Mini split lines frosting up

[Marc]

Ok.  Another question: does the frosting in cool mode go all the way back to the indoor section?  Or does it begin and end within the outdoor section?

Edited June 9, 2019 by Marc

[John Dirks Jr]

The lines are currently concealed at the evap end.  However the visible portions of high line on the exterior of the condenser do frost up.  And that frosting continues up the line into the jacket.  But I can’t see very far up the jacket.  

[Marc]

Looks like a classic case of low refrigerant charge.  This assumes that the air filter and evap coil are both clean, since the unit is new, that the evap fan is working and that air is moving through the evap coil and finally, that the indoor temps are 70 or higher.

The frost begins at the evap coil, becoming ice that eventually completely encapsulates the coil, stopping all air flow.  Thereafter, frost makes it way up the vapor line all the way to the outdoor section.

There's a chance that there is no refrigerant leak, that it's been making ice since the installation but the off cycles have been long enough to melt the ice...until now.

 

Edited June 9, 2019 by Marc

[John Dirks Jr]

Then wouldn’t that mean the low pressure line would be frosting?   Because it’s the high pressure side returning from the evap that’s frosting, not the low side. 

[Marc]

I think the story on those 2 coiled tubings and the bubble thingy are a capillary tube in parallel with a check valve.  The check valve opens in cool mode so that the capillary tube in the outdoor section is bypassed, allowing the capillary tube, or expansion valve, in the indoor section instead, to drop the pressure and start the liquid evaporating.  In heat mode, the check valve closes, forcing the returning liquid to go through the capillary coil in the outdoor section, causing the returning liquid to evaporate in the outdoor coil so it can collect heat.  The indoor capillary tube likely has its own check valve that opens in heat mode.

Perhaps there's a problem with the check valve (bubble thingy) not opening as much as it should, making it an...ahem...obstruction of sorts.

Obviously, I haven't been of any help.

Edited June 9, 2019 by Marc

[John Dirks Jr]

Marc, you have been a great help.  Double checking my thought process is important.  Tomorrow I will call the Mr Cool tech line.  I’ll let you know how that discussion goes. 

[John Dirks Jr]

Tech guy at Mr Cool is suspicious of improper refrigerant charge, either high or low.  I ordered my own manifold gauge set.  When it gets here and I get the numbers, I’ll  post back.  He wants to see 120-150psi in 80 degree ambient. 

[Marc]

I use 115 to 120 for vapor line, checked when indoor ambient is at target temperature.

Liquid line depends on outdoor temps.

What kind of torch do you have for brazing?

[John Dirks Jr]

I have a MAP torch.  Is that good enough?

[Marc]

Try it on some scrap pieces of copper.  Oxy/Acytl is all I've ever used for brazing with silver solder.

[John Dirks Jr]

I’m not yet convinced that brazing will be needed.  We will see what happens when the tools get here. 

[John Dirks Jr]

When refrigerant is recovered prior to the proper recharging of a system, can that recovered portion be put back in?  Obviously you would weigh it.  Then add the remaining weight to top off the system? 

[Chad Fabry]

1 hour ago, John Dirks Jr said:

When refrigerant is recovered prior to the proper recharging of a system, can that recovered portion be put back in?  Obviously you would weigh it.  Then add the remaining weight to top off the system? 

One recovers refrigerant to a recovery tank, not to the virgin tank. When I was in the automotive business, I never used the recovered product because there was no assurance of purity. I sold it to a recycler. Unless you know for sure what's in your guy's tank, I'd be slow to ask for recovered product.

 

[Marc]

Refrigerant can be re-used in the same system as long as the compressor hasn't burned out.  You'd need a recovery tank to remove the original charge.  Like Chad said, the virgin tanks have a check valve in the neck, can't put the toothpaste back in the tube.

I've never charged an AC system by weight before, except for my truck's AC, but you could charge your mini-split that way.  You'd need a scale on par with the weight of your tank.  A bathroom scale would be too crude.  I used a mechanical scale for my truck: a 10' long 2X10 with a pivot in the middle, the recovery tank sitting on one end and a dead weight with one can of Hunt's Steam-Peeled Tomatoes, whose weight matched the stated refrigerant charge for my AC, on the other.  When perfectly balanced, remove the tomatoes and charge until the scale balances out again.  Distance from tomatoes to pivot has to equal distance from tank to pivot.  It's very precise...and fun.

Edited June 12, 2019 by Marc

[John Dirks Jr]

72 degree ambient.  System hasn’t been run in two days.  Vapor side reading 150psi at idle (not running)

So, this indicates there has not been a loss of refrigerant.  Am I correct?

[John Dirks Jr]

Wait.  When running it drops to 35psi.  

[John Dirks Jr]

 

13 hours ago, Marc said:

Refrigerant can be re-used in the same system as long as the compressor hasn't burned out.  You'd need a recovery tank to remove the original charge.  Like Chad said, the virgin tanks have a check valve in the neck, can't put the toothpaste back in the tube.

I've never charged an AC system by weight before, except for my truck's AC, but you could charge your mini-split that way.  You'd need a scale on par with the weight of your tank.  A bathroom scale would be too crude.  I used a mechanical scale for my truck: a 10' long 2X10 with a pivot in the middle, the recovery tank sitting on one end and a dead weight with one can of Hunt's Steam-Peeled Tomatoes, whose weight matched the stated refrigerant charge for my AC, on the other.  When perfectly balanced, remove the tomatoes and charge until the scale balances out again.  Distance from tomatoes to pivot has to equal distance from tank to pivot.  It's very precise...and fun.

I have an electronic postal scale with 30lb max capacity.  It measures in increments as low as 1/10 ounce.  It also does grams.  This type of scales would be adequate wouldn't you think?

[Marc]

The photo, when the unit isn't running, indicates 150 psi which, for 410A corresponds to a saturation temperature of 52 degrees (look at the R410A temperature saturation scale, the outer blue one).  If I assume that both indoor and outdoor temps are at 72 degrees, this means there is no longer any liquid refrigerant left in the system.  When there is at least some liquid and some vapor in the system, no matter how little or how much, pressure will be at saturation.  So your system is all vapor, unless its 52 degrees outside.  That would mean it has lost most of its refrigerant, I'd guess about 90% at least.  That's a really fast leak and, in my book, a good sign because it'll make it easier to find.

Edited June 13, 2019 by Marc

[Marc]

I would not run this system anymore until its fixed.  When refrigerant is low, oil circulation, which prevents the compressor from overheating and failure, suffers.

[Marc]

1 hour ago, John Dirks Jr said:

 

I have an electronic postal scale with 30lb max capacity.  It measures in increments as low as 1/10 ounce.  It also does grams.  This type of scales would be adequate wouldn't you think?

That would be ideal if you bought an R410A under 24 lbs.  A 30lb weighs 6 lbs empty, 36 lbs when new.

Edited June 13, 2019 by Marc

[John Dirks Jr]

Thanks Marc,

what would be a normal “resting” pressure at 75 degrees ambient?  Ball park

[Marc]

220.  Its on your gauges.

Edited June 13, 2019 by Marc

[Jim Katen]

How do you plan to buy the refrigerant without a license? 

[John Dirks Jr]

Jim,

An acquaintance of mine is EPA certified to handle refrigerants and has begun helping me service this system. 

We discovered a poorly connected fitting which has been fixed.  Although the system had leaked down, any remainder was evacuated, the system vacuumed and recharged by weight according to the information on the data plate.  The repaired fitting was tested and verified leak free. 

The system is working great again so l'm hoping there are not other leaks.  I was not here the entire time he did the work so if anything is missing from my description,  I'm sure he did it correctly.  We'll see how things go and if needed, I'll call him back.  

[BADAIR]

just keep the hares at bay