Sanyo 24KHS72 AC/HP DIY install project

[Xringer]

Originally Posted by MN Renovator

Typically you know an A/C unit is low on refrigerant if you run the unit and it freezes the evaporator even with the blower on full speed and the evaporator is clean. It might be a bit cold outside to run such a test though and I'm not sure if there are any pressure checks in the outdoor unit that might cut back output if it thinks it might be freezing the evaporator.

I am not familiar with this test. It sounds a bit odd to me.
That's a cooling mode test? If it is, the evaporator coil would be in the inside unit.?.

Does freezing the evaporator coil means it get extra cold inside and the fan
could not bring in enough warm room air to keep it from freezing (or frosting over)?

I think the weather might be too cold to try this. Yesterday when I took
the pressure readings, it was warm and I had a short window before the rain storm hit us..
Since this morning, it's dropped 25d F.. (it's 30 now).


Regarding those old readings, a Sanyo tech guy told me they looked low..
I didn't see that.. These new readings seem to be lower in general..

[MN Renovator]

I probably shouldn't have mentioned it. Yes, it's occurs during cooling and usually its not a test but rather something that usually is a sign of a problem when enough of the gas charge leaks out.

You seemed to have a decent response from Sanyo when you called in the original warranty issue on your first outdoor unit. Have you contacted them to ask them about the high power draws that your unit goes into?

[Xringer]

Actually, I had been trying to get them to figure out the excess power problem on the 1st unit, before it went south.

And, the day we installed the new unit, and I emailed the east coast service manager,
telling him the new outdoor unit was working exactly the same as the old one.
And it had the exact same excess power problem!

There was no response. And, the unit worked fantastically all summer..


Back then, I had a theory, the factory installed the wrong firmware in the system,
they had used a 36,000 BTU control program, instead of the 24,000 BTU.

If the same board is used in multiple models, they might even be using
the same version firmware, with jumpers to tell it the exact model info.
It could have a bad jumper config.
But, I don't have enough detailed info to substantiate these ideas.
I need the factory shop manual!

This year, I'm theorizing about the amount of R410A in the system..
Could it be too much? Or too little?

[S-F]

Hey Xringer, when it gets real cold, as in close to 0) does your Sanyo put out any heat? I'm trying to get it together to build a house in Northampton (we have a very similar climate to you) and am thinking of going with only a mini-split for HVAC. I won't need much heat as the house will be insulated to pretty close to passivehaus levels.

[Xringer]

Most of the time when it gets down under 10deg F, I'll just shut it off and use backup.
It will put out some heat, but it's not very efficient at all. I would rather use backup
than let the Sanyo run at 2,000 watts, while only pumping in 8,000-10,000 BTUh.
It's not enough heat anyways, when it's extra cold.
Plus, the high-power bug (after defrost) makes
it a PITB if it's also humid too.. Frost is a real problem..

I'm working on a Hack to limit the input power, and it might eliminate the power surges..

[S-F]

Hmmmmm. The place I'm thinking about building will probably have a heat load around 10,000 BTUH. I wonder if I could make this work with a Fujitsu system.

[Xringer]

There are newer mini-splits around that will work down to zero nicely.
For a 10,000 BTUh low-loss house, the Sanyo might do fine..

The thing you have to remember is, the average really cold temperatures around here,
are going to be about 25 deg F. For those infrequent Zero degree nights,
two 1500w (5118 BTUh) plug-in space heaters will put out over 10,000 BTUh.

[AC_Hacker]

Originally Posted by S-F

Hmmmmm. The place I'm thinking about building will probably have a heat load around 10,000 BTUH. I wonder if I could make this work with a Fujitsu system.

S-F,

What was the outdoor & indoor design temperature you used to arrive at the 10,000 BTU/hr figure?

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

If the overall performance at various Wet Bulb temperatures is assumed to be fairly similar (pretty safe bet), then percentage changes on Xringers Sanyo can be applied to Fujitsu's posted specs.

Column "A" is Wet Bulb temps in F.
Column "B" is Xringers chart, assuming 65 F inside
Column "C" is projecting the 18K BTU Fujitsu performance against various temps
Column "D" is projecting the 12K BTU Fujitsu performance against various temps
Column "E" is % output based on Xringer's chart, which was used to get columns "C" and "D"

...so it looks like the 12,000 BTU Fujitsu will be ok (meaning it would perform at your design temperature) down to the usual 25 F degrees, after which it will be insufficient.

...and the 18,000 BTU Fujitsu should get you down to 0 F.

Here is a chart I cranked out to graphically show the relationship:

As I recall, the Fujitsu is advertised to keep working to -17, but you better double check that number.

So design temperature is actually quite important, and should be arrived at carefully.

Ditto heat load.

-AC_Hacker

* * *

[S-F]

I don't have certain plans yet so I have no certain heat load either. I was just estimating. But whatever number I come up with will probably be 0 outside and 65 - 70 inside.

[Xringer]

Are going to build in Northampton, Massachusetts?

Because it's not too cold there, on average..

Northampton, Massachusetts (MA) profile:



So, like I said before, For those infrequent Zero degree nights,
some plug-in space heaters will do the trick.
If, you get a good tight, insulated house..

Even I can use space heaters to keep it from getting too cold in my 1956 low-end ranch.
(I think this house was about $12,000 new).

There have been rare times, when it's gotten down to single digits and stayed there for days.
But, if you do your windows right, the solar gain during the day will be a real energy saver.

Hehehe, check this out..


Eco-homes ("green", environmentally friendly buildings): An introduction from Explain that Stuff!

Is that an air heater in the middle? Or hotwater maker?