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Old 26-05-2009, 19:41   #1
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What Size Inverter?

I am installing a 900A/hr house bank, including a 100amp Charger/Inverter Mastervolt Combi & a 100amp Mastervolt Charger.

My DC system is a standard "down-under" 230 Volts DC. I am trying to decide whether to go with a 2000 watt or 2500 watt Combi.

My microwave and other existing equipment draw around 1000 watts, however I note some electric kettles and other appliances can draw between 2000 -2200 watts.

I suspect I can find 230volt DC appliances under the 2000 watt level, but am now wondering, should I have that "500 watt margin of error"?

Would be intersted in others opinions ... based on your own personal experience.

Thanks in advance.

William
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Old 26-05-2009, 20:40   #2
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The rated capacity of Invertors do not take into account line loss. Also I would always have a buffer zone for when someone plugs in something new. Just make sure your wiring is properly sized.
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Old 26-05-2009, 20:46   #3
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Quote:
Originally Posted by Pelagic View Post
The rated capacity of Invertors do not take into account line loss. Also I would always have a buffer zone for when someone plugs in something new. Just make sure your wiring is properly sized.
Be assured I will be increasing the size of my battery leads to accomodate either wattage. Don't know as yet whether the addl 500 watt difference will also increase wiring size.

Feel free to elaborate on that wiring matter. Also perhaps you can elaborate omnn the primary point above: i.e. "line loss", the impact of that, and specifically (i.e. an example) of in what way does does that impact?

Gracias in advance.
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Old 26-05-2009, 20:48   #4
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High amp loads get pretty hard to totally compute. There can be initial surges that go even higher than rated capacities. It is possible to measure the appliances on shore for more details. Wire sizes gone wrong can lead to melted wires and potential fire danger that is very real. Placement of the Inverter should be such that you have shortest possible wire runs to the battery.
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Old 26-05-2009, 21:05   #5
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goodness!

Quote:
Originally Posted by BlueSovereign View Post
I am installing a 900A/hr house bank, including a 100amp Charger/Inverter Mastervolt Combi & a 100amp Mastervolt Charger.
A 900 AH house bank is going to weigh more than a quarter of a ton.

Why?
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Old 27-05-2009, 05:39   #6
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Quote:
Originally Posted by BlueSovereign View Post
... My DC system is a standard "down-under" 230 Volts DC...
... I suspect I can find 230volt DC appliances under the 2000 watt level...


I expect that you intended to say that your system is a standard "down-under" 230 Volts AC (Household Alternating Current).

Quote:
Originally Posted by BlueSovereign View Post
Be assured I will be increasing the size of my battery leads to accommodate either wattage. Don't know as yet whether the add’l 500 watt difference will also increase wiring size.
Feel free to elaborate on that wiring matter. Also perhaps you can elaborate on the primary point above: i.e. "line loss", the impact of that...


I expect that the noted “Line Losses” are referring to Voltage Drop, of most impact on the DC Battery Input side of the inverter.

See the explanation at “Ohm’s Law & Boats” (post #1)
"Ohm's Law & Boats"

See the DC wire sizing charts at:
http://www.cruisersforum.com/gallery...=500&userid=79
&
http://www.cruisersforum.com/gallery...=500&userid=79
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Old 27-05-2009, 06:20   #7
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Bash wrote:

Quote:
A 900 AH house bank is going to weigh more than a quarter of a ton. Why?
I've had eight Trojan T-105s (900 amp hours - 496 lbs) for a house battery bank for over 15 years. I also have a 110v watermaker, a 110v refer system, 2500 watt hart inverter (with 130amp charger), and 125 amp alternator. That system has always worked well for me!

Why not?
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Old 27-05-2009, 08:21   #8
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Peter is absolutely correct - initial start-up loads on many appliances are significantly higher than rated; for example, most 1000 watt microwaves will initially peak at about 1200 or more. In the end result, a 2500 watt inverter will give you a greater margin, expecially if you are anticipating using more than just one appliance at any given time.

Brad
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Old 27-05-2009, 08:35   #9
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In addition to what has been written so far, Inverter capacity decreases as ambient temperature increases, I recall seeing a chart from either Mastervolt or Victron and as I am in the tropics I had to go for a much bigger inverter to deal with my expected loads.
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Old 27-05-2009, 09:44   #10
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Besides short leads to batteries, make sure the inverter can breathe fresh air as well.

Steve B.
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Old 27-05-2009, 23:33   #11
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Besides short leads to batteries, make sure the inverter can breathe fresh air as well. Steve B.
Unfortunately short leads will not be an option.

That's why I'lll be going to 70mm cables to address this issue.

Looks like I will also be going with a 2000 watt unit as the want 25% more for a 2500 watt unit ... sorry there is not a linear relationship when building a 100amp/2000watt inverter/charger vs. a 100amp/2500watt inverter/charger!
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Old 28-05-2009, 03:23   #12
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I trust you mean 70 square mm cable, or 138,100 circular mils (a little larger than #2/0 AWG @ 133100 cm); which should allow you to mount the 2kW inverter about 10 feet from the batteries.
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Old 28-05-2009, 04:42   #13
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I ended up getting the 3000W Victron inverter/charger and am glad I did. My main load, an 1800W Espresso Machine, actually draws quite a bit more by the time it gets to the inverter and the 2000W inverter I had originally planned would not have been sufficient.
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Old 28-05-2009, 06:04   #14
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Blue Sovereign, I understand that cost is always a factor, but isn't 2500 watts 25% more than 2000, making the 25% increase in cost linear?

Brad
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Old 28-05-2009, 06:40   #15
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Blue Sovereign, I understand that cost is always a factor, but isn't 2500 watts 25% more than 2000, making the 25% increase in cost linear? Brad
That's my point, re-read what I wrote. From a manufacturing cost perspective, in reality a 2500 watt inverter/charger should not cost 25% more than a 2000 watt one.
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