30 amps times 120 volts equals 3600 watts (in theory).

Before you upgrade to 50 amps, it may be that your main breaker only supports one 15 amp circuit.

Boat panel upgrade first? Two 15 amp circuits?

Cheers,

That is an AWFUL lot of current to be pulling through any 30A shore cord, let alone 50A service. IMHO electric heaters can be one of the most dangerous additions to ANY boat..

These heaters pull HUGE amounts of current, load the fragile male/female prongs on the cords/sockets/pedestal to dangerously high levels for the piss poor environment they are in and this can lead to FIRES..

What is more expensive diesel or burning down your boat and potentially the marina..? How about one electric on low supplemented by the diesel?

Heaters - 2 X 1500 = 3000 = 25A
Water Heater - 1 X 1500? = 1500 = 12.5A

Just with the heaters and the water heater you're looking at 4500 watts. 4500 watts is 37.5A and 7.5A beyond your main breaker...... I have not even begun to add in for the battery charger or any other AC loads some of which are absurdly high such as a microwave, coffee maker, toaster, hair dryer etc. etc...

With everything running you may be bordering on needing more than 50A service.... Perhaps the easiest bet is to simply add a second 30A service. 50A shore cords run upwards of $500.00 - $700.00 EACH!!!! That is a lot of diesel....

Personally I don't like to see any marine shore power cord loaded to more than 80% of its rated capacity. This means about 24A for a 30A cord set and 40A for a 50A cord set. I still hold to these values even with the new Smart Plugs because the dock pedestal still uses the old crappy twist lock which has MINIMAL contact area, especially for the corrosive environment they live in.. When I do, see them loaded this way, I see them fail at very high rates. The off the shelf, when new, laboratory rating bears little meaning in "real world" of the destructive marine environment. This is why I feel a MUCH safer way to handle on-board AC is to NOT overload the cord sets to any more than 80% of its rating...

This is what happened to one customer who thought running multiple electric portable electric heaters on-board was a good idea. Oh, and this was 50A service. He now heats with a Webasto diesel FHA heater and spends far less per season, on winter heat, than he did for electricity...
[IMG]http://www.pbase.com/mainecruising/image/144339208.jpg[/IMG]

2 new 50A shore cords and the inlets cost him nearly $1400.00, just in parts.... Ouch!

Please think twice before using MULTIPLE 1500W heaters on a boat, even with 50A service.

BYW I want to live in an area of the country where 3000 watts of electricity is less costly than diesel heat.....:D

Here's a few more where high loads were involved:
[IMG]http://www.pbase.com/mainecruising/image/147215196.jpg[/IMG]
[IMG]http://www.pbase.com/mainecruising/image/147215197.jpg[/IMG]

PLEASE, PLEASE, PLEASE be careful electric heaters are no joke.......

I had an Espar diesel heating system installed in my C36 two years ago. I highly recommend it (diesel heat, not necessarily the brand). I successfully used a single electric 'cube' heater without burning up my cord or connectors, but I also inspected and cleaned the connections often. I never tried to use 2. Using one I could not keep the boat nearly as warm as the diesel does. And the diesel has the added advantage of working at anchor, which was my primary reason for having it installed ( I hate being tied to the dock).

On my prior boat, a C30, I needed 2 cords joined with a water proof plastic connector designed for the cords. The cords welded themselves together inside that connector, most likely after using the cube heater. No fire, and nothing quite as drastic as in Maine Sails pictures, but it sure got my attention.

The diesel system wasn't cheap, maybe $5000 professionally installed, but it should add value to the boat if my wife sells it after I die :)

btw, there are a couple diesel installations in Jibsheet, a 375 in April '11, and mine's out there somewhere, though I couldn't find it.

[QUOTE=FlyMeAway;15509][B]

I already have a Webasto hydronic diesel heater. I get your point about expenses, but running the cost of running the Webasto all the time is not just diesel but also wear-and-tear on the heater. Like an engine, the Webasto (a $3k unit) has a useful life measured in hours. [B]Given that I live aboard[/B], running it as my primary heat source will reduce its effective useful life to about 2-3 years AND significantly increase maintenance costs.
[/QUOTE]

2-3 years??? I have live aboard customers with both Webasto and Espar hydronic and FHA heaters that are well into their 15th year. OTR truckers use these heaters constantly and they run reliably for decades. The maintenance costs on them are not that outrageous if you learn to DIY.... Don't be afraid of your Webasto they are very reliable units..

[QUOTE=FlyMeAway;15509][B]I do really like the idea of just adding a second 30 amps instead of going up to 50 amps[/B]. What would be required for this other than running the necessary wiring inside the boat? Do I need to completely replace the electrical panel?

I have been very, very assiduously checking the cords and my smartplug (no corrosion visible) and have [B]never[/B] been running these at more than 750 watts each (1500 total) for more than just to check what happens when I up the wattage a bit (the circuits trip!). I was previously running a single 1500 watt heater and then switched to two 750s. These heaters don't run *all* the time because they are thermostatically controlled and shut off at around 70 degrees ambient.

I already have a Webasto hydronic diesel heater. I get your point about expenses, but running the cost of running the Webasto all the time is not just diesel but also wear-and-tear on the heater. Like an engine, the Webasto (a $3k unit) has a useful life measured in hours. [B]Given that I live aboard[/B], running it as my primary heat source will reduce its effective useful life to about 2-3 years AND significantly increase maintenance costs. I'd rather have two cheap $60 heaters I can replace at Target, with an adequate electrical system, then put wear-and-tear on a $3k system that I'd much rather use only when I'm on the hook.

But to get an idea of the general energy economics: to keep the boat at 62 degrees when I'm not there, and 70 or so degrees when I am, costs me roughly a tank every two weeks or $125. There is also the load on the diesel heater, which is not designed for continuous use (to keep the boat relatively warm to prevent mildew). Anyway, here in the Pacific Northwest, electricity is approximately 6 cents per kilowatt hour. Running my heaters for the whole (they're the Vornado models that turn off when they hit the right temp) cost me $55 in total monthly electric during our moderately cold October. In September, which was much warmer, I had the heaters break down (fan failure, not electrical) and I spent nearly $300 on diesel![/QUOTE]

Easiest way is:

30A shore power inlet - 30A breaker (unless wire run to panel is less than 10') - Galvanic Isolator (for ground wire) - small AC panel with 30A main breaker & a couple of branch breakers - outlets...

P.S. You might consider an ELCI main breaker with those types of loads...

My Webasto is ca about 1989 and going strong. Granted we don't live aboard but we cruise year round in the PNW which means it sees a LOT of use. Previous owners of my boat clearly cruised back and forth from Portland OR to the BC Gulf Islands, which would include about a 100% duty cycle for the heater for that trip if it was me!

I have an old (no longer supported) Air Top model, not a hydronic which would be nice.

Hi David, I spent a couple of months in winter on my boat two years ago. As I am docked a couple of hundred yards from you I think my experience is relevent. I had one 1500 watt heater and one much smaller. I just about froze to death. It was very cold at night, particularly when the wind was high as it will be at times for the next few months.
The truth is, these boats have zero insulation. The hull has a lot of square footage of contact with some pretty cold water and above the water line the wind will find it's way into the smallest holes and there are a lot of them.
I am not saying to find other living arangments, but I am saying it is not ideal.
If it were me I think I would look into buying a seriious electric heater and re-wiring the plug to match the 30amp shore power plug. Run a dedicated line from shore power to this heater. Put whatever protection in the line that you are comfortable with. At the end of the season toss it all in your shore locker until the next cold sets in.
Minimal cost, maximum flexability and little chance of damaging the boats internal wiring. Additionally there are the minimum of those pesky connections which can fail with high loads and our environment.
Just a thought

I'll look the next time I'm at the boat but I think that the circuit breaker is 30 Amp which would support my 2 heaters plus minimul charging. I do remember blowing the breaker when the microwave was on so I just turned the heater off while cooking.
At one point I closed off the front cabin as I sleep in the aft berth but that proved to be a big mistake as there was major condensation up ther after just a few days. So I had to heat the whole boat and that is a big chore.
Good luck. At least the showers on shore are nice, hot and seem to have unlimited hot water.
Another note. Those docks get super icy in some conditions, add in high wind.....I used to wear my PFD sometimes just to walk to shore...at that time I was almost on the end and that long walk could be treacherous.

I have a 30A mains breaker but all of my outlets share a 15A breaker. I can just run a pair of 750W units without tripping but adding any load and I am pretty close.

The solution if one must run more than 1500W is to split the outlets in the boat into port and starboard (or fore and aft) 15A circuits. On my 1983 vintage boat, all the outlet wires run to a bus bar mounted behind the electrical panel, and the bar is fed from that one 15A breaker. All it would take would be to split the bus bar and grab a vacant 15A breaker. The hardest part would be figuring out which wires go to which outlet, which is not that hard.

30A is lots of power to be putting directly into the boat. If you need more I think the idea of taking shore power directly to a big electric/oil heater with it's own inline breaker would be a much better plan.

We have a lot of big boats in our Yacht Club so the docks are all wired for 50 amp outlets. Almost everyone plugs a "pigtail" into the 50 amp outlet which then splits it to two 30 amp plugs. Even the largest boats seem to all have several 30 amp connections rather than one 50 amp.

What you need to do is add another 30 amp circuit to your boat and dedicate it to AC and heat. This would also allow you to easily operate in a marina with only 30 amp outlets.

If your going to add a second circuit, I ran across this kit while looking for something else.
[url]http://boatwiringstore.com/boat-wiring/ac/[/url]
It says: "Your marine shorepower kit arrives with everything you need to complete your onboard connections quickly and correctly." But doesn't exactly what is included, wiring, etc.