Sanyo 24KHS72 AC/HP DIY install project

[S-F]

Yeah I'm in Northampton. It does get cold some times here but it's not really much different that where you are. I grew up in Maynard, my mother still lives there, and we seem to actually have milder weather here. And the house will extremely well insulated (12" walls and the like) so that's not a concern. The HVAC guy just called and said that the heat load calcs will be dome tomorrow. Now I just need to pick out a mini split. I need 2 wall mount units. One for each floor.

[Xringer]

I guess you have seen my pics of the little snow shed over my Sanyo..
It works great for keeping the rain dripping down the wall from getting into the air input.
Not so good for blowing snow, but it works to keep the snow from piling up right at the air input.

Since you are designing from the ground up, you have an opportunity to pre-posistion
your mounting pads or wall mounts, to avoid precipitation and/or direct summer sun..
Maybe by having extended roof over-hangs?



In a light wood frame house like mine, a wall mount would make the outside unit noise conduct into the house..
Make it sound like a window unit!
But, if you preplanned a solid mounting wall, where any vibration would be
blocked or conducted into the ground support..

Or perhaps a small elevated deck (to get above the snow line), just for your outdoor units.?.

Brick?? Nice! This might not be too noisy..


Another brick wall..(painted).

If there was an over-hang.?.

[Xringer]

I'm talking about my latest invention..

http://ecorenovator.org/forum/applia...r-limiter.html



At about 7AM this morning, conditions were ripe for a defrost run..

time, temp, dewpoint, humidity
07:00 33.1 °F 32.0 °F 96%

I looked at the TED and saw 1400-1600w steady.. (should have been abt 500w)
I knew it! I looked at the indoor unit's LEDs
and there was the Slow Blink of Defrost mode!
An IR scan of the indoor coil was 62 deg F..

I went outside and saw a bit of ice on the bottom side air intake,
and a lot of water under the unit. Ice was gone off the rear (main) intake.

Back inside, I monitored the indoor coil heat and power use.
A few minutes later, the cycle paused and the power dropped to 60w.
The Defrost LED had stopped blinking.. Next comes the Horrible Surge!!

Cycle #1:
Soon, it started stepping up in power. Within 2 or 3 minutes, it hit the set-point.
At bit over 2300 watts, the 'power limiter' browned out the 230 power,
and the cycle started all over again.. (The indoor coil was still under 65F).

Cycle #2:
As the power incremented upwards, I noticed the indoor coil was getting warm.
Now up to 70 deg F! But, the 'power limiter' kicked in again..

Cycle #3:
As the power ramped up this time, the indoor coil got even warmer.
It was a bit over 80F (and climbing) when the power leveled off at 1940 watts..
It stayed at 1940w for a while as warm air surged into the room..
Then, 1930w, 1920w and slow it decremented downwards!!

It settled down at 490-500 watts and is running like a top now..

It's still early, but I'm calling this experiment a Success!

Cheers,
Rich

[S-F]

Xringer, I can't help but thinking that something isn't up st snuff here. I don't think you should need to go through all of this to make your unit work. Have you engaged Sanyo support on this issue?

[Xringer]

One of the tests done on installation day, is the High Power mode.
So, I've known about this problem since day one.
Yeah, I've talked to Sanyo and my dealer support about it.
They have no clue and their suggestion is to call an AC guy.
Have him pull and weigh the charge.

Since the unit runs great otherwise, (and most AC guys have no clue what a mini-split even looks like),
I'm trying to figure this problem out for myself.
I've taken one pressure reading this year in heating mode (seemed normal)
and plan to take another reading in AC mode, when it's warmer out.

If the cooling pressure is not to spec, my troubleshooting idea,
is to top-off or recover a small amount of R410A
and then try the High Power test.. Maybe it just needs some fine tuning.?.

If the pressure is normal, then it's likely a firmware fault and there is nothing
I can do about it locally. I'll have to contact the backroom guys in Japan
and get them to burn me some special software without the subroutine marked,
"Massive power boost for impatient Americans, who want instant gratification".

I think that boost is really just a waste of money anyways..

[MN Renovator]

"I think that boost is really just a waste of money anyways.."

Good thing its not setup like the central air units where it kicks on strip heat for the defrost cycle and when slightly behind the thermostat or if running a non-strip system finishes the entire call for heat on whatever the aux heat is(nat. gas, propane, oil, etc.).

[Xringer]

Got another defrost this morning, and it did the usual high-power run afterwards,
but after it got One quite reset (from my gizmo), it came back on and stayed under the setpoint..(Warmer outside this morning)

We are really starting to like this new gizmo..

[mrd]

Originally Posted by AC_Hacker

I was looking over Xringer's chart, and also some on-line Fujitsu specs.

For the 12RLS, Google gave me this link which contains this chart on page 74:

[Xringer]

Between 5 & 50 degrees outdoors, the difference in power use is tiny(160w).
And the BTUhs only fall by 33% ?? (w/ 70f indoors).

That seems to be pretty dang good..

[mrd]

Originally Posted by Xringer

I set it to 22C, because the house was at about 21C. If I called for 25C or hit
the High-Power button, the power use would start increasing in 10-20 watt steps
every second or two, until the system was drawing around 3,600 watts.
(The max it should use is about 2,600 watts)..

I'm trying to prevent the system from going into over-load, since I think it's not good for the life of the system.
I suspect the old outdoor unit failed after it ran up to 3,600 watts too many times.

One of the problems I'm having with the system is the 3.6kW surge after each defrost cycle.

I was looking at the service manual for your unit, page 41 mentions the CT/peak current cut-off control. It indicates it will reduce compressor speed or "operation is interrupted automatically" to keep current draw below 22.5 amps. I would assume if they set the current limit here, then the system is designed to handle current surges this high.

The previous page also shows the compressor discharge temperature is controlled, so your compressor shouldn't be producing excessive temps if functioning correctly. I see a high pressure switch shown in a few diagrams, so I assume there is a high pressure cutoff.

I've been observing my Fujitsu operation the past few days, and I've watched the defrost cycle a few times. During the cycle, the interior heat exchanger drops down to a minimum of 10F according to my IR thermometer. Shortly after, the unit kicks back into heating and has to bring that exchanger back up by about 100F or so.. The quicker it gets back up, the sooner you can resume heating, so it seems logical this would be when the system uses a maximum amount of power.

If you think there are excessive pressures in the system, but not high enough to trigger the high pressure switch, then I would assume either your refrigerant charge is wrong, or the system wasn't engineered properly.