Saturday, 28 January 2012

Inverters

My one main concession to the civilised world was ice. I really did not want to spend several years with warm beverages. Now the boat does have a large fridge with a small compartment which can make ice, but does so in small quantities and very slowly.

I bought a small desktop ice maker, about the size of a breadmaker or small microwave oven, in the paperwork it claims to consume only 140watts of power, on the land this would be nothing, but as per usual on a boat everything is difficult.

I already had a 300 watt pure sine wave inverter from my old boat, an inverter turns the 12v dc from a boats batteries into 240v ac just like what comes out of a socket in a house. The inverter claims 600w surge capability, so I hoped this would power the 140w ice maker. Not a chance! plugged it in and red lights lit up when the compressor in the icemaker tried to start up.

The problem with things electronic that have motors in them , is their start up surge ,which may be several times the devices normal power use. The general rule of thumb is about 3 x the devices rated power will normally get them started. Well this rule of thumb did not prove right for me. Trying to be a cheapskate and save money I ordered a 500w pure sine wave inverter which had a 1000w surge rating, plug in the ice maker, red lights again, it cuts out.

So I did a little research ,only to find out that icemakers consume 2100w on start up, granted only for a small amount of time,but long enough that the surge capabilities of most inverters can't keep up with it. I ended up having to get a 2500w inverter just to run a 140w appliance.. ....Who'd have guessed! (I should have, I've got a degree in electrical engineering, homer simpsom dooh moment)

So if any of you out there are considering running things on inverters, which have motors in them, be aware you'll need a far larger inverter than you think, don't buy a small one and waste your money!

I would also recommend sticking with pure sine wave units, the modified sine wave inverters (ie square wave) can play havoc with many electronic items, they are a little cheaper, but this is one case where cheapness could cost you big time later down the road when it destroys the things you plug into it.

Notice the 500w is exact same as the 300w mmm

Testing the 2500w only to run a 14ow load, crazy!

3 comments:

  1. don't always believe what you read :)
    2500 to run 140 , those ice lumps better be good.

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  2. lol I hope its not using all of those 2500watts!

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  3. There are really a lot of things to consider when you wanted to buy new accessories for your boat. Better be wise when you do so.

    Semi-Custom Boat Cover

    ReplyDelete

Thanks for your interest!

Nic n Steve.