mini split evac setup question

[LS6 Tommy]

Lastly - can anyone tell me what the best procedure is for disconnecting from the service valve? I disconnected AFTER releasing the refrigerant in the lines and had a small amount of refrigerant escape from that schrader valve. It was enough gas escaping that it didn't seem to be all that graceful to me so there must be a better way to do it! The only other thing I can think of would be to disconnect before releasing the refrigerant.... but instead of refrigerant escaping, it seems like this would let air and moisture into the system, right?

Always release the refrigerant charge before removing your hoses. Get low loss hoses and you won't lose much of any refrigerant. No freeze burns on your fingers, either.

Tommy

 

[CA_Tallguy]

OK, been messing with the Harbor Freight vacuum pump today to see if I am going to return it and I think that I will. It just isn't pulling down as far or as fast as I think it should and it is making some noises. When I first got it, and dead-headed the micron gauge to the port, it pulled down to single digit microns almost instantly. Now it struggles a bit to get to 150 and doesn't pull much lower.

I'm going to be doing another mini-split install in a few weeks and will probably order something like this Robinair 1550 at Amazon for about $40 more than the HF 2 stage 3cfm. It is 5cfm, two stage, and reviews are excellent. http://amzn.to/1Ia2dvd

This FJC 5cfm "offering two-stage like performance" *is* the same price at Amazon as the HF 2 stage 3cfm.... http://amzn.to/1Ia3hiC

The FJC looks very much like the HF pumps and if you look at the placement of the different things on the Robinair pump it seems like both might be made by the same chinese mfg. Who knows. The thing is that the warranty may be better with the Robinair and maybe the FJC -- HF is only 90 days with reciept. PLUS I noted in some of the reviews for Robinair that people were able to talk to Robinair tech support! Give that a try with HF! LOL

For those of you looking for a cheaper version and in case you are not near a HF location, well there is this FJC pump at Amazon that again looks like the HF models. This one says it is 1.5cfm vs the low end one at HF which they *say* is a 2.5cfm pump. http://amzn.to/1Ia4KWe

This is the FJC 3cfm model at amazon.... http://amzn.to/1hXlaw2

NOTE: both of those last 2 FJC models look identical to the HF pumps and they say "Single stage pump using Twin Port Technology for performance like a 2 stage performance" -- makes me wonder if they are indeed identical to the HF pumps and if the higher end HF pump is truly a real 2 stage unit as advertised.

You don't save much by going with HF or the FJC units over this Robinair unit.... looks so similar to both of the other low cfm pumps that it may be the same thing. http://amzn.to/1EeLdsy

 

[monkeyspanners]

OK, been messing with the Harbor Freight vacuum pump today to see if I am going to return it and I think that I will. It just isn't pulling down as far or as fast as I think it should and it is making some noises. When I first got it, and dead-headed the micron gauge to the port, it pulled down to single digit microns almost instantly. Now it struggles a bit to get to 150 and doesn't pull much lower.

If you have not done so, change the oil in the vac pump, they need regular oil changes to be able to pull low vacuums as the oil gets contaminated with moisture over time and use.

Also check all the rubber gaskets in the gauge lines or adapters, they are another favorite for causing poor pump performance.

Finally, some designs of vacuum gauge get contaminated with oil during use and need cleaning periodically, follow the manufacturers instructions for this.

 

[dreasoner]

I change the oil in my pump after every install. I drain the oil hot and refill. This is overkill probably but I am able able to pull down to approximately 10-20 micron on a 10 year old robinair pump. I also flush my pump reguarly with flush fluid that is available at most HVAC parts houses. I change hose gaskets on a as needed basis on my manifold and micron gauge. I prefer the older analog micron gauges to digital but they are less forgiving to abuse and harder to find used.

 

[CA_Tallguy]

I'm going to be doing another mini-split install in a few weeks and will probably order something like this Robinair 1550 at Amazon for about $40 more than the HF 2 stage 3cfm. It is 5cfm, two stage, and reviews are excellent. http://amzn.to/1Ia2dvd

SCORE! I picked up the above pump for $88 from Amazon "Warehouse Deals" and it just arrived. It appears to be completely new and unused, and even the oil included was sealed. Tested it out and it works great, sounds smooth, pulled down to sub 100 microns very fast. The box for the unit was kind of munched up is all that appeared wrong with it.

Shipping was free (2 day with my Prime membership) and with Amazon's excellent customer service I wasn't worried about ordering it as I knew they would stand behind it and make return easy if it wasn't up to par.

I don't see any more at that price right now (you would find the under "more new and used" at the link above) but if you are in the market for a pump you might try keeping an eye out for this or another pump via Amazon's Warehouse deals. So my 5CFM 2 stage name brand pump with live tech support people to talk to at Robinair if needed cost me about the same as a single stage Harbor Freight 2.5 cheap model pump without any service or tech support help that is worth anything.

 

[dreasoner]

Congratulations, you got a smoking deal on that pump. Keep oil changed and it will last many years.

 

[diamondracer]

Hey guys thanks for all the useful information - I finally got around to evacuating my lines. I did end up getting the above robinair 5cfm pump from Amazon. I've never used a vacuum pump but it sure seems like an awesome pump for the price - weighs a substantial amount.. that surprised me. Sucked my lines down to <100 microns very quickly. It is pretty quiet too.

I've kind of been running the pump off an on today and recording some numbers. So the first time I brought it down < 100 microns, it jumped up to like 1200 or so after 10 mins. Then as I've had time throught the day I have been running it about 30 mins or so (which would bring it down to 50 - 70 microns). So 2nd reading it jumped to about 940 after 10 mins. 3rd time it was at about 840, then abouti 700. I had about a 2 hr 20 min break after this and it read about 1250 when I started it up again. This time after 10 mins it only jumped up to 440. Then I vacuumed it down again for 30 mins, checked after 10 mins and it was at about 230. This is where I'm at.

Does this seem OK? It seems to me like it is just working out the moisture. I think I'll run it one more time tonight, read the gauge in the morning after sitting 10+ hrs, run it one more time, then release refrigerant and do some primitive leak checking w/ bubble soap. Any reason for concern at this point? I did do my own flares and used nylog on flare faces (seems debatable whether this is a good idea or not).

Thanks

 

[diamondracer]

update - after leaving it set overnight, it read 3000 microns this morning. Is this still OK ?

 

[CA_Tallguy]

Sorry I missed your posts diamondracer --- did you get it all sorted out? Sounded like you were doing pretty well when you got to 230 after 10 mins. As per the chart I posted a couple pages back, it would seem to indicate you have a "tight dry system" but I would be more confident if you were still pretty stable around the same number after 30+ minutes. As that chart shows, you want a flatline and not something continually climbing.

Trying to hold a vacuum is pretty tricky and depends on many things (as far as I could figure in my limited experience). What was your setup like for checking your vacuum? Did you open and close valves to check it? Or was the vacuum open to your gauge continually overnight? Where was your gauge in relation to the service port? What else was open or closed?

I don't think you want to see your vacuum rising continually as that means a leak, (or maybe an incomplete evacuation on a long line set?). The question is if it is a leak, is it in your refrigeration/vacuum gear or in your line set. I tried to put a valve RIGHT at the service port so I could TRY to isolate it.

I didn't feel like my vacuum was stable until I kind of "burped" the system with refrigerant as I described previously. Or a nitrogen purge seems like it would be similarly helpful.