Fujitsu AOU24RML1 + (2)ARU12RML multisplit installation

[mrd]

I've also run into another snag in this process. After correcting the flare, I performed a 400psi pressure test with nitrogen. I used some bubble leak detector spray from the local hvac supplier, not dishwashing liquid (that stuff corrodes the copper!) No noticeable bubbles. I then made a mistake in using the vacuum pump to assist in removing the nitrogen. Apparently the instruction manual states not to use the pump on a pressurized system. Some funny high pitched noises occurred while removing the nitrogen.

Then I pulled a vacuum with the help of the micrometer. Then broke the vac with some nitrogen again. Then vac again.. I was working on a triple vac. But at this point my micrometer suddenly lost a vacuum reading. Not sure what happened.

I connected the hose directly from the vacuum to the micrometer, but it still doesn't read anything. I don't know if the vacuum is shot, the hose is shot, or the micrometer is shot. The o-rings inside the hose look really bad, I think I may have over-torqued the hose connections.. I'm going to try replacing the o-rings tomorrow, if the local shop has some. Hopefully my pump is OK.

[S-F]

I'm sorry to hear about your difficulties but it looks like you've got it under control. Best of luck putting it all back together. If you need a hand with any thing give me a holler. I don't know where Milford is but my grandparents live in Wilmington and I'm due for a visit any way.

Your project is pretty awesome. It has brought the idea of ASHP to my mind for my new build. Could you please give more details about the process? Do you have all the duct work done? More pictures please! I have about 1,000,000 more questions but I'll refrain from posting them haphazardly and will wait until I have them all collected. But any more information you can give on your project would be highly, HIGHLY appreciated as I might be going the same route but in a colder climate where ASHP can suck wind when you need it the most (i.e. -10 f.)

Edit
s$@t. You must have written the last post while I was writing mine. May the force be with you.

[Xringer]

I've seen that before. It's from making the flare skirt too thin, (too much muscle),
or it's from over-tightening the nut, Causing the compression nut ring/hole
to squeeze the copper flare thin.

The only other thing that I can think of, is the flare angle.
I was told these flares are different than the standard US flare of 45 degs.
I think they are 37.5 degs or something like that.
The tech guy also told me that he used the 45 flare kit and never had a problem.
Said the nut pulled the fare skirt down into a good seal, when installed.

[mrd]

Originally Posted by S-F

I'm sorry to hear about your difficulties but it looks like you've got it under control. Best of luck putting it all back together. If you need a hand with any thing give me a holler. I don't know where Milford is but my grandparents live in Wilmington and I'm due for a visit any way.

Your project is pretty awesome. It has brought the idea of ASHP to my mind for my new build. Could you please give more details about the process? Do you have all the duct work done? More pictures please! I have about 1,000,000 more questions but I'll refrain from posting them haphazardly and will wait until I have them all collected. But any more information you can give on your project would be highly, HIGHLY appreciated as I might be going the same route but in a colder climate where ASHP can suck wind when you need it the most (i.e. -10 f.)

Edit
s$@t. You must have written the last post while I was writing mine. May the force be with you.

Thanks for the compliments! Milford is near the middle of Delaware, just over an hour from Wilmington. I've detailed much of the project here and in my blog.

Start with a good Manual J calculation. Then you can size the equipment and ductwork appropriately. I used this ductulator, after the Manual J told me how many CFMs per room, to help size the ductwork (and balance the duct pressure drops.) There's a post in my blog where I detail how to size the ducts, it's actually pretty intense if you want to do it right!

I switched plans from using ductboard for the trunk to using sheet metal. I looked at material and tool prices, and considered the ductwork is in conditioned space, and I want to avoid fiberglass in the air if possible. I found a really simple cheap brake for about $260. It's very limited in what it can do, but I found a duct assembly method in the SMACNA HVAC Duct Construction Standards manual that is doable and pretty simple.

I haven't yet fabricated the trunks, but I did make some 10x3-1/4" exhaust duct for the bathroom. This was good practice. I also fabricated a 10x6 fitting for the grille at the end of that duct, which was incredibly time consuming. Probably better off purchasing fittings

I'll get some pics of the vent duct, brake, other materials and tools. It shouldn't be long before I start fabricating the trunk, and I'll try to remember to take pics during the process. I'd be happy to answer any specific questions about anything!

[mrd]

It appears the vacuum problem I encountered was due to a low battery in the micrometer. I had ignored the indicator, and once I replaced the battery I got normal vacuum readings again.

After verifying the micrometer & vacuum pump were working, I decided to pressurize the lines with nitrogen at 350psi and let it sit for a few days, to watch for any slow leaks that perhaps the bubble test didn't reveal. In the mean time I did some rough plumbing. I've been seeing a slow drop in pressures of both circuits, which I found odd. I wouldn't expect them both to leak at similar rates, if either did have a leak.

I also found this thread, in which an experienced tech indicates a pressure test on a split system should be at low pressure (~100psi) because the service valves tend to leak. If this advice were taken to heart, it seems the robust method of installation is to recover & recharge, with a pressure test inbetween.

Sigh. Why is HVAC such a pain in the butt. Manufacturers should ensure they use quality service valves to prevent pressure test leakage, but should contractors assume the valves aren't leaking when they pressure test the lines with the valves closed? There's no way to really know if the valves leak between the unit and lines. It seems prudent to not make the assumption. I think I've come across just one thread where an installer said the valves tend to be faulty and the unit should be recover/recharged at every install. Though perhaps one is enough.

Given the pump-down I've gone through it's sensible to recover/recharge, but I still want to see this system hold a nitrogen charge for a few days before I have it charged with a weighed amount.

[AC_Hacker]

Originally Posted by mrd

...because the service valves tend to leak. If this advice were taken to heart, it seems the robust method of installation is to...

When I installed my mini-split I used some of that assembly lube that the HVAC guys refer to as 'snot' on the faces of the flares, on the threads of the flares, and on the faces & threads of the service valve caps.

I also used a homemade crows foot wrench and a beam type torque wrench to tighten down the flares to spec.

I don't remember using the torque wrench on the service valve caps, but it might have been a good idea.

I didn't have a nitrogen setup when I installed mine, or a micron valve. I used a borrowed vacuum pump of unknown quality, and let it run for a couple of hours, before I did the R-410a release. On hindsight I was taking more risks than I should have. The methods you guys are using are far superior... But in my case, things turned out OK.

Mini-Split running for two years and no leaks or problems to report...

-AC_Hacker

[Xringer]

I had the same half dead battery problem the other day.. I did not notice the battery icon [~~] on the LCD..
Could not get anything to work.. Just displayed "----", until I installed a new 9V..


When I did my over-night pressure test, I did see a drop in the morning.
And later saw the pressure come back up when the sun came out and things slowly warmed up.
The temperature of your metering hardware is also a factor.


If you are using 350 psi (per the manual?) and it back-feeds into the pre-charge,
that seems like a warranty issue. It shouldn't back-flow. Those valves are
designed to block high pressure from either side, without blow-by.

Just make sure it's turned all the way down, and pretty tight. That 350 psi is going to
push the o-ring (or gasket) down even tighter. (The pre-charge resting pressure is much lower than 350).

[S-F]

How's the house coming? You haven't updated the blog in a while? How's the heat pump working out?

[mrd]

One of the circuits wasn't leaking, for some reason my hoses weren't fully seating on one of the service valves. I just had to give it a few more turns to see the true pressure. The other circuit was slowly leaking; This was the same one I repaired the flare on. When I installed the flare nut I hadn't fully torqued to spec as I didn't want to repeat the problem. I tightened this flare nut up some and the pressure stopped dropping. Then I vacuumed and released the charge.

I've been using the system for the past few days while I'm doing rough plumbing, turning it on when I arrive and off before I leave. There is not yet ductwork so they are just heating the crawlspace. I won't know how well the system heats the whole house for a while yet, not until it's drywalled & insulated.

It does a good job of heating the crawlspace though It's much nicer than working in 40F. It's a quiet system, the blowers are remarkably quiet even when I'm right next to them. The outdoor unit makes a little noise when the compressor is running fast, and is almost silent when it slows down. I set the system to sense the indoor temperature at the blower, so as the crawlspace heats up the compressor slows down. The sound of the outdoor unit reminds me of a refrigerator, nothing like the clanky compressor sounds I'm used to hearing from outdoor units.

[mrd]

I have uploaded some pics of the ductwork fabrication process here - or here if you can't access the other album photos. Fabricating your own metal duct is very time consuming. And painful (lots of cuts and working on your knees.) I now realize one of the great benefits of the ductless systems are that they are ductless!

My trunks are installed and I will be running the flex lines next. This involves installing the bend support as per my plans. More pics and details will follow.. eventually