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Old 26-02-2013, 10:52   #16
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Re: Heating / Air Conditioning - What's the Consensus ?

Thiss might be a stupid idea but her it goes: Coud it be possible to use the diesel heater to heat the A/C water intake? A small Heat exchanger as the end of the heat-loop, just before the central heat water enters the heater and you will still have hot domestic water, and hot radiators in th cabins.

.manitu
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Old 01-03-2013, 00:03   #17
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Re: Heating / Air Conditioning - What's the Consensus ?

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Originally Posted by sparklegirl50 View Post
...... You also have the problem of condensation. ......I think your daughter will be happier (speaking as a girl), if she does not have to worry about her stuff being ruined by indoor rain...
Condensation????

The only condensation is on the compressor unit which should be collected and fed to a shower sump or drained overboard. The air coming out is dry and on our Cruiser unit there is an automatic 4 hour dehumidify cycle that can be used during winter when not on board.

The heat pump idea is very efficient as it takes heat out of the water when heating the boat. So 1 Kw of electric energy put in will give 3 Kw of heat out. If you pay for your leccy in winter then this is a great saving.
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Old 01-03-2013, 08:01   #18
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Re: Heating / Air Conditioning - What's the Consensus ?

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Condensation????

The only condensation is on the compressor unit which should be collected and fed to a shower sump or drained overboard. The air coming out is dry and on our Cruiser unit there is an automatic 4 hour dehumidify cycle that can be used during winter when not on board.

The heat pump idea is very efficient as it takes heat out of the water when heating the boat. So 1 Kw of electric energy put in will give 3 Kw of heat out. If you pay for your leccy in winter then this is a great saving.

You're missing her point based on your lack of experience with a heat pump in a similar climate. She's talking about condensation within the cabin based on the i ability of a heat pump to effectively heat the boat in the temperatures we see around here. The water can dip into the 30's F. in the dead of winter.

As for efficiency, you should apply for a patent and publish your method in a journal if you have found a way around the laws of thermodynamics so you can get 3Kw of output from 1Kw of input. I think a Nobel Prize is as good as in your pocket.

Heat pumps are incredibly inefficient at extreme temperatures as they need to run virtually constantly to transfer what little energy they can extract from their energy bank. In the winter, when the water is a handful of degrees above freezing, there is very little heat that the pump can pull from it to transfer to the air.
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Old 01-03-2013, 08:26   #19
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Re: Heating / Air Conditioning - What's the Consensus ?

Heat pumps are very efficient when the delta t is relatively small. In temperature differences of 30 degrees or more they become inefficient and costly. They work well on boats because the water temps are more stable than air.
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Old 01-03-2013, 08:43   #20
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Re: Heating / Air Conditioning - What's the Consensus ?

Suijin,

sorry for disagreeing violently, but you should have kept the scathing sarcasm out of your post - it's just too tempting.

Heat pumps are governed by the Carnot equation. If you elevate the temperature from 273 K (freezing temperature) to about 50 degrees C (which is usable for heating) your theoretical COP (coefficient of performance) is around 6. Losses and inefficiencies make it about 3 in real life.

This has nothing to do with creating energy. As the name says, the heat pump takes energy out of a heat source (in this case the ocean) and "pumps" it up to a level that is usable. It still costs energy, but less. And contrary to your opinion the ocean (or any liquid) is much better than air to draw energy from since the specific heat is so much bigger.

Oliver
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Old 01-03-2013, 08:50   #21
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Re: Heating / Air Conditioning - What's the Consensus ?

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Suijin,

sorry for disagreeing violently, but you should have kept the scathing sarcasm out of your post - it's just too tempting.

Heat pumps are governed by the Carnot equation. If you elevate the temperature from 273 K (freezing temperature) to about 50 degrees C (which is usable for heating) your theoretical COP (coefficient of performance) is around 6. Losses and inefficiencies make it about 3 in real life.

This has nothing to do with creating energy. As the name says, the heat pump takes energy out of a heat source (in this case the ocean) and "pumps" it up to a level that is usable. It still costs energy, but less. And contrary to your opinion the ocean (or any liquid) is much better than air to draw energy from since the specific heat is so much bigger.

Oliver
So you agree with the statement that 1 Kw of electric energy consumed by the heat pump produces 3 Kw of heat? That is what the poster said.

Regarding my opinion that the heat pumps are poor choices for heating in areas where the water temperature approaches freezing, I stand by that opinion. The fact that water is a better conductor of energy than air is completely irrelevant to what I said. Yes, marine heat pumps may be more efficient than those that use air as their heat bank, but that does not make them more efficient than other marine heating methods in colder climates.
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Old 01-03-2013, 08:57   #22
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Re: Heating / Air Conditioning - What's the Consensus ?

On our last boat (Catalina 36) we had a WABSCO Forced Air Diesel Heater... It worked great for the San Francisco winters (and Summers :-) ) and burned something like a cup of diesel per hour.

On our present boat we have Marine Air AC Units... They wroked good for heat in San Francisco, but hte water temp stayed in the 50's.

Were these AC units really showed there colors was when we started cruising in the tropics and spent a rainy season in Central America. They reduced the humidity to the point the inside of the boat had very little mold.

Although we have three units on the boat, we never usually run more than two at a time, which keeps the boat comfortably at 75 degrees without shade covers on the cabin.

Talk with a marine AC guy about how many you need and were to install them. Outside drilling the thru hulls, there is nothing hard about instlling those either.
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Old 01-03-2013, 10:02   #23
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Re: Heating / Air Conditioning - What's the Consensus ?

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You're missing her point based on your lack of experience with a heat pump in a similar climate.....As for efficiency, you should apply for a patent and publish your method in a journal if you have found a way around the laws of thermodynamics so you can get 3Kw of output from 1Kw of input. I think a Nobel Prize is as good as in your pocket.
I'm glad to see that Oliver L has put you in your place - somewhat too politely in my opinion. There's always one old fart who comes back with abusive comments when I post my experiences of heat pumps.

Your scathing sarcasm demonstrates what is so often wrong with these forums where people hide behind silly names and even worse, silly avatars.

A COP (coefficient of performance) of 3 (1 Kw in and 3 KW out) is quite normal for a marine based reverse cycle heating cooling system like mine. I have used it for heating in extreme low temperatures in the UK where the water temperature is 4 degrees C (40F) and in Turkey for air conditioning where the air temperature is 50 degrees C (122F). The COP will change at extreme ends of the spectrum and may go as low as 1 - it still works, but the energy you put in maybe the same as you get out. In normal situations a COP of 3 is normal - no Nobel Prize is needed to achieve these results.

"Ignorance isn't what you don't know - it's what you think you know that is incorrect."
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Old 01-03-2013, 15:13   #24
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Re: Heating / Air Conditioning - What's the Consensus ?

Well I'm happy to take my comeuppance and admit that I was both ignorant as well as uncivil. I apologize unreservedly and sincerely to you sailinglegend on both counts, and also to all those reading the forums.
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Old 01-03-2013, 16:42   #25
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Re: Heating / Air Conditioning - What's the Consensus ?

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Well I'm happy to take my comeuppance and admit that I was both ignorant as well as uncivil. I apologize unreservedly and sincerely to you sailinglegend on both counts, and also to all those reading the forums.
It takes a big man to admit an error; which is ridiculous, actually, considering the universiality of brain farts -- we all have them -- but there you are.

So kudos to you.
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