Vac Down Procedure.

[mendoza]

Hey guys, Ive just turned third year in my HVAC instillation apprenticeship here in Melbourne Australia and really enjoy my trade especially the refrigeration side of the instillation.

Just recently my folks have baught their first air conditioner for the home after living there for 8 years a Mitsubishi split system with 3/8 and 1/4 pipe work with r410 connections.

I have fitted several wall hung splits in the field but I am yet to commition one, my question is regarding the vac down procedure.

Its an easy back to back install with 3m of pipe work, but due to conflicting information I am unsure of the vac process.

I own a Rigid flaring tool and am about to purchace a 4cfm 1 stage vac off ebay and 410 gauges.

So here Iam a keen third year seeking advice from the more experienced guys in the trade.

How should I start my vac down?

[nike123]

Hey guys, Ive just turned third year in my HVAC instillation apprenticeship here in Melbourne Australia and really enjoy my trade especially the refrigeration side of the instillation.

Just recently my folks have baught their first air conditioner for the home after living there for 8 years a Mitsubishi split system with 3/8 and 1/4 pipe work with r410 connections.

I have fitted several wall hung splits in the field but I am yet to commition one, my question is regarding the vac down procedure.

Its an easy back to back install with 3m of pipe work, but due to conflicting information I am unsure of the vac process.

I own a Rigid flaring tool and am about to purchace a 4cfm 1 stage vac off ebay and 410 gauges.

So here Iam a keen third year seeking advice from the more experienced guys in the trade.

How should I start my vac down?

When you buy your vac pump, also buy instrument which will see what that pump doing.
Since vacuum should be between 500 and 1000 microns (millionth part of 1 inch of mercury) you cannot see that with your regular gauges.
You need to purchase electronic vacuum meter.

More informations you could get by searching this forum with vacuum and evacuation as search terms.

http://www.refrigeration-engineer.co...earchid=892130

[Tesla]

Hi mendoza
Welcome to the forum. Follow nile123 advice and search the forum. I would advise against a 1 stage vac pump and consider a 2 stage, and all the best for your career ahead.

[position1]

Hi Everyone

I would like to go over the vac down procedure so I can confirm some of the finer details.

Equipment:
Vacuum pump
Manifold, Guages and Hose Set
Micron scale vacuum gauge (usually digital)

With the high and lo side of the manifold shut I connect the yellow charging line to my vac pump.
I then connect the blue lo side hose to the low side service port on the system. I connect the red high side hose to the high side service port.

At this point if i see pressure on the gauges, the system is not empty and its refridgerant needs to be recovered. Otherwise I continue.

I disconnect the blue lo side hose from the lo side service valve on the compressor. I then connect my micron gauge in between the blue lo side hose the the low side service valve.

I then open both lo and high sides of the manifold completely and the valve in the charging hose. I turn on the vacuum pump. I run the vacuum pump for a few minutes.

The micron gauge will start reading at about 10000. The vacuum pulls down towards or below 100 within only a few mins (I only work on smaller split type systems).

I then close the valve on the yellow charging line. I then close both lo and high sides of the charging manifold. I then turn off the vacuum pump.

The vacuum should hold without the micron gauge increasing much. Typically not more than 50 or 100 micron. If it does increase to above 1000 or 2000 microns within 15 minutes, this could indicate a leak or water vapour in the lines. In this case vacuum it down again and wait another 15 minutes. If the vacuum goes up again about 1000 or 2000 microns you have a leak.

Otherwise you have no leaks and are ready to charge the system or crack the valves holding the refrigerant in the condenser. But before you can charge the system or crack the valves, you must remove your micron gauge, as these typically won't cope well with the high pressure of refrigerant.

My questions are:
When I vacuum down the system and shut the valve isolating the vacuum pump from the system the pump is still running. It loads load up a bit More and even changes its tone a bit. Is it bad to run the vacuum on a very small volume (like just the charging hose) for a long time (say 10 or 15 minutes) ? Can I hurt my vacuum pump pulling high vacuums for long periods of time (say 10 or 15 minutes) ?

When I disconnect the micron gauge and reconnect the blue low side line to the service valve for charging, some air inevitably enters the system. Is this bad ? Are the low loss fittings on my hoses bad ? The micron gauge doesnt have a low loss fitting, or at least not like the hoses, should it ?

Thanks for your help.

Ben