Final mini-spilt install Qs.
 

Hello All,

The info I've found in other threads regarding DIY mini-split installations has been invaluable, and I am very appreciative.

I am now at the stage in my own, 3 zone, install that it's time to pressure test, evacuate, and release the 410a. I purchased pro equipment to do the job and I just have a few lingering questions I'd like answers to, along with any advice, before proceeding.

First, the manufacture and seller of my unit, Thermocore, does not recommend pressure testing the system with nitrogen. They say pulling and holding a deep vacuum is check enough. It just seems to me that applying pressure is a better way to check those flare connections. Opinions/advice?

Next, if I do test with nitrogen and there are no leaks, I assume that I evacuate the nitrogen with the vacuum pump in the same operation as pulling the deep vacuum ahead of releasing the 410a, correct? Does pulling the vacuum assure there is no nitrogen left in the system to contaminate the refrigerant?

I will begin with fresh oil in the pump. Will I need to change the oil between each zone vacuum operation?

Next, I am using a core removal tool on my hose setup. After pulling the deep vacuum on a zone, do I reinsert the valve before I release the refrigerant, or after?

And lastly, am I correct that I proceed one zone at a time? Meaning, beginning with zone A, pressure test, evacuate, release refrigerant, power test, then on to zone B, according, then zone C?

Thank you, Scott

You are headed in the right direction, sir. All the assumptions you are making are correct. Yes, it is better to pressure test to pre-stress the flares. You want to remove your valve core, pull a vacuum, pressure test with n2, pull a deep vacuum, reinsert your valve core, verify deep vacuum, then open up the zone to refrigerant. Only connect or disconnect the gauge set while the piping is at or above atmospheric pressure.

Good luck and may you save lots of money on the install. While you're at it, take lots of pics for us to see.

Why remove the valve core on king valves with flare fittings? I remove valve cores before I braze to protect them from the heat.

Thank you for the encouragement, jeff5may. I actually did talk to several HVAC guys about the job and none of them havd ever done a mini-split, which didn't surprise me since they are unheard of in my area (western WA), and they don't want to work on something they didn't sell and install, themselves, which I also expected. I should have the tools in-hand early next week and will let you know how it goes with pictures.

Somebody somewhere long ago recommended to remove the valve cores to speed the evacuation process. The train of thought is that with a bigger hole, one can move more gas in and out faster. Especially when one is using a large displacement vacuum pump, on a large commercial multi-zone system, the large pump and a coreless valve can pull a pretty deep vacuum in a jiffy.

I myself only pull valve cores if I have to. As long as the thing doesn't leak, I'm happy with taking a few minutes extra to get there. I do change the o-rings in the cover caps most every time, though.

When I did my installs I did not remove the valve cores. A little more time was not big deal as I was not being paid by the hour. :) I am a novice with HVAC.

Hey scottmcll, any updates on your install?