Vacuum won't bring mini-split line set to minus 30

[HowshouldIknow]

Hello group, I purchased two Hessaire 12k mini-splits. I installed one mini-split, and vacuumed the line set to minus 30 as directed. No problems. After installing the second 12k unit, I tried to vacuum the line set to minus 30 but the gauge only reads minus 15. I repeated the vacuum over 5 times. Left the vacuum run for up to three hours with no movement in the gauge. The arrow continues to point to minus 15. I contacted Hessaire customer service and was told there may be a leak in the line set couplers. We checked the line set couplers and did not find any leak. The pump with gauges I used is a new unit, 1/3 hp, purchased off Amazon. The pump was successfully used to vacuum the first of two mini-split line sets. I filled the pump with the proper amount of oil. The pump blows white smoke while trying to vacuum the line. Is that normal? Does anyone know? Any suggestions on what the problem could be? We can't vacuum the second line set to minus 30.

 

[wdwtx2.0]

Try to pull a vacuum on just the manifold gauges.
See if it will pull down to -30.
The "white smoke" is vacuum pump oil being turned into microscopic droplets, and water vapor.
If you can pull to -30 on the gauges, you have a leak in the unit, or line set.

 

[#40Fan]

Remove the lines from the A/C unit and either cap them or stick your finger over the line. Run pump and see if it will pull 30 inches. If it does, there is a leak in the lines on the A/C.

Couple ways to find the leak. Fill with compressed gas or while pulling the vacuum, spray water on the fittings and look for it being sucked in.

 

[wdwtx2.0]

while pulling the vacuum, spray water on the fittings and look for it being sucked in.

You only want to check for leaks with positive pressure.
You never, EVER want to introduce water into a system.

 

[Quattrohead]

The vacuum part of the gauge is so tiny you really can't depend on it. If you are unsure, pull your vacuum to whatever the gauge will show and leave it for 24 hours and see if it actually changes.

 

[hwy17]

Does the vacuum decay once stopped or does it stay locked at -15?

I would guess bad gauge. Connect gauge only to vacuum pump if you can to test.

 

[hwy17]

Altitude will also affect the reading I think. But 15 inches would be like 15k feet.

 

[Ampster]

I had borrowed a vacuum pump from a friend who was a retired refrigeration tech. The newer refrigerants like in my heat pump system required more vacuum than the old refrigerants and I had to buy a new compressor.

 

[bolhuijo]

The vacuum part of the gauge is so tiny you really can't depend on it. If you are unsure, pull your vacuum to whatever the gauge will show and leave it for 24 hours and see if it actually changes.

This is probably the best you can do given the tools you have. Ideally you have a separate Micron gage just for vacuum testing. Pull it down to 500 microns, stop, wait 10 or 20 minutes and hope it doesn't rise above 1000. Moisture in the lines is trouble - the vacuum will run and run trying to get all the water to vaporize and exit.

 

[HowshouldIknow]

Does the vacuum decay once stopped or does it stay locked at -15?

I would guess bad gauge. Connect gauge only to vacuum pump if you can to test.

Hello hwy17, thank you for your reply. Once stopped the gauge stays at minus 15. Can you explain clearer when you wrote "connect gauge only to the vacuum pump". I'm new to vacuuming. Previously installed three DIY Mr. Cool systems. This vacuum pump is brand new. I used it once to vacuum the line to the first of two mini splits. It did vacuum the line down to minus 30. Trying to figure out your suggestion...Should I unscrew the blue line from the vacuum to the mini split condenser service port and then...? How do I test the gauge? Just run the vacuum?

 

[HowshouldIknow]

This is probably the best you can do given the tools you have. Ideally you have a separate Micron gage just for vacuum testing. Pull it down to 500 microns, stop, wait 10 or 20 minutes and hope it doesn't rise above 1000. Moisture in the lines is trouble - the vacuum will run and run trying to get all the water to vaporize and exit.

Thanks for your reply. I'm new to vacuuming down a line set. The first line set went well. But not the second unit. I don't see a measurement for microns on the needle gauge. I watched and followed YouTube DIYers. Purchased the same gauge and vacuum pump they used from Amazon. I've left the pump on for three or more hours and the gauge won't go below -15. Any suggestions?

 

[HowshouldIknow]

This is probably the best you can do given the tools you have. Ideally you have a separate Micron gage just for vacuum testing. Pull it down to 500 microns, stop, wait 10 or 20 minutes and hope it doesn't rise above 1000. Moisture in the lines is trouble - the vacuum will run and run trying to get all the water to vaporize and exit.

Try to pull a vacuum on just the manifold gauges.
See if it will pull down to -30.
The "white smoke" is vacuum pump oil being turned into microscopic droplets, and water vapor.
If you can pull to -30 on the gauges, you have a leak in the unit, or line set.

Thank you for your reply. Would you please explain how I perform that? I'm new to vacuuming a line set. "pull a vacuum on just the manifold gauges" ??Remove the blue hose from the condenser service port?? And then what? I have a yellow hose connected from the gauges to the vacuum pump. Should I remove the yellow hose and connect the blue hose directly to the vacuum? Confused but beer helps.

 

[hwy17]

Hello hwy17, thank you for your reply. Once stopped the gauge stays at minus 15. Can you explain clearer when you wrote "connect gauge only to the vacuum pump". I'm new to vacuuming. Previously installed three DIY Mr. Cool systems. This vacuum pump is brand new. I used it once to vacuum the line to the first of two mini splits. It did vacuum the line down to minus 30. Trying to figure out your suggestion...Should I unscrew the blue line from the vacuum to the mini split condenser service port and then...? How do I test the gauge? Just run the vacuum?

I don't use a manifold so I don't know what the connectors are like on them.

I mean to connect it somehow vacuum > gauge, with no lineset involved. If it reads 15 that way then I doubt the vacuum is only pulling 15 so the gauge is wrong.

If the gauge is wrong, I think you can still use it, those gauges are only good to tell vacuum yes or vacuum no anyway.

 

[Checkthisout]

Thank you for your reply. Would you please explain how I perform that? I'm new to vacuuming a line set. "pull a vacuum on just the manifold gauges" ??Remove the blue hose from the condenser service port?? And then what? I have a yellow hose connected from the gauges to the vacuum pump. Should I remove the yellow hose and connect the blue hose directly to the vacuum? Confused but beer helps.

It's a way to diagnose what's going on.

You're pulling a vacuum on the gauges themselves so as to isolate those two items to see if the issue is with the pump or Gauges before diving into looking for a leak in the system.

In other words pretend the ac system doesn't exist and hook just the Gauges to the pump and turn the pump on and see what level of vacuum you get.

 

[wheelman55]

You might have a bad flare connection in the line set.

To fix cut off the old flare, make a new flare with an ORBITAL flare tool.

Good luck.

 

[bolhuijo]

Thanks for your reply. I'm new to vacuuming down a line set. The first line set went well. But not the second unit. I don't see a measurement for microns on the needle gauge. I watched and followed YouTube DIYers. Purchased the same gauge and vacuum pump they used from Amazon. I've left the pump on for three or more hours and the gauge won't go below -15. Any suggestions?

There is no micron measurement on the needle gage, they are not sensitive at all in the vacuum range. Real micron gages (like this picture) cost quite a bit more but they can tell you if you have a tiny leak or not.


I think the best test you can do with the gear you have is to connect it up and vacuum it down as best you can to the -15 as indicated on your needle gage, then close the valve, turn off the pump and see if the needle moves slowly back to zero. If you have a leak so large that the pump can't get the vacuum down to -30 (ish) on the gage, I would think the pressure would return to zero pretty quickly after the pump stops. If it stays put at -15 for a long time then maybe that gage is just cheap and/or broken.
I've been down the youtube rabbit hole on this topic and there are tons of good videos.

 

[HowshouldIknow]

It's a way to diagnose what's going on.

You're pulling a vacuum on the gauges themselves so as to isolate those two items to see if the issue is with the pump or Gauges before diving into looking for a leak in the system.

In other words pretend the ac system doesn't exist and hook just the Gauges to the pump and turn the pump on and see what level of vacuum you get.

Thank you. I disconnected the blue hose from the condenser service port and then disconnected the yellow hose from the center of the gauges. With the gauge open, the gauge didn't move while the pump was on. When I closed the gauge while running the pump, the gauge moved to minus 30. What's does that tell you? Please let me know. Thanks!

 

[wheelman55]

AC Service Tech on YouTube has good videos on splits.

 

[HowshouldIknow]

I disconnected the blue hose from the condenser service port and then disconnected the yellow hose from the center of the gauges. With the gauge open, the gauge didn't move while the pump was on. When I closed the gauge while running the pump, the gauge moved to minus 30. What's does that tell you? Please let me know. Thanks!

 

[HowshouldIknow]

Remove the lines from the A/C unit and either cap them or stick your finger over the line. Run pump and see if it will pull 30 inches. If it does, there is a leak in the lines on the A/C.

Couple ways to find the leak. Fill with compressed gas or while pulling the vacuum, spray water on the fittings and look for it being sucked in.

Thank you. If there is one or more leaks wouldn't the leaks be only where the couplers are connected? From the air handler or where the line connects to the condenser? I used Nylog on all fittings before securing them together. I disconnected the blue hose from the condenser service port and then disconnected the yellow hose from the center of the gauges. With the gauge open, the gauge didn't move while the pump was on. When I closed the gauge while running the pump, the gauge moved to minus 30. What's does that tell you? Please let me know. Thanks!

 

[740GLE]

You could bend a line so much it crimps and cause a pin hole leak, but again the gauge would move soon as you stopped the vacuum

 

[hwy17]

I disconnected the blue hose from the condenser service port and then disconnected the yellow hose from the center of the gauges. With the gauge open, the gauge didn't move while the pump was on. When I closed the gauge while running the pump, the gauge moved to minus 30. What's does that tell you? Please let me know. Thanks!

Tells us your gauge can read -30 so you do need to keep troubleshooting the -15 reading before proceeding.

Vacuum the lineset to -15 and then turn the vacuum off and see if it holds -15 or loses vacuum.

 

[wpns]

When I closed the gauge while running the pump, the gauge moved to minus 30. What's does that tell you?

That your pump will pump down to -30 and your guage reads properly. Now find your leak

 

[HowshouldIknow]

Try to pull a vacuum on just the manifold gauges.
See if it will pull down to -30.
The "white smoke" is vacuum pump oil being turned into microscopic droplets, and water vapor.
If you can pull to -30 on the gauges, you have a leak in the unit, or line set.

The blue gauge went to -30 when it was connected directly to the vacuum pump. What do you advise next? There doesn't seem to be a noticeable leak where the couplers from the indoor air handler are attached to the line leading to the condenser.

 

[Brett V]

The vacuum part of the gauge is so tiny you really can't depend on it. If you are unsure, pull your vacuum to whatever the gauge will show and leave it for 24 hours and see if it actually changes.

THIS ^^^