Vac pump has lost oil back into the system

[hyperion]

One of our engineers was working on site today and had left the vac pump running on the pipework of a new A/C install. He returned to the pump an hour or so later to find that the power had been turned off. Initial thoughts, not to worry, that will just take another hour to get back to the same position.
He then noticed that the vacuum in the system had drawn the oil out of the vac pump.
Never had this happen before.
Any helpful thoughts how we go about trying to get this oil out of the pipework?
The condensing unit is above the air handler and the valves are still shut on the condensing unit.

[monkey spanners]

Undo the pipes onto the outdoor unit valves and hope all the oil drains out. May be worth cutting the pipework back and replacing.

Back in the R22 days I wouldn't have worried so much but wouldn't chance it on a new system.

[chemi-cool]

Strange. Vac pump suction is on top, vac oil at the bottom.

Did he connected the vacuum hose to the pump's drain?

[Tycho]

Strange. Vac pump suction is on top, vac oil at the bottom.

Did he connected the vacuum hose to the pump's drain?

Could be a faulty back valve on the vac pump, if the valve failed, it could pull some oil back up through the pump... not all, but maybe enough to show low level in the glass.

Hyperion: I'd investigate further before I started pulling down pipes, make sure it's just not low level on the pump, or that the pump tipped over :) Better safe than sorry :)

[Grizzly]

Loosing the oil out of a vacuum pump is to be expected if the power fails.
That's why decent pumps have an isolation valve on the pump suction.
So the prior to turning the pump off you isolate the pump
The bigger the system the greater vacuum created.
Which in turn will suck the oil out of any pump.
I regularly charge large recips and screws with oil (Top Up's) by pulling a deep vacuum in the suction side.
And having a hose into the oil drum, topping up the drum with fresh Oil from another.
Until the required amount is needed.

I don't know the system you refer to!
Would blowing out from another point with OFN be practical?
Good Luck Grizzly