# A workable idea for an off-grid Airconditioner?

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Registered Users Posts: 8
Right now, air conditioning is difficult to do with the power budget an off grid home usually has. The biggest obstacle is the cost of batteries. Not only are the batteries expensive, but they die like flies...lead acid batteries last what, 8-10 years at most? And they lose capacity the entire life cycle?

So I have been trying to figure out on paper a solution. And I thought of one that is both simple, elegant, and the numbers work very well on paper.

First, while the cost of batteries has stayed fairly constant over the last few years, the cost of the solar panels have not. Sunelec.com will sell you panels in bulk for 98 cents a watt. Also, while batteries last perhaps 8 years, the panels last at least 25 with acceptable performance at the end of lifespan (meaning they don't really need to be replaced at 25, you could just add more panels to the array every 10 years to make up for the capacity loss of aging panels). With ultra-cheap panels, generating the energy needed for an air conditioning system is actually plausible, especially since the times of year that the A/C is needed the most happen to be the same timespans that the solar systems produce the most electricity.

Anyways, the solution is simple. Purchase a geothermal airconditioning/heat system called "water to water", where the output of the geothermal system is heated or cooled water. A 3 ton system draws about 2500-3000 watts electric. Have at least that wattage in panels, and a small battery bank to act as a buffer. The water-water system will send the cold water to an uninsulated 550 gallon storage tank in a closet in the center of your home. By my math, this tank will cost about \$300 and store 46 killowatt-hours of potential energy if the water is chilled to 45 degrees and the target temperature in your home is 80 degrees farenheit. With a coefficient of performance of 3.5 for the geothermal system, that's the same as \$2200 worth of lead-acid batteries from sunelec (assuming you discharge the batteries to 50%). Moreover, a quality water storage tank stored inside (so no UV exposure) made of quality plastic and filled with fresh water will probably last at least 25 years. While a battery bank will need to be purchased about 3 times for that time span. So it's 20 times cheaper for water tanks. 550 gallons might or might not be enough storage, it depends on the thermal load of the house.

To extract the cold, a small DC pump would circulate the water through a heat exchanger (they make commercial air handlers that use chilled water or you could use a car radiator) and you have a fan blow air over it and a duct system. Install an energy recovery ventilator with the intake vent sucking air from the closet the tank is in (to remove condensation...need a drain in that closet as well and to make the walls out of a material that can withstand moisture) and have the air coming from outside for the ERV go to the air intake for your heat exchanger and A/C system.

The tank doesn't need to be insulated - any cold that escapes the tank into your house just means that the air handler fans and pumps need to run less - this actually boosts efficiency. You could alternatively use more expensive tanks that can take hot water as WELL as cold and use the system for heating in the winter the exact same way. (alas, the insulated tanks that can take hot water are very expensive - \$3600 for a 500 gallon one.)

You'd use an Arduino board to control the system : if the A/C is armed, then when the incoming power from your solar array exceeds a certain level (the arduino board would have a data link to your inverters) and the charge in your battery bank is above a certan threshold, you turn on the A/C and run it until either the water in your storage tank is at ~45 farenheit or the charge in your battery bank drops below a certain setpoint. (because clouds obscured the sun or other power draws in the house drained your battery or whatever)

One final state : at a certain point on some days the water in your system will be pretty warm, and running a heat exchanger won't make sense any more. You'd have your system switch modes : the water-air heat exchanger would shut down and you'd use the cold water from your tank as the water source for a swamp cooler.

Note that the water in the tanks would not be pressurized, it would basically be a cistern. Glycol and anti-fungal additives might be needed, although they might reduce cooling performance.
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Re: A workable idea for an off-grid Airconditioner?

You can get industrial batteries (forklift/traction) that will last out towards 20 year life... Obviously not cheap, tend to have a bit more power loss, and need more distilled water.

There are some new air conditioners which are very off-grid friendly... About 2x as efficient as a typical window air conditioner, and they use an internal VFD (Variable Frequency Drive) that reduces starting surge current to near zero, and allows you to choose a low speed setting and run 300 watts all day long.

There are heat pump versions which can be pretty nice for some heating too (assuming you have enough sun in the winter).

Sanyo mini split AC (inverter/variable speed)

If you have a well insulated home/building, off-grid AC systems are getting practicable now.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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Re: A workable idea for an off-grid Airconditioner?

Interesting idea, I had readsomething like in with an ice block refridge, I'm not sure your including the cost of square footage space in the house, as this would be a sizable chunk of real estate nearly needing a secial built house, I think the 4x4 plastic shipping cubes are around 300 gallon? and would require taking down a wall in most homes. more things to think about.

Of course as has been often stated swamp coolers work only with dry climates. I think the split AC units have very high effiecentcies, if your redesigning a home, extra insulation and a setup for 1 or 2 of those units might make more sense. The "window shaker" works OK for my tiny cabin with 6" thick walls, but you have to leave to cook or use the facilities...
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
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Re: A workable idea for an off-grid Airconditioner?

You can go direct from PV to compressor motor and bypass DC-DC charge controller, battery and DC-AC inverter losses. Take compressor spun by brushless DC motor, power it from 3 phase brushless motor inverter, input of which is connected directly to PV array. With some software magic inside this inverter, you can make it behave as MPPT controller. Chill water in large cistern as thermal storage, or freeze it.

I would use this method to share cooling load with structure's existing HVAC system. In winter, system can be reversed to harvest ground-source heat. But, still there may be times when system sits idle, because outside temperature is perfect.

Advantages are: No energy storage batteries to install and to replace, no battery charge controller, no 240VAC 60hz inverter. Higher system efficiency - less PV panels needed. No dealing with grid-tie permissions - making it easier to DIY guerilla style. Less wiring.
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Re: A workable idea for an off-grid Airconditioner?
AntronX wrote: »
You can go direct from PV to compressor motor and bypass DC-DC charge controller, battery and DC-AC inverter losses. Take compressor spun by brushless DC motor, power it from 3 phase brushless motor inverter, input of which is connected directly to PV array. With some software magic inside this inverter, you can make it behave as MPPT controller. Chill water in large cistern as thermal storage, or freeze it.

I would use this method to share cooling load with structure's existing HVAC system. In winter, system can be reversed to harvest ground-source heat. But, still there may be times when system sits idle, because outside temperature is perfect.

Advantages are: No energy storage batteries to install and to replace, no battery charge controller, no 240VAC 60hz inverter. Higher system efficiency - less PV panels needed. No dealing with grid-tie permissions - making it easier to DIY guerilla style. Less wiring.

Alot of work and you would not have electricity at night without batteries. One of the advantages as Bill points out of an efficient heat pump is you do not have the 30% duct loss. It would be a nice project though!
"we go where power lines don't" Sierra Nevada mountain area
htps://offgridsolar1.com/
E-mail offgridsolar@sti.net

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Re: A workable idea for an off-grid Airconditioner?

Another reason for doing it this way is that the whole idea here is to make the costs reasonable. They sell these plastic water tanks for cheap. You wouldn't need to cut out a wall necessarily...you could use several smaller tanks in parallel rather than one large tank.

That's the reason not to use those "solar friendly A/Cs" or to develop your own motor controller for an A/C compressor that works without batteries. You can buy yourself a 3 ton ground source A/C system for approximately 5 grand, new with a warranty. Including all of the piping you need to bury in the ground.

I think from an electrical standpoint if you used a 240 volt 60Hz inverter-charger, during the day when the A/C is running and the sun is out the energy would go straight from the inverter to the A/C. I don't think internally the inverter is sending those amps to the battery bank and then withdrawing them again - instead it is sending a small amount of current to keep the battery charged and the rest bypasses straight to the load.

The inverters used in this system would be the kind that offer a "bypass" feature...mentioned in these forums...where they power a load with the excess energy after the battery bank is charged. So the A/C system wouldn't be started until the battery bank for the buffer is charged.
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Re: A workable idea for an off-grid Airconditioner?
Alot of work and you would not have electricity at night without batteries.
I am mainly interested in this way of connecting compressor motor to PV to bypass unnecessary power conversion steps. Take 95% efficient brushless motor inverter and 95% efficient iron core-less brushless motor, connect to PV directly and you get 90% DC to kinetic efficiency. Since motor inverter can vary it's DC current draw and communicate with MPPT battery charge controller, they both can run from same PV array at the same time.
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Re: A workable idea for an off-grid Airconditioner?
Gmonroe wrote: »
You can buy yourself a 3 ton ground source A/C system for approximately 5 grand, new with a warranty. Including all of the piping you need to bury in the ground.

.

If you live in an area where an air source heat pump is OK then they get close to the same COP for considerably less money.

Russ
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Re: A workable idea for an off-grid Airconditioner?
AntronX wrote: »
I am mainly interested in this way of connecting compressor motor to PV to bypass unnecessary power conversion steps. Take 95% efficient brushless motor inverter and 95% efficient iron core-less brushless motor, connect to PV directly and you get 90% DC to kinetic efficiency. Since motor inverter can vary it's DC current draw and communicate with MPPT battery charge controller, they both can run from same PV array at the same time.

Yes I am interested also and "get your point" I just want that MPPT to also look at the conversion down to 24V and 48V.
"we go where power lines don't" Sierra Nevada mountain area
htps://offgridsolar1.com/
E-mail offgridsolar@sti.net

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Re: A workable idea for an off-grid Airconditioner?
...I just want that MPPT to also look at the conversion down to 24V and 48V.
I am not following, please explain.
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Re: A workable idea for an off-grid Airconditioner?

In times past, I did find a solar panel powered VFD that output 3 phase power... More or less what you are asking for. It was not cheap, and I cannot find it now.

I did find one or two places that referenced solar powered VFD's, but the websites seemed to be dead.

Obviously, it can be done... Grundfos pumps, Sun Pumps, and other companies do this all the time for their products.

I would call Sun Pumps and see what they say... they have a controller that is being closed out that may do what you want (no specs. listed). But, in any case, they may be able to point you to a VFD controller that meets your requirements.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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Re: A workable idea for an off-grid Airconditioner?
Gmonroe wrote: »
To extract the cold, a small DC pump would circulate the water through a heat exchanger (they make commercial air handlers that use chilled water or you could use a car radiator) and you have a fan blow air over it and a duct system.

I don't think this will work very well.

I looked into something like this once and it turns out that for a radiator to be effective you need a fairly significant difference in temperature between the input fluid and the input air.

If the air temp is only 80 degrees then you really don't need cooling. When the air temp gets up to 85, you might be able to get the exhaust air down to 80, but putting 80 degree air into an 85 degree house won't make much difference, maybe 1-2 degrees.
As the heat load increases the water temp increases and your cooling rapidly become less and less effective.

If swamp coolers work, then just use one of those from the get go. No need to waste internal storage space on a water tank. The effectiveness of swamp coolers doesn't change much using cool water vs warm water.

If you really want to maximize efficiency you could go with a two stage swamp cooler. They are almost as effective as AC (colder output air than traditional swamp coolers) and don't increase the internal humidity as much as traditional swamp coolers.
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Re: A workable idea for an off-grid Airconditioner?

Couple of things. I am familiar with geothermal and I agree water to water is the most efficient way to go. It is what we have and use.

Storage of 550 gallons of cold water. You would have to significantly chill the water to hold a good amount of energy or lack of energy. The further the delta T or temperature difference the less efficient the system becomes but the more energy stored. The weight of 550 gallons is something that needs to be considered at 8 lbs a gallon you’re looking at 4400 lbs, that is a lot of weight; I would think more than standard floor system is designed to support, but don’t know for sure.

Also if you don’t insulate the tank you will get cold spot in the house and most importantly you will get a lot of condensation on the tank itself which will have to be dealt with, not a huge concern, but something to keep in mind.

And yes it is fairly easy to add a water coil to your furnace to exchange the cold water and evenly distribute it around the space and could easily be done with a pump controlled by a thermostat.

I basically do this, but primarily with heating, using solar to heat up our indoor pool or 16,500 gallon storage tank. Raising it just one degree will easily carry me through 2 days of heating. I could do the same thing in summer, cooling the pool, but I doubt it would be useful as a pool at 40F

Also make sure you take advantage of the “de-super heater” using it to generate your domestic hot water needs as well. In summer it’s a win win heating your water and cooling your home.

I also cool the house down when we have excess solar available and use the house as the buffer. I can often carry us through the night.
3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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Re: A workable idea for an off-grid Airconditioner?

Back in the 70's I had a set of plans for a Thermal Storage in a tank you poured under a garage floor like a swimming pool when building. I passed on it because I was afraid it would crack. The concept has been around for a long time. I am sure it could be done with success. There are plenty of houses that have two water wells that you can pump from one and inject back into the other. Water cooled/heated heat pumps have been around for a long time, my last boat had 4 of them, big pain keeping the water pumping 24/7.

Here is something I found when I was searching for those plans. Today there is a lot more of " off the shelf " stuff then when I was fooling with it. Bottom line you can spend a bunch of money and it might work and it might not.

http://www.greengaragedetroit.com/index.php?title=Mass_Thermal_Storage
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Re: A workable idea for an off-grid Airconditioner?

Now I am certainly not an expert, but I have read about this type of "air conditioner" used in CA (certain article comes to mind). However they were using cheaper electricity at night to freeze large tanks of water, then in the day using it for air conditioning via cold water.

So, I would think with some number crunching this could be a viable option for cooling. The only question.. could you get the water cool enough!? Keep us posted!

TBR:cool:
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Re: A workable idea for an off-grid Airconditioner?

Yup, I've read about those systems, too. The time-of-use overnight is correct, and they used the original air-sourced A/C pump to do it. Additional valves are installed to redirect the cold into the storage tank. I think I read about it in Homepower.
4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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Re: A workable idea for an off-grid Airconditioner?

Also in the case where your using a traditional AC at night with off peak or cheap power the air tends to be much cooler which makes the system more efficient as well.
3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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Re: A workable idea for an off-grid Airconditioner?
AntronX wrote: »
I am not following, please explain.

If, as you say you had a controller that ran the heat pump DC side directly, it would be a wasted array when as you said when the season did not require a heat pump. If the controllers mppv could track the heat pump requirement and also have an algorithm that could dump excess power to a 24/48 V charger there would be no wasted resource. Of course the whole concept of living offgrid means there always seems to be a storage problem at some point of the yearly cycle.
"we go where power lines don't" Sierra Nevada mountain area
htps://offgridsolar1.com/
E-mail offgridsolar@sti.net

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Re: A workable idea for an off-grid Airconditioner?
AntronX wrote: »
I am mainly interested in this way of connecting compressor motor to PV to bypass unnecessary power conversion steps. Take 95% efficient brushless motor inverter and 95% efficient iron core-less brushless motor, connect to PV directly and you get 90% DC to kinetic efficiency. Since motor inverter can vary it's DC current draw and communicate with MPPT battery charge controller, they both can run from same PV array at the same time.

If you were using something like a Sanyo mini-split, it would take an over-sized
PV array to run it. And when the clouds came by? Batteries are the solution.

One bad feature of my 24,000 BTU Sanyo cool/heater is the power surges
they built into the control firmware.
This morning, it was coasting along (heat mode) at 480w.. But when I clicked it up from 21C, to 22C..
It quickly stepped up it's power use to 1,700w before slowly backing down
back to 400-500w range.

Our Sanyo does go into standby when the house hits the set-point,
so it's not going to average a continuous 400-500w on most days.

On many days, the over-all daytime average is going to be less than 350w.
During the last 16 hours, it used an average of 294w per hour.
For 5 hours, early this morning, it was below 30F around here.
And the Sanyo was holding the house at 21C.

---

My solution for day-time only off-grid use, is to buy a 48vdc to 230vac
2.5kW inverter and run the Sanyo during the day only.
If it's too hot after the sun is low, then go back to the grid..

My 48v 115Ah battery bank should be able to supply 400-500w during
short cloudy periods. If the bank SOC gets too low, back to the grid again.

I'm still trying to find out if any off-griders are using a MSW inverter!

Cheers,
Rich

(This PC is using 180w off my solar backup, as I type this).. :cool:
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Re: A workable idea for an off-grid Airconditioner?

A Sanyo set to Low will not spike like yours does (which is on Auto). Just want the OP to be clear on that - you can control the max wattage, just don't use Auto. Start it on Low in the morning after the battery bank has hit float so you can get ahead of the heat curve, and by the time its hot outside you have effectively stored cold in all the objects inside your house to carry you through the heat of the day (I know, you don't really store cold but the analogy makes it easier to equate it with a chemical battery).
4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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Re: A workable idea for an off-grid Airconditioner?
techntrek wrote: »
A Sanyo set to Low will not spike like yours does (which is on Auto). Just want the OP to be clear on that - you can control the max wattage, just don't use Auto. Start it on Low in the morning after the battery bank has hit float so you can get ahead of the heat curve, and by the time its hot outside you have effectively stored cold in all the objects inside your house to carry you through the heat of the day (I know, you don't really store cold but the analogy makes it easier to equate it with a chemical battery).

Right !
Of course with a larger array you can set to medium and a higher differential. The same thing with high and so on. It is still for us one of the sweet things in life. Zero problems over three years now.
"we go where power lines don't" Sierra Nevada mountain area
htps://offgridsolar1.com/
E-mail offgridsolar@sti.net

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Re: A workable idea for an off-grid Airconditioner?
techntrek wrote: »
A Sanyo set to Low will not spike like yours does (which is on Auto). Just want the OP to be clear on that - you can control the max wattage, just don't use Auto. Start it on Low in the morning after the battery bank has hit float so you can get ahead of the heat curve, and by the time its hot outside you have effectively stored cold in all the objects inside your house to carry you through the heat of the day (I know, you don't really store cold but the analogy makes it easier to equate it with a chemical battery).

I know exactly what my particular Sanyo does. I've got a TED on it.

It uses an unchanging level of power, once the house is stabilized.

But, I would like to draw your attention to the very 1st peak in this plot.
Notice the green & blue plots are together at power up?

Now, what happens when you turn up the heat from 70 to 72?

In my experience, the power usage is going to double. (approximately).
So, if I'm using 500-600w to heat my house, and want it warmer,
I'll likely see the power increase to 1200 to 1800 watts.
If it's pretty cold out, the peak could easily reach 2200watts.

That peak doesn't last very long, before it's back down to normal again.
(30 seconds, to a couple of minutes, depending on outdoor temp).

It makes no difference what mode it's in. Auto and manual, both seem
to work about the same, when it comes to requesting a change in temp.
That seems to be the way they programmed it.

If I request a 5 deg temperature change (in manual or auto mode),
this Sanyo will try to use all the power that's available.
Once it goes over 3.5kw, the over-load or over-pressure switch will kick in
and it will shut down completely.
There is a button on the remote that will do this, it's marked "High Power Mode".

It's not just a problem with mine, but a few others have seen this same bug.
I've gone to the trouble of building a precision electronic circuit breaker
to keep my Sanyo from trying to drain the grid..
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Re: A workable idea for an off-grid Airconditioner?

Yes, I understand yours does that in heat mode, but Daves doesnt spike in cool mode (the OP is asking about cooling). I didnt think yours did either when cooling.
4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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Re: A workable idea for an off-grid Airconditioner?

What was described is a classic compressor Short Cycle. Could be any number of things. First guess would be the one that get's me from time to time. Inverter is in power save mode and cannot ramp up fast enough to give compressor enough current. That starts a cycle if the compressor trying to start and overloading because of high head pressure.

1) low battery Voltage
2) to small of wires ( battery to inverter )
3) glitch in controller board
4) no delay for re-start ( 5 minutes )
5) weak capacitors

It takes some time to run down all the possibilities. Chicken or the egg kind of thing.

I have had a reversing Valve that wouldn't switch fast enough and stall a compressor. I don't know if the Sanyo switches when it calls for heat or cool.
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Re: A workable idea for an off-grid Airconditioner?
techntrek wrote: »
Yes, I understand yours does that in heat mode, but Daves doesnt spike in cool mode (the OP is asking about cooling). I didnt think yours did either when cooling.

Yeah, cooling too. If we come home to a hot house, we have to click the
cooling setpoint up to match the house temp, at power-up.

Once it's running for a few minutes, I'll check the power.
If it's normal,then I'll lower it one degree.
After the power peaks and drops back down, I'll click another degree down. And Repeat.. :grr

Nowadays, I don't have to be so careful.. My gizmo keeps Ms. Sanyo from going nuts..

At 9.5 amps, it drops a few cycles and causes a calm re-start..
• Solar Expert Posts: 529 ✭✭✭
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Re: A workable idea for an off-grid Airconditioner?
What was described is a classic compressor Short Cycle. Could be any number of things. First guess would be the one that get's me from time to time. Inverter is in power save mode and cannot ramp up fast enough to give compressor enough current. That starts a cycle if the compressor trying to start and overloading because of high head pressure.

1) low battery Voltage
2) to small of wires ( battery to inverter )
3) glitch in controller board
4) no delay for re-start ( 5 minutes )
5) weak capacitors

It takes some time to run down all the possibilities. Chicken or the egg kind of thing.

I have had a reversing Valve that wouldn't switch fast enough and stall a compressor. I don't know if the Sanyo switches when it calls for heat or cool.

I'm pretty sure my Sanyo reversing valve stays in the selected mode,
unless the mode has been placed in Auto. Then, it will switch back and
forth between heating and cooling as the house temp moves above and below the set-point.

I think the "glitch in controller board" is a firmware routine that's called Instant Heat (or Cool).
For some reason, Sanyo decided that American's are too impatient to wait
for their Sanyo to heat or cool..

http://www.minisplitsystems.com/sanyo.html

"The SPW DC inverters use Advanced Digital Hybrid (ADH) technology for better, smarter and more cost-efficient yearround climate control. Immediately following start up, the DC compressor operates at maximum power to provide almost instant heating or cooling. As the desired air temperature is reached, a special Pulse Width Module automatically adjusts the compressor's frequency to exactly meet the cooling or heating requirements of the room. The result is exceptionally precise temperature control, less noise and significant energy savings."

Anyways, that 'maximum power' (Or Go Nuts) mode is a problem for some Sanyo owners.
I've found it's triggered during power up, if there is a 2 or more degree call for heat of cooling.
And of course it starts 'maximum power' when the HIGH POWER button is pressed..
And worse of all, it starts sucking 'maximum power' after a defrost cycle at 4AM!! :grr

So far, nobody has figured out the exact reason..
Mine might have a little too much or too little R410a in it..
I've done a winter pressure reading(looked normal) and when it gets warmer,
I plan to do a summer reading. If it's also normal. On to plan C..
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Re: A workable idea for an off-grid Airconditioner?

I got the following from a Sanyo site. In the heat mode the reversing valve is energized. When the unit goes into a defrost cycle the valve is de-energized and the unit goes into the cooling mode to defrost and the heat strip kicks in. So, with the strip you would be using a lot of power. The same increasing the temperature with the remote up 2 degrees, that's how most heat pumps work.

I don't know what model you have, KHH2672R, THH2672R and the THH3672R. All have heat strips.

A option would be to unhook the heat strip, if that's your problem and live with the cold air it put out for 5 minutes or so.
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Re: A workable idea for an off-grid Airconditioner?
I got the following from a Sanyo site. In the heat mode the reversing valve is energized. When the unit goes into a defrost cycle the valve is de-energized and the unit goes into the cooling mode to defrost and the heat strip kicks in. So, with the strip you would be using a lot of power. The same increasing the temperature with the remote up 2 degrees, that's how most heat pumps work.

I don't know what model you have, KHH2672R, THH2672R and the THH3672R. All have heat strips.

A option would be to unhook the heat strip, if that's your problem and live with the cold air it put out for 5 minutes or so.

http://www.sanyohvac.com/products.php?id=24KHS72

Yeah in defrost it pumps a little heat out of the house to melt the ice and snow.
The indoor coil gets cold, but they keep the indoor fan off, so the temperature loss is minimal.
(Edit: While in Defrost mode the LED blinks every 4 seconds, and the power stays around 1700watts.
The problems comes when defrost is over. It goes into Warp Speed mode.).

I have the 24KHS72 and the only heater is on the Crankcase. It runs all the time.
http://i46.photobucket.com/albums/f147/Xringer/NCL/outdoor.jpg

When the Sanyo is not going to be used for a few days, we shut off the breaker.
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Re: A workable idea for an off-grid Airconditioner?

It really runs the crankcase heater 24x7? You would think they would put a simple thermostat inline. How much does it draw?

I know our air source heat pump draw about 15w when the crank case heater kicks on. I also know it does cycle and runs more the colder it is out. Once its warm or I should say hot doesn't come on at all.
3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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Re: A workable idea for an off-grid Airconditioner?
Brock wrote: »
It really runs the crankcase heater 24x7? You would think they would put a simple thermostat inline. How much does it draw?

I know our air source heat pump draw about 15w when the crank case heater kicks on. I also know it does cycle and runs more the colder it is out. Once its warm or I should say hot doesn't come on at all.

Right now, it's warmer out and the TED is displaying 20w. When it cold out,
it mostly displays 40-60w. So, I'm not sure if it's actually a controlled heater,
or my TED meter does a poor job at low power levels.

I was worried about the heater at first, but using the Sanyo cuts so much
from our (oil) heating & (wall shaker) cooling bills, 20-60w isn't really a concern anymore.

IMHO, the mini-split is the best home improvement investment we've ever made.
When I start running it off Solar during daylight hours, it will be even better! ::D