Upgrading AC System

[R&B]

We own a french built boat that we live aboard in the US. The AC system inplace now is to say the least very light..(wires 14G with a 20A main breaker and 2 outlets) Since we liveaboard and the weather gets cold I feel the need to upgrade....our intentions are to stay in the states and the caribean.....Since I will be living aboard full time with the wife and two kids(and their gadgets) and I will need significant heat to heat a catamaran...I was thinking 110v 50A service....Here is where I get a bit confused ( it doesnt take much)...A west marine sales guy suggested that I go with a 240v 50A service.......since I was on my lunch break I didnt get to pick his brain, and have not seen him since......could anyone explain the advantage of this??? I have been through the books but cant seem to find it....Thanks

[senormechanico]

Power measured in watts delivered is voltage x amperage. Since wire gauge is the limiting factor in current capacity, a 240 volt system can deliver twice the power at a given current. Example, 120 volts @ 20 amps is 2.4kilowatts. 240 volts @ 20 amps is 4.8kilowatts.

I'm not much of a marina type, but if a 50 amp shorepower plug will deliver 240 volts, that might be your best bet. Check to see if 240 volts is available first.


Steve B.

[Pblais]

Personally we run each of our two boats one monohull 33 ft and a second monohull 36 on 1 30 amp connection and both have reverse cycle AC. Since you have a small electrical panel now I can't see you needing 50 amps unless you really want to rewire the whole boat.

At this point with what few details I see in your post I'm not sure the West marine guy was correct at all and it seems you current wiring may or may not be adequate. In any event the install of both new wiring and an AC unit is big job so you may want real professional help.

You'll be running an AC powered A/C unit and it needs it's own breaker on the AC side of the panel. I would have someone examine you panel and get the correct details of how it's laid out before anything else.

The A/C unit will needs a water pump">raw water pump and through hull then the wiring to it and the ducts to distribute the air. I'm not sure how many BTU's you might want on a 39 ft Cat. Some of the Cat owners could get you closer. based on the BTU's required then you pick the unit(s) and that will tell you how many amps you need.

Note that in Maryland when the water gets really cold the reverse cycle heat isn't that great, but when it's say 50 F it will work very well. The heat can work better than the cooling. We found the reverse cycle worked well here in the lower Chesapeake through November. Right now it's not that great (we don't have to haul out).

[btrayfors]

R&B,

Many marinas have 230 or 240 volt systems on their power poles. However, their normal use is with a splitter to provide, e.g., two 30A 115V AC lines. Mine is like this.

Unless your boat is fitted with all 220v appliances, including all the things you're going to use as a liveaboard, you're going to have to do something to resolve differences between the 220V European system and the 115V U.S. system.

A 220V system can effectively use smaller wiring than a 115V system to deliver the same wattage, since AMPS X VOLTS = WATTS. So, a U.S. hair dryer which draws 10 AMPS on 115V AC is roughly equivalent to a 220V European hair dryer which would draw only 5AMPS....and could, therefore, use smaller wiring.

You're located in Maryland, I believe. I'd suggest you contact a qualified marine electrician and at least talk with him before you do anything. It could save you a LOT of money and heartaches in the long run. If you'll shoot me a PM, I can recommend someone in the Chesapeake area.

Bill

[R&B]

Thanks Guys
Paul as for rewiring the boat I feel as if it needs to be done any way since there is only 1 main line into a into a breaker panel of Three lines 2 for the 2 outlets and 1 for the battery charger.....All the lines are easily tracable and frankly the wires dont look in great shape.....The boat is 15yrs old with no upgrades....I feel it is a clean canvas....as far as A/C is concerned I am planning to put in a cruiseair version with resistance heating unit.....I am planning on having a pro give it a look....but I have learned I need to have as good of a knowledge base as the pro's not to get screwed......And it cuts down on the cost to get some preliminary work done .....Thanks again for you advice.....

[AnchorageGuy]

R&B, A big consideration for a reverse cycle heat/AC unit in the chesapeake in the winter is that when it gets cold the unit will not heat the boat. These units are rated for outside water temp and once you reach that threshold you no longer have heat so consider this in the planning stage. You may consider an AC only system for summer with a diesel fired furnace, if you carry diesel, for heat in the winter.

[R&B]

Chuck
This unit works on resistance heat no water pump is needed......It is an electric heater that is circulated with the blower from the a/c unit.....

[never monday]

R&B,
Why not just split the HVAC and battery charger off to a seperate 30A cord and panel. Every marine out there has 120/30A, you'll just need to schlep 2 cords. Build in the ability to parallel the cords if necessary.

[R&B]

Just to clear it up a little ......I am looking to upgrade my AC electrical system.....which will incorporate my air cond as well.....

[never monday]

I was clear on that.
14g will handle most everyday loads from appliances. I typically install a 10g drop from a 30A socket then split the circuits with 14G.
Now, dividing your loads to two separate and distinct 30A services might be a better cost effective way to go. you'll need to replace less of your current wiring. Just add the second socket, master and subs, pull the HVAC, battery charger and critical 120v devices to the new panel. that leaves you with a complete 30A drop for appliances.

I do this every day and do have a clue contrary to popular belief.

[colemj]

Keep in mind that wiring runs in a catamaran can be quite long - often times 3-4x that required for the same purpose in a monohull, depending on how the chases are run. Personally, I think 14g is too light given the lengths I expect will be needed. It is definitely too light for bringing the mains into the panel.

Mark

[AnchorageGuy]

R&B, Sea Trek has twin shore power outlets on the boat, as Pat suggets, with one dedicated to the boats main electrical panel and the second to a smaller panel with only the Heat/AC and the battery charger and both are connected with one shore power cord and a 30Amp Y pigtail. All runs to the panels are #10 wire. Works just fine and is an easy install. We generally are plugged into a 125 volt 50 outlet on the dock with a 50Amp to 30Amp pigtail adapter. This seems to be more and more standard in most marinas.

[Pblais]

I think it's clear that with a cat and the desire for a new electrical that the job of the A/C is really after the bigger issue of the electrical system. That includes batteries and charging as well. After it's all done you need the whole system working together properly. A 15 year old system may or may not need a total replacement. In any case if you are spending that much money it's a good idea to rework the whole system. You may find some wiring is OK but I would not assume it.

I would start with a diagram of what you have and then look at all you want and see what has to go and what can remain. I think you can find a lot of information on general electrical systems here in the forum. Pat has put out a lot of good advice plus we have Rick our resident electrical guru that has many posts on the topic. It's a good idea to really look at every thing electrical and evaluate what is up to the job and what goes. when you have to run that much wire it won't be done better than right now without a serious extra cost.

For books Nigel Calder's book rates pretty high and is a great overview of the issues. I would include all the issues with batteries and charging as well as AC power since they eventually meet at the panel.

[PBzeer]

Having just rewired my AC, from a very poorly done original job, I replaced all the wiring (it was Romex, for pity sakes). I ran 10ga from the shorepower connector to a new distribution panel, then 12ga to A/C and W/H, with 14ga for the outlets and battery charger.

As said above, the best thing to do is diagram it out first and get a firm idea of what you need.

[R&B]

Guys I am sorry I was not trying to say anyone didnt understand what I was saying I wanted to narrow in my question about the AC wiring itself....but as usual all your advice is greatly apprectiated......