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mrsmelly

Inverter size

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Hi Peeps

Asking those in the know please a few questions re electrical set up. At present I have an all singing and dancing combi with power assist etc etc. Works brilliantly but it will go bang one day so I am deffo going seperates when it does and will be buying the equipment asap to have in stock so change when it goes bang. I did have a new victron combi but sold that to a forum member as he needed one quick and has retained his combi set up. Main questions are my boat is and will remain all mains equipment so What size inverter do I need for the under counter mains fridge? it needs to be big enough to start up on demand and run the fridge but needs to be no bigger as I intend wiring direct to mains when on shore power rather than at present set up through the combi. The fridge is the biggest piece of equipment it will need to power as when off grid the inverter is fridge telly etc but I have a travel power which will run the washing machine. So smallest that will do fridge and telly please. Will say a 1200 suffice if a good quality one?  Oh and just a thought will a quasi sine do or does it have to be pure sine again?

Thanks in advance re any suggestions.

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To answer the question re quasi-sign (which is basically just a fancy name for ‘square wave’) motors run hotter and with less efficiency on anything other than sine. So your fridge or freezer will last longer on sine wave. Whether or not the shortened life will be significant is moot...

 

hope that helps. 

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A pukka 1200va inverter will happily cover those needs with capacity to spare Tim.  I recently replaced my Mastervolt Combi 2500 with a Victron Phoenix Compact 2000 inverter, which is the sister unit to their 1200.  We use some kit at 1200 - 1600 watts, so the bigger one was the choice for us and I'm pleased with it.  It'll handle 4000va for starting current, so the 1200 probably does 2400 briefly too.  I found the 2000 at 600 quid, but most places are quite a bit more - I'll remember where I got it eventually!  Built like a brick outhouse, runs cool and its normally silent. Not cheap though, and for what you're running, and with the travel power available, you could go for a smaller model if you sacrifice the flexibility of the spare capacity.  

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Should be OK. On our boat share we have a 1 kW PSW (2 kW peak) invertor which runs fridge and odds and ends for charging. The fridge is A+ and even in hot French weather only draws 14 W average, 65 W peak. Our invertor was from Sunshine Solar <https://www.sunshinesolar.co.uk/prodshow/1000W___24V_Pure_Sine_Wave_Sunshine_Power_Inverter/VP100024.html>

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Inverters which weigh more usually have low frequency transformers and can take a bigger surge current than the high frequency brigade.  More importantly than output size is the no load current, not the standby current as often you will find that the inverter won't pick up from standby when you want it to, so you end up having it on 24/7. My victron will not come out of standby for my fridge but will for my TV work that one out.  Remember you must not be able to connect the travel power output to the inverter output.  Inverters don't like it up em! they take up smoking.

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35 minutes ago, Detling said:

Inverters which weigh more usually have low frequency transformers and can take a bigger surge current than the high frequency brigade.  More importantly than output size is the no load current, not the standby current as often you will find that the inverter won't pick up from standby when you want it to, so you end up having it on 24/7. My victron will not come out of standby for my fridge but will for my TV work that one out.  Remember you must not be able to connect the travel power output to the inverter output.  Inverters don't like it up em! they take up smoking.

Thanks. My present set up is done by a wizard. There are some sockets in the utility room that only work when travel power is on or when on shoreline so it is at the moment impossible to run the washing machine by mistake from the inverter. All the other umpteen sockets throughout the boat work through the inverter but by some magic from the travel power I think when that is running. By inverter I mean combi. When not on landline it sleeps at 0.3 amp but will fire up on demand by the fridge so perfect. It is a bloody good and silent combi as you say. However it will go bang one day and is now eleven years old and I am deffo going seperate when it does. I think I understand how to re do the wiring and luckily there is a proper source switch fitted already to make things a tad easier for me but I will be asking Nick and others on the forum what is realy needed come the time. The charger bit is of course simple. Its SIMPLE that is needed on boats unless of course you are an electric wizard then complex is fine.

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As a rule of thumb take the maximum wattage output of the installation.

As an example, the inverter output should be 130 % of the maximum output of the installation.

If the fridge requires 1000 watts to start then the inverter should have a minimum output of 1400 / 1500 watts.

When specifying an inverter always have around 30% in reserve. 

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20 hours ago, Keith M said:

As a rule of thumb take the maximum wattage output of the installation.

As an example, the inverter output should be 130 % of the maximum output of the installation.

If the fridge requires 1000 watts to start then the inverter should have a minimum output of 1400 / 1500 watts.

When specifying an inverter always have around 30% in reserve. 

Thanks. How can I find what power it needs to start the fridge?

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3 minutes ago, mrsmelly said:

Thanks. How can I find what power it needs to start the fridge?

You can’t, easily. 

 

A 1200W inverter would be fine. A 1000W inverter would probably be fine. A 750W inverter might work.  A 500W inverter almost certainly wouldn’t cope. 

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7 minutes ago, WotEver said:

You can’t, easily. 

If the fridge already is in position.

If there is already an inverter (or hook-up lead) already connected

 

Couldn't you just plug one of those watt counting meters in and watch very carefully for the quick peak of consumption ?

Would they react quickly enough ?

 

51bqrxNFccL._SL1200_.jpg

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9 minutes ago, WotEver said:

You can’t, easily. 

 

A 1200W inverter would be fine. A 1000W inverter would probably be fine. A 750W inverter might work.  A 500W inverter almost certainly wouldn’t cope. 

😂 Flippin marvelous innitt. I guessed a 1000 would do it but am thinking of plumping for a 1200 I will see what comes up at the right price 👍

1 minute ago, Alan de Enfield said:

If the fridge already is in position.

If there is already an inverter (or hook-up lead) already connected

 

Couldn't you just plug one of those watt counting meters in and watch very carefully for the quick peak of consumption ?

Would they react quickly enough ?

 

51bqrxNFccL._SL1200_.jpg

Ive got one of those somewhere. Doubt it would be quick enough???

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9 minutes ago, mrsmelly said:

Ive got one of those somewhere. Doubt it would be quick enough???

Try it and see.  Some of them have a min/max setting that will update faster than the display does.

 

If it doesn't work (you don't believe the results) it hasn't cost anything to try.

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27 minutes ago, TheBiscuits said:

 

Oh, and Sunshine Solar have some stuff on sale ...

 

https://www.sunshinesolar.co.uk/catshow/Pure_Sine_Wave_Inverters_12V/PureSineWave12V.html

 

£389 for a 3000W or £339 for a 2500W for another week.

Thanks for the link. I think although am not sure that I want a low frequency inverter as my kit usualy is. They are bigger and heavier and more expensive but are silent without fans often cutting in and iirc are better for long term 24/7 use but I am more than happy to be informed otherwise as high frequency stuff is cheaper.

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I installed the 3000W version of this a couple of years ago, when the magic smoke came out of the noname 3000W inverter on the boat.

 

It's smaller, quieter and eats less amps when doing nowt.  The old LF inverter used to draw about 4.5A when sat there doing nothing.  It could do much less but needed a draw > 40W to fire up so was useless for phone chargers, radios etc.

 

The Sunshine runs fanless until it needs to - the washing machine doesn't fire up the fan even when heating water but it's only a 1300W Candy.  The big chopsaw or the electric chainsaw (both > 2000W) fire up the fan if run for a bit, but I have the engine running to use them so can't hear it anyway. :D

 

It's been on 24/7 since I installed it, apart from when the old batteries died last summer and I was waiting for a delivery from tayna.

 

The only two gripes I have about it is that the battery cables provided need binning not using, and the optional remote switch has too many flashenblinkenlights on it.

 

Add a bit:

 

Three gripes - it was not on sale that low when I bought it!

Edited by TheBiscuits

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1 hour ago, TheBiscuits said:

I installed the 3000W version of this a couple of years ago, when the magic smoke came out of the noname 3000W inverter on the boat.

 

It's smaller, quieter and eats less amps when doing nowt.  The old LF inverter used to draw about 4.5A when sat there doing nothing.  It could do much less but needed a draw > 40W to fire up so was useless for phone chargers, radios etc.

 

The Sunshine runs fanless until it needs to - the washing machine doesn't fire up the fan even when heating water but it's only a 1300W Candy.  The big chopsaw or the electric chainsaw (both > 2000W) fire up the fan if run for a bit, but I have the engine running to use them so can't hear it anyway. :D

 

It's been on 24/7 since I installed it, apart from when the old batteries died last summer and I was waiting for a delivery from tayna.

 

The only two gripes I have about it is that the battery cables provided need binning not using, and the optional remote switch has too many flashenblinkenlights on it.

 

Add a bit:

 

Three gripes - it was not on sale that low when I bought it!

Cheers. I only need a small ish output as travel power does the heavy stuff but its good to hear your opinion on the kit. What does it draw when switched on and doing nothing?

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Just now, mrsmelly said:

Cheers. I only need a small ish output as travel power does the heavy stuff but its good to hear your opinion on the kit. What does it draw when switched on and doing nothing?

About half an amp.

 

They do make these from about 50W to 4000W, and I would suggest looking at the 1000W one for what you want it to do.  It will spike to 2000W so should easily be able to start the fridge compressor, just keep an eye on the random sales they do - there is usually something at half price on that site.

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Just now, TheBiscuits said:

About half an amp.

 

They do make these from about 50W to 4000W, and I would suggest looking at the 1000W one for what you want it to do.  It will spike to 2000W so should easily be able to start the fridge compressor, just keep an eye on the random sales they do - there is usually something at half price on that site.

Fab I will.

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17 hours ago, TheBiscuits said:

 

 

The only two gripes I have about it is that the battery cables provided need binning not using, and the optional remote switch has too many flashenblinkenlights on it.

 

 

 

I like the flashing lights. They help me find the toilet in the middle of the night.

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7 minutes ago, Onewheeler said:

I like the flashing lights. They help me find the toilet in the middle of the night.

It's probably them waking you up and you go to the loo whilst you are awake! :D

 

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On 08/01/2019 at 14:45, TheBiscuits said:

It's probably them waking you up and you go to the loo whilst you are awake! :D

 

If I ever walk past my inverter whilst heading for the loo in the night, I hope the lights do wake me up or things will end badly for me! :help:

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It's not a matter of inverter rated output per se but what instantaneous current the device will provide to start the fridge. In practice that means a 1200W inverter. 800 is too small, there aren't any / many 1000w units available in general circulation.

Bimble sell such a  unit for a reasonable sum - but it's 24v - and I assume  you're 12v, so I didn't bother to make a comment earlier.  I tried 'several' units and the lowest power rated one to work was 1000w rated. It even started a two motor large fridge freezer without any problem.

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38 minutes ago, OldGoat said:

It's not a matter of inverter rated output per se but what instantaneous current the device will provide to start the fridge. In practice that means a 1200W inverter. 800 is too small, there aren't any / many 1000w units available in general circulation.

Bimble sell such a  unit for a reasonable sum - but it's 24v - and I assume  you're 12v, so I didn't bother to make a comment earlier.  I tried 'several' units and the lowest power rated one to work was 1000w rated. It even started a two motor large fridge freezer without any problem.

Thanks. I was initialy thinking 1200 but I reckon 1000 now will prob do. The present combi is 1500 with power assist etc etc but in reality with travel power fitted I only ever run tv and fridge off it when out and about and a bit of fone lappy charging which I do when engine running anyway. I am going to look out for a bargain for my spares bin. There are some quite cheap stuff out there at only 2/300 quid but I will probably plump for another mastervolt or victron. I will then buy a 20 amp charger with the ability to run the 12 volt when plugged in thingy. My stuff all works awesomely well but it will go bang one day and be replaced with seperates.

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