Inverter Size

With54With54 Registered Users Posts: 21
Any suggestions/recommendations on size and which pure sine inverter to purchase for the cottage? I generally power a mini refrigerator, energy saver lights, a television, satellite receiver and sometimes an Ipod. Would the Morningstar 300 handle this load?

Thanks for your input.

Comments

  • icarusicarus Solar Expert Posts: 5,359 ✭✭✭✭
    Re: Inverter Size

    Calculate your loads, in total, and how many will be running at once. My guess is tht the bugaboo is going to be the fridge. Get a kill-a-watt meter to actually measure what these items draw, both running and starting.

    The Suresine 300 I s a great inverter.

    Tony
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Inverter Size
    With54 wrote: »
    Any suggestions/recommendations on size and which pure sine inverter to purchase for the cottage? I generally power a mini refrigerator, energy saver lights, a television, satellite receiver and sometimes an Ipod. Would the Morningstar 300 handle this load?

    Thanks for your input.

    Nope.
    Refrigerator, even a small one, has some nasty start-up current. It may draw 120 Watts running, but can easily blip over 600 to start. That's the Morningstar's limit.
    And you'd be surprised how fast a few lights, a TV (up to 200 Watts depending on type/size/settings) and satellite receiver add up.

    So don't guess. Get a Kill-A-Watt and takes some readings on what you want to power. Either at "home" from the utility or at the cabin with a generator. It won't grab the refrigerator's start-up current, though. If it weren't for that little problem the MS 300 might suffice. Or two (nothing says you can't run multiple inverters off the same battery bank).

    Could you get a propane 'frige? Lots of money, but depending on how long you're there ... Maybe a used 3-way from an RV? Otherwise you're probably in for a 1 kW (or more) unit.
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Inverter Size

    The Suresine 300 would definitely be the way to go - - except for the fridge! It will not start your fridge. Fridges and freezers as noted already, are, as they come out of the factory, infamous for their difficult starting. I do run a fridge and two freezers single file, one at a time on a Suresine 300, but ONLY after MAJOR modifications to the compressor circuitry that are unique in values to each individual compressor, which proves they don't have to be the way they are on the showroom floor, but hey, the manufacturer saves a few cents on each unit.
  • icarusicarus Solar Expert Posts: 5,359 ✭✭✭✭
    Re: Inverter Size

    'coot, your stealing all my best lines.

    Seriously, most "little fridges" are terrible engy hogs. Little "apartment fridges " can often use as much power net//net as a good engy star full siized fridge. I would seriously consider a l/p fridge. A 10 cu ft Dometic will use 1500 BTUs/ hour, with a duty cycle less than 50%. (a gallon of propane contins ~79,000 BTUs/gallon so it will r un better thn a week on one gallon of Propane)

    Tony
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Inverter Size
    icarus wrote: »
    'coot, your stealing all my best lines.

    Seriously, most "little fridges" are terrible energy hogs.

    Tony

    VERY true! Their energy consumption is nothing short of disgusting! And it's so unnecessary, but the manufacturers obviously couldn't care less:grr
    Most people think because it's small, it won't use much energy. HA! Think again!
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Inverter Size

    A Kill-A-Watt meter is a handy device for determining running current, and total KWH, but is way too slow to measure startup current. Same goes for most clamp-on ammeters. I bought a special Fluke meter (model 334), designed to measure In-Rush current. World of difference between what it measures, and what something like the Kill-A-Watt measures as far as startup current.

    As others have mentioned, a small fridge can draw as much current as a larger fridge. Both of my full sized fridges have a 1/4 HP compressor. The side/side door Energy Star fridge in the house consumes 2.15 KWH per day. The more basic fridge (freezer on top) in the hot garage only consumes 1.15 KWH per day. My lesson learned is an Energy Star sticker isn't worth much. Short of testing it yourself, don't think you'll get useful data from the manufacturer.

    Both of these fridges are frost free, and draw about 600W during the defrost cycle. They only draw 114-146W with the compressor running.

    I haven't measure the startup current of either fridge yet, but have measured a few other things that surprised me by how much current needed during startup. A 5000 BTU A/C unit = 22.6A, a Dewalt Emglo 1.8HP air compressor = 53.8A, a Dometic 13,500 BTU roof top RV A/C unit = 50.5A. Appliances with motors take a significant spike of current to get the motor spinning. Once it's running, it might only take 1/5 of the startup current to run.

    Prices of Pure Sine Wave inverters have come way down. I paid $349 for a Xantrex 2000W (1800W continuous) PROwatt SW sine-wave inverter. Got it at Camping World last year on sale. It will easily run all your devices. The no-load current draw is < 0.8 A. The no-load current draw for the MorningStar SureSine 300W inverter is 0.45A. Great little inverter, but it's not going to start your fridge.
  • mike95490mike95490 Solar Expert Posts: 8,471 ✭✭✭✭✭
    Re: Inverter Size

    if you are real clever, you could wire the fridge thermostat, to a relay to start the inverter, and save the idle losses, and hope the fridge does not need power 24/7 to run it's computer chip
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • With54With54 Registered Users Posts: 21
    Re: Inverter Size

    Thanks for the feedback. Could someone explain how to connect two inverters to the same 12 volt battery bank? I may continue with the 3000 Modified Sine Wave Inverter but also also add the MorniingStar Pure Sine 300 which would be used 90% of the time. Looks like I need an LP fridge.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Inverter Size
    With54 wrote: »
    Thanks for the feedback. Could someone explain how to connect two inverters to the same 12 volt battery bank? I may continue with the 3000 Modified Sine Wave Inverter but also also add the MorniingStar Pure Sine 300 which would be used 90% of the time. Looks like I need an LP fridge.

    (+) to (+), (-) to (-). Each inverter has its own wires, sized according to its potential current draw, and its own fuse sized to protect the wire. Simple as pie. They don't need to 'talk" to each other as the AC out will be entirely separate (unlike "stacked" inverters which are coupled on both AC and DC to provide more power/Voltage). Batteries don't care where the load is going to, and charge systems simply charge the batteries. Right wires, right fuses; everything's fine. :D
  • mike95490mike95490 Solar Expert Posts: 8,471 ✭✭✭✭✭
    Re: Inverter Size

    Before you buy that LP fridge, you may want to at least try the mini-fridge on the morningstar 300 and see if it will work. It's spec'ed at 600w for 10 min, but I don't know what it's 1sec surge capacity is.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Inverter Size
    mike90045 wrote: »
    Before you buy that LP fridge, you may want to at least try the mini-fridge on the morningstar 300 and see if it will work. It's spec'ed at 600w for 10 min, but I don't know what it's 1sec surge capacity is.

    If you're a wiz at such things and have access to a range of different value motor start capacitors, you can try adding capacitor start to the mini fridge compressor and it MIGHT start on the Morningstar, IF you hit on whatever the exact, best value capacitor happens to be for that particular compressor. Otherwise, I fully expect it will be an instant, or almost instant shut down of the Morningstar on overload. The Morningstar will wait a few seconds, then try again. After 3 tries, it shuts down for good and you must manually remove power from it until it's red LEDs go out, then repower it for another 3 tries. Been there, done that. But had to add extra relays, autotransformers etc along with the cap start, and replace the varistor starter with a relay to control the start winding, before they would work on the Morningstar.
    It can be done, but it ain't gonna be simple, or easy.
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