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Dr Bob

12V distribution panel problems

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Ok, someone clever required to help me understand my 12V distribution panel. Defo no fish jokes until at least 10 constructive replies.

A pic of this vintage (2002) panel and the wiring on its backside below.

Last year I had a couple of instances with the water pump switch. Normally when turning on/off there is no light on the illuminated switches. When the problem with the water pump happened, the water pump stopped working and the switch for the pump illuminated. I solved it by taking one of the unused switches and putting in place of the duff one. Same happened a couple of months later and I replaced it with another unused switch. I then went out looking for replacement switches but only came up with the one in the panel pick (bottom of right hand column). I think I have now found a supply of the illuminated switches.  I was then a happy bunny knowing that when a switch went bad, it would illuminate and I knew  to replace it.

Fast forward to last week. The hob ignition decided to start playing up and needed lot of ignition sparks to keep the burner alight (a Thetford 3 burner hob -18 months old). It seemed to be worse when the water pump was running. Then the ignitor stopped 'clicking'. Decided to put the hob ignition wire from the panel on another switch and it all seemed fine with the hob working well. No lights on the duff switch this time. Did a bit of poking around with my multimeter and the switch that was bad was another switch - the one with the Nav lights on it - on the right hand bank. When that one was turned on, 50% of the time about 8 of the 20 switches lit up  and didnt work. The other 50% of the time the whole panel was fine. I have now removed that switch and the panel is working well. When I did my original 'poking' at one time I found a max of 9V on the centre (distribution) pins of the right hand bank but ignored it. In hindsight the duff switch was pulling the voltage down.

My questions are

i) how does this panel work?

ii) and why can one switch affect another one by reducing the voltage available?

If you look at the pic of the wires in the other pic, look at the top row of switches / circuit breakers. Furthest right is the circuit breaker with 2 contacts. C1 furthest right is the supply +ve to the breaker. Next along to the left  C2 is the other side of the breaker which feeds the input to the switch C3. Next is C4 the output from the switch which goes off down the boat to the 12V load. Final switch is C5 which is a black wire providing a connection to all the C5 contacts down the panel. This black wire does not seem to connect to anything off the panel or to the other side of the panel. I assumed this was an earth wire that the switch used to complete a circuit to illuminate the switch if anything went wrong but I can't see how that works. Putting a voltmeter on C5 and the other lead to earth gives 12.7V (Battery at 12.7V). So, totally confused about the role of the black wires on C5 or how the switch illuminates. Is the black wire on C5 live because one or two of the switches are bad?

Bottom line is that I am running out of good switches and not sure new (cheap) chinese ones will last. My switches are 16 years old so probably are on their last legs. Maybe I need a new panel. Some seem cheaper than others but again I would worry about quality of those switches.

 

 

 

Panel.jpg.8d976ab06868334caadacd4f29f8a742.jpg

wires.jpg

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I have no real magic solution. However,

I have a similar panel (same style, different components) and have found that the components get 'dry' with age. internal cables were rigid and stiff which somehow created dry joints.

The feed cables are inadequate for the rated current(s) - and even juggling with input feed locations so that the highest power devices are nearest the fed cable doesn't quite solve the problem.

Try remaking the Lucar clips tension and rethinking the power layout.

That said, the only device with which I have any problem is the Mikuni heater on initial startup - where is doesn't like the voltage drop. It really needs a 30 amp breaker.

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3 minutes ago, OldGoat said:

I have no real magic solution. However,

I have a similar panel (same style, different components) and have found that the components get 'dry' with age. internal cables were rigid and stiff which somehow created dry joints.

The feed cables are inadequate for the rated current(s) - and even juggling with input feed locations so that the highest power devices are nearest the fed cable doesn't quite solve the problem.

Try remaking the Lucar clips tension and rethinking the power layout.

That said, the only device with which I have any problem is the Mikuni heater on initial startup - where is doesn't like the voltage drop. It really needs a 30 amp breaker.

Thanks OG.

The breakers dont seem to be a problem. I've never seen any of them pop.

We dont really have any high power demand on the panel, the water pump and vacuum toilet pump are probably the highest duty and they dont pull any more than 7A - maybe more on startup.

 

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Well until someone clever comes along with some fish jokes, my twopenneth worth. 

 
These things are often down to poor connections. Make sure you have good clean tight connections on all circuit breakers and switches. 
 
Make sure at the pump/cooker end the connections are good, and there are no significant volts drops. 
 
Make sure the circuit breakers and switches are  suitably rated for the current equipment. Has the water pump/cooker spec been upgraded since installation without consideration to circuit breakers/switches?
 
Check negative bus bar connections in panel.
 
When you changed switches, I assume you kept the breaker rating the same. (or are all switches and breakers rated the same on the panel?)
 
Have you heard the one about the two fish in a tank?..............

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We had a similar panel in Copperkins, except ours was a bit down market with fuses rather than switches. The switch is supposed to illuminate when the circuit is switched on. IIRC, each switch has 3 contacts : power in, power out and a negative, which provides a return for the light, whch is connected internally between "power out" and the negative. Ours was wired in a similar fashion, with the live side of the fuses daisy chained together, and a link from each fuse to its appropriate switch. There was a similar daisy chain arrangement for the negative line on the switches. If a fuse blew, the sign was that the switch was not illuminated, despite being switched on.

 

 

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It looks as if the power is daisy chained to the switches. A bad connection anywhere in the chain could cause the problems you have. You could disconnect all the wiring from the switches clean the contacts and tighten the spades.

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Turn off all the switches and meter again between C5 and negative. I would expect it to be open circuit; your previous reading probably came via the lamps in the switches that were in the on position. This should show that the black wire going off panel needs a negative connection. Turn the switches back on and briefly touch a test wire between C5 and negative to see if the switches illuminate. If all is well find a permenant neg for the off panel wire.

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OK, thanks all.

It does seem from what Iain and eeyore said that the black daisy chain on C5 should be negative and that the switches light up when on, but off when a fuse blows. That is the opposite of what is happening with the light coming on when the switch goes bad.   Just left the boat for a few days so can't check at the moment but first is to see if there is any voltage on C5 with all the switches off. There isn't a connection from the C5 daisy chain to earth as it shows 12.7v with the voltmeter. I wonder if the previous owner removed it? 

Given the limited info I have given you, and if C5 isn't connected to earth (it can't be as I get 12.7v on C5), how can a light come on in the switch if the switch (or another switch) goes bad? - there doesn't seem to be any -ve on the panel?

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1 hour ago, Dr Bob said:

 

Given the limited info I have given you, and if C5 isn't connected to earth (it can't be as I get 12.7v on C5), how can a light come on in the switch if the switch (or another switch) goes bad? - there doesn't seem to be any -ve on the panel?

Have you ever found yourself traveling behind a car with a broken negative/earth on a rear lamp connector? All sorts of odd things happen when they brake or operate the indicators. Similar thing happening with your panel.

Edited by Eeyore

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You have a poor negative feed to the panel, the lights are grounding through other circuits instead.

 

Those breakers have a habit of going open circuit unless tripped occasionally I have found.

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1 hour ago, Boater Sam said:

You have a poor negative feed to the panel, the lights are grounding through other circuits instead.

 

Those breakers have a habit of going open circuit unless tripped occasionally I have found.

Sam...I thought you'd blocked me!?

Yes, I agree about the poor negative feed. I cant see any negative connection so the negative must be going down one of the circuits.

Now I know the black C5 wires are meant to be connected to earth, I will have another look with the multimeter. One of the C4 (or C3) connectors on one of the switches on the right hand side of the panel (from the front) must be shorted out to C5 - with the previous owner having disconnected the earth connection to C5.

I wonder if some people would disconnect the earth so that the switch lights dont come on. With 10+ switch lights on - it would be like Blackpool illuminations at the back of the boat at night - and our bed is at the back. Do others disconnect the earth wire?

8 hours ago, Eeyore said:

Have you ever found yourself traveling behind a car with a broken negative/earth on a rear lamp connector? All sorts of odd things happen when they brake or operate the indicators. Similar thing happening with your panel.

Agreed.

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I'd say it's wired up wrong, the neons switches are supposed to light when switched on. It would be madness to design a switch that only ever lights up when it's faulty.

 

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2 minutes ago, sirweste said:

It would be madness to design a switch that only ever lights up when it's faulty.

It would make perfect sense to me. But then, i am a bit strange. 

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what makes sense is a switch that lights up when switched on. Then if it failed / burnt out, when switched into either on or off it would not illuminate!

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3 minutes ago, sirweste said:

I'd say it's wired up wrong, the neons switches are supposed to light when switched on. It would be madness to design a switch that only ever lights up when it's faulty.

 

 That makes a lot of sense. Its plainly daft to light a switch when its not on. And even dafter to light it when the breaker is tripped unless its a tell tale in which case it would be across the breaker terminals.

 

Dr Bob love, I would not block you when you need help, only when you are taking the golden water on others' posts. I noted you requested no humour on your post...................................

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14 minutes ago, Boater Sam said:

. I noted you requested no humour on your post............................

Erm, no he didn't. 

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1 hour ago, Dr Bob said:

Sam...I thought you'd blocked me!?

Yes, I agree about the poor negative feed. I cant see any negative connection so the negative must be going down one of the circuits.

Now I know the black C5 wires are meant to be connected to earth, I will have another look with the multimeter. One of the C4 (or C3) connectors on one of the switches on the right hand side of the panel (from the front) must be shorted out to C5 - with the previous owner having disconnected the earth connection to C5.

I wonder if some people would disconnect the earth so that the switch lights dont come on. With 10+ switch lights on - it would be like Blackpool illuminations at the back of the boat at night - and our bed is at the back. Do others disconnect the earth wire?

Agreed.

Dr Bob,

I think most of the weird effects you are seeing are due to the earth wire being disconnected. Without it and with the earth ends of the switch illumination bulbs being connected together by the black daisy chain wire, the bulbs are acting as resistors connecting the switched power load side of each switch together. This will give the variable effects, depending on which switch is on and what the load on the other end is doing, hence the thing where the oven ignitor behaves differently, depending on if the water pump is working or not. What has been created is a very complex resistor network, the effects of which would take a lot of analysis and head scratching to work out and a huge number of possible permutations, depending on what is turned on. With the earth wire connected, the resistance to ground is effectively zero, compared with that of the bulb and the bulbs won't be backfeeding other circuits.

 

There are likely two ways to solve it.

  1. The Blackpool Illuminations route. Reconnect the daisy chained black wire to a good earth. At the moment panel is like the rear light clusters on a rusty old Ford car with the brake lights flashing when the indicator switch is flicked.
  2. The All in Darkness route. Disconnect the black daisy chain wire from each switch and remove it completely, so that the bulbs cannot provide a resistive path between the switched power output from each switch. Means you can get some sleep.

 

A good test would be to take option 2 and remove the black wire daisy chain from the switches. If the problems go away, then the backfeeding theory is right and you can decide if to go option 1, or 2 for a long term solution.

 

Jen

Edited by Jen-in-Wellies
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I don't think what I put below is correct in your case as in the photo it looks like the switch light earths are all common.  However, if the daisy chain is in fact the supply to the switches it could be.

 

There is a way of wiring the switch and breaker so that the light is only on when the breaker is open, (including poor connections) but this would only work with reasonable loads, and may result is the light being dim if feeding a single led lamp which would also be dim.

But if the switch is for things like pumps, and other loads taking say an amp or more it would work.

Basically the switch and breaker would be wired - 

 

The feed (+12v) to the switch is connected to the switch + terminal with the output terminal being connected to the breaker which is then connected to the load.  The switch light (earth terminal) being connected to the load side of the breaker.  That way the light would be - 

 

Switch       Breaker     Light

off             n/a            dark 

on             closed       dark

on             open         bright

 

 

Added - this way the switch light would be on if the connections from the switch to the breaker, or the breaker itself was faulty or of course open.

It's not something I would do, but I can see some might.

 

 

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Just to save my heart rate can everyone please stop talking about ‘earth’. There is no earth involved. It’s the negative return or if you prefer, simply the negative. 

 

And I agree with everyone who’s said that there’s a missing/faulty negative connection to the panel. I’d also agree that the panel isn’t really fit for purpose - have a look at the BlueSea offerings. 

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You could make your own Dr Bob, Mine is a metal box fitted with aircraft type circuit breakers. Cost Sicksquid...........sorry, you said no fishy jokes didn't you?

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17 minutes ago, rusty69 said:

You could make your own Dr Bob, Mine is a metal box fitted with aircraft type circuit breakers. Cost Sicksquid...........sorry, you said no fishy jokes didn't you?

Whole bunch of 1A and 3A breakers here: https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F264188713243

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38 minutes ago, rusty69 said:

Yep, those are the type I have. How did you guess?

When I worked on flights sims all of those breakers were 1A but had different current rating labels depending on what they were supposed to be. So a hydraulic pump breaker might have a ‘15’ label but behind the panel it was still a 1A device. This was done so that simply by setting a single bit on the computer you could pop the breaker. 

 

It was a very tedious job setting bit 1, then bit 2, etc to check that they all worked correctly, only livened up occasionally when you’d find a big vitreous enamel wirewound resistor glowing like a bar fire because some numpty had fitted a real 25A breaker instead of the dummy 1A with a 25 label. :)

 

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6 hours ago, Boater Sam said:

 

Dr Bob love, I would not block you when you need help, only when you are taking the golden water on others' posts. I noted you requested no humour on your post...................................

No, humour was definitely allowed but with conditions:rolleyes:

6 hours ago, Jen-in-Wellies said:
  1. The All in Darkness route. Disconnect the black daisy chain wire from each switch and remove it completely, so that the bulbs cannot provide a resistive path between the switched power output from each switch. Means you can get some sleep.

 

Jen, what a wonderful solution. That's the way to go in the short term.....at least to see how it performs.

 

Thanks to everyone else. I got there in the end. I wonder if the switches that have gone 'bad' in the last few years are actually ok but just with a bit more resistance across the terminals.

 

2 hours ago, WotEver said:

 

And I agree with everyone who’s said that there’s a missing/faulty negative connection to the panel. I’d also agree that the panel isn’t really fit for purpose - have a look at the BlueSea offerings. 

I think you are right that a new panel is the way to go in the long term. but its more about 15 year old switches and breakers rather than functionality. I much prefer no light when on so it is dark at night. I will have a look at the blue sea stuff and also Rusty's approach but I have a feeling that buying 14 switches and 14 breakers will be almost the cost of a new panel.

I wonder what's in the blue sea stuff.? ?

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