2 Solar panels to run old freezer after hurricane

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Matt Gruber
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2 Solar panels to run old freezer after hurricane

Post by Matt Gruber » Fri Jul 14, 2017 6:37 pm

go to page 2 for freezer mods.
solar details here:
https://endless-sphere.com/forums/viewt ... 41&t=89370
Last edited by Matt Gruber on Thu Sep 07, 2017 2:28 pm, edited 2 times in total.

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Re: grid tie inverter, but no grid, will it work?

Post by Hwy89 » Fri Jul 14, 2017 7:24 pm

Nope it won't work without a live grid connection. Get a non grid tie type it will likely cost less.
I have doubts about your plan. I think you will need a battery bank to provide the amps when the compressor starts. Low voltage and insufficient power on motor start is a sure way to release the magic smoke.

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Re: grid tie inverter, but no grid, will it work?

Post by Alan B » Fri Jul 14, 2017 10:29 pm

Elaborating a bit on what Hwy89 said,

Grid tie inverters require the grid input side to have a proper sinewave voltage present, then they phase to it and add current to it. For safety they won't output power when the grid is dark, otherwise they might injure electrical workers trying to work on the grid when it is intentionally powered off.

Solar panels are very unstable power sources, and standard inverters need a more stable source, such as batteries, to work from. They will error out on panels alone.

Perhaps you could use a very small battery bank, and rely on the inverter shutdown when the batteries deplete. When the panels are again providing power (and the batteries have charged somewhat) you could restart the inverter.

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Sat Jul 15, 2017 6:20 am

Hwy89 wrote:Nope it won't work without a live grid connection. Get a non grid tie type it will likely cost less.
I have doubts about your plan. I think you will need a battery bank to provide the amps when the compressor starts. Low voltage and insufficient power on motor start is a sure way to release the magic smoke.
Hwy89
That was exactly my plan, until i saw a small $99 freezer at home depot. they claim it needs 65-90 watts, and only 1.2 amps on start. :shock: so if true it could start on 200w panels in bright sun. Yet mfg cautions not to use an inverter :evil: so i thought i may need a sine wave inverter, not sure what is in my UPS APC NS 1250, probably high quality since they guarantee it wont damage your equipment. Just kicking around ideas. thanks!

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Sat Jul 15, 2017 6:27 am

Alan B wrote:Elaborating a bit on what Hwy89 cal workers trying to work on the grid when it is intentionally powered off. >>>> matt responds: i expect in the future, it will break the tie when the grid goes dark. and keep the house on solar power! why it doesn't do this now is beyond me.

Solar panels are very unstable power sources, and standard inverters need a more stable source, such as batteries, to work from. They will error out on panels alone.

Perhaps you could use a very small battery bank, and rely on the inverter shutdown when the batteries deplete. When the panels are again providing power (and the batteries have charged somewhat) you could restart the inverter.
.
Alan
Yes my UPS APC NS1250 will run 2-3 minutes at 150w on weak sla's. i guess i'm back to using sla's for now. just kicking around ideas while i wait for my PWM controller to come in. i'm not sure if the ups could take 30-40+volts, so i hope the controller will reduce that.
Thanks!

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Re: grid tie inverter, but no grid, will it work?

Post by fechter » Sat Jul 15, 2017 2:11 pm

I have a Meanwell sine wave inverter made for 48v. Works well from my 52v (14s) bike battery. I used it the other day when I had a power failure. I just used it to watch TV, but it worked great and I had plenty of capacity in my battery.
"One test is worth a thousand opinions"

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Sat Jul 15, 2017 4:22 pm

HI FECHTER!
that is what caught my eye with the 22-50v input on that grid tie, i could run it on my 10s bike battery.
i ordered this step down buck so i can try running the UPS :
http://www.ebay.com/itm/300W-20A-Buck-C ... 2749.l2649
here is how APC describes the UPS inverter.
"stepped approximation to sine wave. Peak and RMS values equalivalent to the utility."
Is this what "SINE WAVE INVERTER" means?
Good to hear from you!
matt

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Re: grid tie inverter, but no grid, will it work?

Post by Alan B » Sat Jul 15, 2017 11:54 pm

That is not a sine wave. That is called a "modified sine wave", but it is really a stepped square wave with 3 values - 0, +peak and -peak. By timing it they generate something that has less distortion than a pure square wave, but it is still fairly poor compared to pure sine wave. Some loads will fail with a modified sine wave, others run ok or make some extra noise.

Your PWM solar regulator should be set for the SLA voltages, so it will not let the raw panel voltages get through. The SLAs will provide some "inertia" and the voltage should ramp up slowly, but be stopped by the charge controller before it gets too high as the batteries charge.

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Re: grid tie inverter, but no grid, will it work?

Post by billvon » Sun Jul 16, 2017 1:00 am

Matt Gruber wrote:That was exactly my plan, until i saw a small $99 freezer at home depot. they claim it needs 65-90 watts, and only 1.2 amps on start.
I wouldn't believe that until I had seen it, using a scope and a current probe.
so if true it could start on 200w panels in bright sun. [/quorw]
As others have mentioned that won't work with a standard grid tie inverter. Might work with a large solar array and an SMA inverter; they have a "secure power" option that can be used without grid present. But if that fridge needs 1kW to start for even a single cycle then your array has to be >1kW - and it won't start unless you are in full sun.
i thought i may need a sine wave inverter, not sure what is in my UPS APC NS 1250, probably high quality since they guarantee it wont damage your equipment. Just kicking around ideas. thanks!
I think that's a mod-sine; again, check with a scope.
--bill von

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Sun Jul 16, 2017 4:51 am

Alan B wrote:That is not a sine wave. That is called a "modified sine wave", but it is really a stepped square wave with 3 values - 0, +peak and -peak. By timing it they generate something that has less distortion than a pure square wave, but it is still fairly poor compared to pure sine wave. Some loads will fail with a modified sine wave, others run ok or make some extra noise.

Your PWM solar regulator should be set for the SLA voltages, so it will not let the raw panel voltages get through. The SLAs will provide some "inertia" and the voltage should ramp up slowly, but be stopped by the charge controller before it gets too high as the batteries charge.
.
Alan,
So how do they make a sine wave? Can't i just open up an inverter and look for what?
Thanks for your help!
matt

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Sun Jul 16, 2017 2:27 pm

billvon wrote:
Matt Gruber wrote:That was exactly my plan, until i saw a small $99 freezer at home depot. they claim it needs 65-90 watts, and only 1.2 amps on start.
I wouldn't believe that until I had seen it, using a scope and a current probe. (billvon wrote).
.
Yes, the quality of the mfg. answers is suspect, so i will disregard their saying not to use an inverter. 2 users say it worked fine, and numerous youtube videos show freezers used on inverters of all types.
once i get everything, i'll do a test- all day if the sun is out.

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Re: grid tie inverter, but no grid, will it work?

Post by billvon » Sun Jul 16, 2017 2:58 pm

Matt Gruber wrote:So how do they make a sine wave? Can't i just open up an inverter and look for what?
It's going to be hard for a non-technical person to tell just by looking. Easiest way is with a scope; look at the output and see if it's a sine wave or not. A less reliable way is to use a cheap (non-RMS) digital multimeter and see if the voltage it senses is way out of whack with what the voltage rating of the inverter is.
--bill von

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Sun Jul 16, 2017 4:23 pm

bill
it is a moot point. as any inverter will often run a fridge.(not always, hence my test)
i will plug it into my solar/SLA/ UPS and if it starts OK, doesn't make noise, and runs all day, then i'm done. my old freezer has a strong surge, so i'll be happy if it starts. i'm thinking if it kicks out, i'll try adding a long cord, and try again. maybe the long cord will limit the amps long enough for a start. maybe not, but easy to try.
then only 111watts running.
thanks for your replies! not a hot topic! LOL
Last edited by Matt Gruber on Sun Jul 16, 2017 4:58 pm, edited 1 time in total.

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Re: grid tie inverter, but no grid, will it work?

Post by Alan B » Sun Jul 16, 2017 4:24 pm

They use higher frequency PWM to make sine waves.

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Re: grid tie inverter, but no grid, will it work?

Post by Hwy89 » Sun Jul 16, 2017 4:37 pm

I've used APS UPS units as inverters for several projects and have not experienced any problems in reguard to the waveform. Never powered a freezer but have run refrigerators TVs and small kitchen appliances without problem. I have always believed that they produced a sine wave because of all the sensitive equipment they are designed to protect.
Your experiment should work as planned but would work better if you replace the tired SLA batteries with fresh ones. I also recommend disabling the sonalert beeper in the UPS or it will drive you crazy with it's chirping.

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Sun Jul 16, 2017 5:02 pm

HWY89,
thanks! good news!
i'm going to use better 10ah SLA's instead of the bad 7ah. won't fit in the case, but that is OK.

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Re: grid tie inverter, but no grid, will it work?

Post by Alan B » Mon Jul 17, 2017 12:42 am

Computers don't need pure sine waves.

Motors often generate additional heat due to the harmonics vs the motor inductance.

Some peripherals such as laser printers can be damaged by modified sine waves. Any controller that uses SCRs to control power or heat generally require a sine wave to work correctly.

Modified Sinewave inverters are much cheaper, and UPS systems generally use the lowest cost tech they can. Computers don't care, their power supplies just make low voltage DC anyway. If you put a temperature sensor on the motor and try pure sine and modified sine you may see a difference in motor heating. It still may be ok.

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Mon Jul 17, 2017 5:22 am

Alan
i think that is a good idea. i'll run the new freezer for say, 2 hrs and check it with my IR gun, and then recheck on the inverter. if it gets really hot, i need a new inverter.
:)
i've got 2 surplus 0.2a 4" 48vdc fans , paid $1.50 years ago. they work great down to 20v. one i'll put on the freezer motor, the other for a breeze in the kitchen, hooked direct to the solar.
.
edit
tested the 4" fan 1 watt, .05a at 20vdc, so about 2 watts to cool the freezer motor 24-28vdc.
i expect the motor to be more efficient, and use less watts to cool the food.

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Tue Jul 18, 2017 6:13 am

SLA UPS test:
freezer started right up, sounded good, used ~3-7 watts extra on inverter. ~114w
tried 5000 btu AC, started right up, but made a growl sound, 384 watts.
plugged UPS into vac, growl went away, took plug out of vac, ups kicked out as SLA's dropped to 7v. annoying chirp to alert me :roll:
won't be using ac on inverter from solar 200w. but if i get a sale someday and add 800+ watts, i may be tempted, if i grow to like solar power. not sure yet. :wink:
.
weak link my be the controller, not here yet. sla's plug into it, and it sends pwr to ups.
thanks guys for all the comments!
.
Q:
What if i start the freezer, and then hook up a buck to the sla's set to 28.8v, and the buck connects to the 30-40v solar? i plan to put a 40a rectifier in series so power can only go into the sla's, not from the sla's into the buck. Should i add some 50v 4700mfd caps across the solar? how about a 4-8w light bulb so when the freezer shuts off, there is some load? this is a good hobby, it makes you think about everything :mrgreen:
buck on order:
http://www.ebay.com/itm/300W-20A-Buck-C ... 2749.l2649

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Wed Jul 19, 2017 6:22 am

Todays test:
350w hot plate on a motor speed control on my non-sine wave inverter.
found it difficult to set, but set it on 127w.
back on 120vac it was 235w, so clearly it did not like being abused :)
still waiting for solar controller :(
.
SMA makes a grid tie that works like they all should. in a grid failure is goes off grid and supplies 1 circuit with 1500 watts of solar. ask amy at alte.
costs 1200 :roll:
.
Turns out i have 2 LA's that i forgot about, in my 2 antique cars. So i don't have to buy any for emergency power, just make up a harness to connect them in series to my UPS. Ordinary LA's are terrible for deep cycle, but work fine up to 15-25% DOD, which will run my freezer 1-2 hrs no sun, and then will recharge in full sun while powering the freezer.
The main objection i had to buying a battery was that they go bad as there have only been 2 hurricanes in 28 years. BUT i do keep the cars running, so an easy FREE source for energy storage.

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Re: grid tie inverter, but no grid, will it work?

Post by Kneelb4ZOD » Tue Jul 25, 2017 5:23 pm

My advice is to avoid modified sign wave inverters like cancer. Some devices may even void the warranty if you run them under modified sign wave power. Any device that uses a capacitor fed power supply is dangerous to run on MSW... that includes a lot of small electronics. Things will often run under powered - anything with an AC motor, so your fridge, microwave and so on will be under-powered and potentially overheat. Variable speed devices that use semiconductor-controlled rectifiers won't work properly. Fluorescent lighting will be terrible. The list goes on and on. The noise will damage sensitive electronics over time. It's very dirty power. By comparison, pure sign wave inverters have some noise, but outside of some niche areas like studio audio equipment which needs a very clean power source, everything you can run on grid power will work on a PSW inverter. Why get an AC inverter if you can't run a lot of the things you need to power in your house? They are cheaper, because they are trash. Unless you're getting the inverter only to serve a specific purpose with equipment which you know will work fine on dirty power, then I think you will regret it in the long term. MSW... Gross.
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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Wed Jul 26, 2017 5:37 am

Knee
i got a free freezer and a free UPS. if either burn up after the next hurricane, i'll take your advice. i plan a test every 6 months, will run the freezer for 1/2 to 1 hour, mainly a battery test, but also a test of your theory. there are numerous utube videos of freezers running on any inverter. none burned up, a few would not start.
my tv , LED's, radio, ebike, scooter, hotplate, and fan, ALL run off DC, so no problem there. all these will work without an inverter! These are why 2 solar panels are a great idea.
i plan to run the freezer 2-3 days before a hurricane, on grid ac, to make 50-100lbs of ice before the power fails, so, i'll be set for 2+ days with ice.

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Re: grid tie inverter, but no grid, will it work?

Post by Kneelb4ZOD » Wed Jul 26, 2017 7:07 am

Matt Gruber wrote:Knee
i got a free freezer and a free UPS. if either burn up after the next hurricane, i'll take your advice. i plan a test every 6 months, will run the freezer for 1/2 to 1 hour, mainly a battery test, but also a test of your theory. there are numerous utube videos of freezers running on any inverter. none burned up, a few would not start.
my tv , LED's, radio, ebike, scooter, hotplate, and fan, ALL run off DC, so no problem there. all these will work without an inverter! These are why 2 solar panels are a great idea.
i plan to run the freezer 2-3 days before a hurricane, on grid ac, to make 50-100lbs of ice before the power fails, so, i'll be set for 2+ days with ice.
With that context it sounds like a pretty good plan actually, just in general I would caution people against them. cheers :)
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Re: grid tie inverter, but no grid, will it work?

Post by amberwolf » Wed Jul 26, 2017 2:54 pm

FWIW, if it's a chest-style freezer, then there are two methods I've seen for those to shed the heat from the compressor coils. One is in a rear-mounted/under-freezer mounted setup, and the other is built into all the side and front and rear surfaces.

If it's like the latter you can't add any insulation to those surfaces while it's actually running (but you can wrap it in blankets or any other thick insulation jacket, thicker the better, after power fails to help insulate it further, as long as you be sure to remove them when power comes back on. This could add a LOT of time to keep it cold inside).

If it's made like the former, you can add on styrofoam sheets to quite a thickness to all sides without exchanger coils, whatever's practical for the area it's in, and even put insulation under and over it if it's only a rear-mounted heat exchanger. Depending on how it's mounted a rear exchanger can even be moved away from the freezer a bit and add even more insulation between it and the freezer. This can all be done and still ahve it running with the insulation on it, and it will take much less power over time to keep the stuff cold inside it.

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Re: grid tie inverter, but no grid, will it work?

Post by Matt Gruber » Wed Jul 26, 2017 5:16 pm

amber
good ideas!
i plan to put inside, on top, a styrofoam lid under the lid. this is because the door seals leak cold.
anytime i see more on trash day, i'll pick up good pieces for the sides.
it has a coil on back. can lift one side an inch or 2.
cheers!

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