3/8″ vacuum hose to 1/4″ port
It’s getting pretty chilly in my neck of the woods, and my new mini-split heat pump needs to be charged. The one time I did this job before, I used a 3/8 vac rated hose to 1/4″ port on a valve core removal tool. Unfortunately, that hose was apparently loaned out and never returned. I have a 3/8″ to 3/8″ vac rated hose, but I need to connect it to the 1/4″ port on the core removal tool. I don’t have an HVAC supply store nearby, only a normal hardware store. Can I just use a 3/8 to 1/4 NPT pipe adapter to make this connection? Can/will it hold a vacuum down to 20 microns? Trying to make due with what I have, as this weekend would be far more enjoyable with a little heat.
Thank you.
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Hey Austen.
I have zero experience with this work, but wanted to give your post a bump to see if any other GBA Members could help. Hope you are staying warm...
If you are talking about a hardware store brass fitting then those should be ok if you can find the right type of threads. If this is just on a test set it’s less of an issue too since it won’t be connected for a long period of time. If you need to use a thread sealant, that DOES need to be something that will be ok under vacuum.
You’d be surprised what will work in a pinch. I had a 20 ton air conditioner at work with a leaky soldered (!!) fitting that we couldn’t fix right away. I wrapped a sheet of butyl rubber around the fitting and tightened a pipe clamp over it (tightened until the rubber started to squish through the slots in the pipe clamp). This temporary patch actually stopped, or at least significantly reduced, the leak until we were able to evacuate the system and braze the fitting on properly.
Bill
If you're talking about a metal adapter, it will have no problem holding just about any vacuum you can throw at it, as long as it fits and seals properly.
It should work but the best way to do it is with minimal connections. The more connections the more places it can leak. I use nylog on all my connections as well. I read in your other post that its really cold there. Fittings and orings are more prone to leaking at very cold temperatures.
Here is a picture of my setup I used when installing my Midea Premier floor console. Vacuum rated hose from pump right to the core tool. Make sure you get the microns down as low as you can. Mine bottomed out at 198 microns and held. It can take awhile especially on a multi split and I think cold temperatures might significantly slow the process down.
This is the perfect set up, it pulls vacuum so much faster.
I will say I did not have a problem pulling a deep vacuum on a pressure rated hose, but it was a calculated risk.
The problem is always that non-vacuum rated stuff (except for metals) will sometimes “boil off” stuff under vacuum and contaminate your vacuum system. You’ll see this as never getting down to the micron level you expect to be able to reach. Things like sealants are especially prone to this.
Bill
A professional grade vacuum rated hose is around $50. I have an Appion but CPS also makes them. They seem to be the 2 big names the pros use. This same poster in another thread posted his yellow jacket hose leaked. Why take the chance over a $50 hose on a couple thousand dollar system and risk getting moisture or contaminants in it. Moisture in a system turns into acid when mixed with the refrigerant oil and greatly reduces compressor lifespan.