Increased Draw in Amps causing problems

[MicroKap]

This past weekend, while running my salon a/c and master stateroom A/C, I flipped the breaker for the hot water heater to take a shower. I noticed a large surge in the AMPs that were being drawn. Last season, I was able to run four A/Cs in and salon and cabins and my hot water heater at the same time with no problem. My dock has 208V 3phase electric service and I run the service through a Buck Booster to increase volts 10% (I know it also decreases AMPs). I first replaced the two heating elements in the hot water heater (4,500 watts each in a 40 gallon A.O. Smith as stated on the mfg. label). No improvement. The salon a/c system was completely replaced last year and worked flawlessly and continues to seem as such.

Two things worry me. The first is that the systems listed above (plus, engine block heaters and refrigerator) are pulling more amps and second, it's the dock's breaker that is flipping, not one on the boat.

Anyone have any ideas?

 

[Angela]

I recently had the very same encounter. After I replaced the hot water heater with one that had 4500 watt elements, the surge in amperage was such that I could basically run the hot water heater and nothing else. I replaced the elements with 1500 watt elements and problem solved on the boat's end. However, I kept tripping the dock's breakers. I have 50 amp service, but it would trip when I pulled only 35 amps. The marina tried several things, and eventually put me on a 60 amp breaker back at the big box and removed the breakers from my pedestal. Well, that didn’t work all that well either. Upon further inspection, the marina found that the wiring running from the big electrical box to my boat was insufficient to carry the 50 amp load due to the age/condition of the line and the length of the run. So, they ran a new, bigger line for me. That almost did the job, but then two other big boats moved in on this dock. Florida Power had to install a second transformer. So far, I’m doing well. Running all three central AC systems, the dryer, etc. without electrical problems. Just waiting for my power cord to melt, I suppose..... (and it wouldn’t be the first time I’ve done that). But seriously, I do monitor the amps when I’ve got all the juice flowing because when I did melt a power cord on my prior boat, it welded itself to the side of the boat and to leave the slip, I had to cut the wire and leave the plug stuck to the side of the boat. It wasn’t fun to fix. It wasn’t until I melted the same one again in the same week that I started monitoring power usage. Forum member, Egaito, had the pleasure of running new power supply lines from the connection to the boat’s panel, after chiseling out the melted plastic and fiberglass!

Back to your problem....you may want to have the marina look at the supply line going to your pedestal. It may have corroded in the marine environment to the point that it’s not giving you enough juice anymore, or it may simply be too small to handle your load now, but if you’re not blowing the boat’s breaker, I’d start looking at the other side of your power which is what I did and therein lied the problem in my case.

Ang

 

[TedZ]

Whenever i have a problem like "it used to work" and it is electrical i look at the supply voltage. It does not take much of a voltage drop to increase the amperage a lot with a fixed draw such as resistance heat. Other heavy users "downstream" from you can lower the supply voltage which starts the problems, like on busy weekends.

As an aside, many of the larger hot water heaters have dual thermostats. You can wire and set those so that both elements seldom come on at the same time which helps the large amperage draw.

Ted

Ted

 

[Fanfare]

I installed a switch on the cover plate of the thermostats so I can turn off the upper thermostat for times it is not needed. This turns out to be almost always. Don't have much need for lots of hot water in the tropics. This cuts the electrical load of the water heater in half. It also extends the life of the heating elements.

In the 50MY the hot water heater has a switch with a red indicator light located right in the galley. With the original 30 amp 110v system you were expected to shut down the water heater when cooking or otherwise using a lot of electricity. How times have changed!