NOTES ONLY! 
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!

 

DDNS– Dynamic DNS- is used to track by name a changing IP address at, for example, your home or office equipment.
It could be used to reach into equipment at home while away, Etc.
office.mysite.com is easier than 206.171.54.21

Security implications are detailed elsewhere

YOu might try any number of services like https://www.noip.com/free  to do this for you but I always prefer to Roll my Own. Plus, it’s hard to find reliable free ones any more

My particular solution involves use of the domains.google Google Domain Registry (Currently $12 a year) to do so-
They give you FULL control over all of your DNS entries, and are, naturally, super-reliable and do not bug you with confusing up-sells.

You could move your Domain Name Registration to their service
(very useful in itself!) or, well,
just register some name just  for this purpose alone : )

Most ISPs (Internet Service Providers) issue you a single “Public IP address”– a number drawn from a huge pool of unique addresses assigned to things connected to the internet,

Your router will perform Magic so multiple private addresses and machines show up ‘behind’ this address- But we are concerned with the Public-pointing WAN (Wide Area Network) facing single IP address, not the LAN (Local Area Network) things going on behind, 

The ISP does not guarantee that you will maintain the same IP address over any period of time.
You could pay (usually a lot) of money to get a fixed IP address but there is no need,

This may be like returning to your same favorite campsite regularly  and finding you have a different spot assigned to you- or not- Each time. You may even be moved while staying there.

Somehow there needs to be a way to give you an easily identifiable way for this changing numeric address to be published so friends and outsiders can find you as a fixed name
It’s easy to assign a fixed name to a fixed address for a server like 
www.artoflogic.com but- when the IP address changes randomly…?

It’s pretty easy to find out what your “Public IP address” is and even who gave it to you with sites like this one 
https://whatismyipaddress.com which you could then note down in hopes it does not change,- But we need an automated way.

So that’s the first step- some scripted way to catch the current IP address. The second step is to “publish” it to DNS in some way,

I’ll mention just one very reliable solution  I have found using domains.google

You will then need to follow the steps here to create a DDNS entry.
https://support.google.com/domains/answer/6147083

Registered Name Example: site.com, dynamic DNS entry home.site.com. YOu will end up with a Very Ugly Username and Password (which, for Security, you cannot pick yourself!)

The instructions above will list potential “DDNS Clients” but here’s where it gets Interesting- I found several listed there simply did not work because the HTTP protocol many of them use is deprecated in favor of the HTTPS used to discover your IP address.
DD-WRT.COM (More Later) has a config DDNS setting that does not work for this very reason 

What about if you have a Linux box? there’s a PERL script called DDCLIENT but as of writing it did NOT seem to enjoy configurations for Google

Try This (on One Line). It requires “curl” to “get” the current IP address using the given ugly username/password pair from above,
seperated by a colon, that were generated by the Google Dynamic Dns Configuration above. You could adjust or remove the final
” | /usr/bin/logger -s -t ddns”
whose only purpose it to log the update to something like /var/log/messages

0,15,30,45 * * * * root /usr/bin/curl -4 –user-agent curl -s -get https://Given-Ugly-Username:Given-Ugly-Pasword@domains.google.com/nic/update?hostname=home.site.com | /usr/bin/logger -s -t ddns

Troubleshooting!
Note: If you visit the URL given above in a web page  you will see the web page wants a proper working username/password pair
in order to
1) Locate the IP request address the user was using
2) Update the Google Dynamic DNS address within Google
for home.site.com from the address found in 1)
All of which must exist and be valid : )

Therefore, when done, “Outside On the Internet and Elsewhere” your Home or Office current IP address (Updated in this case every 15 mins by the CRON job that triggers the script)
can be known by name

If you do nothing else, this in no way changes your Security- Hackers typically will scan address blocks not names,
so simply getting a Name assigned achives nothing for them.

Now when you configure your Router to permit “Holes” in your Firewall (think VPN Inbound) etc, that situation changes completely.

Note the script DOES NOT need to be run inside your Router (although it naturally would be if you use for example, Linux Firmware in your router like http://dd-wrt.com) and can be run on any machine “Behind” your firewall as it reaches “out” onto the Internet– Nothing reaches “In”

Notes:
– Every 15 mins. Cron Update should be Fine, Any more often than that may annoy Google to the extent they stop listening
– Google  typically spots if there is no change in address from the previous check and does not touch the DNS entry (no need)
95% of Queries are like this,
My home office IP address has remained fixed for months even after router re boots but is NOT guaranteed to be so by my ISP : )

To make a Hot/Office PC now reachable by name OUTSIDE from the Internet you will need to ue your Router’s “Port Forwarding”: Feature. This is where security implications come in. 
For starters avoid using “DMZ” which means EVERYTHING reaching the router on all ports goes to a particular machine
Forward ONE thing at a time. Be VERY clear about the Security Implications of what you will do next- and also consider it may not be necessary anyway to remotely reach your home/office PC if you use something like http://www.teamviewer.com which achieves its functionality by the Remote and Host machine both logging in “forwards” through a Proxy Server managed by TeamViewer.
 
A great easy to do the port forwarding correctly is listed here:
https://portforward.com

Personally: I use a SINGLE ssh Port, normally over Port #22 but moved to a non-well-known Port number higher than 1024,
like 2468, though which all my access is “tunneled” to machines inside my Network.
This is what you might call a Single Point of Failure for everything.

YOu can google some of the wording above to make more sense of it– the subject of a whole other article in itself!

best of Luck!