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-   -   Need some electrical/shore power advice, please (http://www.sailnet.com/forums/gear-maintenance/33867-need-some-electrical-shore-power-advice-please.html)

FrankLanger 06-20-2007 04:03 PM

Need some electrical/shore power advice, please
 
Despite reading various books on boat electrical systems, I seem to have a learning block and it doesn't really make sense to me. I would really appreciate answers to a couple of questions:

My boat has 30 amp shore power capability, but the marina we are travelling to only has 15 and 20 amp on the docks. If I minimize our electrical use to cabin lights, stereo and periodic water pressure pump for drinking water, will I have a problem? The marina says "no problem" and is willing to loan us an adaptor cord.

Second question: We would like to anchor out periodically, and have a Link 1,000 inverter and two group 27 house batteries (separate from the group 24 starting battery). My wife would like to use her 1500 watt hair dryer for about 5 minutes once per day. The inverter manual says it can take slightly higher loads for short periods without tripping the breaker or overheating. I have been hesitant to have my wife try the hair dryer--can anyone advise if it would be ok to use or not? Also, when at our normal dock, with 30 amp AC shorepower, can she use the hair dryer on the boat, or does the shorepower go through the inverter and potentially cause a problem?

Thanks for any help on this.

Frank.

sailingdog 06-20-2007 04:23 PM

Hooking a 30 Amp Shore Power system on a boat to a 15 or 20 Amp system is not a problem generally, as you are rated for that much current... but the adapter cords are a shock hazard and you really need to find a marina that uses proper shore power outlets.

As for the inverter... if it is properly wired, she should be able to use the hairdryer when on shore power with no problem, regardles of whether you are at a 15, 20 or 30 Amp shore power connection.

While I can't speak for using it on the batteries alone, I wouldn't use it based on the size of your house bank, which is only about 200 amp hours, and the 1500 W hair dryer will be drawing the equivalent of 125 Amps or so at the batteries when it is on... not a good idea... don't think your DC-side wiring is sized for it.

FrankLanger 06-20-2007 04:55 PM

Thanks for your quick and helpful reply.
Frank.

SEMIJim 06-20-2007 05:19 PM

Quote:

Originally Posted by FrankLanger
Second question: We would like to anchor out periodically, and have a Link 1,000 inverter and two group 27 house batteries (separate from the group 24 starting battery). My wife would like to use her 1500 watt hair dryer for about 5 minutes once per day. The inverter manual says it can take slightly higher loads for short periods without tripping the breaker or overheating.

I assume the "1000" in "Link 1000" refers to its load-handling rating. If that's the case, 1500 watts isn't "slightly higher," it's a 50% overload. I imagine the inverter will give up pretty quick with that kind of load.

ebs001 06-20-2007 05:21 PM

Adapter cords would only be a shock hazard if they are defective. All outlets have to be properly fused ie a 15 amp outlet has to have a 15 amp fuse or breaker a 20 amp outlet a 20 amp breaker etc. Therefore you cannot seriously overload a circuit. I say seriously because circiuts should only be loaded to 80% of the circuit capacity, but a 15 amp breaker will not trip at 80% of the rated load. The loads you wish to put on will be fine provided you don't have significant other loads if your wife uses her hair dryer, which draws 12.25 amps.
As far as using the hair dryer with a 1000 watt inverter, it does not have the capacity to run a 1500 watt load for anything more than a momentary surge current. Do not.

hellosailor 06-20-2007 05:23 PM

Frank-
After my niece blew a breaker with her new hair drier, I had a few words with some makers. Apparently there's been a hair drier war in the US for a while, 1500 Watts is about the smallest you'll find...even though that alone is more than the power load that is supposed to be on many single-line circuits in houses. (117VAC nomimal, 10A per leg, = 1170 watts.) given older home wiring, and the 1600 and 1700 W driers out all over now...the company that made hers, and half the private-label ones in the US, sent her a 1400W special model as a replacement. They're familiar with the problem.

The only problem you might have running on shore power, is that 1500W will still try to draw 1500W even if you have lower voltage, i.e. 107VAC, at which point it will draw over 14 amps. Dunno if your wiring on the boat is sized up to handle that.

Personally I'd suggest checking your own wiring on the AC runs to see if that's OK, and looking into a "travel" drier that has a lo-med-high switch on it, which often means 800-1100 watts on the two lower settings. Blows a lot less breakers that way.<G> If her drier has two heat settings--avoiding the high one should also make it draw substantially less watts, sometimes a piece of tape over the switch is all you need.<G>

sailingdog 06-20-2007 05:58 PM

Quote:

Originally Posted by ebs001
Adapter cords would only be a shock hazard if they are defective. All outlets have to be properly fused ie a 15 amp outlet has to have a 15 amp fuse or breaker a 20 amp outlet a 20 amp breaker etc. Therefore you cannot seriously overload a circuit. I say seriously because circiuts should only be loaded to 80% of the circuit capacity, but a 15 amp breaker will not trip at 80% of the rated load. The loads you wish to put on will be fine provided you don't have significant other loads if your wife uses her hair dryer, which draws 12.25 amps.
As far as using the hair dryer with a 1000 watt inverter, it does not have the capacity to run a 1500 watt load for anything more than a momentary surge current. Do not.

A lot of the adapter cords are a shock hazard since they are often far lighter and less well waterproofed and insulated than the marine shore power cords. They also introduce a break in the insulation in the middle of the cord, which can be a serious problem.

FrankLanger 06-20-2007 07:14 PM

Thanks for all these helpful replies--any more opinions are welcome, but you've given me lots to think about and tips on what to watch for and to avoid.
Thanks again!
Frank.

ebs001 06-20-2007 07:54 PM

SD, I think you had better define "shock hazard" for me. An adapter cord which is smaller guage may present an electrical hazard because it could overheat with amperage higher than it's rating, but it's not a shock hazard. Insulation is to protect against a given voltage and seeing as we are dealing with 120 volts the insulation has to be adequate for that voltage no matter the amperage. Without knowing what kind of adapter the marina is going to loan him you have suggested that Frank is entering into a very hazardous situation. I personnaly think that it at worst it may be slightly more hazardous even if the marina gives him home made adapters. A lot marinas have outlets on their dock pedistals that are not "in use" waterproof and the use of adapters at this marina presents no more of a hazard.

SchoonerMISTRESS 06-20-2007 08:12 PM

Skip thinks that the inverter would not handle it, however, you could try running the engine at 1/2 throttle, set to charge the house bank, and it is possible the inverter might let it work. We have four times the amps and can run the 1500 watt microwave, but do not use it too long or everyday. He feels a better and more efficient method would be to place the wife on the bow, turn engine on and motor around till her hair is dry.
Kathleen
aboard
Schooner MISTRESS


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