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Old 11-07-2014, 08:23 AM   #21
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Originally Posted by hollywood8118 View Post
Your comparing apples and cucumbers..
You have to figure the CUBIC volume when looking at HVAC.. and I bet the house is five times the size.. at least.
I spend a average of $ 50 a month on electric load to keep a 40' trawler 55 deg. in the winter.
I spend a average of $180 a month on electric keeping a 3000 sq. ft home with 18' ceilings in part of it.. including a 1600 sq. ft barn.. the home is a air source heat pump set at 68. The house has a occupant load of three.. one being a teenage daughter that I swear lives in the shower.

The point is the house has a HUGE load by comparison. Another factor is most conventional marine ac systems that are also used to heat are pretty much worthless at 45d. water temps as the exchangers are not big enough to get enough heat out of the water. Most mini splits will produce down to 32d air temps, some in the low 20's.
They have no fouling issues in heavy nutrient rich waters. Would I want one on my current boat.. no way. not enough room to have the evaporator. But if I had a 50' plus with a upper deck with a lot of room I would consider them.
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Ok, point well taken. But even allowing for that, and given the boat is even more "porous" than the house, I still don't see the big savings. Our boat system worked own to 40 degree water temps, never had it in anything less than that. It makes a difference if you have them running almost constantly.

Having lived with the mini-splits in subfreezing weather, down to the teens, they really struggle, we use small ceramic heaters when it gets cold. You don't need to have the big ugly wall unit, by the way. Each of our two systems, because of the issues retro fitting them to the legacy house design, has one wall unit and one built-in-to-the cieling unit, that latter of which serves a couple of rooms and a bathroom via ducting. So I wouldn't be surprised if you could adapt one to work where an existing split marine system once dwelled.

Another approach I've seen was a play on the Manatee set up illustrated (dang those are great boats!). Two different guys (one on a Hatteras Yachtfish, the other on a Marine Trader) took a modern window air conditioner and installed them in the console of their flying bridge with lots of ventilation, then fashioned a duct for supply and return air down into the salon. Seem to be fairly happy with that so far, or they just ain't tellin'.
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Old 11-07-2014, 09:00 AM   #22
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Mini split systems are great. I have one in my house and have loved it since it was installed. However, I would have hesitations with using one in a marine application. There is a lot of vibration on a boat; and these units are not designed to withstand it. The supply and return lines for the refrigerant are copper compression -- not ideal for a vibration prone environment. I would also be concerned about whether the manufacturer would honor a warranty in such an installation. Most of these units (including mine) require that it be installed by a licensed contractor and the warranty card to be signed by them. I doubt a licensed HVAC contractor would perform a marine insallation.
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Old 11-07-2014, 10:15 AM   #23
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Are you claiming that I am wrong about the efficiency of heating or cooling water vs. air or are you on another track entirely?
read the post again..

Apples=Boat
Cucumbers=House

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Old 11-07-2014, 10:56 AM   #24
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read the post again..

Apples=Boat
Cucumbers=House

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Not apples or boats. Efficiency of heat exchange. Anywhere. So?
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Old 11-07-2014, 02:52 PM   #25
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Not apples or boats. Efficiency of heat exchange. Anywhere. So?
Clearly, Hollywood in post 13 quoted and was replying to Caltexflnc.
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Old 11-07-2014, 03:11 PM   #26
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Clearly, Hollywood in post 13 quoted and was replying to Caltexflnc.
And just as clearly, in post #19 I was asking Hollywood if he thought I was wrong about the efficiency of heat transfer to water rather than air. He has not answered this question.
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Old 11-09-2014, 07:54 AM   #27
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And just as clearly, in post #19 I was asking Hollywood if he thought I was wrong about the efficiency of heat transfer to water rather than air. He has not answered this question. __________________


Perhaps because the efficency of the exterior cooling or heat source is NOT what makes an efficient system , today.

THe old marine split systems are sad compared to the efficiency - electric in with cold or heat out,, of a modern setup.

Sorta like asking is a drip feed carb better than the updraft style , there is an answer , but it is not in terms of efficiency.
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Old 11-09-2014, 08:30 AM   #28
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And just as clearly, in post #19 I was asking Hollywood if he thought I was wrong about the efficiency of heat transfer to water rather than air. He has not answered this question. __________________


Perhaps because the efficency of the exterior cooling or heat source is NOT what makes an efficient system , today
the efficency of the exterior cooling or heat source is NOT what makes an efficient system ...................

Are you saying it is not more efficient to extract heat from 60 degree water than from thirty degree air?

I hope not.
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Old 11-09-2014, 11:38 AM   #29
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the efficency of the exterior cooling or heat source is NOT what makes an efficient system ...................

Are you saying it is not more efficient to extract heat from 60 degree water than from thirty degree air?

I hope not.

The efficiency of a heat pump system has many variables that all play a part in it's design. The medium in which the system draws heat (or dumps heat) Plays a part.. but just a part. There are pumps, fans, solenoid valves all drawing power that all into the use of energy to complete the system.

The use of water to extract/shed heat is very efficient, but it comes with its own set of problems. On a boat these are open systems that work much the same as the cooling on our boats. The big issue is the amount of water that goes through the ac is much less and can quickly attract growth in high fouling areas.. the main engines benefit from movement and high volume and are less prone to growth related clogging.

Very high efficiency up to 24SEER is possible with the compact mini split system through the use of low draw solenoids, variable speed compressors, soft start, higher spec compressors, digital temp controllers,etc.
Marine AC systems are way behind the times if compaired to the higher end mini split systems.

As I have previously stated, these systems will still produce heat BELOW freezing outdoor air temps.. but efficiency of course drops as the unit has to work longer to produce the same BTU's.. but a water exchange system really struggles when water temps drop into the 40's... of course I am addressing heat only in this statement.

A boat has to be of adequate size to have the compressor of a mini split on deck somewhere and still look decent. No way I would do one on my Ocean Alexander.. not enough deck space.

Of course this is my opinion .. formed from my experience in both very complex land based and marine AC systems, if you don't like it I don't really give a crap.
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Old 11-10-2014, 07:22 AM   #30
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Are you saying it is not more efficient to extract heat from 60 degree water than from thirty degree air?

In terms of the ON BOARD results ,YES < YES < YES more heat or more cold at lower electric cost is what counts as efficient.

Most folks dont give a hoot about the internal workings of heat transfer , they just care about being warm or cold (as desired) at the lowest electric co$t.

The rest is arguing how many angeles are on the head of a pin..Great with free beer.
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Old 11-10-2014, 08:11 AM   #31
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Would be interested to see some actual specifications at various temps rather than general speculation. All I know is from rough extrapolating comparing the two in the same climate and the same air temps, I haven't been strongly impressed. There may well be a difference, but it just hasn't jumped out at me.

BTW, I noted the extra maintenance factor for the marine system, our boat being in a very high growth area ( I even had a diver come every month in the winter) when I was making my comparisons.
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Old 11-11-2014, 07:03 AM   #32
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Would be interested to see some actual specifications at various temps rather than general speculation.

>Very high efficiency up to 24SEER is possible with the compact mini split system<

Most folks just use the gov SEER rating for their comparisons.

The gov is usually wrong , but for comparison A vs B they should give you the idea.

Any idea what the SEER of an ancient boat system was claimed when new?
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Old 11-11-2014, 11:02 AM   #33
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Would be interested to see some actual specifications at various temps rather than general speculation.

>Very high efficiency up to 24SEER is possible with the compact mini split system<

Most folks just use the gov SEER rating for their comparisons.

The gov is usually wrong , but for comparison A vs B they should give you the idea.

Any idea what the SEER of an ancient boat system was claimed when new?
I doubt they gave a seer rating as there isn't ( to my knowledge ) any govt. energy standards for boats... especially older systems.

This one specs a SEER up to 27.2 on a Fujitsu mini system..

Wall Mounted 9 - 15,000 BTU Hi SEER - Fujitsu Ductless Mini-Splits

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Old 11-12-2014, 06:13 AM   #34
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The problem with that Fujitsu is it is 240V , which is not common at every dock, and most small boats use 120v setups .

There are 120V units and as time goes on there will probably be more 120V units built , but so far no marine or RV air cond folks are willing to scrap the current antique system and embrace the future.

This is no doubt caused by the lack of OTS parts a system can be assembled from.

So far all the efficient setups are complete Systems .
Simply repainting systems (like Westerbeak or Ford Econo Power ) might not work.

The big boat folks ( Meters , not feet) that have to pay for electric at a slip will probably be the first to use the Mini Splits for new builds..

Eventually the smaller boats will have a recess or two where the units can be mounted outside .

No more midnight shutdowns to clean jelly fish out of the seawater cooling setup!!!

No mote expen$ive toaster heat (electric heat element ) when its cool !
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Old 11-12-2014, 07:47 AM   #35
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The big boat folks ( Meters , not feet) that have to pay for electric at a slip will probably be the first to use the Mini Splits for new builds..
!
Well, I've got meters, maybe only 11 of 'em, but I've got 'em.

I am definitely interested in doing something radical with my Marine A/C system. Seeing the installation on the Hong Kong Manatee is good enough for me, but as Cal pointed out, establishing the cost/efficiency factor to swing one in favor of a Mini-Split over a marine system is just not clear. I may try it anyway but I'd sure prefer a 120V from a good Mfg..
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Old 11-12-2014, 08:17 AM   #36
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I am hoping the marine AC units will catch up with today's standards in residential HVAC

The new mini splits are amazing the efficiency in heat transfer is amazing we have a 2013 mitsubishi that I think is a 24 seer

now if there was a way to take that unit and pass water through for the cooling in theory you would increase the heat transfer by over 20 times ( my memory form engineering school was water is 20-30 times more efficient then air at transfering heat)

that being said I would stay away from non Marine HVAC units on a boat unless you had a house boat
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Old 11-12-2014, 05:51 PM   #37
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Comparing a new, high efficiency unit intended for residential and commercial use to an older marine unit doesn't really accomplish anything. It's apples to cucumbers.

For many of use, obtaining the highest possible efficiency at the expense of appearance, space efficiency and longevity just doesn't make sense unless you are powering the unit with your genset or inverter or if you're paying for metered shore power. Many of us pay a fixed rate for electric power.
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Old 11-12-2014, 08:51 PM   #38
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Why couldn't one make a Hybrid with heat exchange from keel cooling or coils submerged in Sea Chest. True, thin coil material wouldn't last long in salt by itself, but with a sacrificial metal bonded, maybe.
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Old 11-13-2014, 07:47 AM   #39
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It should be noted that while most marine refrigerators use air to air heat transfer (and warm the galley in the process), more efficient units are available that work much like the typical marine air conditioner, transferring the heat to sea water.

Same principal, moving heat from one place to another.
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Old 11-13-2014, 08:13 AM   #40
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>It should be noted that while most marine refrigerators use air to air heat transfer (and warm the galley in the process), more efficient units are available that work much like the typical marine air conditioner, transferring the heat to sea water.<

The sailors are the most concerned with efficient refrigeration , as many have only solar or the main engine to produce electric.

Most sailors do not replace a sea water fridge machine ,with another, as the complexity and electric cost of a pump make up for any claimed gains.

The hassle of no refrigeration while hauled out is a big looser for sea water cooling too.

The reefer run times are mainly set by the size of the box and the heat transfer ability of the box contents.

The new mini splits are more efficient at cooling , and a snap to install compared to water cooled marine stuff , BUT the huge advantage is HEAT , where many will put out 5X as many BTU as a toaster heat element for the same amps cost.

For a live aboard this could be a real difference , my last slip was $.25c a KW , with oil heat , I didnt care , but many new-bees try electric thinking its cheap, till they get the first months bill.
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