly bring the temperature to your comfort level. They automatically slow down to as little as 1/2-to 1/3 the full load capacity when it's not needed.

A lot of people think it's more efficient to set your thermostat at one place and keep it there -- that's bunk. The unit is at its most efficient when it runs full blast without stopping, and it rate of heat exchange between inside and outside [and thus the total BTUs required] depends on the difference in temperature over time.

[Bill Dufour]

The flare nuts are a wierd size. Not really metric not really English. I think I ended up using one metric and one English wrench at the same time. I bought crowfoot wrenches ahead of time to use with my torque wrench. For the big pipe I bought a tubing bender. much better then the spring type bender.
Bill D

[Steve Catts]

Great! Being in Houston will allow me to avoid that -13 issue! Although this last winter makes me wonder! I'll call Pioneer.

[Jack Frederick]

The manufacturer of my unit warrants DIY installs.

There's also Mr Cool units which are made specifically for DIY installs. The only problem with those is that you may have excess lineset rolled up next to the outdoor unit.

If if there is excess line set you do not want to leave it coiled. It will trap oil in the low spots. Lay off excess line set in a serpentine fashion.

[Thomas Crawford]

Great! Being in Houston will allow me to avoid that -13 issue! Although this last winter makes me wonder! I'll call Pioneer.

Interested in what you come up with, especially on the oversizing. Trying to figure out a unit in the next week and a half or so.

[Bob Bouis]

I've been looking at the Pioneer units as well - price is great and the warranty is reasonable. I see you got the unit with the high SEER rating at 20.8 which runs almost $300 more than their 17 SEER unit. If the primary difference is energy efficiency, the cost to operate is only a few bucks a year difference. What am I missing that would make the more expensive unit worth the extra cost?

Efficiency is not a good reason to get high seer units for a shop if you're not going to cool it 24/7.

I have a 500 sf +/- garage in Houston. 9' ceiling. Well insulated. Two exterior walls with brick. No windows. Two single doors - pretty well sealed. Most of the 'rule of thumb' tables suggest a 12,000-BTUh unit. The Pioneer 12k unit ranges from 4500BTUh to 16700BTUh. I don't want to come up short but also know that oversizing can be a problem. Can anyone offer some thoughts about if the 12k will do or do I need to upsize to the 18K (7600BTUh to 24800BTUh)?

The rule of thumb is really off here. For starters that BTU range probably isn't what you think it is; IIRC it's the max and min btus the thing will put out while running full blast in varied environmental conditions. Air conditioners are heat pumps, so they produce less cooling the hotter it is outside. Cool temperatures inside also reduce efficiency.

For 500 sq ft that was used intermittently as a shop I would go with 24k. 18k would be the minimum.

[Bob Bouis]

If I can elaborate. The reason mini splits have such high efficiency ratings is that they're really good at keeping a space 78 degrees over the course of a year, all day and all night (hence "SEER, seasonal energy efficiency ratio [or whatever it stands for; the first word is seasonal]. The SEER test is designed for continuously occupied spaces. "Seasonal" cooling is mostly low demand where the variable speed of the mini split makes it very efficient. When a mini split runs full blast on a hot summer day, they generally aren't any more efficient than any other air conditioner [look at the EER rating].

If you're just using the thing to make your garage cool when you want to work in it, you're better off getting a bigger, nominally less efficient air conditioner so you can bring the temperature to where you want it fast. It's not just more convenient, it's more efficient. The reason is that the BTUs required to keep a space a certain temperature depend on the difference between the indoor and outdoor temperatures over time, and the total BTUs and thus total energy use depend on time. So, all things being equal, it takes the same amount of btus to keep your garage 30 degrees cooler than the outside for 8 hours as it does to keep it 10 degrees cooler for the whole day. I know which one I'd rather have for my garage. Now, that might be a bit misleading as the a/c efficiency falls off somewhat as the temperature difference increases, you don't set your thermostat based on temperature difference, etc., but it's a real consideration. If you have to run the a/c for 4 hours to get it to the temperature you want you've had a lot more heat transfer back into your shop during that time than you would if you'd spent 1 hour doing it with a bigger unit -- less efficient (not to mention a PITA).

Of course running the a/c 24/7 helps to control humidity (though not very well; get a separate dehumidifier). Dehumidifiers raise the temperature a little which lowers relative humidity. Air conditioners obviously lower the temperature which raises it. And the most humid time of the day is the coolest (early mornings, it's where dew comes from). Two strikes against air conditioners as dehumidifers.

[Robert Hayward]

I have no schooling regarding HVAC sizing, efficiencies or anything else related to it. With that said, before I did my mini for my garage shop I asked a commercial chiller expert friend for advice. I was more or less told to get one ton at the highest SEER in my price range. Running the thing 24/7 here in the Tampa Bay area my electric bill went up $25 in the month of August, the hottest month. Less in other months.