DIY Mini Splits
#28
Thooks brings up an important point, it takes some time to pull that much of a vacuum with a good pump.

I wouldn’t mind mounting the stuff but I think I’d defer to someone else when it came time to wrench the connections.
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#29
(05-08-2018, 08:31 AM)thooks Wrote: For those playing at home-

Like Blackhat says, you'll need to pull down below 400 microns of vacuum.  Takes a decent pump and what it really means is your piping and connections better be tight.

I recently replaced a split system in my house and did most everything except run the refrigerant piping and put a larger flue through the roof.  The guy I hired to come finish up put his vacuum pump on the refrigerant piping and started it up.  It took nearly an hour to pull down below 400 microns.

What this does is make darn sure the piping is leak-free.  Can you imagine a vacuum pump pulling on a system for over an hour?  The slightest imperfection is going to show up quickly.


And I'm sorry, but I would NOT consider installing a ductless / mini split a DIY project.  Nope.

These are fairly small systems, my small vacuum pump (the smallest HVAC one that Amazon sold) was easily able to pull the system down as far as could be read on the manifold gauges within 15 minutes, once all leaks were fixed.  I kept the pump running for over 2 hours (checking on it to make sure it was not overheating) to ensure that the system was pulled as low as that pump could pull and to ensure all of the moisture that could be evaporated out of the system, was.  I agree that it is not something that would be a typical DIY project since you do need to buy (unless you can rent) a vacuum pump that would likely never be used again, but the typical DIY'er.  As I stated in a previous post, a DIY could do approx. 90-95% of the work up to the point of pulling a vacuum.
Paul
They were right, I SHOULDN'T have tried it at home!
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#30
(05-08-2018, 08:40 AM)Pirate Wrote: After pulling vacume, and opening valves, did you measure pressures, or did it work fine?

Are you asking me?  Honestly, I can't remember if I left the gauge on.  I would think I did just to see if the low side pressure (the only side that has a port to check pressure) was in range of where it should be, but then I don't know if my gauge set went up that high, I was using an automotive set, R410a works at very high pressures.  I know it has worked well, no indication of being low on refrigerant since I put it in.  As I said in my previous reply to the OP, I did have an issue with one of the thermistors (I suspect it was the one in the inside unit because I was spraying a lot of paint that summer and fall, at the time I was not running it for AC since I had not run the condensate drain outside, when I started the HP back up in the winter, it threw an error code).
Paul
They were right, I SHOULDN'T have tried it at home!
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#31
Back in the early 70's I worked at a garage, and we installed hang on acnin cars. After installing and hooking up vac pump, we let suck down all nite! No moisture in that system!
Temps at registers was just above freezing!
I long for the days when Coke was a soft drink, and Black and Decker was a quality tool.
Happiness is a snipe free planer
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#32
(05-06-2018, 08:38 PM)blackhat Wrote: They aren't compression fittings, 99% are flare fittings.  Flaring sounds easy but when you start hitting the 500 psi range they have to be right for a long time.  The unit connections are usually a unique thread, your standard refrig gauges and hoses don't fit.  You need at least one adapter.  You don't just need a vac pump, you need a vac pump capable of pulling a very deep vac, below 400 microns and preferably below 200 and staying there.  You can't measure those vac levels with a gauge set, you need a reliable digital gauge to verify your vac.  You most definitely should not use compressed air to pressure test your lines, it contains moisture and possible contaminants.  A nitrogen tank is the correct pressure test means.  Oh, by the way, you have to get a regulater for that tank. Now, if your lines are outside the factory charge limits, you need to weigh, within a 1/10 ounce, the additional amount of refrigerant required.  A bath room or kitchen scale won't do that.


There are a significant investment in specialized tools to do the job right. I would expect a tech to be on site roughly 3 hours.  $100/hr???
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#33
I installed my own 12 years ago and have had no problems. Mine (Mitsubishi Mr Slim) came with pre-charged line sets and the compressor was also pre-charged. Run the electric, and hook up the lines and a drain and turn it on. If your lines are to long just do a loop with no kinks. Pay close attention to the slope of the drain so you don't have a wet floor under the inside unit. I like the splits because they can be placed just about anywhere with a minimum of effort. Mine was delivered to my door for $1100 and change in 2005. Best quote I got was $3300 from the locals.
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#34
(05-08-2018, 08:31 AM)thooks Wrote: For those playing at home-

Like Blackhat says, you'll need to pull down below 400 microns of vacuum.  Takes a decent pump and what it really means is your piping and connections better be tight.

I recently replaced a split system in my house and did most everything except run the refrigerant piping and put a larger flue through the roof.  The guy I hired to come finish up put his vacuum pump on the refrigerant piping and started it up.  It took nearly an hour to pull down below 400 microns.

What this does is make darn sure the piping is leak-free.  Can you imagine a vacuum pump pulling on a system for over an hour?  The slightest imperfection is going to show up quickly.


And I'm sorry, but I would NOT consider installing a ductless / mini split a DIY project.  Nope.

I've done it. 3 zone 36K BTU.  I wouldn't do it again with current job and family responsibilities.  Took about a month of nights and weekends and I invented some new swear words along the way - mostly due to tight working conditions when installing ceiling units.

I did have a pro vac down the system and then spin the valves to charge the lines.  Took 30-40 minutes.  He is a neighbor.  My wife baked him a pie and I bought him $100 Harley Davidsen gift card.  He was pretty happy with that!
You are frequently puzzled by things you tell us you fully understand. - Bob10 to EH 9/22/16

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