Shore power voltage & Tripped Breaker w/ Hot Water & A/C

[sdaly66]

87' MK I

Staying one night at Baltimore Harbor Marina this weekend.  They're asking me what kind of shore power I need.

My first response was to reply "AC", but I didn't watn to tick them off.  LOL

So can anyone tell me what amperage I need.  50? 100? something else?

I can't find anything in prior posts or in the manual.  I can see that there's a 30 amp breaker in line, does that mean 30 is my max?

Never thought about this before.  Hooked up at my home marina has never been a problem.

[Stu Jackson]

30 amps, thirty, 30 it is!

Page 32 of 66 (PDF page) of the manual: http://www.c34.org/manuals/1988/1988-C34-Owners.pdf

You're right, the breaker size is the "giveaway" as is the plug prong configuration.

[sdaly66]

Thanks Stu, you're a lifesaver

[Stu Jackson]

I forgot to note that usually the dock service determines what you get and there are 20, 30 and 50 A service usually available.  You can use adapters at the dock end of your own power cord.  You could get away with a 20A dock service if you don't have air conditioning.  It's rare that the full 30A is ever used - even when plugged in, do you run the HW heater with ALL the light and every receptacle being used?  Some boats with air conditioning have (2) 30 A boat plugs or have upped their single point service to a 50A.  I don't know what YOUR boat has. If you get a dock with 50A service you're fine, too, except for needing the adapter.

So, for grins & giggles, AC could mean air conditioning, too!   

[sdaly66]

Gotcha.  No A/C (air conditioning) on board, and we're pretty frugal with the electricity in general.  Having spent the past few years with a C 250, one learns to be REALLY frugal.

Thanks again for the info.  Looking forward to a night on the town, and i know the admiral is gonna enjoy the health club at the hotel that they partner with.

[Footloose]

The marina needed to know so that you are at a slip with the proper size receptacle.  The twist lock plug are different sizes for 20, 30 and 50 amps.  I have been at a transient slip with a 50 amp outlet.  It is a no go situation.  If you use an adaptor like Stu talks about you will be protected by you breaker if you are at a 50 amp station.  Without ac you could turn everthing on and probally not exceed 20 amps.

[sdaly66]

I am once again, amazed and grateful at the speed and helpfulness of the folks here.

Thank you all.

[Stu Jackson]

Dave's right IF you don't have an adapter ("I have been at a transient slip with a 50 amp outlet.  It is a no go situation. ")

Some harbors provide you with one (for a refundable fee).  For instance, Pillar Point Harbor, 18 miles down the coast from San Francisco, has lots of 50 A boxes at their docks, since it's a working fishing fleet harbor.  The harbor master can provide you with a pigtail adapter from the shore end of your 30 A power line to the 50 A plug at the dock box.  They stick it on your credit card for $100 and return it when you return the pigtail.

I've considered making up my own from Home Depot materials, just haven't gotten around to it.

[Footloose]

Stu,

I have also thought about making my own adapter but the parts are way more expensive than you might think.  I would probally buy a pre-made pigtail if I were to go for this.  The last time I priced a 50 amp male twist lock plug and a 30 amp female twist lock it came to about $50.

[Stu Jackson]

Dave, that's a bargain.  The Marinco 121A 50A male to 30A female is $150 before tax.

[Ron Hill]

sadly :  Anytime you need more than a single 30amp service you have more than the factory put on the boat!! 
If you screw around with 50 amp (220v) you had better have an adapter to only take the current off of 2 pins for 110v!!   

[Stu Jackson]

The Marinco (Model 6152SPP-25, 25 foot, they make 50 footers, too) 50A PowerCord Plus® Cordset - 50A, 125/250V is indeed both voltages.  Please note that if properly wired (at both ends), plugging into a 50A outlet in the United States will still get you 120V AC.  We used an adapter as noted in a previous post, with no trouble.  If you check a basic AC wiring book, you'll see that the different voltages are for different taps off the four wires available in this cordset.

[Bob K]

Here's something you might find interesting.....I made the mistake last year of turning on the hot water heater while the air conditioning was on.  The breaker did not blow, as I would have expected it to if overloaded.  Rather, it functioned fine for a day or so while plugged in at a marina, and then melted mid-afternoon the next day.  The stink was a dead give-away.  Luckily we were on board, as we were waiting out a spell of bad weather.  After turning off all power and unplugging from shore power, I could feel the panel was very hot at the main 30A breaker. A secondary 30A main breaker located closer to the AC plug (in the lazerette) was running cool.  So I guess the panel breaker had a defect (?), started to heat up, and went into thermal runaway.  So I replaced the breaker, and no longer try to "see what she will do"!   If I turn on the hot water, I give the A/C a rest.    I don't think the combined amperage was over 25A, but obviously the breaker could not handle it.  So I now make it a point to feel the panel every now and then to make sure it is cool ragardless of what I have running.   

[Stu Jackson]

That's a good idea, Bob, and thanks for the warning.  Very important.

One of things pointed out a number of times about the hot water heater is that it need not run all the time.  It heats up in about 15 to 20 minutes and will give you hot water for a long time.

You are wise in just turning it on for that short time, maybe even right when you plug in before you start your A/C, and then turning it off and keeping it off until the hot water runs out (which would be a few good showers and lotsa clean dishes!).

You can do the math on the load:  1,500 watts for the heater, only you know the draw from your A/C, and the start, and restart as it cylces, load of the compressor is the most telling constituent of that load. 

I assume that you have also checked the wiring after your breaker failure.

The other thing to consider is the quality and condition of all of the connections behind the electrical panel's face, in addition to the breaker.  While I'm sure yours is clean as a baby's bottom, I have seen some that are like the other kind of the baby's bottom, and were just situations where the worst was about to happen.

Mom's still right, cleanliness does count.

[sdaly66]

Good advice, thanks.

Of course, I wouldn't know what it's like to have air conditioning.  LOL