Engine rewire, wiring diagram ?

[Steve C Cronin]

I am still trying to get my head round the fact that you need a 250 Amp fuse in the house supply???

Do you really have wiring which will handle a continuous current of 250 Amps (500Amps peak)!

Your wiring will get hot, melt and short out long before that fuse will blow.



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He must be running his windlass etc. off the house.

 

[lenseman]

He must be running his windlass etc. off the house.

Nope, that is run from the engine battery and it already has a 100 Amp fuse anyway.

Seems like a totally crazy system.


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[VicS]

He must be running his windlass etc. off the house.

His original intention was to run the windlass of the engine battery via its own (100amp?) fuse but whichever battery it runs from it will need its own fuse sized as recommended by the windlass manufacturer

The 250amp mega fuses are needed because he wants to be able to use either battery for engine starting.

 

[lenseman]

His original intention was to run the windlass of the engine battery via its own (100amp?) fuse but whichever battery it runs from it will need its own fuse sized as recommended by the windlass manufacturer

The 250amp mega fuses are needed because he wants to be able to use either battery for engine starting.

I agree and that has been suggested by pvb in an earlier thread but, it is crazy.

That fuse will NEVER blow and therefore is redundant. The starter motor is usually only on for 10 seconds(?) and for the rest of the time the domestic (house) circuit will probably only pass 10-15 Amps (not the 40 Amps as has been suggested)?

The whole scheme seems to be an exercise in covering all bases and adding so much complexity that it becomes a snakes nest. Why not take 200 miles of 3-core mains via an RCD (of course) so that you can always have access to pontoon electricity?



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[VicS]

Seems like a totally crazy system.
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The system has evolved in an attempt to satisfy most, if not all, of his original requirements. I made my suggestions earlier and the circuit at the beginning of this thread is the OPs attempt to put my ideas together.

PVB has suggested a simpler circuit, which I'd be happy with, although it omits some of the original ideas/ requirements. His circuit looks very much simpler because he has also made a better job of drawing it out.

Now its your turn to come up with a less crazy system.

The guy is not a electrician. He is shopfitter and joiner.

 

[pvb]

That fuse will NEVER blow and therefore is redundant. The starter motor is usually only on for 10 seconds(?) and for the rest of the time the domestic (house) circuit will probably only pass 10-15 Amps (not the 40 Amps as has been suggested)?

As you claim to be a marine engineer, I'd have imagined you'd have been more aware of electrical requirements. Fuses are there to protect wiring, and are sized accordingly. In normal operation, the fuse should indeed never blow, but that's not what it's there for. It's there to prevent the boat catching fire if there's a short in the wiring. The wiring has to be chunky to cope with the OP's requirement to be able to use the house bank to start the engine.

 

[Steve C Cronin]

His original intention was to run the windlass of the engine battery via its own (100amp?) fuse but whichever battery it runs from it will need its own fuse sized as recommended by the windlass manufacturer

The 250amp mega fuses are needed because he wants to be able to use either battery for engine starting.

Sorry to appear dim bsut on tablet at present. When back on laptop will be able to too and fro properly

 

[xeitosaphil]

First let me thank everybody for their input and thanks PRV for your simplified wiring diagram. I certainly did not want to have you spend all your time preparing wiring diagrams, but am very grateful for it anyway, and it has given me an insight to prepare another one.

I just wish I had a little more insight into the in-depth workings of 12v circuitry, which it is apparent I don’t have, hense the need for some advise.

As others have mentioned my wring diagram was a little involved and I have made yet another which I hope will be more suitable and hopefully it will be the last one.

I have got rid of one ammeter ( engine side) but kept the house one in the hope it will indeed monitor charge and discharge current to and from the house bat /bank.
As this is an alteration and not a new installation I have to try and alter the circuits as cost effective as possible using my current layout and alterations. Therefore I have decided to keep the 1-2-both switch and I have already purchased the VSR and Isolator, but not the 50m2 so need to finalise the length of cable runs etc.
The mains battery chargers are also already installed so they will be staying but with the option of using the engine battery one or not. Which has a de-mountable plug connector permanently fixed to engine battery?
Winch supply cables are also staying but putting in a fuse just after the engine 250A mega fuse also included in house bank. There will also be 30A fuses in Charger supplies, and a 60A in Alternator, 40A in Distribution Fuse board and a 100A in the windlass supply next to Engine Battery which also has a 80A Lofrans Fuse trip switch fitted at chart table.
I will have to look into the fuse situation in more depth as Mega fuses will except loads for fixed times but also have quick blow times in comparison to the percentage of the amount of over- load. There is a table I have seen somewhere but can’t remember where at the moment.
By keeping the 1-2-both switch I can start from house or engine battery and isolate both individually but still charge either battery by setting to Both if the VSR goes down. Not quite sure if I should keep the Negative switch, in the VSR sensing line to battery as suggested for isolation should the VSR go down.

Hopefully this new layout will get approval but still glad and grateful to except feedback if not. Philip

 

[VicS]

Sorry to appear dim bsut on tablet at present. When back on laptop will be able to too and fro properly

Some tablets do make you feel dim.. Seroxat is one of the worst.

 

[VicS]

Hopefully this new layout will get approval but still glad and grateful to except feedback if not. Philip

I cannot see any problems with that. It falls short of your original requirements with regard to current monitoring but its a trade off with simplicity.

Its a pity to have to use the old selector switch just as the linking switch but full marks for ingenuity!

You will fit the Smartgauge to the house bank following the manufacturers instructions presumably.

 

[xeitosaphil]

I cannot see any problems with that. It falls short of your original requirements with regard to current monitoring but its a trade off with simplicity.

Its a pity to have to use the old selector switch just as the linking switch but full marks for ingenuity!

You will fit the Smartgauge to the house bank following the manufacturers instructions presumably.

Yes Vic not quite sure exactly what it will be monitored but hopefully it will monitor all in and out of house bank including the alternator charge Via VSR.

With everybody’s feedback telling me I was looking to monitor too much, I thought I would try this solution after seeing PRV’s simple diagram.
It would have been nice to monitor same of engine bank but as you and others have said, it’s not really necessary, and Smart Gauge will tell me volts anyway. It’s already fitted as manufacturer’s instructions, but I needed an ammeter to monitor discharge rates and thought it would be nice to monitor both banks if possible.

I never knew there was such a need for all the fuses, the boat and wiring layout is 38 years old and the only fuses it has, is on the distribution fuse board about 20 in all, but nothing back to the batteries. Doesn’t seem to have been a problem over the years, but I suppose things and ideas move forward?

 

[lenseman]

. . . . Hopefully this new layout will get approval but still glad and grateful to except feedback if not. Philip

The 40 Amp fuse is far too large for your usage (are you using 40 Amp+ cabling to the distribution panel) plus, as you only have a VHF radio (7 Amps on Tx) and Nav/Steaming Lights (6 Amps Max if using filament bulbs) plus cabin lights, you would be pushed to be demanding more than 15 Amps maximum.

If, at a later date, you install AIS, Radar then you can increase the fuse assuming the wiring is rated higher than the current drawn.

Another thing, you have a 100 Amp fuse for the Winch but you also have a 50 Amp fused switch. Perhaps you need to think about this?


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[xeitosaphil]

The 40 Amp fuse is far too large for your usage (are you using 40 Amp+ cabling to the distribution panel) plus, as you only have a VHF radio (7 Amps on Tx) and Nav/Steaming Lights (6 Amps Max if using filament bulbs) plus cabin lights, you would be pushed to be demanding more than 15 Amps maximum.

If, at a later date, you install AIS, Radar then you can increase the fuse assuming the wiring is rated higher than the current drawn.

Another thing, you have a 100 Amp fuse for the Winch but you also have a 50 Amp fused switch. Perhaps you need to think about this?


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The 40A fuse for the distribution cable which is 10mm Tri rated which is rated at 70A the fuse is just to protect the supply cable. The distribution outlets are individually fused at ratings for the instruments they supply it has been suggested by some it should be a 70A fuse but I thing this un necessary.As said in my last post I will be reviewing the fuse situation with regards to Mega fuses to get the correct ratings for the wiring anyway.

The Windlass is a Lofrans with a 1000W motor which at max chat would consume 83A the recommended cable for up to 29' by the manufacturer is 35mm2 which is what I have, the Carling Switch switch circuit breaker http://www.ecs-marine-equipment.co....r-handle-actuator-visi-rocker-item-26986.html is rated at 80A and has worked fine for the last 12 mnths cruising so I don't see it as a problem!

I think you are getting mixed up with the 50A Digital Ammeter Gauge?

 

[lenseman]

. . . . . . the Carling Switch switch circuit breaker http://www.ecs-marine-equipment.co....r-handle-actuator-visi-rocker-item-26986.html is rated at 80A and has worked fine for the last 12 mnths cruising so I don't see it as a problem!

I think you are getting mixed up with the 50A Digital Ammeter Gauge?

No, I wasn't getting confused at all but I do admit a typo due to poor rendering of the diagram as it looked like a 50 Amp Fused switch.

That being said, what I am suggesting is the futility of protecting a switch with a maximum continuous current of 80 Amps with a fuse at 100 Amps. Switch costs £30 and fuse costs £3.

Interestingly, the technical specification for that particular switch states in the 'Specification' that the current handling is only 30 Amps which makes the 100 Amp fuse 'protecting' the switch as a bit strange? I think there is a typo on their web page but notwithstanding that, I would down-rate the 100 amp fuse to 80 Amps and hopefully it will blow before the switch burns out.


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[xeitosaphil]

No, I wasn't getting confused at all but I do admit a typo due to poor rendering of the diagram as it looked like a 50 Amp Fused switch.

That being said, what I am suggesting is the futility of protecting a switch with a maximum continuous current of 80 Amps with a fuse at 100 Amps. Switch costs £30 and fuse costs £3.

Interestingly, the technical specification for that particular switch states in the 'Specification' that the current handling is only 30 Amps which makes the 100 Amp fuse 'protecting' the switch as a bit strange? I think there is a typo on their web page but notwithstanding that, I would down-rate the 100 amp fuse to 80 Amps and hopefully it will blow before the switch burns out.


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The diagram is very small on the site I don't know why, its full size on my computer. I think it might be as it was done in Paint program and saved as a picture file.
I have found though if you enlarge on it on the PBO site and then zoom in on the computer it is very clear.

I take your point about the ratings , but I thought that the 100A fuse ( as recommended by the manufacturer ) would protect the wiring and the 80A continuous rating would protect the winch as the 83A max would only be short term and only be in a snarled anchor situation.

I suppose I could upgrade the switch trip circuit breaker to a 100A just to be sure.

 

[lenseman]

. . . . I take your point about the ratings , but I thought that the 100A fuse ( as recommended by the manufacturer ) would protect the wiring and the 80A continuous rating would protect the winch as the 83A max would only be short term and only be in a snarled anchor situation.

I suppose I could upgrade the switch trip circuit breaker to a 100A just to be sure.

A new switch will cost ~£30 which as you state is working perfectly well. A new fuse will cost you £3.

I would down-rate the fuse to 80 Amp as this fuse will handle an inrush current of 150 Amp peak.


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[VicS]

Yes Vic not quite sure exactly what it will be monitored but hopefully it will monitor all in and out of house bank including the alternator charge Via VSR.

Now looking at it more closely in response to your specific question I begin to see the snags, if snags is the right word.

As you have drawn it ( nice big clear diagram on my computer BTW) with the house battery charger negative connected directly to the battery negative the ammeter will not see the charging current from the house battery charger .... BUT ... here comes the hiccup ... if the VSR is a dual sensing one, and I think you said it is, as the battery becomes charged the VSR will close and the engine battery will also be connected to the charger. The engine battery charging current will then be seen by the ammeter as a discharge.

Moving the charger negative connection to the other side of the shunt ( to the negative stud) will solve both issues.

If you use the engine battery charger instead, although you now have no ammeter to show the current going to the engine battery, when the VSR closes the current going to the house battery will be shown correctly by the house battery ammeter.

On the fuses issue. Don't fit fuses larger than necessary to supply the current to circuits connected to them....... that may mean you can reduce the size of the fuse in the feed to the distribution panel possibly also in the winch circuit but the winch maker may reccommend a fuse size large enough to carry a high initial current

As far as wire sizes go they should always have a max safe working rating greater than the fuse supplying them ... so that in the event of a fault the fuse will blow before the wire overheats and sets fire to your boat.

In all but the shortest of cable runs the wire size will probably have to be greater, much greater even, than the max safe working rating in order to control voltage drop. The longer the cable run the heavier the wire will have to be.

 

[xeitosaphil]

A new switch will cost ~£30 which as you state is working perfectly well. A new fuse will cost you £3.

I would down-rate the fuse to 80 Amp as this fuse will handle an inrush current of 150 Amp peak.


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Thanks David,

Will reduce the Fuse to 80A and see how it goes @ £3 a go it makes total sense, I can always uprate it if needed but probably won't need to.

Have you a link to Mega fuse ratings and blow times , I saw one once but can't remember where it was now, only I need to look at all the others as well.

 

[lenseman]

Thanks David,

Will reduce the Fuse to 80A and see how it goes @ £3 a go it makes total sense, I can always uprate it if needed but probably won't need to.

Have you a link to Mega fuse ratings and blow times , I saw one once but can't remember where it was now, only I need to look at all the others as well.

You could try here:

http://bluesea.com/productline/overview/430

or here:

http://bluesea.com/products/5143

Normally, a fuse is rated as continuous current but will pass a peak current (in-rush current) for a limited time.


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[pvb]

Mega fuses have a very useful slow-blow characteristic, to avoid nuisance failures. Here's the current/time chart...