Electronics Circuitry Protection From Voltage Spikes

[kstage]

Last summer my boat suffered a devastating electronics melt-down, presumably as a result of transient voltage spikes from a faulty voltage regulator.* While I have fuses and appropriate circuit breakers installed, I know that they really only offer protection from fire and over-heating of wires....little in the way of protecting delicate circuit boards from voltage spikes.* I am searching for a way to protect these delicate instruments (GPS, VHF radio, Chartplotter, Autopilot, AIS) from a possible future event.* Does a good, reliable quality component exist so as to protect my electronics from high voltage spikes from the alternator/voltage regulator? I have a 12V system with alternator, Balmar voltage regulator, with separate house bank and starting battery, including Xantrex Smart charger and Echo charger with Link 20 monitor. * I assumed (incorrectly) that I had enough circuitry protection.* Thanks for any suggestions.

Key

 

[Forkliftt]

Good question! Welcome aboard!

 

[Marin]

You appear to have one of our all-time favorite boats, a 37' Victory Tug. Lucky you.

Your question seems to be one best asked of an experienced marine electrical shop. There are surge protectors and whatnot available for AC, of course, but DC is a different matter. I've always held to the somewhat tongue in cheek notion that the purpose of the fuse in the power line of an appliance is to let you know when the appliance has been destroyed, as it's the job of the appliance to protect the fuse.

Perhaps some sort of master fuse in the line (if there is just one line) that feeds all your electronics would be a solution if you could determine the correct fuse rating. So you'd have this fuse ahead of the indivdual appliance fuses. I would have thought that the boat's battery would have acted as a sort of "cushion" to protect the electronics from bad power from the alternator or voltage regulator but perhaps not.

Anyway, if it was me, I'd be on the phone to the marine electric shop we use with the question.

Let us know what you learn.

 

[FF]

Not the best, compared to a real surge supressor , but if you size the CB to protect the supply wires and install a fast blow fuse in line just before the item , that might help.

The fuse should be as close to the actual amperage being used by the item as you can.

Measure with a meter , not just read the nomenclature plate.

Yes there may be a couple of nusance blows , but that the price of some protection.

And be really GLAD you dont have an electronic engine , or you could be 6K to $12K poorer each time.



-- Edited by FF on Friday 21st of May 2010 06:34:31 AM

 

[Capn Chuck]

Sizing a fuse or circuit breaker for the exact amperage or close is simply asking for a lot of aggravation you don't need and pretty much guarantees you will be replacing fuses and resetting breakers about every day. The fuse should be sized for the maximum amperage the circuit will carry and add about 20% for inefficiency. It should never be sized larger than the maximum amps the wiring will handle. You are trying to protect from major damaging surges on your system and the fuses and breakers designed for individual items will protect them and should be the manufacturers recommended size since they tend to err on the side of caution. Chuck

 

[RickB]

kstage wrote:Does a good, reliable quality component exist so as to protect my electronics from high voltage spikes from the alternator/voltage regulator?

Yes, there are several off-the-shelf solutions. If it was (as is more likely) high voltage surges of longer duration than simply spikes, take a look at these devices:

http://www.bender.org/voltage_relays.aspx

There are other manufacturers with similar products. If you are worried about true "spikes" such as switching transients then simply putting diodes and or varistors across the circuits you wish to protect will help a lot.

http://www.circuitprotection.com/rov.asp



*

 

[Chris Foster]

Something to consider:

It's unlikely that "transient voltage spikes" from an alternator could do major damage.* The battery makes a pretty robust surge protector against anything the alternator can put out.* If the regulator loses its mind and applies full field voltage for an extended period, you'll boil the batteries dry and then burn things out, but that'll take some time ... not a "transient spike"

However, if there is any way that the circuit to the battery from the rest of the electrical system opens intermittently (loose connection or failing battery switch, or perhaps the battery switch was accidently turned off when the engine was running), you can indeed wipe stuff out pretty quickly.* The alternator rotor has a bunch*of magnetic energy in it, and if the load disappears, it's going to be dumped somewhere.* That can cause a very high voltage spike for a fraction of a second.* It'll wipe out the alternator diodes if the alternator output is disconnected while it's running -- in your case, it sounds like your electronics sacraficed themselves in order to protect the alternator

You might take a look at this:

http://www.fisheriessupply.com/productgroupdetail.aspx?cid=7963&keywords=alternator&radkm=on&km=entire

It's essentially a transient suppression diode that can absorb the energy from the rotor until it dissipates.* But definitely take a careful look at battery switches, cables, connectors, etc to see if there's any possible way that the batteries can intermittently disconnect.

 

[RickB]

Chris Foster wrote:You might take a look at this:

Yeah, look at it but know that you can buy 1 of those diodes from Mouser for*about 50 cents and spend another buck on some heat shrink and ring terminals.

Plus, all that thing is*made to do is protect the alternator from burning up.
*

 

[kstage]

My deepest thanks for all the input so far.* And, yes, this was more than a "transient voltage spike".* The details are as follows.* On my Cummins engine, to replace the thermostat, one needs to remove the alternator.* Having never done this before, I decided to have the do the work.* The mechanic doing the job shorted out the* leads from the removed alternator on two large rings he was wearing on his hand (he had not disconnected the batteries).* This spark and short was so large that it actually welded his two rings together!* After all this was "repaired", on the shakedown cruise to test the thermostat (which worked), I noticed slowly all my instruments fading to black and smelled burning wire.* I had surmised that the voltage regulator was fried because when we returned to the dock and measured voltage output from the voltage regulator, it was in excess of 18V.* So, I am just trying to be proactive (and a bit paranoid) to do all I can to prevent this from happening again.....likely it will not, but I am interested in the best prevention possible....short of using that mechanic again!* Thanks again to all for the informative and helpful replies.* And, ps...his hand is fine!

Key

 

[Marin]

Actually, using that mechanic (assuming he's a good one) is probably the best insurance you can have against repeating the problem because it's a sure bet that, while he may make other mistakes in his career, he'll never make THAT one again .

 

[RickB]

kstage wrote:

The mechanic doing the job shorted out the* leads from the removed alternator on two large rings he was wearing on his hand (he had not disconnected the batteries).

What was that guy doing for a living before last summer when he decided to be a mechanic?

Two big rings, batteries still connected ... the equivalent of Marin's aircraft mechanic disconnecting the ground lead on the mags so he could inspect the propeller.

 

[Chris Foster]

Not much you can do to protect yourself from a runaway regulator.* There's too much power being produced to shunt it anywhere (hundreds and maybe thousands of watts).

Your best bet is to have a voltmeter in addition to your other engine gauges.* If it goes nuts, about all you can do is shut down the engine (practical only if you have a twin engine boat), or run at low RPM and load down the electrical as much as you can until you can get somewhere that you can do repairs.

Last fall, I noticed that my battery voltage was hitting over 16 on a short trip - traced the problem to an open ground on the voltage regulator on the starboard engine.* If I didn't have the voltmeter and had done a full day trip, probably would have boiled the batteries dry and done in a buncha stuff like happened to you.

 

[Steve]

Wearing a ring or rings around any sort of machinery is very dangerous. I know personally 5 guys (one who wore the nickname Nubby for the rest of his life) who had fingers or parts of fingers ripped off when their rings got caught on machinery or one guy who jumped from a step and his ring got caught on a protrusion of a railing. Years ago my father in law used to be a welder, one day a "BB" of molten steel found a tiny hole in his glove and stuck to his wedding ring the ring immediately heated up and burned his finger ,not off, but so badly they had to cut the ring off to treat the burn.
Same goes for wearing loose clothing around rotating shafts of any kind cloth can wrap around the shaft and break or pull off a a limb.
Steve W

 

[FF]

"Sizing a fuse or circuit breaker for the exact amperage or close is simply asking for a lot of aggravation you don't need and pretty much guarantees you will be replacing fuses and resetting breakers about every day. The fuse should be sized for the maximum amperage the circuit will carry and add about 20% for inefficiency."


GASP!!!

This is a really great way to set the boat on FIRE.

The concept is a CB controls the max current for each wire , based on the WIRES capacity.

BUT a wire that is happy feeding a small user with out a line fuse is a huge danger.

A VHF may only require 5A , and powered with just a 20A breaker in the line will require the VHF to absorb over 20A to shut it down.

The extra 15 A is enough to start a FIRE if the set fails.

A 5A slow blow fuse would solve the problem of large power to small users.

AFTER a lightning strike , there is usually damage to most equipment .

 

[Capn Chuck]

If a VHF is 5 amps the circuit needs to be 5 amps plus 20% or 6 amps. How would this possibly start a fire. not sure what kind of math you used to come up with 20 amps but it must be some of that fuzzy math. Chuck

 

[FF]

If a VHF is 5 amps the circuit needs to be 5 amps plus 20% or 6 amps. How would this possibly start a fire. not sure what kind of math you used to come up with 20 amps but it must be some of that fuzzy math. Chuck


Most boats I have been aboard had circuit breaker panels with a std size wire and a CB to protect it.

I have never been on a boat that was re wired , so a 5A user would be fed with a 5A wire , a 8A user fed with an 8A wire .

The boat builders do not know the future loads so simply wire (#10 if it was a good builder #14 on a cheapo) and protect the wiring with the rated CB for that wire.

This system also allow many smaller users to be run off a single circuit , rather than multiple individual circuits . So a few dozen circuits will operate the boat , rather than dozens and dozens of wiring runs to each individual user.And zero hassles when gear changes over the decades.

The nicest I have seen from a Volt drop point of view was a boat with a "ring" circuit.

This was a set of huge!! wires # 01 that ran around the entire boat and back to the batt set.

Each individual user had its own fuse for protection .
The ring wire set had its own off switch and was protected by major fuses not CB ( HC built).

The boat was very unusual , engine (DD 6-71) in the fore peak , but was completing its 3rd circumnavigation,unfortunatly it was wood , so we didn't purchase her.

 

[JD]

FF wrote:



The nicest I have seen from a Volt drop point of view was a boat with a "ring" circuit.

This was a set of huge!! wires # 01 that ran around the entire boat and back to the batt set.

Each individual user had its own fuse for protection .
The ring wire set had its own off switch and was protected by major fuses not CB ( HC built).

I thought that I read someplace several years ago that SeaRay or someone was going to start using this concept in there production boats.* In addition to the system FF describes it used RF circuit breakers for each tap.* The panel had a switched*sending unit and the corresponding*circuit breaker was at the component.

Anybody remember this and is any builder using such a system?*