Have seen this about lately but never took much notice of it. My take which could be wrong ,or right is.....
Basically the current will be spit in half and run through each fuse rather than one fuse. This might allow for a greater inrush current . Could also allow for a slightly higher current and a longer blow time rather than a single 10amp fuse. But if 1 fuse blow the other will blow and you have to replace 2 instead of 1. Other thing could be redundancy. 5 amps might be enough but if for some reason 1 blows the second will keep it going. As i said I have not had a look at it.
Anyways someone the does know the answer will let us know.

-- Edited by Corndoggy on Wednesday 1st of January 2020 03:09:03 PM

It is not at all clear how it is wired as we can not see the right hand side of the fuse connections.
OT - those auto blade fuses are notoriously unreliable.
Cheers,
Peter

In theory at least, 2 X 5A fuses in parallel will act as a single 10A fuse, but only if they carry exactly equal current each.
Not a recommended practice.
Cheers,
Peter

Mike Harding wrote:

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I think it's because the person who wired it was an idiot.

Two fuses in parallel do not work in the same way as one fuse in series. Rewire with one fuse and wire of the proper rating.

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 The guy or gal who wired it was certainly not an idiot Mike. If you look at the job done its quite professional. They new enough to work out they could do it that way with 5 amp fuses, which works successfully and can be left that way. 

Perhaps they didn't have any 10amp fuses.

So it comes down to what fridge he has and the maximum current rating of that fridge, to ensure it is protected properly.

Whenarewethere wrote:

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My 3.0kVA UPS has 3 fuses in parallel. Also each battery pack has the same, & for each set of batteries in series within the battery pack. If one fuse blows all 3 will blow.

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 They seem to be using them this way as it's been said that say a 250amp fuse can be large and they will use 3 x 80amp fuses in parallel  to get it up to the mark and be smaller in size. As said in theory they should share equal currents and blow at the current for an 80amp fuse, then blow the other 2. Why do it on a small circuit like a fridge has me. Would say it is ok like that but i wouldnt have done it that way. Also to me it doesn't look like a very well done job.

-- Edited by Corndoggy on Wednesday 1st of January 2020 06:48:00 PM

-- Edited by Corndoggy on Wednesday 1st of January 2020 06:50:05 PM

Corndoggy wrote

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Also to me it doesn't look like a very well done job.

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It's not a well done job that's why I am redoing it all. I just wanted to understand why he would do that. Especially when a 10 amp fuse would have sufficed.

I must be so lucky. Never had a problem with blade fuses that I can remember

Well since you have taken exception to my comment re "professional job" , I'll explain. The job i was referring to and you were asking about is the Fridge Yellow cable and 5amp fuses.

I blew up your photo which shows the "Yellow" Fridge cable well lugged and connected, as a pro would do!! This indicated to me he new what he was doing paralleling the 5 amp fuses, for whatever reason.

The rest of the installation is of course a disgrace.

I agree if you are to rewire it all, you would would use one fuse, possibly a 7.5amp if you can get away with that on compressor start. For Normal running, a 10amp is too high for a 2.25 current draw.

 

Hi Teekay, If they are blade fuses, it is not unusual as it is a continuous current for the actual fuse holder to get slightly warmer, and this can cause the tenson on the fuse holder to reduce, causing it to get warmer, the original job was done to reduce heating in the fuse holder, it is not uncommon with 3 way fridges to just about kill their fuse holder with 20 amps continuous when driving. The type of fridge being installed may not have been known when wired. Just an idea why.

Fuses should firstly be rated to protect the cable, not the appliance.
Cheers,
Peter

On topic, but not directly related to this exact issue, I have found that the quality of blade fuses has deteriorated over the last few years. The actual fuse bit works as designed but the plastic housing are now so sub-standard they will melt well before the fuse ever blows - think of the fuse as a jug element encased in plastic.

I stumbled across these at RTM https://www.roadtechmarine.com.au/standard-blade-circuit-breaker-20a-manual-reset/p/SF2335 at $6 a pop they aren't cheap but they are actually a circuit breaker that plugs into the standard fuse hole. They never have to be replaced (if they 'blow' they are just reset like a normal circuit breaker) and the plastic never melts.

 

Dave

-- Edited by BT50 Dave on Tuesday 14th of January 2020 05:07:51 PM