Valve core removal tool failure

[jjrbus]

I have been following a couple AC forums for 4 years and do not recall this being discussed. I have a CPS VCRT, 4 years old and used 3 times installing mini's and now the 4th time after replacing an evaporator coil. It is a CPS Pro, who would buy a CPS Hack model? Do not know where this fits in the quality range but came in the Daikin mini split install kit I bought.


After replacing the evaporator coil on my Daikin mini I did a nitrogen pressure test to 400 psi and it held for 14 hours so on to vacuum.

I cannot get the microns below 500, so do a triple evacuation and can't get below 500. I wont go into all the details but it is acting strange. Vacuum to 500, turn off vacuum pump and it raise's to 3500 and then drops to 1200 and holds. Some time on the net and start to suspect the VCRT or the CPS micron gauge. So I ordered a new Appion VCRT. Set it up and drew down to 300 microns and rose to 340 microns overnight. I have a harbor freight vacuum pump so believe 300 is the best I will do!


DIY can be very frustrating at times, this is one time I should have asked on the forum instead of trying to figure it out!

 

[fitter30]

Did u change the oil in the vac pump? Oil can look clean but it has some water vapor in it that raises the vapor pressure. When triple evac was the vac broken by nitrogen? Did u let the nitrogen sit for 30 minutes or more before blowing it to pick up any moisture. As for as removing the cores there is so little volume in your system and using a gauge manifold with a minimum of 6' of hoses another few minutes of running the pump shouldn't be a big deal. When pump manufacturers list the cfm their pump will produce there not pulling it through a gauge manifold. Heres some good videos that might give u some more insight.

HVAC Technician Tips - Training Videos - Work Smarter Not Harder

HVAC technician tips - We help technicians learn how to work smarter and get the best performance out of your YELLOW JACKET® tools and equipment with these how-to training videos.

yellowjacket.com

 

[danski0224]

It is very difficult to obtain "stable" micron readings on a system undergoing a repair. There's oil in the system, and the oil can trap refrigerant.

There can also be refrigerant trapped in the compressor.

I have found that the different valve core tools perform differently.

I have checked them in the "off" position, and they leak.

Every connection is a leak point.

Every hose is a leak point. The hose itself, the crimps and those hose gaskets at the ends.

Every little part on the manifold gauge set is a leak point. The fittings in the manifold, the knobs (valves), the gauge and hose connections.

The micron gauge is sensitive enough to pick all of this up. This is why evacuation needs to be done with the minimum of hoses and no manifold. Vacuum hose diameter is important. The relevant term is conductance.

The smaller the system being evacuated, the bigger the problem that leaks pose.

At some point, you have to know your equipment (tools). Did you test your vacuum pump with the micron gauge? It should pull down to 50 easily. Oil should be changed each time, or before it's used if it sits. Yes, it matters. Test it with old oil and then new.

This is why "testing with vacuum" is NOT good. The vacuum blank off test is only supposed to be done for a matter of minutes.

Even pressure testing with nitrogen has issues. There's all of those potential leak points and temperature compensation.

Tru Tech tools has a bunch of free videos on HVAC tool use, including pulling and checking a vacuum. Jim Bergmann puts out some great training material. There's hours and hours of it. All free.

 

[jjrbus]

Thanks for the responses and the links, greatly appreciated. I spent a lot of time on this, fresh vacuum pump oil, breaking with nitrogen, switching hoses and valves around, rented another vacuum pump to see if mine was faulty. hooking gauge directly to pump gave me lower readings. Being interrupted by Florida rains, naps and doing other things, waiting for new parts, dragged it out for several days. Could never get below 500 microns when using VCRT.

New VCRT, pumps down much quicker and lower. 170microns in a short amount of time, I am impressed! Decays to 290 with the pump off 15 minutes.

 

[danski0224]

Who makes that micron gauge coupler with the valve?

 

[motterpaul]

I have been going through exactly the same thing. The biggest problem is finding a reliable VCRT. I finally opted to get the Appion 5/16 to 1/4" VCRT so I would not need an adapter. Those adapters seem to be major leak points during vacuums. I am just accepting that the way all the guys in the vids do it - two VCRTS, the first as mentioned above and the second to isolate the micron gauge, is the way to go.

I also found out a lot about vacuum pumps by reading today. One thing that confuses me is oil viscosity. Supercool sells oil with a 68 rating, and also at a 47 rating. The lower 47 is 30% more expensive. What's the difference? My pump only says to use "high oil" but my reading indicates 8 is high oil. BTW: the brand name of my pump was dissed, but it is the same pump SuperCool sells (just different name).

That video above on cleaning a VCRT is something else. Who knew there would be so much maintenance just on the equipment? I'm used to the digital domain where most fixes are keystrokes.

 

[jjrbus]

I spend more time on the computer trying to figure out how to do things as I do actually doing anything! My pump is a Harbor Freight pump, I use the pump oil from NAPA as it available in small quantities and low priced. I believe it is referred to as a high oil? It has worked well on my cars and mini's but will look into it eventually. It is a Mastercool oil.

I decided against a 2nd micron gauge and bought a angled adapter, it will be very obvious if it is an issue. I do not use gauges and keep hose and connections to a minimum, especially as I have cheap equipment!

I will spend today researching if I need to add oil to system after installing new evaporator coil. I know on cars there are charts indicating how much oil to add after replacing a part but find nothing on mini's, I asked on a couple forums but no response so far!

https://www.napaonline.com/en/p/NTE783910?cid=paidsearch_shopping_dcoe_google

https://www.amazon.com/dp/B08Z468YHB/?tag=atomicindus08-20

 

[LS6 Tommy]

Less is more. Too may potential failure points with adapters and extra valves. The Appion core tools are the best in the industry. Connect your micron gauge directly to the servie port on the core tool.