electric upgrade help

[UNIQUE_NAME]

hi all,

i have 2 16k cruiseair a/c units (1 new compressor) that draw about 28 amps running. any sort of volage drop on the dock pushes me over 30amp blowing my cartridge fuses. (were you lucky enough to have a schematic on hand when yours first blew?)
only being able to run 1 at a time is becoming a quality of life issue.
planning to upgrade my service to 50a/125v, currently have 30a/125v to the selector switch. according to my schematics, from the selector switch downsteam was setup as 50a on the house side as well as the a/c side.
with regard to the 30a slow blow cartridge fuses, should i just
get new 50a fuse blocks along with 50a slow blow catridges or is there a better way to go?

thanks
jim

[Banshee36]

You are also going to have to put in bigger wires when you increase the fuse sizes or a nasty fire could happen. I put in two 30 amp services and have no problems, when I do it is usually on the Marina side.
JW

[campbellde]

Hello Jim,

The amperage sounds about right. I have the same boat as you and used to have the same problem, until I switched slips. The voltage problem went away then.

I do not have in-line fuses. I have two breakers, one per line, 30 amp, located behind the door under the back wall. These are directly behind the shore power connections. If I remember correctly, #8 wire was used to feed these breakers and to feed the switch. #8 should be good for more than 30 amps.

Not sure if mine was originally wired this way or changed at some point.

Dan

[UNIQUE_NAME]

campbellde:
my power inlet is on the stb side. lines run in the space between the salon and aft cabin bulkheads across to the a/c electrical panel. (the fuses are located behind the access point on the salon stb aft bulkhead)
the a/c panel is located in the port closet next to the stairs leading to the aft cabin. your setup is different than this?

jim

[campbellde]

Jim,

Sounds like the set-up is the same, except I have breakers instead of fuses in the same spot.

I replaced the AC inlet when I thought I was having a problem. It was then that I noticed that the wires were #8, a bit over sized for a 30 amp circuit.

[Boatsb]

I disagree with the #8 being oversized. Per the NEC and the ABYC you need 10/3 MINIMUM for 30 amps and its a Hatteras so #8 makes some sense. Longer runs, Voltage drops at the dock and older connections make a differance. Ijust replaced the power to the 2 ac units on my 41C. 1 16K and 1 7K which will be upgraded to a 12K. 30 amps is fine for this with NOTHING else on the circuit. If I am out visiting a marina that does not have good power I will have just enough. At my slip ( second from the hard ) the power is great and no drop. I have headroom. The problem I see is no headroom with the 10/3 if I was pushing 2 16K systems and I would pop the breakers once in a while.

[TedZ]

Hi,

Are you getting enough water? 28 amps sounds on the high side to me for a constant amperage draw of two units. Are you using the Hatteras meter or an Amprobe to do the measuring? I would only trust an Amprobe or a CT (current transformer) around the wire and a seperate meter. If you are off on water flow, they will blow fuses/breakers due to high head pressure. Look at the AC units and see what they are supposed to draw and be governed accordingly. I am not happy having you run more than 30 amps on a 125 VAC leg unless you are certain there is no weak link anywhere...i.e. transportation in the fuse boxes, bus bars etc. etc.

In my world 50 amp 125 VAC is seen but not commonly. The 50 amp is 250 volt and they get fed directly and split in the boat or split to two 125 VAC circuits by the power cord adapter.

Please be careful.

Ted

[Boss Lady]

All your major loads should be on seperate legs of the incoming 220 volt service, your boat was originally designed with a balanced load electrical system. You should have one A/C on one 110v leg and the second A/C unit on the other 110v leg. If someone changed this then you will have both loads on one circuit, and when you turn on your stove one side of the panel will have a huge overload. I have seen this problem before, because most shore power is 110v single phase, and you have to have a pigtail splitter for your shore power cord, and run it to two different 110v recepticles if 220v service is not available at the dock. If your boat was used further north, the PO would not have seen a problem, due to less demand for the compressor with milder temps, but down south they will be on all the time. If you don't have the wiring diagram you can get a copy, call Sam's and ask them how to get a copy. As far as wire size goes, you also have to account for temperature when selecting wire size, because all wire size loads given in the cheat charts are given according to amperage at a specific temperature, if the temp goes up, say in the engine room, then you must go to the next wire size.

[UNIQUE_NAME]

boss lady:
i have 2 seperate 30a/125v incoming feeds. 1 supplies the house panel, 1 for the a/c panel.

tedz:
yes, waterflow is fine. the plates state 13 - 14amps, so i am in the ballpark.
according to my schematics, the only "weak link" is from the inlet to the selector switch. past the switch is 50a breaker. i have run the gen and powered both a/c's without issue.

jim

[MarioG]

what size of generator do you have?