What size fuse for inverter (1 Viewer)

Feb 16, 2013
19,504
51,185
uttoxeter
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24,713
MH
ambulance conversion
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50 years
I have now fixed a 500w inverter in the van , just for light duties and a slow cooker, most it will be probably 200w, , I have put a normal spade fuse inline on the positive line next to the battery, and put a 20 amp in it that didn't blow so now I have a 15 amp in it and it seems to be working fine, now I have seen things on the net that says you need anything up to a 100 amp , why? If my 15 amp isnt blowing with the cooker plugged in , is that ok.
Thanks
 

scotjimland

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Jul 25, 2007
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what size is the cable.. ?

that is what determines the fuse or CB size.. it is sized to protect the cable..

If you don't know the cable size , was it supplied with the invertor ?

If so I wouldn't worry.. at full load the invertor would draw 40 A ..
so you will be safe using the 15A fuse.. that is equal to a load of 180 watt

The 200watt cooker will draw 16.7 amps so it may eventually blow the 15A fuse.. in which case use the 20A Fuse

Cable%2BRating%2BTable.jpg
 
Last edited:

Lenny HB

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Oct 18, 2007
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You never know what you are going to plug into it in the future so providing your cable is suitably rarted I would fit a 50 amp fuse, I have a 100 amp fuse in line with my 1000 watt inverter.

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OP
OP
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Feb 16, 2013
19,504
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what size is the cable.. ?

that is what determines the fuse or CB size.. it is sized to protect the cable..

If you don't know the cable size , was it supplied with the invertor ?

If so I wouldn't worry.. at full load the invertor would draw 40 A ..
so you will be safe using the 15A fuse.. that is equal to a load of 180 watt

The 200watt cooker will draw 16.7 amps so it may eventually blow the 15A fuse.. in which case use the 20A Fuse

Cable%2BRating%2BTable.jpg
Thanks for that , I am useing 6mm cable , wasn't thinking of melting the cable , more if the inverter crashed or the cable got cut or some other calamity, it came with cable for a fag lighter but I am useing maybe three times that, so I was right first time then,
Makes a change(y):)
 
OP
OP
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Feb 16, 2013
19,504
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You never know what you are going to plug into it in the future so providing your cable is suitably rarted I would fit a 50 amp fuse, I have a 100 amp fuse in line with my 1000 watt inverter.
I would rather have one that will blow quick, that's why I went for as little as possible (y):)
 

Autowbars

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Dec 1, 2012
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A 100 amp fuse is way over the top.
That will take some load to blow.

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JeanLuc

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Nov 17, 2008
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Not making any comment about the good advice you have been given regarding fuses, but I think I might be concerned about a 500w inverter that was supplied with a 'fag lighter' plug. Most such sockets are rated at 10 or 12 amps and your inverter can draw over 40 amps. Not great!
 
OP
OP
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Feb 16, 2013
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Not making any comment about the good advice you have been given regarding fuses, but I think I might be concerned about a 500w inverter that was supplied with a 'fag lighter' plug. Most such sockets are rated at 10 or 12 amps and your inverter can draw over 40 amps. Not great!
I know that that's why I havnt used them(y)

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Autowbars

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Dec 1, 2012
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These should not be sold with a power point plug.
If advertised as max output they can NOT get it from a cig, power point
 
OP
OP
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Feb 16, 2013
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These should not be sold with a power point plug.
If advertised as max output they can NOT get it from a cig, power point
Can't argue mate, but put , inverters, in ebay, everything up to 3000w come with cig plugs, why?
 

Roadroamer

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I am thinking of fittting a 3500w 7000w pure sine wave inverter and I am baffled as to what size fuse/circuit breaker help please
 

Lenny HB

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7000 w will be the peak power and the inverter will probably trip well before that.
So I would say 350 amp would be OK.

For an inverter of that size I take in you have a minimum of 750a/h of batteries and a means of recharging them like 750 - 1000 watts of solar.
 

Jaws

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I am thinking of fittting a 3500w 7000w pure sine wave inverter and I am baffled as to what size fuse/circuit breaker help please
A 6mm bolt should be about right !!! LOL !!!

And before anyone gets all twitchy it is a joke and not to be taken seriously !!!

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Roadroamer

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Oct 10, 2017
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the reason for fitting a large inverter is I had a 2500w 5000w inverter which went bang using a 1500w coffee maker and the supplier said it is not man enough for it so rejected my warranty claim
 

Lenny HB

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Oct 18, 2007
52,684
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On the coast in West Sussex
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the reason for fitting a large inverter is I had a 2500w 5000w inverter which went bang using a 1500w coffee maker and the supplier said it is not man enough for it so rejected my warranty claim
Should have got tough with them, should have been fine. Carthago and Hymer only fit an 1800 watt inverter for a 1400w coffee maker.
2000 w will be more than enough. Just buy a quality one.
I have a cheap pure sine 1000w runs an 800W kettle & 1000w iron OK.
 
Last edited:
OP
OP
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Feb 16, 2013
19,504
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would like to add to this , mine has never blown a 15 a fuse so why you would put a 200 a has always baffeled me , you would think it would have to be on fire before it blew one of them.

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Roadroamer

Free Member
Oct 10, 2017
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is your 15a fuse in the thick cable between the battery and inverter?
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
52,684
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On the coast in West Sussex
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658
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Hymer B678 DL
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Since 2008 & many years tugging
would like to add to this , mine has never blown a 15 a fuse so why you would put a 200 a has always baffeled me , you would think it would have to be on fire before it blew one of them.
If you have a 1000w inverter and use a 1000watts on the output it will draw around 90 - 95 amps on 12v.
Likewise a 2000w inverter will draw 180 - 190 amps when loaded to 2000w.

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Sep 1, 2018
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I phoned the importer of my inverter to check fuse size , they told for my 1500w unit it was a 150amp fuse
so I’m assuming 500w would be 50amp but lennys sizes sounds good to me
 

SuperMike

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Apr 28, 2010
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I have our 3000w pure sign wave inverter, using 25sq mm cable, fused at 120A, kept going, not in this country, by 400w of solar. The only time it does any real work is the 900w kettle or toaster, on for just a few minutes, the rest of the time it’s charger, tv and stuff like that. :gum:

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Aug 5, 2018
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a
A 6mm bolt should be about right !!! LOL !!!

And before anyone gets all twitchy it is a joke and not to be taken seriously !!!
works for my 250 amp welder in the garage, not blown a bolt yet. Could only just about get the lid of the plug back on though :D
 
Aug 5, 2018
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a
We used to have to do that with 13A plug tops when that was the only thing available to plug the welders in:giggler::giggler::giggler::giggler:
Oh Snap :D Works a treat (Couldn't be arsed to fit a 16 amp blue plug and rewire a socket for it :D)
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
52,684
147,591
On the coast in West Sussex
Funster No
658
MH
Hymer B678 DL
Exp
Since 2008 & many years tugging
I have our 3000w pure sign wave inverter, using 25sq mm cable, fused at 120A, kept going, not in this country, by 400w of solar. The only time it does any real work is the 900w kettle or toaster, on for just a few minutes, the rest of the time it’s charger, tv and stuff like that. :gum:
Never going to work at 3000 watts with that size fuse.

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