Fujitsu AOU24RML1 + (2)ARU12RML multisplit installation

mrd · 02-20-11, 06:38 AM

Vacuum & Bubble test

The vacuum pump was loaded with oil following the instructions. I found with the correct volume of oil, the oil sight gauge still showed low oil after the pump warmed up. I kept topping more up until it suddenly had too much oil, and a small oil mist came out the exhaust. Oh well. I tested the unit by connecting it directly to my micron gauge, expecting it to be able to pull down to 50 microns, as per spec. However, I don't believe it reached anywhere near that.. perhaps in the mid-200s? I forget the exact number, but I decided it was low enough to use (have a million other things to do on this house, let's go!) :P

I hooked up the center hose of my manifold gauge to the service port, and the low-side hose was connected to my micron gauge. The high-side was connected to the vacuum pump. I since have read that the high-pressure gauges aren't designed to be exposed to low vacuums.. It still seems to work fine.

I pulled a vacuum, it reached the high 200s. As soon as I closed the manifold gauge valve it would shoot back upward.. slowing to around the mid 600s iirc. I did this a few times, running it for a good while (20min+) then shutting the valve and letting it rise.

I did not procure nitrogen to use for pressure testing, and for dehydration assistance, despite knowing this is recommended. I did look around at the big box stores for nitrogen, but didn't find any and just decided "oh well let's get on with it" Doh.

The valve for the vacuum pump was closed, the pump shut off, and then the service port valve was cracked. The manifold pressure gauge popped up to around 30 PSI and I then closed the valve. I went around the flares with soapy water, checking for about 5 mins. I did this again around 70 PSI, then around 130-ish? No bubbles.

The next day I did the same for the other lineset, and then I opened both valves fully, finished wiring the system, then let it sit another day. The manual stated to wait 12 hours after connecting the system to power to "protect the compressor."

(I've since realized the suction side of the compressor is likely heated during this powered delay, to encourage vaporization/migration of liquid refrigerant away from the compressor. The compressor can be damaged if it tries to compress a liquid instead of a gas. An accumulator is present in some systems, including this one, on the suction side of the compressor to contain liquids and prevent them from reaching the compressor. The accumulator can get full, however.)

Test run

The next next day I started up the system, tested fans at full speed, tested the heating. It was mid 40s outside. Plenty of heat came out of the indoor blowers. The system was quiet. The outdoor unit fan was plenty strong for being so quiet. There was a small amount of noise from the outdoor unit, the compressor I guess? But very quiet, compared to a traditional outdoor unit.

I started to cover the outdoor portion of the copper lines with insulation, as I hadn't done so yet. The lines were very hot so I shut off the system and at this point I noticed a tiny little bubble slowly form and pop on the outside flare nut. I looked more closely and saw another form and pop.

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02-20-11, 06:38 AM	#12
mrd Apprentice EcoRenovator Join Date: Feb 2010 Location: Milford, DE Posts: 106 Thanks: 5 Thanked 9 Times in 9 Posts	Vacuum & Bubble test The vacuum pump was loaded with oil following the instructions. I found with the correct volume of oil, the oil sight gauge still showed low oil after the pump warmed up. I kept topping more up until it suddenly had too much oil, and a small oil mist came out the exhaust. Oh well. I tested the unit by connecting it directly to my micron gauge, expecting it to be able to pull down to 50 microns, as per spec. However, I don't believe it reached anywhere near that.. perhaps in the mid-200s? I forget the exact number, but I decided it was low enough to use (have a million other things to do on this house, let's go!) :P I hooked up the center hose of my manifold gauge to the service port, and the low-side hose was connected to my micron gauge. The high-side was connected to the vacuum pump. I since have read that the high-pressure gauges aren't designed to be exposed to low vacuums.. It still seems to work fine. I pulled a vacuum, it reached the high 200s. As soon as I closed the manifold gauge valve it would shoot back upward.. slowing to around the mid 600s iirc. I did this a few times, running it for a good while (20min+) then shutting the valve and letting it rise. I did not procure nitrogen to use for pressure testing, and for dehydration assistance, despite knowing this is recommended. I did look around at the big box stores for nitrogen, but didn't find any and just decided "oh well let's get on with it" Doh. The valve for the vacuum pump was closed, the pump shut off, and then the service port valve was cracked. The manifold pressure gauge popped up to around 30 PSI and I then closed the valve. I went around the flares with soapy water, checking for about 5 mins. I did this again around 70 PSI, then around 130-ish? No bubbles. The next day I did the same for the other lineset, and then I opened both valves fully, finished wiring the system, then let it sit another day. The manual stated to wait 12 hours after connecting the system to power to "protect the compressor." (I've since realized the suction side of the compressor is likely heated during this powered delay, to encourage vaporization/migration of liquid refrigerant away from the compressor. The compressor can be damaged if it tries to compress a liquid instead of a gas. An accumulator is present in some systems, including this one, on the suction side of the compressor to contain liquids and prevent them from reaching the compressor. The accumulator can get full, however.) Test run The next next day I started up the system, tested fans at full speed, tested the heating. It was mid 40s outside. Plenty of heat came out of the indoor blowers. The system was quiet. The outdoor unit fan was plenty strong for being so quiet. There was a small amount of noise from the outdoor unit, the compressor I guess? But very quiet, compared to a traditional outdoor unit. I started to cover the outdoor portion of the copper lines with insulation, as I hadn't done so yet. The lines were very hot so I shut off the system and at this point I noticed a tiny little bubble slowly form and pop on the outside flare nut. I looked more closely and saw another form and pop. :\ Last edited by mrd; 02-24-11 at 05:07 PM..