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isphh 10-20-2019 03:54 AM

Nordhavn 40 electric issue
 
I have just completed a survey of a Nordhavn 40 that has an electric issue. The boat’s electric system is powered by two 30 amp circuits, one circuit for the three AC units and the other for the house. The first problem is that the 30 amp circuits each have a 50 amp breaker that needs to be immediately changed to a 30 amp breaker. The boat has three AC units and 30 amps can’t run them all. Is this how the boat is configured by Nordhavn? Should I add a third 30 amp circuit? I’m not sure how to solve this problem. The Chesapeake is hot in the summer so all three AC units are needed.

GregBrannon 10-20-2019 04:42 AM

Is the ultimate solution to be both a shore power and generator powered system? Upgrade one or both 30-amp circuits to 50-amp? Add a 50-amp circuit for the AC units?

OldDan1943 10-20-2019 05:18 AM

Quote:

Originally Posted by isphh (Post 812944)
I have just completed a survey of a Nordhavn 40 that has an electric issue. The boat’s electric system is powered by two 30 amp circuits, one circuit for the three AC units and the other for the house. The first problem is that the 30 amp circuits each have a 50 amp breaker that needs to be immediately changed to a 30 amp breaker. The boat has three AC units and 30 amps can’t run them all. Is this how the boat is configured by Nordhavn? Should I add a third 30 amp circuit? I’m not sure how to solve this problem. The Chesapeake is hot in the summer so all three AC units are needed.

I moved from a N46 (2X50amp leg) boat to a AT34 (2X30amp leg) boat. I have two A/C and can run them off of one 30amp leg and the house on the other 30amp leg. I will admit, the 30amp house leg can be a challenge. You learn pre-planning and load shedding. SIGH

My best advice is to contact Nordhavn for guidance, for a start.
Realize the Nordhavn, according to Nordhavn, is a 'semi-custom' boat. Nordhavn may or may not maintain records how your particular boat was configured when it left the factory. Then you have no idea how or what the various owners, before you, modified the boat and/or its electrical system. I would still start with Nordhavn.

Consider having 'soft starts' installed on the A/Cs. I have no experience with the 'soft starts' but, I have seen them recommended in similar cases on other boats.

Can you run all 3 A/Cs on the generator?

I agree with you on the 50amp breakers on a 30amp boat. Doesn't seem like a good idea, in my feeble mind.

I hope the above helps.

johnrupp 10-20-2019 05:24 AM

Since you need more than 30 amps on the one circuit I’d change service to 120/240 50 amp service. That will give you 50 amps of 120 volt to each bus.

John

Porgy 10-20-2019 07:16 AM

We have been liveaboards for over seven years on our N40 and experienced temps over 100 on the bay. We found that two a/c running- salon and cabins have been sufficient. The PH is warmer but at the dock we don’t spend as much time there. We also have Phifertex shades for the PH and interior shades in the salon, both of which help a great deal.

Ours is likely somewhat newer and is wired the same as you describe. Therefore, I’d suggest your surveyor may be mistaken regarding the need to downgrade circuit breakers. Assuming yours is similar to ours, there should be 32A circuit breakers between the shore power inlets and the “Ship’s Service Selector” switch. Ours is in the medicine locker. From the switch, 4ga. cable is used to the distribution panel (and its main panel CB) and also from that switch to the a/c panel (and it’s main CB.) As alluded to above, this is to accommodate the full output of the generator. Yours (I’m assuming you have one) is likely 8k or 66 amps. You still have to manage loads but, you can simultaneously run “nearly” everything on generator.

The owners manual should have electrical diagrams which should be consulted rather than relying on the above and the possibility that specs have indeed changed and the distinct possibility I have no idea what I’m talking about.:)

I know of at least one 40 that went the 50 amp cord route allowing them to run all three a/c’s at once. While we are considering that, there are some caveats: The cord is a big heavier python to wrestle, more expensive and more expensive to replace burned plugs. If you can’t find a 50 amp pedestal, you’ll have to reverse Y 30s so you’ll only have 30 amps anyway. The cable between the inlet and the main selector switch is 10ga. And will need to be replaced, likely to 6ga as will the aforementioned intermediate circuit breakers. No showstoppers, just considerations, and all in all probably preferable than adding a third 30A circuit.

Good luck with your purchase.

OldDan1943 10-20-2019 08:02 AM

SMILE, My AT34 30amp --- I have ofter thought about shifting to 50amp just so I can own the world, electrically. Over time, I have learn to plan when cooking on my electric stove and temporary load shedding. I can safely use 2 burners and the microwave. If the water heater comes on or I attempt to include the over, your interior 120vt world goes dark. Of course, if both standard resistant electric heaters are on, don't try to add anything else or again, the boat will go dark.
In my case, the largest loads are the stove, the oven, hot water heater and electric heaters.
Life is a learning experience and so are boats.

DavidM 10-20-2019 08:07 AM

Changing the two 120V 30A circuits to two 120V 50A circuits supplied by one 240/120V shore power connection will be difficult. All of the wiring from the new 240/120V shore power inlet may have to be upgraded to #8 to deal with the higher potential current (although it may have been wired for 50A originally from the factory). Also not all marinas have 240/120V power available but you can usually find two 120V 30A circuits on all with an adapter for the ones who do have 240/120V power.


So why not move one of the air conditioners over to the other, probably lightly loaded 30A circuit. This may pose some problems with the raw water pump if it is common to all three A/Cs but move the A/C that you use the least so that the other two are always on and supplying the raw water pump from the original 30A circuit.


Another problem as noted above is that a 30A circuit is marginal for running two 16K btu A/C units.


David

OldDan1943 10-20-2019 09:03 AM

Quote:

Originally Posted by djmarchand (Post 812966)

Another problem as noted above is that a 30A circuit is marginal for running two 16K btu A/C units
David

I guess that 'spains why I have a 16K and a 12K A/C units.

Maerin 10-20-2019 09:12 AM

You indicate that your system is equipped with 50A breakers. If the cabling is #6, you may not have as much problem converting to a 240V/50A cable as some have suggested. There are so many variables involved that it's clearly beyond the forum to make that determination. You'll need a qualified ABYC marine electrician to make the call. Still, I'd definitely move to the 50A cable, there are so few places where 50A is NOT available that it is almost never an issue. As you noted, you already have experienced issues with dual 30A service. It's inadequate for your application. A smart wye would be a good investment to insure you're adaptable for those rare locations that are strictly 30A.

If you do convert, you'll need to be aware of the pitfalls of converting those dual 30 services to 50A, specifically neutrals and in particular neutrals and inverter circuits. An ABYC electrician will be aware of those issues, and dealing with them early on will help you avoid problems connecting to shore power that has been recently upgraded and is GFCI/ELCI equipped.

So your upgrade would provide you with a connection that requires only a single cable, won't nuisance trip, and will have the capacity to power all loads without fussing with what can be run when, etc. You've got a world-class vessel, get the power un-fussed! Plug in, turn on, and relax.

Good luck with the solution!

Ski in NC 10-20-2019 11:46 AM

Someone might have added a third ac. Probably a mistake to have all ac's on one 30a service. Agree with Dave: See if you can move one ac breaker to the other panel.

twistedtree 10-20-2019 03:42 PM

Are you a member of the Nordhavn Owners Group on groups.io? If not, I highly recommend joining. Ask there and you will get all the answers you could ever want about your 40.

OldDan1943 10-20-2019 03:59 PM

Are all 3 A/Cs 16k??

Comodave 10-20-2019 04:09 PM

First I would have a certified marine electrician come do a survey of the electrical system. If you stay with the dual 30 amp inlets then move one of the A/Cs to the other 30 amp service. Or go to 50 amp service and problem solved. But when the electrician is there have him check for proper neutral connections so you won’t trip the ELCI on newly wired docks.

IRENE 10-21-2019 12:14 AM

Quote:

Originally Posted by Porgy (Post 812962)

Ours is likely somewhat newer and is wired the same as you describe. Therefore, I’d suggest your surveyor may be mistaken regarding the need to downgrade circuit breakers. Assuming yours is similar to ours, there should be 32A circuit breakers between the shore power inlets and the “Ship’s Service Selector” switch. Ours is in the medicine locker. From the switch, 4ga. cable is used to the distribution panel (and its main panel CB) and also from that switch to the a/c panel (and it’s main CB.) As alluded to above, this is to accommodate the full output of the generator. Yours (I’m assuming you have one) is likely 8k or 66 amps. You still have to manage loads but, you can simultaneously run “nearly” everything on generator.

The owners manual should have electrical diagrams which should be consulted rather than relying on the above and the possibility that specs have indeed changed...

We are also wired as Porgy indicates, confirmed by our wiring diagram. The good news is, there may be no problem with what sounds like a prospective boat.

Welcome to TF and Best Wishes


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