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Steel hull - electrical ground
Hello everybody,
I have just upgraded from a GRP 30ft sloop to a steel hull 40ft sloop. Everything is in excellent state except for the electrical wiring which will certainly consume most of my winter weekends.... My main worry before everything else is to plan for electrical grounding and I have read the most opposite opinions. Can somebody share his experience with me, please ? Cheers Joao |
Steel hull - electrical ground
I have a 1967 aluminium boat with electrical negative bound to the hull as
well as the ground from the 110v. The boat has no visible sign of any corrosion. ANdré "Joao Penha-Lopes" wrote in message ... Hello everybody, I have just upgraded from a GRP 30ft sloop to a steel hull 40ft sloop. Everything is in excellent state except for the electrical wiring which will certainly consume most of my winter weekends.... My main worry before everything else is to plan for electrical grounding and I have read the most opposite opinions. Can somebody share his experience with me, please ? Cheers Joao |
Steel hull - electrical ground
On Thu, 4 Sep 2003 17:18:03 +0100, "Joao Penha-Lopes"
wrote: Hello everybody, I have just upgraded from a GRP 30ft sloop to a steel hull 40ft sloop. Everything is in excellent state except for the electrical wiring which will certainly consume most of my winter weekends.... My main worry before everything else is to plan for electrical grounding and I have read the most opposite opinions. Can somebody share his experience with me, please ? Cheers Joao Joao, I have a 43 foot steel hull and deck sailboat. I make sure that all electrical wiring and connections are kept away from the hull and deck. I do not ground to the hull and highly recommend that you not ground there either. I even try to keep the engine as disconnected electrically from the hull as possible. For example, the alternator and the starter have their own negative cables back to the battery bank rather than using the engine block as the negative. I recommend the Nigel Calder book, Boatowner's Mechanical And Electrical Handbook (or Manual). I feel that connecting anything electrical to your steel hull is asking for serious trouble. One mistake and you could completely destroy your hull. Lee Huddleston s/v Truelove |
Steel hull - electrical ground
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Steel hull - electrical ground
Lee, how many zincs do you run on the hull or in contact with it? How long do they last? Larry W4CSC Larry, I have four large zinc bricks bolted to the full keel (or cutaway full keel), one on each side at the front and one on each side at the back of the keel. Then I have a smaller zinc near the engine raw water intake. The large bricks are Vetus 25s (not sure what the 25 stands for -- not pounds -- probably metric) I just replaced the large bricks which had been put on in the Spring of 2001. But, Truelove has been docked in brackish water all that time -- unfortunately, due to peculiar circumstances, not even moved during that time. Oddly enough, the small brick (not sure of size -- is a teardrop shape) did not need replacing. The brackish water probably makes the zincs last a lot longer than normal salt water, but being in a marina might make them last shorter due to stray current. I really do not know yet. I am trying like hell to retire ASAP and hope to do some extensive sailing very soon. That will be a much better test. Lee |
Steel hull - electrical ground
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Steel hull - electrical ground
Lee:
Yes, they are pricey, heavy, and hot. Transformers are typically around 95% efficient, so pay attention to heat generation -- they do get hot. I found a bunch of Topaz 5kw ultra isolation transformers when we were outfitting Swee****er in 1995 and bought them at US$100. I still have two. Surplus sales of Nebraska has them new for $1395: http://www.surplusales.com/Transform...tionXmers.html However, the good news is that any transformer is an isolation transformer for our purposes -- it won't do quite as good a job on keeping out unwanted frequencies, but we're primarily interested in 1) keeping out DC and 2)establishing an ungrounded AC system. So take a look at things like https://www.surpluscenter.com/item.a...tname=electric It will do 5KW. You can put in 240 and take out 120/240 three wire just like your house, or put in 120 and take out 120. (240x480 means you can put in either 240 or 480) (120/240 means you can take out 120, 240, or both) (You do 120120 by hooking it up like 240240) BTW, you do not want an autotransformer -- which will change voltage but does not isolate. If you feel more comfortable with a "real" isolation transformer, I ran into a guy at the Maine BoatBuilders' show that was having them made. WesTran Power 5160 NW Five Oaks Drive Hillsboro, OR 97124 (no web site) He was selling a "marine grade" (whatever that means) 6KW unit with pretty good specs for $900. As far as ground fault alarms go, the typical big ship installation is a light in series with a push button wired from one of the hot wires to the hull, and then the same thing on the other hot wire. The two push buttons are on the same actuator (a dpst). The bulbs are typically rated for the system voltage, so when you push the buttons, both come on at half voltage. If there's a fault on either side, that light is shorted out and stays dark, while the other light is getting full voltage, so it's brighter than usual. Like this (sometimes ASCII graphics actually work, maybe): hot1---pb---light---hull---light---pb---hot2 (with the two pb on one frame). Jim Woodward www.mvFintry.com (Lee Huddleston) wrote in message . .. On 10 Oct 2003 07:54:37 -0700, (Jim Woodward) wrote: That was the Royal Navy's choice when they specified Fintry thirty years ago and we will continue this with her new electrical system. The only electrical connections to the hull will be green safety ground and radio ground for the SSB (which is isolated from electrical ground). We will have ground fault alarms on both the DC and the AC systems so that if either gets shorted to the hull we'll know about it early. Shore power will come aboard through isolation transformers. Jim Woodward Jim, Would you have a recommendation for an isolation transformer? The only one that I have found so far ate up a lot of the power before it could get into the boat. That seemed strange to me, but maybe I was reading the specs incorrectly. Also the price seemed to be very high. Of course, protecting my beloved boat from galvanic corrosion is probably worth a lot if that is what is necessary. By the way, you mentioned DC and AC ground fault alarms. Who makes them and are they available to private individuals? Thanks in advance for your help. Lee |
Steel hull - electrical ground
Thanks, Lee. Sorry you're not getting much use out of your boat.
If you have a DC milliammeter function in your Digital multimeter or VOM pocket meter, put it on the milliamp function, sometime, between that hull and the AC ground on the dock. That's the electrolysis current to the electric ground, which is most interesting. I always feel sorry for someone with his engine block hooked to the AC line ground.....eating away at his fizzing zincs. On Wed, 15 Oct 2003 02:14:17 GMT, (Lee Huddleston) wrote: Lee, how many zincs do you run on the hull or in contact with it? How long do they last? Larry W4CSC Larry, I have four large zinc bricks bolted to the full keel (or cutaway full keel), one on each side at the front and one on each side at the back of the keel. Then I have a smaller zinc near the engine raw water intake. The large bricks are Vetus 25s (not sure what the 25 stands for -- not pounds -- probably metric) I just replaced the large bricks which had been put on in the Spring of 2001. But, Truelove has been docked in brackish water all that time -- unfortunately, due to peculiar circumstances, not even moved during that time. Oddly enough, the small brick (not sure of size -- is a teardrop shape) did not need replacing. The brackish water probably makes the zincs last a lot longer than normal salt water, but being in a marina might make them last shorter due to stray current. I really do not know yet. I am trying like hell to retire ASAP and hope to do some extensive sailing very soon. That will be a much better test. Lee Larry W4CSC 3600 planes with transponders are burning 8-10 million gallons of kerosene per hour over the USA. R-12 car air conditioners are responsible for the ozone hole, right? |
Steel hull - electrical ground
Jim Woodward wrote:
Lee: snip However, the good news is that any transformer is an isolation transformer for our purposes -- snip This is not correct. An autotransformer has a single winding and does not provide isolation. Jim |
Steel hull - electrical ground
I think I said that, two paragraphs further along. I guess I assume
that on a post with a lot of techincal content, that the reader will wade through the whole thing before going out and spending money. Jim Jim wrote in message ... Jim Woodward wrote: Lee: snip However, the good news is that any transformer is an isolation transformer for our purposes -- snip This is not correct. An autotransformer has a single winding and does not provide isolation. Jim |
Steel hull - electrical ground
Jim,
Thanks for all the information, leads, and offers. At this point, I do not have enough knowledge to make any kind of informed choice regarding an isolation transformer. Can you direct me to a source where I can read and learn more of what I need to know? Lee Huddleston |
Steel hull - electrical ground
AFAIK, there is only one that meets the ABYC specs, & that is made by Charles Industries (www.charlesindustries.com). Something about isolaitng the ground as well as the conductors. Michael Porter (Lee Huddleston) wrote: Jim, Would you have a recommendation for an isolation transformer? The only one that I have found so far ate up a lot of the power before it could get into the boat. That seemed strange to me, but maybe I was reading the specs incorrectly. Also the price seemed to be very high. Of course, protecting my beloved boat from galvanic corrosion is probably worth a lot if that is what is necessary. By the way, you mentioned DC and AC ground fault alarms. Who makes them and are they available to private individuals? Thanks in advance for your help. Lee Michael Porter Naval Architect / Boatbuilder mporter at mp-marine dot com www.mp-marine.com |
Steel hull - electrical ground
First the usual CYA stuff -- electricity can be dangerous in a whole
variety of ways. If you don't understand it, hire an expert. There's a lot of good information available on the web, including here, but good electrical practice finally comes down to details that you need to do because you've learned, somewhere, to do them right. And BTW, a boat is not a house, so a license to do wiring ashore says nothing about a person's skills in wiring boats. With that said, an isolation transformer is a pretty simple device -- two wires in and two wires out -- although there are often a lot more leads than two, as they can usually be connected for different or multiple voltages. Figuring out the leads is like figuring out how to wire a 120/240VAC motor -- it's just cookbook and often there's a diagram. If not, we have ways.... I usually refer people to Nigel Calder's Boatowner's Mechanical and Electrical Manual for all mechanical and electrical stuff -- in this case there's a diagram and a couple of paragraphs. This is not a bad little piece on the subject: http://www.smpstech.com/qa/qa0002.htm This has more than any ordinary mortal needs to know, but a number of details can be picked out if you're strong enough to ingnore the heavy math. http://www.du.edu/~jcalvert/tech/transfor.htm Aside from actually connecting the thing, the only other issue is sizing. Generally, if you plug into a standard 30A 120V shore outlet, you'll want a 3.6kw transformer (30x120 ~=~ 3.6kw). Larger won't hurt (other than being heavier) within broad limits. Smaller is OK, too, provided you put a circuit breaker on the shore side of the transformer that is the same rating as the transformer. Of course, smaller means you can't run as much stuff.... If you have a larger boat and regularly use 240VAC, then you can run 50A 240 from standard marina outlets, but this takes a 12kw transformer, which is starting to get heavy and pricey. Don't forget, it's got to mounted somewhere that can stand a big weight, is dry, and won't get too hot with a couple of hundred watts being thrown off. It may hum a little, so you won't want it as a pillow. Jim Woodward www.mvFintry.com (Lee Huddleston) wrote in message . .. Jim, Thanks for all the information, leads, and offers. At this point, I do not have enough knowledge to make any kind of informed choice regarding an isolation transformer. Can you direct me to a source where I can read and learn more of what I need to know? Lee Huddleston |
Steel hull - electrical ground
I usually refer people to Nigel Calder's Boatowner's Mechanical and Electrical Manual for all mechanical and electrical stuff -- in this case there's a diagram and a couple of paragraphs. I have the Nigel Calder book and have almost committed it to memory. That is what caused me to want an isolation transformer in the first place. This is not a bad little piece on the subject: http://www.smpstech.com/qa/qa0002.htm Yes, it does give some good information. This has more than any ordinary mortal needs to know, but a number of details can be picked out if you're strong enough to ingnore the heavy math. http://www.du.edu/~jcalvert/tech/transfor.htm Wow! "Ask and ye shall receive." Thanks. I will reread this material until I think that I understand most of it. If I can do that, I doubt that there will be much about transformers that I will not know. Aside from actually connecting the thing, the only other issue is sizing. Generally, if you plug into a standard 30A 120V shore outlet, you'll want a 3.6kw transformer (30x120 ~=~ 3.6kw). The smallest isolation transformer made by Charles Industries, recommended in the next post, just happens to be their 3.6kw transformer. Looks like a good lead. Thank you very much for all your help. Lee Huddleston s/v Truelove |
Steel hull - electrical ground
AFAIK, there is only one that meets the ABYC specs, & that is made by Charles Industries (www.charlesindustries.com). Something about isolaitng the ground as well as the conductors. Michael Porter Michael, Thanks for the lead. The smallest Charles Industries transformer is just the size that Jim Woodward recommends. Looks like a good possibility. BTW, I could not figure out how to find the price on the transformer. Have I just overlooked it on the web site or will I just need to give them a call? Lee Huddleston s/v Truelove |
Steel hull - electrical ground
Miracle of miracles -- something that is "Marine" and not triple the
price. I found it at http://www.cyber-marine.com/ at $679 for the 3.6kva rating. Thanks, Michael -- I wasn't aware of this brand. And, BTW Michael, we talked at the Maine Boatbuilders' Show three years ago -- you sent me a CAD file of a design of yours. Thank you for that conversation, as it was one of many that eventually ended up with our buying Fintry. Jim Woodward www.mvFintry.com (Lee Huddleston) wrote in message . .. AFAIK, there is only one that meets the ABYC specs, & that is made by Charles Industries (www.charlesindustries.com). Something about isolaitng the ground as well as the conductors. Michael Porter Michael, Thanks for the lead. The smallest Charles Industries transformer is just the size that Jim Woodward recommends. Looks like a good possibility. BTW, I could not figure out how to find the price on the transformer. Have I just overlooked it on the web site or will I just need to give them a call? Lee Huddleston s/v Truelove |
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