Hi! some noob questions

flyinghook · September 2018

it seems as though only the civilized world gets inverter fridges that actually save energy. The only fridges I'm finding use as much power or more than mine. at 3x the cost. I will not be doing this.

flyinghook · September 2018

also, it's seemingly been this way for at least 3 years, with no signs of changing

littleharbor2 · September 2018

flyinghook said:

littleharbor2 said:

flyinghook said:

Photowhit said:

Why do you want to disconnect from the grid? Unless you have very expensive electric, the grid electric will be cheaper than solar.

I explained this in my initial post, but let me elaborate. this first setup I built is not changing in function, but the parts will be easily separated from the rest once it is built. I am building a house in 2-3 years, where I am there is no electric at the site and I do not desire to have to have electric run before building my house. then I started thinking and calculating how much it would cost to run my new house off solar vs the grid, and solar came ahead. My electric is only 16c/kwh, but the fees/ect… end up being over $30 a month, which is insane, and this way I save the very likely $3k it would cost to have electric run to my site. so anyway, this initial setup is as I said, 500W of panels attached to 4kwh of batteries, and it is contained in a case to serve as my generator to build my house. as many of these components will be used in the next system as possible, but will be able to be removed to be my portable power unit. the system I'm building now will be a dry run for when I build my house, it will show what I need for capacities, and get my family used to living this way before we live in the new house.

In your calculations showing solar will be cheaper have you factored in the fact that you will be replacing your battery bank every 3 - 7 years? This is usually the equation killer in off grid power.

batteries every 5,

Your first set of batteries aren't likely to last five years unless you have prior experience with battery bank maintenance. Do you have a hydrometer?, know how to use it? know when, how, and when NOT to equalize? Is your battery bank a single string, or multi parallel strings. Charging setpoints all properly set and verified by checking specific gravity of your batteries. ? If so , then you can start with 5 years being the low number to expect from your batteries, IF they are 5 year batteries. What's the warranty say?

Estragon · September 2018

In your location, you'll likely be running the generator a lot in fall/winter. I'm a bit north and west of there in NW Ontario, and there is no way solar alone works from ~Oct-March.

My bank (350ah@48v) is roughly the same as your proposed one, and with a consumption budget of ~3kwh/day (2/3 less than your current consumption), is designed for 2 days no sun, start the genny on day 3. In Nov/Dec, we can go weeks without decent sun.

Where will water come from? Often the need to run a certain size/type of pump tips the balance in a decision between 24v and 48v designs.

The key takeaway from the video, IMHO, is these folks listened to the wrong people in setting up their system and their expectations for how it would work. Lots of people here actually live off-grid, and are well aware of the gotchyas from first-hand experience.

I assume you'll be replacing the electric stove with a gas one?

BTW, what size breaker do you have on the 1/0 wire between inverter and bank?

flyinghook · September 2018

I don't have a well here, but my next house will. I'm not sure what kind, yet, but I already figured to go dc to gain efficiency and save on inverter. Things ive already done to make this easier includes: no central air, I will get a gas stove when the time comes, and no dryer. All my lights are led, but because it's an old house so the layout only allows for a certain amount of efficiency. Our usage is ever decreasing, and once we're have a gas stove the usage will further decrease. I'm also considering moving the freezer outside for winter. I admittedly haven't fused the 1/0 wire because I've only been running a fridge off it so far, but was planning on fusing it, just not sure what size to use

BB. · September 2018

The inverter's installation manual should help... But to give you an idea of the math:

2,000 Watt (max continuous AC load) * 1/0.85 ac inverter eff * 1/10.5 volt battery cutoff * 1.25 NEC derating factor = 280 Amp breaker/branch circuit current rating minimum

Generally, this allows for a 2x surge current (motor starting, etc.) load without nuisance tripping the breaker.
-Bill

flyinghook · September 2018

thank you. I'm down to 6kwh a day from 11kwh last year and 9kwh last month. granted, I've been running my fridge off the solar, but it's not being used optimally.

petertearai · September 2018

hopefully you will get the better fridges ....energy wise within a few years .. Cant see why not ?
Th one i have is this it has been realy good . Uses less than the 299kw per year stated .
https://www.lg.com › Home › Fridges › LG GB-450UPLX

MrM1 · September 2018

On top of the great free info the OP has been provided with here, I would suggest reading these b4 proceeding.

https://www.solarpaneltalk.com/forum/off-grid-solar/off-grid-solar-panel-systems/10394-inverter-size-vs-battery-size-tutorial

https://www.solarpaneltalk.com/forum/off-grid-solar/off-grid-solar-panel-systems/16517-inverter-size-vs-battery-size-tutorial-part-2

flyinghook · September 2018

petertearai said:

hopefully you will get the better fridges ....energy wise within a few years .. Cant see why not ?
Th one i have is this it has been realy good . Uses less than the 299kw per year stated .
https://www.lg.com › Home › Fridges › LG GB-450UPLX

sadly, in the size fridge I'm looking for (700L+), the power usage is the same or worse between a brand new inverter fridge and my 5 year old cheapie fridge, at a premium of 2.5x-6x the cost. I don't know if this is because of the design of the compressors or what, but it makes them a bad idea for me.

petertearai · September 2018

Here the price between fridges of similar size or quality is not realy significant . unless you go to the EXPENSIVE European brands .

Estragon · September 2018

A couple of things to note in fridges; first, ratings have changed over the years, so a rating from 5yrs ago might not be directly comparable to a current rating, and secondly (and important in an off-grid context), the average power consumption masks the peak power needed to start the fridge.

A smallish inverter can run most full-sized fridges, but may not handle starting load. Using a big inverter just to handle the momentary load to start a fridge can result in much larger standby losses just keeping a big inverter lit. Purely for illustration, there might be a 20w difference in idle consumption between the 2 inverters, which would be 20x24=~.5kwh/day, or about 1/3 of the consumption of the fridge itself.

In North America, there aren't a ton of inverter type fridges available, but there are some at prices comparable to non-inverter types. I was looking at one in a size near what you're looking at recently for ~$1,200CAD, roughly comparable to similar non-inverter models. They should definitely not be 2-6x the price. Some features on higher-end fridges, such as ice/water through the door, french doors, etc. not only make them more expensive, they also increase power consumption.

flyinghook · September 2018

a kwh is a kwh, it is a standard, so I'm not quite sure how they would differ year to year? my fridge was only $900. I am seeing all of them for over $2k. Even Canada seems to have more inverter fridges available than here. I guess I could smuggle one over in the trunk of my chevy cruze, lol, the border patrol would never notice one of those.

BB. · September 2018

Standards do evolve (how many times doors are opened, ambient temperatures, etc.).

There was also a scandal related to the self test/reports by the manufactures to as being "less than (as I recall).
accurate":

https://www.nytimes.com/2009/10/19/business/energy-environment/19star.html

One refrigerator manufacturer tipped off the Energy Department that some models from a competitor that carried the Energy Star label did not meet the criteria, the audit said. That problem was also described by Consumer Reports magazine in October 2008 about tests it had conducted. In a settlement last year, the manufacturer, LG of South Korea, agreed to modify circuit boards in the machines already sold, to reduce their consumption and to compensate consumers for the extra power consumed.

The report also noted that while the government said in 2007 that it would conduct “retail assessments” to ensure that all the products carrying the Energy Star logo deserved them, it is still not doing so for windows, doors, skylights, water heaters and solid-state lighting. And the department is not following through to ensure that when inappropriately labeled products are identified, the labels are actually taken off, the audit said.

-Bill

flyinghook · September 2018

yes, but scandal aside (mine's a Samsung, and seems true to it's label), did the standards change between 2013 and now?

Estragon · September 2018

https://www.regulations.gov/document?D=EERE-2012-BT-TP-0016-0045

Appears to be a fairly significant revamp of testing and rating method for stuff like defrost cycles, single compressor/multiple evaporator, etc. Effective from 2014.

FWIW

flyinghook · September 2018

thank you, and noted. however, under 2kw/day is still my goal, and if inverter fridges are supposed to be 30-40 percent better, under 2kw/day should be reasonable.

BB. · September 2018

I am not sure that inverter refrigerators are "that much" more efficient (kWH per day)... However, what they are good at--Instead of needing a (typical) minimum inverter size of 1.2 to 1.5 kWatts to start the fridge, you might be able to get away with a much smaller AC inverter (like a 300 Watt/600 Watt surge model). A "good" inverter fridge, they virtually do not have any surge current--If they draw 120 Watts running, they also draw around a maximum of 120 Watts starting.

Similar for Inverter A/C / Heat pump systems... If you run them at low(er) speeds (and/or keep the thermostat to room temperature spread from getting too large), the Inverter units may draw 300-400 Watts or (100% of the time) vs 1,200 Watts 30% of the time.

Using the Energy Star Website is a good start to figure out kWatt*Hours per day--But they do not give starting/surge current.

https://www.energystar.gov/ (USA registered appliances)

You have to be careful too... There can be "hidden" current draws. For example, it is pretty common for a frost free modern energy starn fridge to take upwards of 600 Watts every ~12 hours (for xx minutes) to defrost the evaporator coils in the fridge.

One poster here tried to disconnect the defrost heater (it is a bit disconcerting to see a glowing dull red Calrod unit in your freezer when the defrost timer turns on). He found that after ~24 hours, the evaporator iced up and the average energy usage went up in the fridge because of poor/non-existent cold air circulation).

-Bill

Estragon · September 2018

Startup surge is definitely the attraction for me considering inverter-type for when (if) my porch fridge dies. Kwh/day is likely more a function of environment, use, features (eg. water/ice through the door), and insulation.

flyinghook · September 2018

good to know, thanks

flyinghook · September 2018

so, what 24v to 240v inverters would you recommend?

Photowhit · September 2018

Magnum, Schneider and Outback all make pretty good stuff.

flyinghook · September 2018

MrM1 said:

On top of the great free info the OP has been provided with here, I would suggest reading these b4 proceeding.

https://www.solarpaneltalk.com/forum/off-grid-solar/off-grid-solar-panel-systems/10394-inverter-size-vs-battery-size-tutorial

https://www.solarpaneltalk.com/forum/off-grid-solar/off-grid-solar-panel-systems/16517-inverter-size-vs-battery-size-tutorial-part-2

I don't like these articles. They blindly claim you need these ratios or fire. this makes no sense, and is not how electricity works. you cannot exceed the current limits of individual components or the whole system in operation, but there's no reason to not have a large battery bank and small inverter, for example.

Estragon · September 2018

I do have a small (300w) inverter on a large-ish (750ah@12v) bank, which works well. The reverse (big inverter, small bank) may not though.

You wouldn't exceed current limits of individual components in normal operation, but you certainly could in a fault condition.

Ratios or rules of thumb are just starting points, and can certainly be tweaked for a given application as long as the implications of doing so are well understood.

petertearai · September 2018

yep , but a large battery and inadequate PV can be a problem. The rules of thumb will help.

Estragon · September 2018

Large bank /small array could be a problem, or not. If you have a generator and don't mind using it when needed, no problem, for example. The rules of thumb are just a starting point.

My only issue with rules of thumb is using them as actual rules. Each application is different, and the "rules" can/should be bent accordingly. Treated as rules of thumb though, they're a useful starting point.

Hi! some noob questions

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