Author Topic: New Ductless install, what follows vacuum evacuation?  (Read 2071 times)

Offline Free Man

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New Ductless install, what follows vacuum evacuation?
« on: March 13, 2015, 01:58:09 PM »
Hi all!

I'm doing a ductless install myself of a new Fujitsu heat pump:

http://m.master.ca/documents/Fujitsu_Installation_AOU36RLXFZ_eng.pdf

The manual does not quite cover how to avoid the inrush of air back into the linesets following a vacuum purge. I'm not using nitrogen, so do I need a service line from the manifold with a valve at the end to shut off, then release some pre-charge refrigerant to bring it back to atmospheric pressure before removing the service line from the service/charging port?
What are the options here? If nitrogen is a must, I can go that route I suppose, but I'm just trying to keep it simple if possible.

Thanks!

Offline Admin

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Re: New Ductless install, what follows vacuum evacuation?
« Reply #1 on: March 15, 2015, 07:46:58 AM »
After installation the refrigerant should still be isolated and contained inside the outdoor unit.  It's always best practice to first pressure test the system with nitrogen, then release the nitrogen.

That looks like a 4 zone system, so connect the gauge to one of the charging ports and start the vacuum pump.  The manual says to run the vacuum pump on each charging port for 30 minutes.  If you have a micron gauge try to get each zone to at least 500 microns for R22 systems and 300 microns for 410a systems.

There is a schrader valve core installed, inside each charging port, that will prevent any air from entering the system.

Offline Free Man

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Re: New Ductless install, what follows vacuum evacuation?
« Reply #2 on: March 15, 2015, 10:51:13 AM »
Great! Thanks so much! I appreciate the help.