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Forum Index : Electronics : Run a standard freezer Off-Grid?
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I've had a couple of people ask me about options for 200 - 300 litre freezers that would work on off-grid setups. We have been through all the danfoss compressor options they are all $1800+ (plus $400 freight) I have looked in the shops and there are freezers available locally that are under the 1Kw per day mark for between $600 to $900. I am thinking the only thing stopping us fitting a standard freezer is a high starting surge current overloading the inverter. I would like to know if there are any freezers that are designed with a lower start current? Or could we tweak it ourselves? I have noticed there are potential relays and start capacitors mentioned as standard parts for some fridges on a few refrigeration forums and companies like Supco sell a capacitor start pack complete with relay. I'm confused, no wait... maybe I'm not... |
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norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
Don`t really follow you here, how small are these off-grid systems? A 1000watt continuos inverter would start one. Off-grid systems using an inverter with 240v appliances, I have experience with all have a 4000 watt plus inverters. We come from the land downunder. Vic |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I run my converted fridge (see earlier post on that) off grid through a 1200W sine wave inverter - no problems starting it at all. The important thing here is a low frequency inverter, mine has a massive toroid transformer in it which can provide the 'kick' to start an induction motor. Klaus |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
That is roughly the area I was looking at, 800 - 1200 Watt sine wave inverter. This is some info on most online store listings for a westinghouse 210L chest freezer Starting current peaks (Amps): 6 (depends on temperature/conditions of compressor when it starts and a supply voltage in different area) Electrolux does not recommend use of alternate energy supply Running current (Amps): 0.6 I have tried a couple of older freezers and they are woeful. 12+ amps starting current. I don't know if that is genuine or voltage slump or even low power factor. I found a article from a boatie saying that he basically "tuned" his freezer by trying different combinations of start & run capacitors resulting in about a 25% reduction in the run watts and 70% reduction in the starting surge watts. I'm confused, no wait... maybe I'm not... |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Here is some data of DC current draw from my 24V (nominal) battery bank when the above mentioned fridge starts up. Initially 20 - 24A which quickly tapers to around 17A for the short time it runs. The donor fridge was not a special economic model, just what was available second hand at the time. My kitchen fridge/ freezer (upside down arrangement) needs only 7A from the battery bank to run, as I cannot hear it starting up from the battery bank location I never saw its start up current. This fridge is fed from a different (1800W) inverter BTW. Klaus |
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| norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
We`ve touched on refrig in an older thread, I`ve been convinced that newer fridges and freezers are fairly economical. My system currently runs a 420l Fridge/freezer frost free (new), a 300l upright frost free freezer (8yr old), a 100l bar fridge(new) and an old 12v 100l upright Norcold (run off 240v through transformer). All are stock standard West or Kelvi`s (Electrolux) except for the Norcold. My consumption from solar off to solar on (ie when panels stop charging to begin charging) varies between 60ah to 100ah (48v) this includes household use of lights, TV etc for a couple of hours each night. With time we have become somewhat complacent about energy conservation, using microwave, turbocooker(thanks Bob tis a beauty), electric toaster, electric pod cofee maker, PC on all sunny day etc. Time has just shown there is no need if the system is sized adequtely and you monitor battery charge ensuring they never go below 70%. I simply monitor with the PC daily using the software that comes with the inverter with a monthly check on cell SG. Fortunately I live in sunny inland NQ and run the generator-charger once a month to ensure it works(1/2 hour) with usually an hour run on some days during the wet. Use 40l of diesel a year approx. Trust the above is of some use and not an overkill, KISS solar really is the way to go off-grid. We come from the land downunder. Vic |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
Norcold, What sort of life expectancy do you expect from your battery bank? (Since things like this gradually deteriorate there will be time that system still works but capacity drops and eventually generator will have to be used more often and eventually batteries will be replaced due to nuisance factor.) George |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
This is a short list of what is available locally. chest freezer Haier-----------------HCF208-------208L--285kw/yr $400 WESTINGHOUSE------WCM2100WC--210L--322kw/yr $500 FISHER & PAYKEL-----H220X--------216L--348kw/yr $450 upright freezer WESTINGHOUSE------WFM1800WC--175L--282kw/yr $600 Haier----------------HFZ-175-------175L--365kw/yr $420 MIELE---------------FN 12827 S----304L--310kw/yr $1600 I am tempted to buy a Haier chest freezer and give it a go with a 1000 watt inverter and see what happens. I think the freezers that I have tested so far are probably a lot older than they look and come from a time when 1000 Kw/yr was considered economical for a freezer. Bit reluctant to borrow someones good freezer to play with and fry the compressor motor. I'm confused, no wait... maybe I'm not... |
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| norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
Life expectancy of batteries are at least 10 years. They are 1080 A/hr thus at 100a/hr overnight Max use they have only drained a little less than 10%. Have really no need for the generator, it is just a backup in case. Have to get back to you in 10 years and see how they`re going. Yahoo2, I`d go for the West or Kelvi, they`ve always served me well. You will not fry the compressors they`ll either start or not. No drama. The sine wave inverters of reputable name give good clean power much better than the Grid. We come from the land downunder. Vic |
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| TronicSavyyJohn Newbie  Joined: 31/03/2012 Location: AustraliaPosts: 20 |
Two bobs worth, Hi All, i recently converted some circuits over. My LG twin fridge freezer has soft start built in. 620Lt max power draw 480Watts. Powering it off an 8ZED Pure Sine Wave Inverter. Backed by GSL MPPT60-1 , twin Powersonic 120aH batteries and 5 panels off ebay. The shocking total, $3475 ish  , the fridge was normally $2500 - Down to $1k flat as fork lift marks down the side. A bit of overkill on the MPPT but was tired of the elcheapo off ebay burning out.
But would like some ide's ont he chest freezer. No one in the whitegoods market has yet to confirm to me a freezer avail with soft start.  |
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| Privatteer Newbie Joined: 09/06/2012 Location: AustraliaPosts: 39 |
I've just started monitoring a few of my items around the house. Mild weather. 24hrs average after several days recording. Fridge - Fisher&Paykel 403L (1yr old) 0.991KWh Freezer - Westinghouse 210L (~8yrs) 1.09KWh Freezer - Westinghouse 150L (~10yrs) 0.858KWh The meter was still on the 150L and max draw recorded was 1234w. Compter 4KWh <--- Ouch. I've still got to track down about another 8KWh a day and there is not much left plugged in. No aircon and gas HWS/cooktop. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I am going through the energy audit process myself right now. Biggest load was a 35 year old 300L fridge which was the first thing to go to the tip. Second biggest load was a computer that usually ran most of the day and consumed an amazing 4.5Kwh. Next thing to go to the tip was the 15 inch CRT monitor that consumed 480 watts, replaced with a 17 inch LCD monitor that consumes 40 watts running. Slowly working around replacing incandescent bulbs with standard 36 watt fluorescent strip lights in several rooms. Other power hogs included numerous transformer plug packs that typically draw 25mA with no load. The dc ones have all been replaced with modern cold running switch mode plug packs. All that was all fairly straightforward. Other loads included a laptop power supply that draws 75mA from the mains, even when the battery is fully charged. I plan to run this off a 24 hour timer so that it only comes on for about an hour every twenty four hours, plenty to keep the battery fully charged. Other loads included two mains powered wall clocks that used around 60mA and 70mA. These were replaced with battery powered wall clocks. Another amazing constant power drain was my garage door opener. This has a fairly big transformer to supply around 30 volts dc at up to three amps for the motor. This transformer draws 80mA constantly twenty four hours per day. What I did was power the circuit board and radio receiver from a 12v switchmode plug pack that only uses 8mA. When the radio receiver detects something should happen, a solid state relay connects the big transformer up to the 240 volt mains for the motor. It works exactly as it did before, but now it only uses 19wH/day instead of 190wH/day. I have a similar problem with my gas space heater. A big transformer draws 45mA continuously even with the beast switched off. At the moment I just pull out the wall plug, but plan a similar modification to what I have done with the garage door opener. Another power parasite were some 24 volt ac plug packs to power my garden irrigation system. These draw 25mA constantly, and I have three of them. Two possible solutions to this that I have not done yet. First would be to run all three off one plug pack and fit a 24 hour timer to turn off the single plug pack during the hours when the irrigation system is not used. Another possible solution is a bit more interesting. The big issue with these 24 volt 600mA ac plug packs is the high magnetising current from the small crappy transformer. What works much better is a microwave oven transformer turned around and run backwards. Usually these are 240 volts in, 2,400 volts out. Connecting 240 volts to the 2,400 volt winding gives 24 volts out. But the interesting thing is that the huge number of turns keeps the magnetic flux in the core extremely low, and magnetising current is only 7mA to maintain that low flux. So if you need 24 volts ac constantly available for something, you can get it from a microwave oven transformer with a very low parasitic no load loss. This may actually be more efficient than using a time clock with an original plug pack. All good fun and it has been a fascinating exercise. If it works as well as I expect, it should just about HALVE my next power bill. As to starting and running a refrigeration compressor from a battery supply. The large inrush current from an induction motor is pretty inescapable. But you could probably run a 250 watt motor from maybe a 350 watt inverter if you provide a large enough capacitor bank to store energy at the 340 volt dc bus voltage. The converter part that steps up the battery voltage to 340 volts dc could be rated for just the final continuous motor running load. The inverter bridge part that converts the 340 volt dc bus to ac is what will see the inrush, and that could be fairly easily uprated with larger MOSFETS or IGBTs. This could be a fairly effective and economical method of sourcing huge motor starting current without having to massively oversize the whole inverter. Cheers, Tony. |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
I admire you chaps for trying to reduce your electricity consumption. You've probably read on other posts that we are off grid and our daily consumption of power is 1.3KWHr. Ok, our cooking is either gas (kitchen) or slow combustion (lounge room). The SC heater has oven, cook top and wet back to heat water. The hot water is also heated by thermal panels in the summer. We have the usual computer (lap top) and LCD Tv, microwave (only gets turned on when required), front loader (cold wash) washing machine. We have a reasonable sided upright refrigerator and a 4ft chest freezer. The latter two are made by Vestfrost Germany and didn't cost much more than your Harvery Norman variety. What I can't understand is the mentality of governments who are hell bent on generating increasingly more electric power instead of legislating for power consuming devices to be as efficient as possible. There is nothing really fancy about our fridge and freezer except that the insulation is good and the 240v compressors are very efficient. We don't need air con as we have pulldown awnings on all windows - it makes a hell of a difference. Keep up the good work David M. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
David, 1.3KwH is an admirable goal and quite achievable. My consumption right now is about 2.4KwH, I could reduce that, but it becomes increasingly expensive to do so. It just requires a totally different mindset when located in a city suburb and already connected to the grid. I even have three phase power available in my garage and workshop. My approach to this was to first measure the actual power consumption of absolutely everything and decide what could be improved upon or eliminated at minimal expense. The final results have astonished me. For an outlay of roughly around five hundred dollars total, which included buying a six month old refrigerator and a couple of LCD computer monitors on e-bay, I have reduced my power consumption by more than half. Payback period for that should be less than two years. I could go a lot further, especially with an even more efficient refrigerator, but it would not be economic to do so. Totally off grid is a very different situation. Cheers, Tony. |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
Further to the above post, we built our home from the ground up (literally. WE) and as such, designed in the electricity saving principles. All up, the infrastructure cost around $15,000. To get the power grid connected to our property (about 500metres) was to cost around $25,000 as at 2005. Ridiculous but that was the optional cost. We are in the process of adding a "grid" connect system (SMA sunny boy) as we have a RAPS system based on SMA sunny island, so the two systems can talk to one another. The idea being that the house will be supplied by the grid tie during the day and the RAPS at night, hopefully extending thelife of the batteries. The grid tie inverter cost about $150 on ebay and I picked up 5x250 watt mono panels for about $1 per watt. The RAPS system also has a 500watt OEM small wind turbine to fill in the gaps when the sky is overcast. Hopefully, the mono panels and the GTI will take care of the overcast days. What we had is more than sufficient, but what the hell, the extra is fairly cheap and it builds in a bit more capacity for back shed jobs. Besides, it is something to do (as if I have lots of free time  )
David M. |
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| norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
Yes, bloody unbelievable what it costs to have a grid connection. Quote for grid supply to our place in 2006 was $72000. 1.2km of wire, although it had to go over a bit of rough ground. At that time the govt had the rural residence solar subsidy ie the govt paid 50% which in our case was just on $50000, thus for an outlay of $25000 we went for solar. At last annual check our average consumption was 5.2Kwhr/day, our system handles this no drama. Very rarely drain below 90% battery capacity, but that is chiefly thanks to our sunny inland NQ weather. Water being our most scarce commodity. We come from the land downunder. Vic |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
thought you blokes might be interested in this. It is an upright freezer with drawers converted to a SUPER Fridge I looked at my mothers upright freezer and saw the potential straight away and have been looking for a cheapie to try it out on, looks like I have been well and truly beaten to the draw on this one. I was going to use a temp controller from Ocean controls. Have to say 165-200w/day then down to 140w/day is damn impressive! I could justify setting one up as a cheese cave and meat curing fridge as well. I'm confused, no wait... maybe I'm not... |
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| norcold Guru Joined: 06/02/2011 Location: AustraliaPosts: 670 |
I imagine there would be one problem with it, because each shelf is isolated from each other in drawers, the top shelf would be the coldest and as you go down each shelf would be warmer then the one above it. I believe that is illustrated by his observations that the top couple of shelves drip moisture. If you were to ensure each shelves evaporator was flooded with refrigerant, then you`d have the top couple of shelves freezing, plus it would consume a lot more power. Probably an adjustable vent on the top and maybe bottom of each drawer would allow convection to carry the heat around would solve this. However once again it would consume more power. Be interesting to see if he finds a work around for that. I know I`d have my beer on the top shelf.
Mobi, How did that grid tie inverter running your system of a day work out? We come from the land downunder. Vic |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I use an all-fridge unit and it collects a lot of water on the back plate and channels it to the centre of the back wall and out the drain hole (till the drain blocks) some of that is from opening the door a lot (for milk) and some is from the temp sensor creating a gap where the fridge can breathe past the seal (I should fix that). With an open area in the fridge I get fairly large temperature gradient from top to bottom and opening the door and losing the cold makes it worse. The drawers certainly help with that problem in an upright freezer. I guess it could be done with a sloping panel under the shelf that drains into a V shaped funnel on the back wall then through a small hose into a container that could be emptied regularly. I'm confused, no wait... maybe I'm not... |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
I have two systems, the first is my Selectronics RAPS with a 30 amp Projecta charge controller and poly panels. That is the one I have been running the last few hot days. The batteries were full by about mid morning. The second is the SMA RAPS with SMA grid tie unit and mono panels. I had isolated the 240vac output from the SMA RAPS, so it was only acting as a battery charger. It shut down because the battery voltage said "full" so I switched it off. Usually the only time I switch on the SMA system is late afternoon or on cloudy days. I haven't noticed any really significant panel output fades on either system. Mind you I have had a few brain fades in this heat. I like the Selectronics system because it switches off when there is no load and goes into "sense" mode. Bliss.... I just came from the shed - SMA had turned off...not needed and wind turbine was in "dump" mode. The best part is the wind has swung to the south west (off the sea) and it is cooling down outside nicely. David M. |
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