Here is my standard post to all things
Yong Heng hope it is helpful.
The Yong Heng "
Simple" version least expensive does not have a water separator you need one.
The "
Auto Stop" version shuts off near 3000psi. Probly
not a good thing for most people.
So you likely want the "
Hardcover" or "
Set Pressure" versions your choice on the 110V or 220V.
https://www.aliexpress.com/item/32824234795.html?spm=a2g0o.store_home.productList_13760454.subject_2 Keep them cool and the oil,
ISO 46 or the equivalent, topped off to the red circle in the sight glass, and don't fill past their spec which is 4350psi. A little less is better than the max, and the Yong Heng should last for years unless you get a bad one. I did my first oil change at about an hour, it was extremely dark colored. I went far longer, between changes, after that.
I have two YH compressors. Bought the second as a backup for the first as I fergot to turn on the coolant pump several times and overheated it until it smoked. It did not like it but it runs fine. Still I did not trust it after that. I
added a switched outlet, to the system, so it turns the pump on before the compressor will power up to keep me from doing that from now on.
The second one, my back up unit, died in about two months bad QC from the factory. Cost me $12, for a new second stage piston, and an hours time to replace it. Then to add insult to injury I fergot to put oil in, the latest unit after I put it back together, and ran it for a couple of minutes without any. So I filled it with oil and it fired up and somehow still werqs fine. The #1 unit that I was worried about, cuz I overheated it so many times, just kept on filling my guns and tanks till I got #2 repaired and retired it.
I do not fill past 4200psi as when I do, all too often, I blow a burst disc. This does not happen on the first or second fill but soon thereafter.
The temperature sensor
only measures head temperature so running it much over 20-30 minutes can overheat the motor and other parts even if ice is used in the coolant. Ice or a container of it, in the coolant, is a good idea especially if you are like me and do not use the full five gallons of water as suggested in the manual.
Keep your water supply level with the compressor to
be kind to the pump and assure a good supply of coolant goes through the compressor.
I recently started using this
Red Line water treatment after I noticed algae growth in my 2.5 gallon water bucket every few months. It seems to have stopped the algae growth problem.
https://www.autozone.com/antifreeze-radiator-additives-and-windshield-wash-fluid/coolant-water-wetter-additive/red-line-water-wetter-super-coolant-12oz/486218_0_0 Keep your moisture filters, guns and tanks being filled above the compressor to
help keep the moisture out.
Purge the system of moisture,
using the screw valves on both sides of the compressor, for a couple of seconds
every five minutes while in use.
Change out your small YH filter
every twenty minutes and set the old one out to dry and use later.
Add a better filter if needed to be sure more moisture and any oil smell is removed from the system. Many of us use this
Tuxing three media filter although, if you feel the need, you can change media types at any time.
https://www.aliexpress.com/item/32891898253.html A smaller one will probly do for many.
https://www.aliexpress.com/item/4000960926898.html?spm=a2g0s.9042311.0.0.2a034c4dL0nrJU Bleed the pressure before you turn the unit off and let it run a few seconds to get the better part of the moisture out of the system. I have found that I blow less burst discs if I bleed before shutting down so I do this religiously.
Let the coolant pump run for a few minutes after shutdown to cool things off.
Here is a video on how to fill a SCBA tank.
https://www.youtube.com/watch?time_continue=157&v=_grx5p_R8D4&feature=emb_title 
