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[QUOTE=Nam515;13439641] works great on cell phones you drop in toilets!

And then you put it to your face ? Does the 5 second rule apply here ?

I did once have a pet raccoon find my phone and decide to wash it in his play pool. It was the first place I checked when I realized I left it in his reach.
Left it in the window sill a few days and It worked like new.

every things boiling point is drastically reduced. the heat gun boils everything off in the vacuum. works great on cell phones you drop in toilets!

Originally Posted by VTP99

Well one example would be on the compressor if the oil was saturated with refrigerant.

I have to agree, you will know if you have oil saturated with refrigerant by looking at your micron gauge and noticing how fast it climbs when you valve off, makes you think you have a bad leak.
I have also seen occurrences where the accumulator and the bottom of the compressor will frost over while pulling a vacuum, makes for a longer pull down time.

Originally Posted by jamessnevets

In what way would one use a heat gun while evacuating an a/c or refrigeration system? It was never mentioned when I was in school or any other time during my years on the job until recently. To my embarrassment, I was questioned by a customer that happened to be a retired Sta-Rite pump engineer with knowledge about pulling a vacuum. I didn't find anything relevant in the thread using a search. If someone can enlighten me, I would be grateful. Thanks!

Well one example would be on the compressor if the oil was saturated with refrigerant.

Heat gun?

In what way would one use a heat gun while evacuating an a/c or refrigeration system? It was never mentioned when I was in school or any other time during my years on the job until recently. To my embarrassment, I was questioned by a customer that happened to be a retired Sta-Rite pump engineer with knowledge about pulling a vacuum. I didn't find anything relevant in the thread using a search. If someone can enlighten me, I would be grateful. Thanks!

Originally Posted by Tech Rob

Here's how it's done...

We used these in the Navy. They where hard piped to our cryo holding vessels. We would keep a vacuum on the outershell to prolong boil off.

After breaking your first vac with nitro, the positive pressure against your micron gauge and pump wont damage anything? I was under the impression that you should not have positive pressure against either of them. So just let the pump pull it down from positive pressure back into a vac?

Originally Posted by jpsmith1cm

You MAY be able to pull a proper vacuum without a micron gauge, but you will never be able to verify that vacuum without the gauge.

Still have Old School Guys here not using Micron gauges

Yes, it is big enough to handle your 3 ton heat pump! It is only a 6 cfm pump, believe it or not. The difference is that it has much more oil and will continue to pump near 6 cfm at 500 microns, while most vacuum pumps drop back to less than 1 cfm at lower than 1000 microns.

That thing can pull an average 800t machine down to 350 microns in a couple of hours.

Originally Posted by kew48

Under a vacuum, if the only force acting on the valve is the spring, wouldn't the valve tend to close?

There's still bulb pressure acting to open the valve.

Originally Posted by hvacrmedic

When you pull a vacuum on the low side the TXV will throttle open, providing that it isn't defective. The forces acting on the seat are bulb pressure, suction pressure, and spring pressure. The bulb provides an opening force while the spring and low side pressure provide a combined closing force. So the TXV can only be closed when the sum of the low side pressure and spring pressure are greater than the bulb pressure. There is no issue with the compressor, you'll be pulling from the compressor case directly through the suction line, and from the discharge side through the suction line, evaporator coil, liquid line, and condenser coil. It's a long path, but those molecules are moving around at the speed of sound, so no problem.

Under a vacuum, if the only force acting on the valve is the spring, wouldn't the valve tend to close?

Originally Posted by BergerMech Rob

Here's how it's done...

That thing sucks!.................

Originally Posted by BergerMech Rob

Here's how it's done...

Would that one be big enough for my 3 ton heat pump??? LOL

Here's how it's done...

JP - That is/was my point. I have never changed my procedure for pulling a vacuum. The Micron guage simply displays that what I was taught and have done for the last 38 years is one of the correct processes. But I am getting tired of people saying that the Micron Guage is what "allows" the proper vacuum to be pulled. It simply displays that a proper vacuum has been pulled. If you don't use one, you simply can't prove what you've done.

Originally Posted by CrispinHvac

if you only pull on the suction side and you have your micron gauge on the liquid line and if you can get it down to 500 microns and the rise is minimal then woudent that be ok?

I have always wondered if you could just pull a vac from the suction side with a txv.

now with the scroll compressor and lets say a non bleed txv wouldent the scroll compressor act like the bleed ?

or maby im confused ?

im not sure lol

When you pull a vacuum on the low side the TXV will throttle open, providing that it isn't defective. The forces acting on the seat are bulb pressure, suction pressure, and spring pressure. The bulb provides an opening force while the spring and low side pressure provide a combined closing force. So the TXV can only be closed when the sum of the low side pressure and spring pressure are greater than the bulb pressure. There is no issue with the compressor, you'll be pulling from the compressor case directly through the suction line, and from the discharge side through the suction line, evaporator coil, liquid line, and condenser coil. It's a long path, but those molecules are moving around at the speed of sound, so no problem.

very well said jp

Originally Posted by bldgcode1

I just saw another thread where it said you can't pull a proper vacuum without using a micron guage. Does the guage somehow make the pump pull a better vacuum? Or is the guage really just letting you observe what your proper practice procedure is doing?

You MAY be able to pull a proper vacuum without a micron gauge, but you will never be able to verify that vacuum without the gauge.

I just saw another thread where it said you can't pull a proper vacuum without using a micron guage. Does the guage somehow make the pump pull a better vacuum? Or is the guage really just letting you observe what your proper practice procedure is doing?

If you're pulling from just the suction side and with your Micron gage on the liquid side and reading 500 microns,you should be OK-even with a TXV. Regarding the scroll compressor, many times after a pull down for an evap changeout, your compressor is valved out of the loop when pulling a vac.