Author Topic: Minisplit HVAC DIY?  (Read 1948 times)

tennisray

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Minisplit HVAC DIY?
« on: February 07, 2020, 09:53:15 AM »
I've read this thread, https://forum.mrmoneymustache.com/do-it-yourself-forum!/is-installing-a-mini-split-a-diy-job/msg1924279/#msg1924279

I decided to go ahead and install in my basement (previous owner finished drywall, so conventional unit would have to rip open sheetrock, and I like the efficiency of the minisplits).

I bought a cheap, Pioneer brand.  I set the indoor unit, cut a hole for the lineset through the wall, and set the outdoor unit. 

My one hesitation is using a (relatively) cheap vacuum pump to vacuum the lines.  Many youtube vids show that diy'ers did this, but I'm not so sure the longevity if they didn't get all the moisture out. 

I asked around and hvac techs want $400 to vacuum/pressure test. It's a 2 hour job, and in talking with them, they don't seem too concerned about getting a deep vacuum (they don't use a micron guage).  So, besides testing with Nitrogen under pressure, it seems like a lot of $. 

I'm willing to take a chance since the unit was cheap ($750) and hoping it lasts 5 years, but wanted to ask for any advice/warnings/motivation others may have.

zolotiyeruki

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Re: Minisplit HVAC DIY?
« Reply #1 on: February 07, 2020, 10:28:50 AM »
The tiny bit of moisture that may remain in the system after you apply a vacuum is unlikely to be a problem.  It's a problem if there is enough to build up ice somewhere where the refrigerant is really cold.  Assuming your system has no leaks, once you evacuate, fill, and seal it, it's not going to get any additional water vapor in it.  So if it runs fine for the first few days, you can pretty much assume it won't cause problems down the line.

I haven't done residential A/C, but I did it on my car once, and it was no big deal.

tennisray

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Re: Minisplit HVAC DIY?
« Reply #2 on: February 07, 2020, 10:53:48 AM »
The tiny bit of moisture that may remain in the system after you apply a vacuum is unlikely to be a problem.  It's a problem if there is enough to build up ice somewhere where the refrigerant is really cold.  Assuming your system has no leaks, once you evacuate, fill, and seal it, it's not going to get any additional water vapor in it.  So if it runs fine for the first few days, you can pretty much assume it won't cause problems down the line.

I haven't done residential A/C, but I did it on my car once, and it was no big deal.

That helps, thanks.  I thought if there was still moisture that I may not find out until it stops working well after a year or so.  Someone else vacuum'd it with the same equipment and his has been running well for almost a year.

Syonyk

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Re: Minisplit HVAC DIY?
« Reply #3 on: February 09, 2020, 12:12:32 AM »
Is a good vacuum pump and gauge set less than $400?  I honestly don't know how much they cost, but I'd call around and see if you can rent a set.

It sounds like you already have a unit, but I've seen mini splits with quick disconnects - pre-purged and everything.  Just snap the lines together.  No idea how long that connection holds up, but I know it exists.

Milspecstache

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Re: Minisplit HVAC DIY?
« Reply #4 on: February 14, 2020, 12:50:51 PM »
The problem with those DIY sets is that you result in a large coil of noticeable refrigerant hose which I think opens up opportunity for theft/damage/etc.  My plan is to buy a pump and gage set and begin doing my own vacuuming the next time.  But I also plan on doing about 4 units this summer for my various rental properties.

dilinger

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Re: Minisplit HVAC DIY?
« Reply #5 on: February 16, 2020, 05:43:21 PM »
Is a good vacuum pump and gauge set less than $400?  I honestly don't know how much they cost, but I'd call around and see if you can rent a set.

It sounds like you already have a unit, but I've seen mini splits with quick disconnects - pre-purged and everything.  Just snap the lines together.  No idea how long that connection holds up, but I know it exists.

I've installed two types; the Friedrich Breeze DIY and the MrCool DIY (both 1 ton units). The Friedrichs didn't last very long; the first had a board failure after about 3 years, and the second developed a leak after roughly the same amount of time. I'm not sure where the leak happened; I had a repair guy out to recharge the lineset twice before I gave up on it, and he couldn't quickly identify the leak.

The older MrCool DIY that I have has been chugging along for roughly 3 years now, and has held up nicely.

The biggest problems with those DIY models isn't the connection; it's the lack of efficiency (they were okay in Seattle where it rarely gets below freezing, but I wouldn't install them where I live now in NY), the visible ugliness of the coiled-up lineset on the site of the house (though I saw a pretty great video where someone buried the extra lineset below the outdoor compressor unit, which is something that I wish I had thought of!), and the cost. The DIY units typically run around $1500, but a similar non-DIY model of the same efficiency and load will be half that.
« Last Edit: February 16, 2020, 05:46:07 PM by dilinger »

tennisray

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Re: Minisplit HVAC DIY?
« Reply #6 on: February 21, 2020, 09:09:01 AM »
I went ahead and installed.  Paid electrician to run the 240v line.  Paid a HVAC tech $400 to vacuum/set up.  All in all, I'm happy (we'll see how it cools when summer gets around).  If I had to do it over, I would have purchased the total DIY kit from Costco, due to their return policy (didn't find out they carried it until recently).  I don't like the idea of the extra line set coiled up, but I would also try to hide it like in that video (I saw that one, too!)

dilinger

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Re: Minisplit HVAC DIY?
« Reply #7 on: February 24, 2020, 07:39:11 PM »
I just noticed that Home Depot now carries a 3rd gen MrCool DIY unit. 22 SEER, 10 HSPF.  That pretty much takes care of any efficiency concerns I had with the DIY models!

tennisray

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Re: Minisplit HVAC DIY?
« Reply #8 on: February 25, 2020, 05:38:59 AM »
I just noticed that Home Depot now carries a 3rd gen MrCool DIY unit. 22 SEER, 10 HSPF.  That pretty much takes care of any efficiency concerns I had with the DIY models!

Yes, I initially was mad I didn't use Costco.com to buy it, but apparently, they only sell the gen2.  Gen3 is easier to work with supposedly.  I'd still advise waiting to see if costco starts selling the gen 3.  Their return policy would make any price difference worth it to me.

I purchased from amazon, since they offered a 3rd party extended warranty to 4years for $77. I figured if I messed something up, that this warranty service may be able to help.

dilinger

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Re: Minisplit HVAC DIY?
« Reply #9 on: March 02, 2020, 02:15:57 PM »

I purchased from amazon, since they offered a 3rd party extended warranty to 4years for $77. I figured if I messed something up, that this warranty service may be able to help.

My credit card has a 24mo extended warranty (on top of the manufacturer warranty) for stuff like this. That *almost* covered my dead Friedrich units, but it was out of warranty by like 2 months.  $77 for an extended warranty would've totally been worth it, in hindsight.

JLee

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Re: Minisplit HVAC DIY?
« Reply #10 on: March 02, 2020, 02:19:30 PM »
I just noticed that Home Depot now carries a 3rd gen MrCool DIY unit. 22 SEER, 10 HSPF.  That pretty much takes care of any efficiency concerns I had with the DIY models!

Yes, I initially was mad I didn't use Costco.com to buy it, but apparently, they only sell the gen2.  Gen3 is easier to work with supposedly.  I'd still advise waiting to see if costco starts selling the gen 3.  Their return policy would make any price difference worth it to me.

I purchased from amazon, since they offered a 3rd party extended warranty to 4years for $77. I figured if I messed something up, that this warranty service may be able to help.

I believe the Costco credit card will add 24 months of warranty even if you don't buy from Costco.

Le Poisson

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Re: Minisplit HVAC DIY?
« Reply #11 on: March 03, 2020, 09:33:44 AM »
How did you folks calculate the size of units you needed for this?

tennisray

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Re: Minisplit HVAC DIY?
« Reply #12 on: March 03, 2020, 12:25:40 PM »
How did you folks calculate the size of units you needed for this?

There are online calculators, but there are a lot of variables. Best bet is get quotes from hvac pros. I had 3 quotes. Two said 12k btu, one said 9k btu. I went with the 12k.

dilinger

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Re: Minisplit HVAC DIY?
« Reply #13 on: March 09, 2020, 11:56:06 PM »
How did you folks calculate the size of units you needed for this?

There are online calculators, but there are a lot of variables. Best bet is get quotes from hvac pros. I had 3 quotes. Two said 12k btu, one said 9k btu. I went with the 12k.

It also depends on factors like insulation. I mostly used 12k units based on very rough living space calculation. They were undersized compared to my prior oil furnace, apparently, so we used space heaters the first winter.  However, the next winter I had insulation blown into the walls and attic (which was relatively inexpensive), and suddenly one 12k units per floor was more than enough to handle even the coldest Seattle winter. When I sold the place, I added a couple 500W Envi wall heaters which are nice looking, relatively cheap, and could provide supplemental heat in case of any polar vortex events making it freakishly colder than normal.