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When is an Inverter 'inverting'?


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This is, I hope, an academic and hopefully generic question to ease my concerns.  We're on shore line most of the time but, when cruising, the cable is a bit short to stretch so we use an inverter, primarily for telly, etc.  We have a recurring debate as to whether the inverter should be switched off when we are not using 240v. 

Having read debate elsewhere about unplugging your home mobile phone/tablet charger when it is not actively charging ('cos the primary winding is still powered up and, if faulty, could overheat) I feel the inverter should be turned off.  But it is not working, ...or is it??

Discuss....., 

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for mains to be available (regardless of whether it is being used) an inverter will be working and using an amount of power to do so (how much depends on how good / bad your inverter is)

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If my inverter is on, but there is nothing using the 240v supply, it uses 4A, (or almost 100Ah per day) - so I always turn it off when not in use. It has a standby facility which uses less, but many things dont request enough power to bring it out of standby - so I never use standby as it is irritating.

better inverters seem to use about 1A when on but nothing is using the 240v supply. I would still turn it off, rather than use 24Ah per day for nothing.

Mine is a Sterling pro Combi S inverter charger 2500W inverter and 80A charger.

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Many thanks for the prompt and helpful responses which go to reinforce the way my thinking was going.  12v fridge so no issues there.  Sterling inverter fitted about seven years ago so fairly modern.  Batteries from the same era but they have had a hard life eg run flat when a split charge relay failed some years ago (replaced).  Despite that, however, they still seem to be going strong.  Never thought the inverter would use that much when in standby - all seems like a good case for following my instinct - I normally leave it for five minutes after using 240v just to see if it wants to run its internal fan, then switch off.

cheers, folks.  I'm much happier now.

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In general the bigger the inverter the more power it will use on standby, I think, and for some reason pure sine ones seem to use more power in standby than an equivalently size modified or quasi sine wave one.


When we had a 300 watt MSW on a previous boat it was small emough not to be an issue, but the 2,500 watt one that was on the current boat was quite a different issue.

The other thing to consider, depending on the manufacturer and quality of your unit is that it is not unknown for some of the cheaper ones to catch fire, so having them on when you don't need to is probably best avoided for that reason alone!

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3 minutes ago, alan_fincher said:

... it is not unknown for some of the cheaper ones to catch fire, so having them on when you don't need to is probably best avoided for that reason alone!

Wow!  Do you reckon, if I put my Ecofan on top of it I could use that to heat the bedroom? ...............

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4 hours ago, Richard10002 said:

If my inverter is on, but there is nothing using the 240v supply, it uses 4A, (or almost 100Ah per day) -

Mine is a Sterling pro Combi S inverter charger 2500W inverter and 80A charger.

My Prosine 1800i in powersave mode only uses less than 4 amps per day, Powersave mode draws only 1.5 watts under no load

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My 1800W PSW inverter draws 0.8 amps if it is on but not supplying anything.  This is not a "power saving" mode because, as mentioned above, some things do not demand enough power to wake it up.  I turn it off at night, but I'm not that bothered during the day.

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3 minutes ago, dor said:

My 1800W PSW inverter draws 0.8 amps if it is on but not supplying anything.  This is not a "power saving" mode because, as mentioned above, some things do not demand enough power to wake it up.  I turn it off at night, but I'm not that bothered during the day.

So around 19Ah per day. That ain’t much for sure. 

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15 hours ago, alan_fincher said:

In general the bigger the inverter the more power it will use on standby, I think, and for some reason pure sine ones seem to use more power in standby than an equivalently size modified or quasi sine wave one.

 

It is related a bit to the inverter size, but much more to the inverter design and quality. Our 2500 pure sine inverter uses 0.75A and that is in normal mode. In the various power saving modes it uses less.

Dont forget that if you are put crusing, it is wrong to multiply the current by 24 to get the battery hit, since for a chunk of that time the engine is running and batteries charging as you cruise. So maybe 16 to 20 is a better multiplier.

We tend to leave our inverter on 24/7 but if we are not planning to cruise the next day, I might turn it off overnight. It’s a convenience thing really, far better to have power just available like in a house than to have to faff around putting the inverter on and off according to whether there is something to be powered or not.

 

Oh and to the OP, modern mains phone chargers don’t have transformers. When there is no load (no phone) connected they use virtually no power, as witness by the fact that they are stone cold (any power consumed must be turned to heat).

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Concerning power usage of inverters, some people will run two inverters. They will have a larger inverter for heavier loads during the day, and a smaller inverter for the lesser loads at night, or during down time. We do that at our farm, in fact. 

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2 hours ago, WotEver said:

It’ll be using 4 amps per second too. ;)

 

Nah, you’re joshing with us. You’ll be claiming it’s 4 Amps per hour in two seconds next! 

But all that aside, I wonder if can you help with another question that’s been troubling me for years. How much does a metre weigh? I can never get a straight answer to this question either. Huh.  

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1 minute ago, Mike the Boilerman said:

But all that aside, I wonder if can you help with another question that’s been troubling me for years. How much does a metre weigh? I can never get a straight answer to this question either. Huh.  

About a kilogram.

I'm sure I have seen people talking about kg metre as a proper unit.

On a related note in old money a foot weighs a pound - now we're torquing!

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15 minutes ago, Mike the Boilerman said:

How much does a metre weigh? I can never get a straight answer to this question either. Huh.  

The crumbly guy got it almost right, it’s one square kilogramme. 

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17 minutes ago, Mike the Boilerman said:

 

Nah, you’re joshing with us. You’ll be claiming it’s 4 Amps per hour in two seconds next! 

But all that aside, I wonder if can you help with another question that’s been troubling me for years. How much does a metre weigh? I can never get a straight answer to this question either. Huh.  

Make up your mind. First you ask the question, then you assert that you can never get a straight answer. What was the point of the question then? Were you looking for a curvy answer?

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