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roof air and appliances
OffShoredreams
#1 Posted : Thursday, April 22, 2010 12:44:30 PM(UTC)
OffShoredreams

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Been pondering on roof air....I am assuming they are rv roof air units??? If they are....theyre not uscg approved! Can rv refrigerators or stoves be used in a BigM ??? I know the rv fridge(110v/lp) has to have ventilation behind it and I know the gas stove cant have a pilot light burning or the whole BigM might be burning...but is this a possible idea??? Oh another thing my BigM had a regular breaker box with a cut extension cord for shore power ran to 3 or 4 house outlets using solid copper triple house wire....the wire is a no no correct? Has to be braided? Is there a marine breaker box??? one last thing...the head (admirals throne) it cant be like an rv toilet where gravity dumps it into a holding tank???? thanx Jon
Trying to sip wine on a beer budget......
32ft. resurrection eventually
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jralbert
#2 Posted : Thursday, April 22, 2010 2:04:06 PM(UTC)
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-First time i've heard that CG has any reg on air conditioning. As long as it isn't in the engine compartment, take your choice, air cooled on the roof or water cooled in cabin (usually under a seat).
-Only reason the fridge needs air space is for venting of the waste warm air it generates. Otherwise, it won't cool very well or at all.
-Correct on the ac wire. Replace that awful setup.
-RV toilet things are fine, in a manner of speaking. If you can tolerate their low capacity, they are legal because they aren't connected to an overboard outlet. You take all the "output" home with you and dump it in a toilet. GO before you leave the dock, have a strong bladder and you will be ok.
Joel Albert, Potomac MD
"Charlie B" - 1988 32' FBS
Twin 318's/FWC/16x15 nibral props
docked Deale, MD
fastjeff
#3 Posted : Thursday, April 22, 2010 11:03:12 PM(UTC)
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Mine came with an RV rooftop A/C unit. It wore out so we installed a new Coleman RV unit. Works well, but the Vee berth area doesn't get as cool (no ducts to there). By nightfall it usually doesn't matter, though.

Jeff
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell

dougrose
#4 Posted : Friday, April 23, 2010 12:05:28 AM(UTC)
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My boat came wired with solid copper romex (3 conductor) wire. I think it is factory. I rewired the AC panel (see elsewhere on this site) using good quality stranded stuff, but the job of rewiring all the outlets just seems like a waste of time. I've had no trouble with it so far - if I do, I will replace with three-conductor stranded marine-grade wire from Skycraft over in Orlando.

The overhead DC lights supplied by Marinette are not marine, they use the metal case as the power return. This is OK when they are mounted in nonconducting plywood. For replacements I have used actual marine lights, with the double-contact bayonet bulb that keeps the case out of the circuit

Does "110v/lp" mean shorepower/liquid petroleum? If so, I would be very careful. Personally, I won't have propane on the boat, it is dangerous. I keep bottles of it for the grill on the aft rail, but I won't have a tank and piping. I always grill out on the hook anyway, can't use the electric stove away from the dock.

Air conditioning: Jeff swears by his roof unit, and the installation is a breeze and cost is half, compared to a marine unit. But the air is hot in Florida, and it doesn't cool off at night the way it does in the Chesapeake. Remember that the roof unit is working with a 95* heatsink, whereas the water around the boat is more like 80*. You get that 15* for free with a marine unit.


1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
Rick100
#5 Posted : Friday, April 23, 2010 1:51:55 AM(UTC)
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The way I see it is there is no difference in air or water cooled condensers, a 16k btu unit puts out 16k either way. Water condensers are smaller than air cooled and are more efficient but 16k out is 16k out. The advantage to the roof mount is in the distribution of the cold air. Cold air falls and would cool more evenly from a roof unit. Air that is blown from the floor or a mid mounted cabinet vent, as on our boats, does not distribute the air as well. I would suggest a unit, roof or marine, with a rotary compressor as they are much quieter. If your boat is a 32 16k will almost, but not quite, get the job done. Rick
When I die I hope my wife sells my stuff for more than I told her I paid for it.
dougrose
#6 Posted : Saturday, April 24, 2010 2:36:48 AM(UTC)
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A British Thermal Unit means one pound of water cooled or heated by 1 degree F. It is around 1000 joules. When rating an air conditioner, what is meant is actually BTUs per hour. It represents heat moved from the cold side to the hot side in an hour.

The amount of cooling power is the amount of heat times the difference in temperature between hot and cold. The capacity in effect depends on the amount of heat moved AND on the temperature difference it has to move it through. Bigger temperature difference, less cooling.

If the hot side is at 120 deg and the cold side is at 50 degrees (fairly normal numbers for a roof unit) then 16000 BTU will cool around 230 lbs of water by a degree. If the hot side is at 90 degrees and the cold side is again at 50 degrees (fairly normal for a water-cooled unit) the the temperature differential has been reduced to 40 degrees and you can cool more like 400 lbs of water by a degree.

These numbers are ideal physics, from that place where objects are always spheres and everything else is vacuum, but they do indicate that it is worth looking at the actual performance of each kind of unit.

My actual experience has been that, in Florida, marine units work better than air units, by a large margin. And, you cannot live aboard down there without air. That said, most of the boats in my marina have window units from Home Depot mounted in cabin windows or the like. And, I have a small (6000) btu "portable" unit that won't cool at all if the sun is up, but does keep the boat dry.


1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
fastjeff
#7 Posted : Saturday, April 24, 2010 3:56:39 AM(UTC)
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Doug is correct: The roof mounted unit does struggle to get the temp down after the boat has been sitting in the sun for days. I've gotten into spraying the boat with water from the hose to get it's temp down.

Jeff
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell

OffShoredreams
#8 Posted : Saturday, April 24, 2010 1:57:23 PM(UTC)
OffShoredreams

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Breaker box???? home depot breaker box is ok? Glad the case grounding was brought up never thought to look to see with the used 12vlights I have. Remember...I am resurecting the dead I saved a BigM from getting chopped and shes a 1972 just like me.<i know it would be cheaper to buy another and scrap her> A total rebuild is what I am doing... the wiring has been stripped,most was gone before I got her. 2 owners before me gutted her because the boat had termites???? ever heard of a BigM getting a case of termites while docked? Also I am redesigning the layout and there will be no lower controls. I have a motorhome that I think i am going to gut but wondered how much of it can be used in the BigM ...it has 2 ac units a porcelan $hitter oh and a 454 that would be nice sittin in the belly of the BigM . can a 32 BigM handle 454's? It is going to be a long hard road but when I am done she will be unique... and Im not worried about resale value cause Im not going to get rid of her thats why I got a BigM so it will last until I die. another thing how about aluminum floors instead of wood??? what about lightining with aluminum floors???hmmm things I just think about lol
Trying to sip wine on a beer budget......
32ft. resurrection eventually
fastjeff
#9 Posted : Saturday, April 24, 2010 10:43:26 PM(UTC)
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One of our guys had a 32 footer with 454s installed in a repower. The motors were so long their front ends protruded into the cabin (it was an Express. I have photos if you're interested.) The trans were 1:1 with tiny props for all that power, so it never ran like it should.

There's a few 440 Mopar powered 32 footers out there from the factory. Love to ride on one!

Jeff
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell

dougrose
#10 Posted : Sunday, April 25, 2010 4:18:25 AM(UTC)
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Actually, you can get a lot of the stuff you will need at Home Depot. I use the plastic electrical boxes and of course the receptacles and plates and all. I cut the unneeded ears off the boxes (some even come with nails) to get them to fit. The only A/C item outside the cabin will probably be the twist-loc shore power inlet: it needs to be the real marine item.

Do not use romex wire, get marine grade 3-conductor 14 ga. from Skycraft:

http://skycraftsurplus.c...0ftboatmarinecable.aspx

My boat came with six active circuits and two spare breakers. Good replacement toggle-style breakers would be preferred over home stuff. I show the rewire of my ac panel under Marinette Repairs » Electrical and Corrosion » AC Panel Rewire - I did not replace any of the factory romex, but I probably should have.

Use the double marine wire for dc. The breakers are 20 Amp, so 14 gauge is big enough but they have 12 gauge in stock, that's what Marinette used:

http://skycraftsurplus.c...torboatmarinecable.aspx

It is much easier to wire by following a diagram. Let me know what you need, and I will put together one for you that may make it easier. I have schematics of the way my boat was wired, and some from other Marinettes.

Lower controls were one of the things I was looking for in a boat. Even in Florida, it can get nasty on the flybridge. But, that is my preference - you don't really need inside controls, and it would be nice to have the extra room.

With engine swaps, think about the props first and then look at what is able to turn them....



1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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