AC on a 30 amp powr cord

[Maynard Rupp]

Many of our smaller Hatts have a 30 amp power source for all onboard air conditioning. I even noticed that the 42' LRCs have that problem. The normal current drain for both of my AC units, (from the manual), including the cooling water pump, is 32 amps. Why did they ever try to run all that with a 30 amp. power source? We have never been able to run both units except when the gen. set is providing the power. The larger Hatts use a single 50 amp source which would only be a problem with both AC, the stove, and some other high drain stuff running at the same time. Our devoted 30 amp source doesn't have enough to feed both units and the pump. Why can't we move the circuit breaker for the pump to the ships power panel??? That would reduce the load on the AC power cord enough to get the current drain back to a workable level on the AC cord.

 

[bigbill]

maynard, there is no reason why you cant draw power for the pump from your other cord,(house line) just make sure you dont overload the other cord.bigbill

 

[SKYCHENEY]

That sounds like a good solution, Maynard. I think you should try it.

Just make sure you look at the wiring schematic. You need to make sure that the pump breaker doesn't feed any other part of the system. You only want the pump to be run on the house cord, not the relays or any other part.

 

[Pascal]

the only issue i see is that if you pop the breaker on the house side and the pump shuts down, your AC units will be shut down by the high pressure switch.

not really a problem, this is why ACs have high press. switches...

 

[REBrueckner]

That's a reasonable solution. Just shut off all power before working in the electric panel.....even dc via your main battery switch just in case you drop a tool...

You will likely find it much easier working at the back of the electrical panel to change circuit breakers....in other words, remove the electric wire feed to your pump from the existing breaker and switch it to another breaker on the other dockside circuit.....not power the existing breaker from the other supply source....this can be a lot less work.....
you can perhaps use the existing breaker for another function not normally used when ac is on if you have no spare breakers....

you'll see what I mean when you get back there if you have solid plate metal jumpers like my 1972 YF....

 

[DCMY #92]

What size and how many A/C units do you have on board? I have two 16,000 BTU units on our 41 that each pull (as I recall) 9 to 11 amps. Of course the starting current is much larger, but I have never had a problem with the 30 amp service tripping even when both units start at the same time.

 

[spartonboat1]

What size and how many A/C units do you have on board? I have two 16,000 BTU units on our 41 that each pull (as I recall) 9 to 11 amps. Of course the starting current is much larger, but I have never had a problem with the 30 amp service tripping even when both units start at the same time.

I agree that they should not pull that much. Notes left from PO showed high amps pull, cured by installing new heads, from which I benefited. I might pull 15-20 amps tops, both heads running, according the AC panel meter.

 

[jim rosenthal]

I have not had this problem, however the digital controls on my AC units have a delay built in and stagger the units on startup so that they don't draw too much current from the single 30amp AC line. I have one 16K unit and one 6K unit and the 30 amp AC line can easily handle them both, providing the cord is tightly connected and in good shape.

They do run better from the generator, I have found also. If I were rewiring the boat I'd have fifty amps coming on board like a more modern one and 240vac units, no question, but from my experience if the marina has good quality power both units run fine. They will freeze you out of there, incidentally.

 

[SeaEric]

My 46 Matthews had a 50 amp 125v coming aboard for the house and a dedicated 30 amp 125v for the Air Cond. Since 50 amp 125v doesn't exist in marinas, I effectively ended up running on 2 30's.

One day I was leaving for a cruise and found my 30 amp Air Cond. cord "welded" into the inlet. That was a wake up call.

I had the shore power inlets rewired into one 50 amp 250v cord. Since I had no 250v equipment to run on the boat, we split the incoming power on the panel into 2- 50 amp 125 sources. We then balanced the onboard load and ended up much better off. I never had any more power issues, except for hauling around the damned heavy 50 amp cord.

The addition of a Glendinning cable master would have made for the optimum system. Unfortunately I had no good available space for the cable master.

 

[SKYCHENEY]

I would also check the dock power, if it is 208, that may be your problem, as I believe the ac units are rated at 220. Lower power more current draw. The only time I have this problem is when staying at a marina with poor power.

That's not the problem. A 30a cord is 120v and any one leg of the 208 service would give you 120v. These must all be 120v A/C units.

 

[Trojan]

My house is on one 30 amp cord and the 16000 btu ACs are on another.

BILL

 

[Maynard Rupp]

These comments are very interesting. The Cruiseaire book calls for exactly what our units are drawing. We have a 16000 BTU unit, and a 10000 BTU unit. When you add up the amperage required according to their book, with the 5 amps for the pump, it comes to 32 amps. When both of our units are running, our onboard amp. gage shows 32 amps. The normal problem is those stupid fuses where the power cord plugs in. They fail quite a bit but sometimes the AC shore power breaker in our main panel pops. Our current problem is a bit different. Either AC alone will pop its respective breaker on the AC panel. I am pretty sure we have a coolant water flow problem. The tubing was cleaned last winter with acid, so that should not be a problem yet. We will have an AC guy looking at it next week. I have a spare impeller for the coolant pump. It does run, but may have lost a beater or something.

 

[jim rosenthal]

I would look at the shore inlet to see if it is corroded, and also take it apart from the back to see what shape the wires are in. You might also open up the plugs on the cable, if they are the kind that you can look in, and see how things look in there. You need good connections all up and down the line even to carry a lot less than thirty amps.

 

[Maynard Rupp]

You are absolutely corect about corrosion. I removed the entire panel in the cockpit and took everything apart. It looked like new, as our boat had not seen salt water until recently. I also bought a new shore powert cord. It is hard to have a 32 amp. draw on a 30 amp circuit for any length of time.

 

[Pascal]

check the flow out of the thru hull and see what you have. reduced flow will cause the units to run longer or even not to cycle at all as the air woudnt' be as cold. If it's really reduced, then the high pressure switch woudl trip on the units.

does the breaker pop when one of them start? if so, it could be a bad start capacitor which causes a higher than normal starting spike.

also one of the compressor could be tired and pulling more amps than normal...

 

[Jaxfishgyd]

My Hatt was wired 30amp service for the boat and 50 amp for the A/C's (per the blueprint).
I changed the 50 amp to 30 amp in 2002 and have zero problems with A/C's running.

 

[UNIQUE_NAME]

My Hatt was wired 30amp service for the boat and 50 amp for the A/C's (per the blueprint).
I changed the 50 amp to 30 amp in 2002 and have zero problems with A/C's running.

my 73 38' is wired, breakered and fused 30a/125v ship service and a/c from shore. the gen a/c supply side is wired and breakered 50a/125v. this is also via the blueprints. what were they thinking? so i can run my 2 16k units on the gen but not on the shore. i wish i knew how 92 got his 16k's to run at 9 - 11 amps

 

[Jaxfishgyd]

The only time I even had my breaker pop while running both of my A/C's was when a lightning bolt hit very close by. When I replaced the 50 amp plug with the 30 amp, the wire going to the panal IS for 50 amp.The amp meter shows me pulling 26 amps....

 

[Trojan]

It sounds like your primary is low. I have 120+ ac volts and have no trouble running 2 16,000 BTU ACs. That 208 volts is probably giving you trouble.

BILL

 

[egaito]

Misty was reconfigured during her refit, so that each each cord runs to a different panel, and there's one A/C unit on each. Each of my A/C's has a separate March pump on it.

The only time I've had trouble, and this might be worth checking in your situation, is when they stuck a big houseboat on the dock with twin 50 Amps. My cords were running hotter, and I was popping breakers and couldn't figure it out. Finally, using a meter, I noticed that voltage on my boat was low when there was trouble (breakers popping). I then tested my cords, then the pedestal...and then all of them on my side of the dock to find the whole dock was low during the heat of the day when the big boat was drawing max power.

The dock didn't have large enough wiring to handle the load in our case, but this could also be caused by corroded connections or weak transformers on the dock.