Here's how to vacuum

[chuckcrj]

Quick question for ya? How do you remove that gauge without breaking vac? You should have an isolation shut-off valve between your service port and micron gauge. They aren't meant to have pressure against them.

I was wondering the same thing, I'm pretty sure those vacuum sensors don't like refrigerant, or oil.

I always hook mine to the system thru a core remover and use 3/8 hoses straight from the pump. Sorry don't have any pics handy.

[hvaceric]

Micron gauges don't measure pressure. They measure temperature using a very sensitive thermistor and through the instruments translation of Molecular activity in the sealed or not sealed system the guage shows microns.

Correct, to an extent. Different manufacturers use different sensor types, some use a heater and thermistor as mentioned above, some also use a heater and thermocouple, Testo uses a strain gauge in the 560. I don't know what type the BluVac uses, it's patent pending.

The display shows pressure relative to absolute zero, which is interpreted from the more sensitive type of sensor used in these instruments, and is displayed in a much higher resolution known to us as microns. This should be correctly termed as microns of mercury.

As a note, some sensors are designed to take pressure. It depends on how they are manufactured.

[jpsmith1cm]

What are you using for a cold trap ?

I've never actually had to use one.

If I did, I would build one out of some very large copper piping or fittings (4" or better) and build a bucket in a bucket type arrangement with provisions to drain any water from inside and fill the inner bucket with a salt/ice/water brine and draw vacuum through the space between the two buckets.

I don't know if I've adequately explained what is in my head. Probably not.

Suffice it to say, fortunately, I've never had to use one.

[jpsmith1cm]

I was wondering the same thing, I'm pretty sure those vacuum sensors don't like refrigerant, or oil.

I always hook mine to the system thru a core remover and use 3/8 hoses straight from the pump. Sorry don't have any pics handy.

Quick question for ya? How do you remove that gauge without breaking vac? You should have an isolation shut-off valve between your service port and micron gauge. They aren't meant to have pressure against them.

Ummm.

Just remove it before charging.

You don't need to remove the schraeder to use a micron gauge. Just hook it up, measure the vacuum and remove it before charging.

At least that is what I do most of the time.

[energy star]

Say again

[chuckcrj]

Ummm.

Just remove it before charging.

You don't need to remove the schraeder to use a micron gauge. Just hook it up, measure the vacuum and remove it before charging.

At least that is what I do most of the time.

Its probably not enough to mention but what about that little sssst when you remove the gauge? It lets a little air in but probably not enough to matter.

[jpsmith1cm]

Say again

Me?

[jpsmith1cm]

Its probably not enough to mention but what about that little sssst when you remove the gauge? It lets a little air in but probably not enough to matter.

Let the pump run for another 5 minutes or so if you're worried about it.

That tiny amount of air isn't going to amount to a hill of beans on anything I work on.

[chuckcrj]

Let the pump run for another 5 minutes or so if you're worried about it.

That tiny amount of air isn't going to amount to a hill of beans on anything I work on.

I know, I'm probably too picky.

A lineset and coil like the OP has a lot less volume than a large refer system though.

[energy star]

Yeah I was referring to your post. After taking the time. I would much rather see you valve off. That little hiss can suck much moister into the system ultra fast.

[jpsmith1cm]

I know, I'm probably too picky.

A lineset and coil like the OP has a lot less volume than a large refer system though.

True.

I work on quite a wide variety of equipment sizes, from stuff that holds a few ounces to stuff that holds almost a ton of refrigerant.

When possible, I use a core remover with a side access fitting for the micron gauge. I guess that is going to let some air in, too. Just never thought about it, I guess.

[ZeroTolerance]

Some people are just way too nit-picky. You are always going to let a minut amount of air enter a system when pulling a vacuum and then removing the hoses. Get over it. There is nothing you can do about it.

[energy star]

When you use two core removers with side access you can install ball valve before the sensor on the vacuum gauge. The YJ comes with one. Or, you could forget about the side access port all together and install your vacuum gauge on the end of the core removal tool (sorta like you have it now) This would allow you to break the vacuum with the charge in the new unit just enough to have a positive pressure in the line set and coil, then close the out door unit off again, remove vacuum gauge (because you can now valve off) and install all hoses and charge line set with any additional needed charge then re-open the service valve. Many ways to accomplish this, but the goal is to have a positive pressure in the line set and protect the vacuum gauge sensor before removing anything from the evacuated line set.