Any experienced mini split experts...opinion on open system

[jav]

I purchased a newer 24K BTUH Sanyo mini split (20 SEER) that was known to have an issue with the inside unit - compressor was declared sound. Being an engineer with universal refrigeration license, I really want some hands-on with this technology as lots of HVAC guys around here shy away from the mini's... or at least aren't willing to delve too deeply into them. Plus the price was right so I bought it.

BUT- It never occurred to me that the licensed tech that removed the system didn't pump it down. When I got the unit home - I found both service ports in the open position and the system completely empty of R410A.

My question is- knowing the system has been open to atmosphere for weeks or months, what's the likelihood that the compressor has been compromised? My plan was to bench setup the system and troubleshoot the inside unit but I'm concerned about the compressor.

Am I rightly concerned? Any suggestions on mitigating damages? I'm not too versed on the mini's but I've not heard of any system oiling requirements/driers etc... thoughts?

 

[acmikee]

just put it on a vacuum pump and you'll be fine
but before you do anything check to see if the indoor unit is still available.

 

[sms1974]

compressor is probably fine you will need to replace any filter driers, if there isn't one in the condenser I would install one in the liquid line. most mini's use POE oil which is hygroscopic meaning it absorbs moisture, a vacuum pump won't pull the moisture from the oil the only way to get it out is the descant in the filter driers, and plan on replacing them again in a year...

 

[justinjoyal]

Blow it out with nitrogen, then vacuum down to 500 microns.

Triple-evac if you feel like it.

I wouldnt install a filter-dryer, but if you do, make sure it flows both ways if you have a heatpump...

 

[rlitman]

compressor is probably fine you will need to replace any filter driers, if there isn't one in the condenser I would install one in the liquid line. most mini's use POE oil which is hygroscopic meaning it absorbs moisture, a vacuum pump won't pull the moisture from the oil the only way to get it out is the descant in the filter driers, and plan on replacing them again in a year...

Install a window with a moisture indicator when you put the filter/dryer in.

I'd be more comfortable making sure all of the oil is drained from the system, and then refill with the correct amount of fresh oil right before recharging.

 

[jav]

Thanks guys. A few things:

This unit is AC only (no heat pump). One of the reasons I bought this was that I have full manuals for it including owners, installation, and service. The documentation is surprisingly thorough allowing component level diagnostics. The inside unit is no longer sold (new) but parts are available- so i wasn't too worried about fixing the one I have.

I was most worried about the compressor possibly rusting/oxidizing due to being open to atmosphere for extended periods. In the technical specs, compressor oil type and capacity is NOT even listed. There is a large note that reads " No addition of compressor oil for R410A- No additional charge of compressor oil is permitted".

I've also read to avoid drawing too deep of a vacuum as it could change the effectiveness of the oil. I'll be shooting for 300-500 microns. I found it odd that there's only a low side gauge port?

As to the addition of a drier and sight glass- I may do that if I get the system fully functional but for now- I need to bench test it to try and fix it and I was trying avoid compressor damage if at all possible.

 

[bzinsky]

I've also read to avoid drawing too deep of a vacuum as it could change the effectiveness of the oil. I'll be shooting for 300-500 microns. I found it odd that there's only a low side gauge port?

Well I mean the vacuum just clears the lines of moisture and armosphere, its not under a vacuum once you fill it with refrigerant. Don't see how you could make it too low.

I'm contesting this mostly because I pulled all 20 of my down to 40-50 microns lol.
Not to mention when you disconnect the vacuum pump, you're going to get a tiny bit of air back in it. Even the smallest amount will raise the reading considerbly. I wouldn't be surprised if when I disconnect at 50 microns, they went back up to 300.

 

[eddieK]

I purchased a newer 24K BTUH Sanyo mini split (20 SEER) that was known to have an issue with the inside unit - compressor was declared sound. Being an engineer with universal refrigeration license, I really want some hands-on with this technology as lots of HVAC guys around here shy away from the mini's... or at least aren't willing to delve too deeply into them. Plus the price was right so I bought it.

BUT- It never occurred to me that the licensed tech that removed the system didn't pump it down. When I got the unit home - I found both service ports in the open position and the system completely empty of R410A.

My question is- knowing the system has been open to atmosphere for weeks or months, what's the likelihood that the compressor has been compromised? My plan was to bench setup the system and troubleshoot the inside unit but I'm concerned about the compressor.

Am I rightly concerned? Any suggestions on mitigating damages? I'm not too versed on the mini's but I've not heard of any system oiling requirements/driers etc... thoughts?

Nitrogen leak test it when you install it...install a liquid line filter drier and do a triple vacuum procedure. It should be fine. I know of no procedure to bench test these units, they (indoor and outdoor) must "talk" to each other.

 

[eddieK]

Thanks guys. A few things:

This unit is AC only (no heat pump). One of the reasons I bought this was that I have full manuals for it including owners, installation, and service. The documentation is surprisingly thorough allowing component level diagnostics. The inside unit is no longer sold (new) but parts are available- so i wasn't too worried about fixing the one I have.

I was most worried about the compressor possibly rusting/oxidizing due to being open to atmosphere for extended periods. In the technical specs, compressor oil type and capacity is NOT even listed. There is a large note that reads " No addition of compressor oil for R410A- No additional charge of compressor oil is permitted".

I've also read to avoid drawing too deep of a vacuum as it could change the effectiveness of the oil. I'll be shooting for 300-500 microns. I found it odd that there's only a low side gauge port?

As to the addition of a drier and sight glass- I may do that if I get the system fully functional but for now- I need to bench test it to try and fix it and I was trying avoid compressor damage if at all possible.

You do not charge these by super heat or sub cooling...that is why they do not have access to both sides of the system. There is a slight possibility there could be something in the compressor but it is hermetic, no way to determine damage without putting it into service.

 

[jav]

Well I mean the vacuum just clears the lines of moisture and armosphere, its not under a vacuum once you fill it with refrigerant. Don't see how you could make it too low.

I'm contesting this mostly because I pulled all 20 of my down to 40-50 microns lol.
Not to mention when you disconnect the vacuum pump, you're going to get a tiny bit of air back in it. Even the smallest amount will raise the reading considerbly. I wouldn't be surprised if when I disconnect at 50 microns, they went back up to 300.

Yes- I understand that but this is taken from:

http://alltemp.ca/wp-content/uploads/2013/10/JB-Principles-of-Vacuum-Presention.pdf

...and it concerns deep vacuum changing the properties of oil within the system already.

" Refrigeration oil has a vapor pressure and,
by going below 200 microns, you will de-gas
particles of the refrigeration oil. Be aware
that if you change the makeup of the oil, it
will no longer be a true lubricating oil"

 

[jav]

Nitrogen leak test it when you install it...install a liquid line filter drier and do a triple vacuum procedure. It should be fine. I know of no procedure to bench test these units, they (indoor and outdoor) must "talk" to each other.

Eddie- by bench testing... I mean to hook up the entire system leaving the compressor on the floor in my shop and putting the inside unit on a bench and "running" the system as if it were installed. That will allow me to probe all the test points to determine which components must be changed. It will also allow me to replace those components on the bench and retest. If I get the system fully operational, then I can pump it down and install it in it's final location (2nd floor of my shop).

 

[eddieK]

Well I mean the vacuum just clears the lines of moisture and armosphere, its not under a vacuum once you fill it with refrigerant. Don't see how you could make it too low.

I'm contesting this mostly because I pulled all 20 of my down to 40-50 microns lol.
Not to mention when you disconnect the vacuum pump, you're going to get a tiny bit of air back in it. Even the smallest amount will raise the reading considerbly. I wouldn't be surprised if when I disconnect at 50 microns, they went back up to 300.

Vacuum's that low will break down the refrigerant oil. This is taught at every level I have attended.

Refrigeration oil has a vapor pressure - by going below 200 microns, you will de-gas particles of the refrigeration oil. If you change the makeup of the oil, it will no longer be a true lubricating oil.

 

[eddieK]

Eddie- by bench testing... I mean to hook up the entire system leaving the compressor on the floor in my shop and putting the inside unit on a bench and "running" the system as if it were installed. That will allow me to probe all the test points to determine which components must be changed. It will also allow me to replace those components on the bench and retest. If I get the system fully operational, then I can pump it down and install it in it's final location (2nd floor of my shop).

In my experience these compressors are pretty hardy - They put them through rigorous slug testing...because people tend to think if they keep it on when it's not cooling properly it will eventually just fix itself. At least they seem to act that way.

 

[jav]

In my experience these compressors are pretty hardy - They put them through rigorous slug testing...because people tend to think if they keep it on when it's not cooling properly it will eventually just fix itself. At least they seem to act that way.

Good to know... now if I can just find the time to play with it. BTW- I've read conflicting info on the outdoor to indoor power/communication cable. I was planning on running 14/3/G inside flexible liquid tight ?? others say you can use straight honeywell TC minisplit cable but I don't see how that can be (code) acceptable - unprotected outside, inside the line cover or through the wall?

 

[justinjoyal]

Not to mention when you disconnect the vacuum pump, you're going to get a tiny bit of air back in it. Even the smallest amount will raise the reading considerbly. I wouldn't be surprised if when I disconnect at 50 microns, they went back up to 300.

You should not disconnect anything until the system is under positive pressure...

 

[bzinsky]

Vacuum's that low will break down the refrigerant oil. This is taught at every level I have attended.

Refrigeration oil has a vapor pressure - by going below 200 microns, you will de-gas particles of the refrigeration oil. If you change the makeup of the oil, it will no longer be a true lubricating oil.

I'm asking to know, not to argue.

But how is the oil going to be subjected to the low microns? When you vacuum the system down, the oil is still in the unit, and is only exposed to the vacuum the split second when you open the king valves.

 

[bzinsky]

You should not disconnect anything until the system is under positive pressure...

I don't believe that is possible without a traditional 3 gauge setup and a tank of 410. I just had a vacuum pump and a micron gauge. Had I left it connected it would have pulled the refrigerant through my hoses. Atleast I think it would.

 

[eddieK]

Good to know... now if I can just find the time to play with it. BTW- I've read conflicting info on the outdoor to indoor power/communication cable. I was planning on running 14/3/G inside flexible liquid tight ?? others say you can use straight honeywell TC minisplit cable but I don't see how that can be (code) acceptable - unprotected outside, inside the line cover or through the wall?

The wire I purchase is outdoor protected (ultra violet) and it is code except in particular circumstances - commercial / industrial etc

 

[eddieK]

I'm asking to know, not to argue.

But how is the oil going to be subjected to the low microns? When you vacuum the system down, the oil is still in the unit, and is only exposed to the vacuum the split second when you open the king valves.

True -

I spend so much time varying between start ups and compressor change outs...I forget that (start ups) and always hold to the less than 500 microns for 30 mins, isolate and be sure it does not rise above 1000 for 10 mins.

 

[Dagny]

I use an imperial 4 valve manifold. Shut the vac valve open the refrigerant.

 

[justinjoyal]

I don't believe that is possible without a traditional 3 gauge setup and a tank of 410. I just had a vacuum pump and a micron gauge. Had I left it connected it would have pulled the refrigerant through my hoses. Atleast I think it would.

It is indeed not possible if you're not working with the proper tools.

 

[jav]

The wire I purchase is outdoor protected (ultra violet) and it is code except in particular circumstances - commercial / industrial etc

Do you see a problem running individual 14AWG THHN inside 1/2" PVC liquid tight between the two units? 'm wondering if that would pose a problem for the communication line?

 

[LS6 Tommy]

just put it on a vacuum pump and you'll be fine
but before you do anything check to see if the indoor unit is still available.

Not so. At a bare minimum the compressor oil needs to be removed, possibly the system flushed, the oil changed and the liquid line drier (and suction line filter drier if it has one) needs to be replaced.

If it had actual water in it, it's junk.


On a separate note, this thread contains some really questionable "service procedures" and concepts...


Tommy

 

[jav]

Not so. At a bare minimum the compressor oil needs to be removed, possibly the system flushed, the oil changed and the liquid line drier (and suction line filter drier if it has one) needs to be replaced.

If it had actual water in it, it's junk.


On a separate note, this thread contains some really questionable "service procedures" and concepts...


Tommy

Tommy-

how would you recommend removing the compressor oil and purging? Do mini splits typically have built in driers?

 

[soob]

The communication / power wire for the indoor unit is low voltage and not subject to the same code restrictions as line voltage. It doesn't have to be in conduit and it doesn't have to be in liquid tight and you can use romex outdoors if you want. At least that's my understanding.

 

[Dagny]

Changing the oil in a hermetic is a pain but Iv'e done it many times. Remove compressor dump oil out suction pipe measure it and replace.

 

[LS6 Tommy]

Tommy-

how would you recommend removing the compressor oil and purging? Do mini splits typically have built in driers?

Changing the oil in a hermetic is a pain but Iv'e done it many times. Remove compressor dump oil out suction pipe measure it and replace.

X2.

Tommy

 

[justinjoyal]

The communication / power wire for the indoor unit is low voltage and not subject to the same code restrictions as line voltage. It doesn't have to be in conduit and it doesn't have to be in liquid tight and you can use romex outdoors if you want. At least that's my understanding.

There is line voltage going to the indoor unit.