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?

 

[Pascal]

chris,

on the 53, all four ACs are on one leg while the rest is on the other leg. in typical use, I'm close to 50amps on the AC side, and arond 10 to 20 amps on the house side...

at somepoint, someone moved one of the AC on the house leg as i guess the four 16k units plus the pump must have been too much together...

 

[UNIQUE_NAME]

i'm running an old onan 6.5. i've had both a/c's, hot water heater and misc cabin stuff running on it at once, just once though....

 

[Hattenuff]

I had a similar problem on previous boat. One factor was overload on the circuit when block heaters kicked in. But I also found that the spring tension in the fuse holders had deteriorated and there wasn't good contact any more. Make sure this isn't adding to the resistance. Circuit breakers would be the way to go if you can avoid water exposure

 

[mstailey]

Jim,
Unless I mis-read your post (runs fine on the gen), you have your answer. Kind of. I'm by no means an electrical expert (lord knows I've posted enough electrical questions here) but I'd start at the source and work toward the boat. It has been my experience though that 80+% of my past electrical problems have originated from the source (marina).

What I do know for sure about electrical systems is if you start trying to re-engineer what Hatteras did for your boat you can get youself into big trouble.

I have the inline fuses with 2 30 amp 120v system like yours. Both of my A/C's and other ship services runs fine with no problems.

Anyway, that's my .02 worth.

 

[Boss Lady]

chris,

on the 53, all four ACs are on one leg while the rest is on the other leg. in typical use, I'm close to 50amps on the AC side, and arond 10 to 20 amps on the house side...

at somepoint, someone moved one of the AC on the house leg as i guess the four 16k units plus the pump must have been too much together...

I would obtain the Hatteras schematics and check your wiring against the original design. I have seen some pretty ugly stuff done. If you are pulling 50 amps on one leg, you cannot really have any other loads on that leg or you will trip a breaker. Your system was originally designed to have all loads balance between the two legs (110 circuits). I have seen a few boats rewired so that if you only have one connection at the marina shore power, the most used items have power, this is why you see all the air conditioner loads on one circuit. This is ok if you don't exceed the breaker capacity, but you canno t turn anything else on that is attached to that circuit without tripping the breaker.

 

[Maynard Rupp]

Our 1986 36C has 2 seperate 30 amp shore power receptacles. One is for the house and the other for AC. We have 2 Cruiseair units, one is 16000 btu, the other is 10000 btu. Our boat also has those old barrell fuses in screw top capsules just below the power receptacles. We have had lots of heat in the fuse holders and on occasion, (more often than I like), blown or cooked fuses. We also show about 28amp. draw on the Hatteras gages when both units are running. I am not sure what the gen set loads are. I know that heat is caused by resistance and have replaced the power cords. I have also removed the entire receptacle panel and cleaned and tightened all the wire hookups as well as cleaning inside the fuse holders. Keep in mind that our boat has never seen salt water so there isn't any obvious corrosion. It seems better now, but still seems to get warm. Because we are moving the boat to Florida, I am getting more AC concious. We just don't use it that often in the Great Lakes. The reverse cycle feature is very important in spring and fall.

 

[Boss Lady]

You need to boil out your A/C heat exchangers on occasion. The marine fouling will reduce the capacity and they will be operating at higher pressures, which can cause increased current demand (heat) in the wiring. I bought modern A/C units from Ocean Breeze Air Conditioning. Electronic controls and all, plus they have heating elements instead of reverse cycle, which works much better here in North Carolina. The price was fantastic and everything was stainless and cupronickel (commercial grade stuff, instead of the normal junk) You can look them up on the web.

 

[SeaEric]

I went to leave the slip one summer day 2 years ago and realized that my 30 amp cord, the dedicated air conditioner service, was welded to the inlet. Not only was the inlet melted, the wire to the panel was also fried for about 3 ft. Not good. The 30 amp was not sufficeient to run the 2 air units at once. The "house" feed was a 50 amp 125 that was pig tailed down to 30 amp 125, as 50 amp 125 does not seem to exist in marina power-dom.

What I ended up doing was to convert the system to run on a single 50 amp 250 cord and inlet, which we break in half on the panel. Now I have each air conditioner on it's own leg of the 50 amp. No more problems. I balanced out the rest of the house load over the 2 legs and have meters to monitor amperage use. It works very well now and I have much less worry about an electrical meltdown. While we were at the redo, I also had a custom engraved panel done that is all back lit. Its awesome, and so was the bill. The qoute was $3500 to $5000. and the final bill was $14,000. In fairness, we added a few "while you're in there's" and other extras, but it was still painful.

 

[Boss Lady]

I am in the middle of completely new wiring. I am converting to 24v and 12v DC as well. This is easy since all the old wiring is gone now. All the equipment will be load balanced between the two incoming 110 source power circuits. The generator will be happier too, since there will be equal loads. I have only seen 50 amp service in one marina and it is brand new and targeted to mega yachts. They also charge mega-yacht prices! I am installing an 8kw Northern Lights genset, which has reserve power even with everything turned on at once. I do not have a conventional oven, or washer/dryer, so the loads are not heavy.