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Posted by on April 17, 2007, 1:42 pm
> I'm learning the trade, and have installed four or five residential
systems
> under the eye of my instructor.
>
> I've started buying some tools: A Robinaire 6cfm vacuum pump, a Robinaire
> thermistor gauge, some decent manifold gauges, a leak detector, basic hand
> tools, etc.
>
> My dad decided to "take the risk", and let me install his new upgrade
> system. I'm going to do all the rough work, then let my instructor check
it
> out before he charges it. But since this is "my" system, and not just a
> "job", I decided to try an experiment, and it's got me a little confused.
>
> My instructor tells me to evacuate the system by "pulling it down as far a
> the pump will take it" then letting it pump for a couple of hours more.
My
> new pump with new oil has taken every system down below 50 microns.
>
> But the Rheem manuals say you only need to go down to 500 microns.
>
> Well, I hooked up dad's system, and pumped it down. Then I shut off the
> manifold port valves, shut down the pump, disconnected the center hose,
and
> put the thing to bed overnight with the manifold gauge still connected.
>
> I wanted to see how well it would hold up overnight.
>
> 18 hours later, I reconnected the center hose to the pump, and pumped down
> the hose until I was below 50 microns again. After letting that 'age' a
few
> minutes with the pump running, I opened the manifold valves, and the
> pressure came back up to somewhere between 275 and 400 microns (finest
steps
> on my thermistor gauge).
>
> It only took about three minutes to drop that back down below 50 microns.
>
> Sorry for the long narrative, but here are the actual questions:
>
> 1) isn't the Rheem 500 micron recommendation kind of HIGH? Especially
> considering that my pump will reliably go below 50?
> 2) Did the pressure rise overnight by what is really a small amount
because
> of diffusion through the rubber hoses, or does that 300-or-so micron rise
in
> 18 hours indicate a leak? I can't disconnect the manifold gauge with a
> vacuum in the system without leaking in even more air than that, so I
don't
> have another type of test I can do for pressure rise.
>
> Thanks... just learning. Hope to have my certificate in about another 8
> months.
>
> LLoyd
If you apologize to Bubba and Noon-Air.... I will answer your questions.
Otherwise, you can be our next little b*tch.
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