Reply
 
Thread Tools Search this Thread Display Modes
 
Old 02-20-2017, 08:30 AM   #1
Veteran Member
 
Semi-Retired's Avatar
 
City: Central Florida
Country: USA
Join Date: Jan 2017
Posts: 40
Auto a.c. onboard?

So a mechanic friend and I were talking and we can't figure why don't boats use an auto type a.c. compressor and system to cool the boat while underway? I understand the condenser would have to be different sense it is normally cool with a fan and air cooled on the front of a automobile. But onboard a.c. uses water to cool that part. So Thats the only difference we can see. In our minds though Thats the only difference. Seems like that would be better than have to run the genny just to have a.c.?

Are we missing something here. And before y'all hammer me, we aren't liveaboards yet but in the process of searching and if its possible, maybe we could try it out... Just thinking outload. We were having a few drinks and the subject came up. But neither of us could answer this. So a light went on, I'll ask this forum. They know more than us..
__________________
Advertisement

Semi-Retired is offline   Reply With Quote
Old 02-20-2017, 08:40 AM   #2
Guru
 
psneeld's Avatar
 
City: ACIW
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 19,124
Lots have done it, I think there are articles on the web and certainly published through the years.

Much of the time by moving across the water (except in some climates some of the time), enough breeze is generated to satisfy people.

So most of the A/Cs are designed for dock or anchored with genset use.

At some point, space on engines can become a premium for mounting a lot of accesories.

But it can be done by the creative.

Other alternatives are a big inverter and alternator or a bell drive genset.
__________________

psneeld is offline   Reply With Quote
Old 02-20-2017, 11:07 AM   #3
Guru
 
djmarchand's Avatar
 
City: Litchfield, Ct/Punta Gorda, Fl
Country: USA
Vessel Model: Atlas Pompano 23
Join Date: Aug 2012
Posts: 4,588
I think you will find that 90% of the A/C usage time for most folks is at the dock or anchorage. You don't want to have to run a big propulsion engine all night to have air conditioning.

David
djmarchand is offline   Reply With Quote
Old 02-20-2017, 11:18 AM   #4
Veteran Member
 
Semi-Retired's Avatar
 
City: Central Florida
Country: USA
Join Date: Jan 2017
Posts: 40
Quote:
Originally Posted by djmarchand View Post
I think you will find that 90% of the A/C usage time for most folks is at the dock or anchorage. You don't want to have to run a big propulsion engine all night to have air conditioning.

David
True and I wouldn't, but I was just thinking that while cruising, we wouldn't have to run the genny as well as the main engines to keep the cabin cool. Wouldn't want the wife to have to use the head if its 100+ degrees in there

And we aren't the type of people to sit in one place too long. We are long haul truck drivers currently so sitting in one place for too long drives us crazy...so we plan to be on the move a lot.
Semi-Retired is offline   Reply With Quote
Old 02-20-2017, 12:39 PM   #5
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 16,543
Size is also a sizable issue. A lot of difference between air conditional an auto and a house. A boat is closer to a house. Note that most vans require two units. Imagine how many for a boat.
BandB is offline   Reply With Quote
Old 02-20-2017, 12:51 PM   #6
Veteran Member
 
Semi-Retired's Avatar
 
City: Central Florida
Country: USA
Join Date: Jan 2017
Posts: 40
Quote:
Originally Posted by BandB View Post
Size is also a sizable issue. A lot of difference between air conditional an auto and a house. A boat is closer to a house. Note that most vans require two units. Imagine how many for a boat.
Yes we have 2 in our 18 wheeler but it is run off of one compressor. But you do make a good point. Not sure how to figure out the btu's or a auto a.c. system
Semi-Retired is offline   Reply With Quote
Old 02-20-2017, 12:53 PM   #7
Senior Member
 
Join Date: Aug 2008
Posts: 217
Prevost motorcoaches have used bus air systems driven off the main engine for years. Nowadays they tend to use large inverters/large alternators to run the roof a/cs. Do some research on the power requirements. The interior size of the coaches is probably comparable with a boat.
folivier is offline   Reply With Quote
Old 02-20-2017, 12:53 PM   #8
Guru
 
CaptTom's Avatar
 
City: Southern Maine
Country: USA
Vessel Model: Prairie 36 Coastal Cruiser
Join Date: Dec 2012
Posts: 1,746
I'm curious too. I was hoping someone smarter than I would post some hard numbers: HP/BTU, BTU's from an average auto air-conditioner, etc.

My uneducated guess would be it wouldn't work well when you needed it the most. I base this on the totally unscientific perception that it takes 2, 16,000 BTU marine units to keep my cabin just a few degrees cooler than outside on a hot day, at great expense in terms of power.

Then again, my car cools down pretty quickly after being in a hot parking lot on a summer day. So maybe it would work.

Inquiring minds want to know
CaptTom is offline   Reply With Quote
Old 02-20-2017, 01:03 PM   #9
Veteran Member
 
Semi-Retired's Avatar
 
City: Central Florida
Country: USA
Join Date: Jan 2017
Posts: 40
Quote:
Originally Posted by CaptTom View Post
I'm curious too. I was hoping someone smarter than I would post some hard numbers: HP/BTU, BTU's from an average auto air-conditioner, etc.

My uneducated guess would be it wouldn't work well when you needed it the most. I base this on the totally unscientific perception that it takes 2, 16,000 BTU marine units to keep my cabin just a few degrees cooler than outside on a hot day, at great expense in terms of power.

Then again, my car cools down pretty quickly after being in a hot parking lot on a summer day. So maybe it would work.

Inquiring minds want to know
Yes I'm looking forbthise same type of answers. My a.c. in my 18 wheeler will make the whole trucks sweat when its really humid outside and that's just a single compressor with two evaporators....
Semi-Retired is offline   Reply With Quote
Old 02-20-2017, 01:18 PM   #10
Guru
 
City: Between Oregon and Alaska
Country: US
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 1,437
Car ac is cooling a much smaller space. In really hot weather, car ac vents are usually pointed at the occupants. Some vehicles have 2 systems to provide comfortable ac. As I remember, an ac compressor needs about 25hp.
Lepke is offline   Reply With Quote
Old 02-20-2017, 01:50 PM   #11
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 7,175
To clear up a few points:

Automotive / truck AC compressors are quite powerful. Most are designed to cool incoming hot moist air as opposed to recirculating cabin air. Cars suffer from lots of heat loading and poor to nonexistent insulation.

The downside will be that cooling production is tied to engine RPM. Not all, but most boat engines are turning lower RPM than truck or automotive engines. Units driven off the engine will necessarily be split units which will be less efficient and more costly to convert to a marine application (think long expensive hoses and custom built water cooled condenser). Unless you're an automotive HVAC tech, finding people to work on your system when your away from home maybe very difficult.

Installing a large second alternator, pure sine wave inverter, and decent battery bank would give you the power to run a normal all in one marine AC and use the inverter for other electrical needs as well.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 02-20-2017, 01:51 PM   #12
Veteran Member
 
City: Baton Rouge
Country: United States
Join Date: Jul 2016
Posts: 42
Not to hijack your thread Semi, but I've wondered why more people don't try "marinizing" a mini-split home ac. I think the problem with a main engine driven car ac is the volume you are trying to cool and the fact that you mostly don't need ac when the boat is underway, assuming proper ventilation.

I could see how a car ac in a limited function could work, for instance to cool only an enclosed pilothouse while underway. But I don't see much point...and I live in a subtropical climate with crazy heat and humidity.

But for the mini-split variable speed systems, I don't know why it can't work.
T4Liberty is offline   Reply With Quote
Old 02-20-2017, 01:58 PM   #13
Guru
 
LarryM's Avatar
 
City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 916
Just as a starting point for comparison purposes. Sanden (Sanyo) manufactures a line of replacement automotive AC compressors in 5, 7 and 8 cu. in. sizes. The output of the 8 cu. in. unit is about 27,000 BTU, or 2.25 tons at 3000 rpm using 6.6 bhp (R-134a at a high-side pressure of 235 psig and a low-side (evaporator) pressure of 35 psig.) For a 5 cubic inch compressor, multiply the capacity by .625. For a 7 cubic inch compressor multiply by .875.

Long ago, I seem to remember a number of around 5 tons for large american cars, but I suspect that requirement has diminished significantly with the advent of smaller and perhaps better insulated cars. The range of Sanden compressor sizes above seems to confirm this.
__________________
Larry
M/V Pelago
LarryM is offline   Reply With Quote
Old 02-20-2017, 02:02 PM   #14
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 7,175
Quote:
Originally Posted by T4Liberty View Post
Not to hijack your thread Semi, but I've wondered why more people don't try "marinizing" a mini-split home ac. I think the problem with a main engine driven car ac is the volume you are trying to cool and the fact that you mostly don't need ac when the boat is underway, assuming proper ventilation.

I could see how a car ac in a limited function could work, for instance to cool only an enclosed pilothouse while underway. But I don't see much point...and I live in a subtropical climate with crazy heat and humidity.

But for the mini-split variable speed systems, I don't know why it can't work.
Have seen it done numerous times on live aboard charter boats and commercial fishing boats. Problem is that the components inside the condenser (outside unit) aren't made for the salt marine environment. They live much shorter lives from corrosion. Also the vibration, bouncing and out of level orientation don't help. Finally, if you're going to run the units all the time, water cooled condensers are more efficient than air cooled. Would you rather try to dissipate heat into 100 degree air or 80 degree water.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 02-20-2017, 02:16 PM   #15
Veteran Member
 
Semi-Retired's Avatar
 
City: Central Florida
Country: USA
Join Date: Jan 2017
Posts: 40
Quote:
Originally Posted by LarryM View Post
Just as a starting point for comparison purposes. Sanden (Sanyo) manufactures a line of replacement automotive AC compressors in 5, 7 and 8 cu. in. sizes. The output of the 8 cu. in. unit is about 27,000 BTU, or 2.25 tons at 3000 rpm using 6.6 bhp (R-134a at a high-side pressure of 235 psig and a low-side (evaporator) pressure of 35 psig.) For a 5 cubic inch compressor, multiply the capacity by .625. For a 7 cubic inch compressor multiply by .875.

Long ago, I seem to remember a number of around 5 tons for large american cars, but I suspect that requirement has diminished significantly with the advent of smaller and perhaps better insulated cars. The range of Sanden compressor sizes above seems to confirm this.
We were considering using a compressor like the one on my semi-truck. I know their built to last a lil longer than a typical car/4 wheeler a.c. but not sure the cu. in. of it though. It is physically a large compressor in comparison to a car/4 wheeler a.c. too
Semi-Retired is offline   Reply With Quote
Old 02-20-2017, 02:19 PM   #16
Veteran Member
 
Semi-Retired's Avatar
 
City: Central Florida
Country: USA
Join Date: Jan 2017
Posts: 40
Quote:
Originally Posted by O C Diver View Post
Have seen it done numerous times on live aboard charter boats and commercial fishing boats. Problem is that the components inside the condenser (outside unit) aren't made for the salt marine environment. They live much shorter lives from corrosion. Also the vibration, bouncing and out of level orientation don't help. Finally, if you're going to run the units all the time, water cooled condensers are more efficient than air cooled. Would you rather try to dissipate heat into 100 degree air or 80 degree water.

Ted
I wonder if its possible to integrate a water cooled marine condenser into an auto system to solve that issue. I'm sure their much better than the air cooled type. Next question would be are they big enuff to be effective. Hard to figure which one to use not going the btu's of a custom system.
Semi-Retired is offline   Reply With Quote
Old 02-20-2017, 02:34 PM   #17
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 7,175
Quote:
Originally Posted by Semi-Retired View Post
I wonder if its possible to integrate a water cooled marine condenser into an auto system to solve that issue. I'm sure their much better than the air cooled type. Next question would be are they big enuff to be effective. Hard to figure which one to use not going the btu's of a custom system.
You could get a water cooled condenser for a custom system. Part of what's over looked here is that the components are matched to each other to make them efficient. There is some system engineering to make them work and be efficient. BTW, a custom, water cooled, AC condenser isn't going to be cheap.

Regarding size, you're putting the cart before the horse. First you need to get a boat and figure out how much AC is required.

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 02-20-2017, 02:44 PM   #18
Veteran Member
 
Semi-Retired's Avatar
 
City: Central Florida
Country: USA
Join Date: Jan 2017
Posts: 40
Quote:
Originally Posted by O C Diver View Post
You could get a water cooled condenser for a custom system. Part of what's over looked here is that the components are matched to each other to make them efficient. There is some system engineering to make them work and be efficient. BTW, a custom, water cooled, AC condenser isn't going to be cheap.

Regarding size, you're putting the cart before the horse. First you need to get a boat and figure out how much AC is required.

Ted
True. We do need the boat first. I was just looking for answers to a conversation a buddy and I were having over a few cold ones...
Semi-Retired is offline   Reply With Quote
Old 02-20-2017, 02:44 PM   #19
Guru
 
ranger42c's Avatar
 
City: Maryland
Country: USA
Vessel Model: 42' Sportfish
Join Date: Aug 2013
Posts: 4,360
Quote:
Originally Posted by Semi-Retired View Post
True and I wouldn't, but I was just thinking that while cruising, we wouldn't have to run the genny as well as the main engines to keep the cabin cool. Wouldn't want the wife to have to use the head if its 100+ degrees in there
FWIW, that's very commonly done, especlally in warmer climes (like where you are) and especially hot months in lots of other places.

Genset starts before leaving the dock, gets turned off after return. (Or sometimes at turned off in anchorages where there might be better overnight breezes.) July and August up here, for example, pretty much mean AC running at least all the time during most daylight hours, ditto most overnights in those months... partly for creature comfort, and partly to take a load off the fridges/freezers. In the grand scheme of things. it doesn't necessarily cost an arm and leg...


Quote:
Originally Posted by T4Liberty View Post
Not to hijack your thread Semi, but I've wondered why more people don't try "marinizing" a mini-split home ac.
There are several thread son it, IIRC. Fred (FF) has often suggested those. The main stumbling block often seems to be (from reading) the outside units not being robust enough for saltwater usage. Another issue is where to mount the outside unit...

-Chris
__________________
South River, Chesapeake Bay
ranger42c is offline   Reply With Quote
Old 02-20-2017, 04:16 PM   #20
Guru
 
kchace's Avatar
 
City: Brookline, NH
Country: USA
Vessel Name: Blue Heaven
Vessel Model: Albin 43 classic double cabin, twin 135 Lehmans
Join Date: Sep 2013
Posts: 1,474
Understand I LOVE my air conditioning, but there is so much airflow under way that I never even think about needing air conditioning. Not to mention that the boat would have to be closed up tight to make it worthwhile. As someone who really doesn't like too much heat, I can totally relate, but you're talking about a totally custom $$$ system which could be easily and far more cheaply taken care of by running the generator. A reasonably well cared for generator will run 10,000 hrs and at something around 1 gph fuel or less, it seems like an easy trade.

Ken
__________________

kchace is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 05:20 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012