Help design my new system please

[AC_Hacker]

Originally Posted by buffalobillpatrick

...Bought a Robinair 15300 VacuMaster 3 CFM Vacuum Pump...

I bought exactly the same compressor, dual stage 3CFM, from Harbor Freight. My only criticism is that the vac pump doesn't have a blanking valve built in. I can buy an accessory blanking valve, but built in would be nicer... but I'm not about to put my pump up for sale because of no blanking valve.

I think it's a great little compressor. It's small capacity is actually a benefit to an non-professional, because it doesn't hold so much oil.


I was surprised to find out what a huge difference fresh oil makes to the performance of this or any other HVAC vacuum pump. As far as I can tell, there is some additive that is in HVAC vacuum pump oil that makes it a very aggressive absorber of moisture. So, you should use new, fresh oil every time you use your vac pump... the difference is measurably large. Regarding the oil, there is a temptation to buy a larger quantity container to save money. But once opened, the oil will continue to aggressively absorb moisture and degrade itself, no matter how tightly you try to reseal it. My supplier sells oil in gallons, quarts and pints. I usually buy the quarts, but I'm beginning to think that it would be better to start buying pint bottles. Right now, I have two partly used quart bottles on the bench that I'm not going to use for a serious pump down. I'll probably use it for an experiment, but I don't expect that oil to perform very well.

And, I was advised to finish a pumping session by draining the oil and filling the pump with unused oil, so that you don't leave corrosive contaminates in the pump. I think this is sound advice.

Also, I saw a few posts back that you were considering which valve core removal tool to buy. It is my opinion that you don't need one. If you were a professional, and needed to get your job done quickly so that you could get on to the next paying job AND you had a high capacity vacuum pump (which you don't) then a core remover would make sense.

Not having a core removal tool just means that you'll have to spend a few more minutes waiting for your pump down. Use that time to reflect on your blessings (you'll only have time to reflect on one or two at the most).

Besides, if you haven't purchased your high silver content brazing rod yet, your spare change will definitely go to that stuff.

* * *

Oh, and another thing... the hoses you have with your manifold gauge set are somewhat permeable to air. This isn't so important for gassing because the gas molecules leak OUT. But it is important when you pump down because then the air & moisture can leak IN. The fix is to buy a black hose for pump down. But, as I understand it, the cheap, crusty old-timers (I qualify on all three counts) use copper tubing for their pump down hose.

-AC

[buffalobillpatrick]

NiHaoMike, "package unit" ? Mine came packaged in a box, hehe

AC "blanking valve" ?

Where can I read about the vacuum & charging process?

I don't think that I will need a Refrigerant Manifold-Gauge Set?

I bought 6x 5' hoses for $4 ea.

I will have 2x service ports on high pressure side & 2x on low pressure side.
With schradder core removal tool on (port1) I can remove core & vacuum out on it's side port, add nitrogen/propane into other (port2) Put schradder core back in (port1) & attach my hose with pressure gauge to monitor filling pressure ???

http://www.amazon.com/Robinair-18560...=ATVPDKIKX0DER

Robinair Valve Core Remover/lnstaller removes and installs the valve core from a 1/4 inch male flare access fitting without the loss of refrigerant. Durable solid brass tool has a ball valve that can be opened and closed in just a quarter-turn rather than a stem-type valve. It is designed with a stainless steel ball and brazed side fitting for durability and long life.

Don't the ball valve do what a blanking valve does?

BBP

[AC_Hacker]

Originally Posted by buffalobillpatrick

...AC "blanking valve" ?

Yup.

It just means a valve that you can close before you shut your vac pump off so you don't lose vacuum. I have noticed that some of the better vacuum pumps have them built in, and I can see that it would be very useful. For instance, if you are doing a long pump down on a system that is large, or that may have a lot of water vapor, you can shut off your blanking valve, change oil, restart your pump and when the pump starts to 'hunker down' (my term), open the blanking valve (or equivalent) and continue pumping.

I bought some little after-market ball valves for hose ends, but I didn't find them to be as effective at holding vacuum as I would like.

I could probably find a good one at my HVAC supplier.

It's not such a big deal, more of a convenience feature... still, I'd like one.

You can successfully complete your build without one... you have enough to worry about as it is.

-AC

[pinballlooking]

Originally Posted by AC_Hacker

Yup.

It just means a valve that you can close before you shut your vac pump off so you don't lose vacuum. I have noticed that some of the better vacuum pumps have them built in, and I can see that it would be very useful. For instance, if you are doing a long pump down on a system that is large, or that may have a lot of water vapor, you can shut off your blanking valve, change oil, restart your pump and when the pump starts to 'hunker down' (my term), open the blanking valve (or equivalent) and continue pumping.

I bought some little after-market ball valves for hose ends, but I didn't find them to be as effective at holding vacuum as I would like.

I could probably find a good one at my HVAC supplier.

It's not such a big deal, more of a convenience feature... still, I'd like one.

You can successfully complete your build without one... you have enough to worry about as it is.

-AC

I had the same issue with the vacuum valves all junk for very low vacuum. I bought three different ones.

http://www.testequipmentdepot.com/ye...cuum/93844.htm
But this one actually worked. Yellow Jacket 93844

Then a small hose to the pump. Yellow Jacket 15012
Yellow Jacket 15012 12", Plus II 1/4" Heavy Duty, Hca Str. x 45°
This one actually worked also.

Here I tested it down to 55 Microns
http://ecorenovator.org/forum/geothe...nstall-11.html

These are pricey but you can really feel the quality in these parts. It would have been cheaper for me to buy these in the beginning than the cheaper ones I bought that don’t work.

[buffalobillpatrick]

pinballlooking, with those, how do you insert valve stem without letting air back in?


Trying to position HX's to minimize tube runs

http://ecorenovator.org/forum/attach...1&d=1395335167

[NiHaoMike]

Originally Posted by buffalobillpatrick

NiHaoMike, "package unit" ? Mine came packaged in a box, hehe

AC "blanking valve" ?

Where can I read about the vacuum & charging process?

I don't think that I will need a Refrigerant Manifold-Gauge Set?

I bought 6x 5' hoses for $4 ea.

I will have 2x service ports on high pressure side & 2x on low pressure side.
With schradder core removal tool on (port1) I can remove core & vacuum out on it's side port, add nitrogen/propane into other (port2) Put schradder core back in (port1) & attach my hose with pressure gauge to monitor filling pressure ???

BBP

"Package unit" means the entire refrigerant charge is confined to the unit. As such, the amount of refrigerant is usually small enough that a crankcase heater is not necessary with a scroll.

You really do want to pull a vacuum from both sides. To do the triple evac, pull a vacuum for 15 minutes or more (or to 1500 microns), break vacuum with nitrogen to 5 PSI (or higher if you're doing a pressure test), let sit for an hour or so, then release the pressure and pull a vacuum again for at least 15 minutes (or 1500 microns), then 5 PSI nitrogen for an hour. To finish off, pull a vacuum down to 500 microns (or a few hours if you don't have a micron gauge), then put in 50 PSI or so of refrigerant. (For a system your size, charge vapor so you don't overshoot the correct amount.) Then get about 5F subcool, tune the superheat to where you want it (measured between evaporator and SLHX, where the TXV bulb and equalization line also go), and charge to 10-25F subcool or until the high side pressure starts increasing.

You'll definitely want a gauge manifold. It could be possible to DIY one by adding a pair of valves (plain ball valves will work as they're temporary) and a few fittings to the gauges and hoses you already bought.

[AC_Hacker]

I might triple-vacuum the Starship Enterprise... but I also think a manifold gauge set is a very useful tool.

You could probably get a good one for cheap from CL. Now that you have a vac pump & micron gauge, you can qualify before you buy.

-AC

[buffalobillpatrick]

I still don't get it?

Then I guess that I don't have a "Package unit" because it don't have refrigerant in it?

BBP

[NiHaoMike]

"Package unit" means that once assembled, the entire charge is inside the unit. Window units and rooftop units are common examples. Contrast that to split systems where the condenser and evaporator are separate.

[buffalobillpatrick]

Found this on CL ?

ac manifold gauge set r134a - $25

BBP