FYI- nothing I say here should encourage you not to get a qualified HVAC person in. All is at Own Risk.
These Notes assume you have figured out how to connect up a split air conditioner and want to vacuum pump out the line set (piping) ready to open the valves to fill the system with refrigerant from its lowest point, visible in this picture:
Steps in using a split ductless air-conditioner
valve core removal tool to install a new system
Examine the Core Removal Tool to see how it works.
Examine the Exhaust port. This is the lowest point on the outside compressor unit (above) to which you will connect and has a cap over it.
It has a “Schrader” valve within to retain the positive refrigerant pressure within your system when it’s running. It needs to be defeated somehow if you are to force air by sucking it OUT of the pipes rather than keep it IN
Your job is to impose NEGATIVE pressure on this valve (a vacuum) to remove air and moisture etc.
Therefore, Ideally, this valve should be either depressed or removed as it’s going the ‘wrong way’ before vacuum pumping to free passage from vacuum pump to line-set.
Your blue extraction hose coupling from the vacuum pump may have a raised brass dimple within that could depress that valve to defeat it,
so that vapor can be drawn out of the piping… But that’s both unreliable and inefficient &
In my experience is highly unpredictable and worse, obstructive, slowing the vacuuming process.
Compete Removal then replacement of this tiny valve is ideal.
(Have some – cheap- spares in case it’s damaged!)
but this presents the dilemma of how to do so without the system equalizing to atmospheric pressure either letting outside air back in or blowing off refrigerant when switching between tasks
Imagine having to deflate your car tire just to replace its valve.
Then you have to refill it.
Same story- But refrigerant is expensive unlike, well, air.
It’s also never Okay to release refrigerant into the atmosphere!
Worse, it’s hard enough to get a decent vacuum-
a tiny leak would instantly ruin it.
This is where the “Valve Core Removal Tool” comes in, an ingenious device that keeps system pressure or vacuum during change-outs
Aside: When sold the line set likely had some pressurized dry nitrogen in it. We assume this is now all flushed and joined-up.
I made the mistake of uncorking this a few hours before joining the line-set flanges. Some air & moisture would get in : (
Join things up promptly on releasing the nitrogen to avoid as little atmospheric air and moisture as possible getting in is the way to go
Attach correct adapter to end of core valve removal tool:
In my case, 5/16” which required an included adapter.
Before attaching anything,
GENTLY depress the pin in the middle of the valve.
Ideally, nothing happens as the pressure should be about the same both sides.
But, being the low-point of the system it’s possible moisture, lubricating oil, refrigerant gas or any combination of the above can come out. Pay Attention!
You should NOT be sucking this stuff-
Venting or bleeding a tiny quality of liquid to gas is OK though. Ask yourself how it got there is this is a New System : )
Now Trial fit the Valve Removal Tool on the “exhaust” port coming from below the Low Pressure (Large) pipe side
Open the ball valve in the tool (handle along the axis of the device.
This will allow you to push the removal spindle forward through the open ball valve up to the point where it meets the Schrader valve.
Be sure the outermost screwed seal for that spindle is finger-tight:
This withstands some pressure either way
Gently “feel” for the farthest end of the spindle engaging the Schrader valve.
GENTLY twist and probe til it engages, Never Use Force!
Gently twist counter-clockwise a quarter turn and wait
Ready your Vacuum Pump blue hose
Ideally you will have a vacuum gage and understand its correct plumbing.
Continue unscrewing 3 or 4 turns- It’s fairly obvious when the valve comes free. Another few turns to be sure
Very Gently withdraw the stem which should have a tiny rubber washer in its tip (Examined it beforehand, didn’t you?) to ‘capture’ the valve center pin..
Pull the stem ALL the way back til obviously it has come though the ball valve
Gently CLOSE the ball valve to 90 degrees
YOu should now be able to unscrew the outermost spindle retainer so the spindle plus valve ALL come out.. Set aside the little valve in a clean place- well actually keep EVERYTHING clean
You are enow free to connect up the blue vacuum pump line finger-tight, but. DO NOT open any valve yet
Turn the vacuum pump on, It should ‘evacuate’ the blue hose all the way up to the ball valve. Even a basic gage should show this happening. albeit inaccurately- they are designed to show POSITIVE pressures so the needle moves a minuscule negative amount. A proper “Micrometer” vacuum gauge is $200-$300 so I did not use one : (
True the pump off & wait.. Ideally that needle will stay ‘put’ for at least a few minutes showing you your pump and lines are okay.
open the ball-valve, start the vacuum pump. I ran mine for 15 minutes and waited 15 minutes 3-4 times while watching that the negative reading on the gauges did not ‘leak’ back when the pump was off. YOu may want to Close the ball valve between pumpings– Just In Case.
The intermittent use lets the pump cool off, lets you check the system can hold that vacuum AND more importantly,
gives time for any moisture to ‘boil off’ under the low pressure.
The ‘books’ say you are supposed to reduce air-pressure to “500 Mils or less” (only measurable using the expensive gage mentioned above)
This turns out to mean that your normal atmospheric pressure of about 29mm of mercury (Barometric Pressure) will reduce to a mere half a millimeter.. or 60 times less.
The ‘harder’ (lower) the vacuum the harder it is to achieve.
Zero is basically near impossible except in a physics lab perhaps-
Or outer space.
Satisfied? Right. This step is critical.
KEEP THE BALL VALVE CLOSED.
Gently open first the top (high pressure) then the bottom (low pressure) 5MM hex screws all the way to the end stop then back them off.
The hissing is the refrigerant abhorring the vacuum in the line set and replacing it with pressurized refrigerant from the compressor where it’s stored, at 600PSI (High) 300 PIS (low)
So! the Valve Removal tool is now under POSTIVE pressure and the vacuum is gone. This is Good as it’s far easier to lose pipes full of vacuum than a tiny percentage of a whole system full of pressurized gas and fluids.
THE BALL VALVE IS STILL CLOSED RIGHT?
Re Insert the spindle plus valve and hand-tighten the retainer nut.
Spindle cannot go all the way in of course as the closed ball valve is preventing it.
GENTLY open the ball valve. A small hiss of pressurized gas is NORMAL. There will be a natural back pressure as you push the spindle forward through the now open ball valve to re insert the Schrader valve.. “Feel” for the moment the valve enters the aperture into which it will screw
You are doing this against the back-pressure of the system but that’s Ok! Hold the spindle knob forward against the gas pressure with your thumb as you turn it gently to thread the valve back in.
This is a skilled gesture which is neither forceful nor difficult,
just requires a “feel” for what’s goin on., followed by a few turns to ‘bed’ the valve.
Pull the spindle back behind the ball valve
Close the ball-valve.
Unscrew the spindle retainer slowly and completely.
there should NOT be any valve attached anymore!
A small trapped amount of gas will escape.
Gently open the ball-valve- another tiny escape of trapped gas should happen, NO MORE. If a lot comes oujtp the valve IS NOT working right,
Now you can unscrew the entire valve removal too.
An old Garage trick is to put a damp finger over the valve opening.
Nothing shook be escaping If your finger is wet you should not see bubbles.
Screw the brass sealing-cap back on, This is. tapered fitting for which no thread compound should be used, and is considered a proper ‘system seal’ rather than the valve, strangely enough
Seal the High and low pressure side 5mm plugs with their brass caps
let’s leave it at that for now- I do have a Freon Leak Detector and studied it carefully BEFORE and AFTER running the system.
Take Your Time! best of Luck!