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Low Voltage to 12v water pump


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3 minutes ago, Kudzucraft said:

All I said was

 

3 minutes ago, Kudzucraft said:

This is where I have to make the assumption that the wire was rated for at least 10 amps

 

Yep, preceded by a big bold NO. So your actual assumption must have been that the cable was rated (not that cables have ratings per se) at a maximum of 10A which, as I wrote, is unlikely in the extreme. 

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32 minutes ago, Rockhopper said:

Thanks Kudzucraft, do you know where we might buy these type of switches for boats at all? I’m struggling to find something online. Alternatively, is there a way of checking if the cable is rated for 15amps?

Aquafax

 

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9 minutes ago, Kudzucraft said:

But it is bad practice to replace fuses with larger one and assume it is OK to do so.

 

But the 15A breaker the OP used is the correct size. We know this because it specifies what breaker size to use on the pump data label. 

 

So in this case it is not bad practice. Do keep up!

 

 

 

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Beaker protect wires from overheating, not devices. The pump may need a 15 amp fuse because of the start up draw. BUT the wire has to be big enough to handle it or you risk a fire if there is a short in the line. That  is a fact. 

 

I don't know what wiring is in the the boat and the OP said they were not knowledgeable on electrics, just saying to replace a 10 amp with a 15 amp is OK could put them at risk of a fire. So it is reckless to say it is OK. 

 

As I have said all along, you need to know what size the wire is to be sure. Not just guess and say "Yes it is safe".

Edited by Kudzucraft
typo
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14 minutes ago, Kudzucraft said:

Beaker protect wires from overheating, not devices. The pump may need a 15 amp fuse because of the start up draw. BUT the wire has to be big enough to handle it or you risk a fire if there is a short in the line. That  is a fact. 

 

I don't know what wiring is in the the boat and the OP said they were not knowledgeable on electrics, just saying to replace a 10 amp with a 15 amp is OK could put them at risk of a fire. So it is reckless to say it is OK. 

 

As I have said all along, you need to know what size the wire is to be sure. Not just guess and say "Yes it is safe".

Since you don't know why do you bother giving advice?

You've shown your ignorance of British boatbuilding practices in the past, so perhaps you should do some proper research first.

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24 minutes ago, Kudzucraft said:

That is about the stupidest thing I have seen posted on here. Electrons don't care if they are in Britain, Sweden or Australia.

But they do care about cable sizes and we know that no british narrowboat builder would wire a pump with 1mm2 cable. 

51 minutes ago, Kudzucraft said:

The pump may need a 15 amp fuse because of the start up draw. BUT the wire has to be big enough to handle it...

Of course it does. And it will be. 

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1 hour ago, Kudzucraft said:

No, sorry I don't.

 

 

What are talking about?  All I said was  

For a 10 Amp rating the cable would have to be only 1mm, it is very unlikely that 1 mm would supply that pump without undo volt drop. idf the cable was 2.5 mm it would be more than adequate to carry 15 amps and I would be very surprised if it was any smaller but I think it would be a safer assumption 

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6 minutes ago, ditchcrawler said:

For a 10 Amp rating the cable would have to be only 1mm, it is very unlikely that 1 mm would supply that pump without undo volt drop. idf the cable was 2.5 mm it would be more than adequate to carry 15 amps and I would be very surprised if it was any smaller but I think it would be a safer assumption 

Exactly :)

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1 hour ago, Kudzucraft said:

That is about the stupidest thing I have seen posted on here. Electrons don't care if they are in Britain, Sweden or Australia.

Thank you for that insulting comment.
Now do some research on what wiring is used in boats in the UK as you obviously do not know what we use.

56 minutes ago, ditchcrawler said:

For a 10 Amp rating the cable would have to be only 1mm, it is very unlikely that 1 mm would supply that pump without undo volt drop. idf the cable was 2.5 mm it would be more than adequate to carry 15 amps and I would be very surprised if it was any smaller but I think it would be a safer assumption 

Quite, but our American "friend" obviously doesn't understand what we use.

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Setting aside the bad mannered comments of Mr Kudz, another possibility is the OP's batteries are heavily discharged. The starting current of a motor tends to rise when supplied by an under-voltage battery thus tripping the original under-rated circuit breaker.

 

As an experiment to test this, the OP could see if the tripping persists if the pump is used with the engine running. If the fault goes away then this supports the theory. Or they could just tell us the exact domestic battery bank voltage when the problem is occuring!

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22 minutes ago, Mike the Boilerman said:

Setting aside the bad mannered comments of Mr Kudz, another possibility is the OP's batteries are heavily discharged. The starting current of a motor tends to rise when supplied by an under-voltage battery thus tripping the original under-rated circuit breaker.

 

As an experiment to test this, the OP could see if the tripping persists if the pump is used with the engine running. If the fault goes away then this supports the theory. Or they could just tell us the exact domestic battery bank voltage when the problem is occuring!

Whilst it’s true that a low voltage will raise the current I don’t think it’s relevant here as the pump clearly states 15A, which is rather a lot more than 10.

 

As the breaker has been regularly tripping it’s been opening its contacts while several amps were flowing. So lots of arcing and hence a very limited life. 

 

The 15A breaker should be fine but should ideally never be switched while the pump is running. 

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6 minutes ago, WotEver said:

As the breaker has been regularly tripping it’s been opening its contacts while several amps were flowing. So lots of arcing and hence a very limited life. 

 

True, but *something* made it start tripping in the first place, and we don't know what. A dying domestic battery bank could be the reason given it was heavily undersized in the first place and possibly only working right at the margin of its capability.

 

Then the batts go flat and the current rises, and the OP says it happens when the washing machine is on too....

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Some times I am forced to wonder if some people read all the posts and have assess each poster as being likely to supply good advice. I think four well respected technical posters from a variety of working backgrounds have stated that the 15 Amp breaker is in all likelihood absolutely fine.  This being based on experience of UK inland boat building practice. Yet we get contradicted by the American.

 

To the OP. Unless your water pump is at the back of the boat it would be impossible to get it to run reliably with cable as thin as 1 sq mm CCSA. Also the "standard" 1 sq mm CCSA cable of as few years ago did not comply with RCD and probably other requirements because it did not have enough strands. Modern 1 sq mm CCSA cable has nearly twice the strands and each strand is thinner.  The absolute thinnest cable that might give a low enough voltdrop over the run is 2sq mm CCSA and as Wotever says may well be 2.5 sq mm or I will add even larger. I don't think you need to worry about the cable size now you have found a good reason for the tripping. However if you are still concerned checking the voltage at the running pump will give us a fair idea if the cable is thick enough for its length of run.

Edited by Tony Brooks
add an ommited T to "at"
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9 minutes ago, Tony Brooks said:

Some times I am forced to wonder if some people read all the posts and have assess each poster as being likely to supply good advice. I think four well respected technical posters from a variety of working backgrounds have stated that the 15 Amp breaker is in all likelihood absolutely fine.  This being based on experience of UK inland boat building practice. Yet we get contradicted by the American.

 

Indeed !!!

 

The boat was originally supplied with a 10 amp pump (previous owner changed it for a 15 amp pump)

 

Boatbuilders would generally work to 3-4% volt drop as maximum

If we take the (suggested) 1mm2 (17AWG) cable over a length of 15 metres with the original 10 amp pump the ACTUAL volt drop would be 5.14v (or 42.8% volt drop)

This would never have happened

 

2mm2 cable would give 2.57 volt drop. (21.4%)

 

The cable could well be as much as 6mm2 (10AWG)

 

UK builders of long thin boats generally work on volt-drop rather than current draw (except on high current items such as inverters)

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I hope that posts 22, 37, 39, 43, 44 and others have put OP’s mind at rest that they’ll be perfectly fine using their 15A breaker for the water pump circuit. 

 

Contributions from others who don’t understand voltage drop calculations are less than helpful. 

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I have found that breakers get tired after a time, especially when running near maximum rating.
People have gasped with horror when they have seen my 12 V distribution board, which employs Hagar 240V AC type breakers. I fitted them on the recommendation of Hagar who say their breakers are tested down to 12V dc (some makes are not suitable.) I have picked up several expensive 12V dc panels in chandlers where the switches and breakers have been AC rated...
For the record, our pump(s) have had 15A breakers for 15 years without problems using 4 mm sq cable (ideally should have been 6 mm sq for volt drop purposes but have been fine.)

Edited by Guest
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15 hours ago, Kudzucraft said:

That is about the stupidest thing I have seen posted on here. Electrons don't care if they are in Britain, Sweden or Australia.

Ahhhh but, the eu does care!! We have to abide by eu law in all things boat over here sorry to say. The eu even stipulates we abide by its RC directive isnt that wonderful. 

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4 minutes ago, mrsmelly said:

Ahhhh but, the eu does care!! We have to abide by eu law in all things boat over here sorry to say. The eu even stipulates we abide by its RC directive isnt that wonderful. 

You will be blaming the vacuum packing of Manx Kippers on the EU next! ?

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1 minute ago, catweasel said:

You will be blaming the vacuum packing of Manx Kippers on the EU next! ?

I hadnt seen that story till I googled it now lol. I have given up on the news as there isnt any lol. Anyway kippers should be banned by the eu along with celery and marmite ?

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14 minutes ago, mrsmelly said:

I hadnt seen that story till I googled it now lol. I have given up on the news as there isnt any lol. Anyway kippers should be banned by the eu along with celery and marmite ?

Not too bothered about kippers or celery myself, but Marmite! I love the stuff :)  A Marmite butty, using white bread with proper butter is one of life's luxuries to me.  My better half hates the stuff :)

Edited by Guest
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