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#1
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12V refrigeration
I may even have it from somewhere before, but the recent conversations on
reefers brought it to mind: Someone on these lists built a direct drive 12V compressor for refrigeration. My recollection has it connected to cold plates. It was designed to do what an engine drive would do, but not run the engine. At the time I saw it, it was new. If they're reading, I'd be interested to see a report on its efficacy. How much power did/does it take to operate? Was the size of the compressor notably less than one on the engine, and if so, what is the relative run time? In the end, are you happy with the outcome? If not, or even so, is there anything you'd have done differently if you were doing it again? Thanks. L8R Skip (and Lydia, by proxy), thinking of how to use the lovely cooling system on the boat without running the engine or the AC air-cooled system, either -- Morgan 461 #2 SV Flying Pig http://tinyurl.com/384p2 "And then again, when you sit at the helm of your little ship on a clear night, and gaze at the countless stars overhead, and realize that you are quite alone on a great, wide sea, it is apt to occur to you that in the general scheme of things you are merely an insignificant speck on the surface of the ocean; and are not nearly so important or as self-sufficient as you thought you were. Which is an exceedingly wholesome thought, and one that may effect a permanent change in your deportment that will be greatly appreciated by your friends." - James S. Pitkin |
#2
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12V refrigeration
Skip,
Some basics: First divide marine refrigeration into two classes, engine driven and electric. Engine driven systems on sailboats are always holding plate systems. The compressor can process a lot of BTUs in a short time while the engine is also charging batteries or propelling the boat which makes them very efficient. They are great if you are on board most of the time and the alternator is your primary battery recharging system. You can freeze the plates as you charge and/or motor. The down side is that you can't leave the boat for more than a couple of days to explore an island and box temps tend to oscillate. Electrically powered systems have one primary advantage: with good controls, shore power, a lot of solar panels or a wind generator and lots of wind they can be made to operate unattended. This can be a distinct advantage if you are off the boat for more than a day or two. They can be further divided into AC and DC systems. AC systems are usually a motor driving either an automotive or small commercial compressor either directly or through a belt. They are closely akin to engine driven in that they normally use a holding plate and can freeze the plates almost as fast but away from shore power the engine usually must be running to generate the power needed to run the motor which means it has the same limitations plus not being quite as efficient away from shore power due to losses in the alternator, battery charging and inverter. DC systems can be divided further into holding plate and evaporator systems and the compressors into discrete compressor/motor assemblies or hermetically sealed compressors. The discrete compressors are similar to the AC system being linked to the motor either directly or via a belt and usually freezing a holding plate. There is a practical limit to DC of 1 1/2 HP motor so they are not as powerful as AC or engine drives. They also tend to be noisy. Hermetic DC systems usually drive an evaporator and are more closely kin to a domestic refrigerator. Most are based on one of the Danfoss compressors which are gradually getting more efficient. They cycle on and off all the time and will therefore maintain a more constant box temperature and, with solar panels or other alternate charging source can operate constantly while the boat is not in use but they can consume 20% to 40% more energy. Skip Gundlach wrote: I may even have it from somewhere before, but the recent conversations on reefers brought it to mind: Someone on these lists built a direct drive 12V compressor for refrigeration. My recollection has it connected to cold plates. It was designed to do what an engine drive would do, but not run the engine. At the time I saw it, it was new. If they're reading, I'd be interested to see a report on its efficacy. How much power did/does it take to operate? Was the size of the compressor notably less than one on the engine, and if so, what is the relative run time? In the end, are you happy with the outcome? If not, or even so, is there anything you'd have done differently if you were doing it again? Thanks. L8R Skip (and Lydia, by proxy), thinking of how to use the lovely cooling system on the boat without running the engine or the AC air-cooled system, either -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#3
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12V refrigeration
Now, with the basics out of the way, MHO: This is not a good idea. It
looks like the worst of both worlds. 12VDC hermetic compressors are pretty well limited to 1/4 HP or less. That will take a looong time at full power to freeze a decent size holding plate. Several makers of hermetic systems do offer holding plates but strongly discourage their use. Skip Gundlach wrote: I may even have it from somewhere before, but the recent conversations on reefers brought it to mind: Someone on these lists built a direct drive 12V compressor for refrigeration. My recollection has it connected to cold plates. It was designed to do what an engine drive would do, but not run the engine. At the time I saw it, it was new. If they're reading, I'd be interested to see a report on its efficacy. How much power did/does it take to operate? Was the size of the compressor notably less than one on the engine, and if so, what is the relative run time? In the end, are you happy with the outcome? If not, or even so, is there anything you'd have done differently if you were doing it again? Thanks. L8R Skip (and Lydia, by proxy), thinking of how to use the lovely cooling system on the boat without running the engine or the AC air-cooled system, either -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#4
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12V refrigeration
I have a 12V DC belt driven setup. Based upon the size of the
pulley on the motor and compressor, a direct drive system would seem to be rather tricky. My motor and compressor are both 3/4 HP. Draws 50A when running. Doug s/v Callista "Skip Gundlach" wrote in message ... I may even have it from somewhere before, but the recent conversations on reefers brought it to mind: Someone on these lists built a direct drive 12V compressor for refrigeration. My recollection has it connected to cold plates. It was designed to do what an engine drive would do, but not run the engine. At the time I saw it, it was new. If they're reading, I'd be interested to see a report on its efficacy. How much power did/does it take to operate? Was the size of the compressor notably less than one on the engine, and if so, what is the relative run time? In the end, are you happy with the outcome? If not, or even so, is there anything you'd have done differently if you were doing it again? Thanks. L8R Skip (and Lydia, by proxy), thinking of how to use the lovely cooling system on the boat without running the engine or the AC air-cooled system, either -- Morgan 461 #2 SV Flying Pig http://tinyurl.com/384p2 "And then again, when you sit at the helm of your little ship on a clear night, and gaze at the countless stars overhead, and realize that you are quite alone on a great, wide sea, it is apt to occur to you that in the general scheme of things you are merely an insignificant speck on the surface of the ocean; and are not nearly so important or as self-sufficient as you thought you were. Which is an exceedingly wholesome thought, and one that may effect a permanent change in your deportment that will be greatly appreciated by your friends." - James S. Pitkin |
#5
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12V refrigeration
The new Glacier Bay system uses a hermetic Danfoss (pretty sure
it is a Danfoss) compressor with cold plates. From what I can gather it works very well. Can even power a 6000BTU air conditioner as well. Doug s/v Callista "Glenn Ashmore" wrote in message news:mV%Ec.54$jp1.21@lakeread04... Now, with the basics out of the way, MHO: This is not a good idea. It looks like the worst of both worlds. 12VDC hermetic compressors are pretty well limited to 1/4 HP or less. That will take a looong time at full power to freeze a decent size holding plate. Several makers of hermetic systems do offer holding plates but strongly discourage their use. Skip Gundlach wrote: I may even have it from somewhere before, but the recent conversations on reefers brought it to mind: Someone on these lists built a direct drive 12V compressor for refrigeration. My recollection has it connected to cold plates. It was designed to do what an engine drive would do, but not run the engine. At the time I saw it, it was new. If they're reading, I'd be interested to see a report on its efficacy. How much power did/does it take to operate? Was the size of the compressor notably less than one on the engine, and if so, what is the relative run time? In the end, are you happy with the outcome? If not, or even so, is there anything you'd have done differently if you were doing it again? Thanks. L8R Skip (and Lydia, by proxy), thinking of how to use the lovely cooling system on the boat without running the engine or the AC air-cooled system, either -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#6
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12V refrigeration
Hi, Doug, and thanks for the bounce.
"Doug Dotson" wrote in message ... I have a 12V DC belt driven setup. Based upon the size of the The one I had in mind (I saw pix of the setup, mounted on a breadboard; the shaft went directly to the compressor) was direct, not belt, driven. pulley on the motor and compressor, a direct drive system would seem to be rather tricky. My motor and compressor are both 3/4 HP. Draws 50A when running. 50A is a *BIG* load. How long does it run per cycle, and per day, typically? And, does that include the water pump, or is that an additional load? Another alternative I've seen, though it's a bit of an around-the-barn approach unless one is hooked up to shore power (recall from other discussions I really don't want to be running engines, whether propulsion or generator if I don't have to, and this would require an inverter). That's a washing machine or other similarly cheaply acquired motor with appropriately geared pulley driving the engine-driven compressor which has been set up with two/double pulleys and a means of quick-change on attitude so as to relieve the engine belt and engage the AC belt. You get the same output as with the engine but without running it. Ideal, perhaps for marina dwellers, but perhaps a bit of a kludge for everyday cruisers on the hook for days at a time, but not really long term. That, of course plus the accumulated draw with the inverter and pumps might be in the same ballpark as yours... L8R Skip -- Morgan 461 #2 SV Flying Pig http://tinyurl.com/384p2 "And then again, when you sit at the helm of your little ship on a clear night, and gaze at the countless stars overhead, and realize that you are quite alone on a great, wide sea, it is apt to occur to you that in the general scheme of things you are merely an insignificant speck on the surface of the ocean; and are not nearly so important or as self-sufficient as you thought you were. Which is an exceedingly wholesome thought, and one that may effect a permanent change in your deportment that will be greatly appreciated by your friends." - James S. Pitkin |
#7
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12V refrigeration
I have to hand it to Kevin. He can squeeze out more heat with less amps
than anybody else in the business but the bleeding edge comes at a price. That GB compressor does look sort of like a BD50 but I just can't imagine Kevin lowering himself to that. :-) Actually the compressor has some subtle physical differences that make some big differences in efficiency and he has licenced the production to one of the biggies like Tecumseh or somebody. The other main difference is the recovery system that sucks the last bit of heat out of the refirgerant. The numbers look impressive but so does the price. Doug Dotson wrote: The new Glacier Bay system uses a hermetic Danfoss (pretty sure it is a Danfoss) compressor with cold plates. From what I can gather it works very well. Can even power a 6000BTU air conditioner as well. Doug s/v Callista "Glenn Ashmore" wrote in message news:mV%Ec.54$jp1.21@lakeread04... Now, with the basics out of the way, MHO: This is not a good idea. It looks like the worst of both worlds. 12VDC hermetic compressors are pretty well limited to 1/4 HP or less. That will take a looong time at full power to freeze a decent size holding plate. Several makers of hermetic systems do offer holding plates but strongly discourage their use. Skip Gundlach wrote: I may even have it from somewhere before, but the recent conversations on reefers brought it to mind: Someone on these lists built a direct drive 12V compressor for refrigeration. My recollection has it connected to cold plates. It was designed to do what an engine drive would do, but not run the engine. At the time I saw it, it was new. If they're reading, I'd be interested to see a report on its efficacy. How much power did/does it take to operate? Was the size of the compressor notably less than one on the engine, and if so, what is the relative run time? In the end, are you happy with the outcome? If not, or even so, is there anything you'd have done differently if you were doing it again? Thanks. L8R Skip (and Lydia, by proxy), thinking of how to use the lovely cooling system on the boat without running the engine or the AC air-cooled system, either -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#8
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12V refrigeration
It surely is expensive.
"Glenn Ashmore" wrote in message news:vo3Fc.249$jp1.15@lakeread04... I have to hand it to Kevin. He can squeeze out more heat with less amps than anybody else in the business but the bleeding edge comes at a price. That GB compressor does look sort of like a BD50 but I just can't imagine Kevin lowering himself to that. :-) Actually the compressor has some subtle physical differences that make some big differences in efficiency and he has licenced the production to one of the biggies like Tecumseh or somebody. The other main difference is the recovery system that sucks the last bit of heat out of the refirgerant. The numbers look impressive but so does the price. Doug Dotson wrote: The new Glacier Bay system uses a hermetic Danfoss (pretty sure it is a Danfoss) compressor with cold plates. From what I can gather it works very well. Can even power a 6000BTU air conditioner as well. Doug s/v Callista "Glenn Ashmore" wrote in message news:mV%Ec.54$jp1.21@lakeread04... Now, with the basics out of the way, MHO: This is not a good idea. It looks like the worst of both worlds. 12VDC hermetic compressors are pretty well limited to 1/4 HP or less. That will take a looong time at full power to freeze a decent size holding plate. Several makers of hermetic systems do offer holding plates but strongly discourage their use. Skip Gundlach wrote: I may even have it from somewhere before, but the recent conversations on reefers brought it to mind: Someone on these lists built a direct drive 12V compressor for refrigeration. My recollection has it connected to cold plates. It was designed to do what an engine drive would do, but not run the engine. At the time I saw it, it was new. If they're reading, I'd be interested to see a report on its efficacy. How much power did/does it take to operate? Was the size of the compressor notably less than one on the engine, and if so, what is the relative run time? In the end, are you happy with the outcome? If not, or even so, is there anything you'd have done differently if you were doing it again? Thanks. L8R Skip (and Lydia, by proxy), thinking of how to use the lovely cooling system on the boat without running the engine or the AC air-cooled system, either -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#9
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12V refrigeration
Skip,
Comments below. Doug s/v Callista "Skip Gundlach" wrote in message ... Hi, Doug, and thanks for the bounce. "Doug Dotson" wrote in message ... I have a 12V DC belt driven setup. Based upon the size of the The one I had in mind (I saw pix of the setup, mounted on a breadboard; the shaft went directly to the compressor) was direct, not belt, driven. I understand that. It is just that a 1:1 coupling would seem not to be able to drive the compressor at it's most efficent speed. That is just my gut feeling based upon my experience which is not extensive by any stretch. I believe my motor runs at 1800 RPM. The pully on the motor is maybe 3 inches in diameter and the one on the compressor is perhaps 10 inches. It requires alot of torque to spin a 3/4 HP compressor under full load. pulley on the motor and compressor, a direct drive system would seem to be rather tricky. My motor and compressor are both 3/4 HP. Draws 50A when running. 50A is a *BIG* load. How long does it run per cycle, and per day, typically? And, does that include the water pump, or is that an additional load? When on ships power I run it twice per day. Once in the morning and once in the afternoon. It generally runs about 40-45 minutes to freeze the plates. This is the most efficient mode. When plugged into shorepower, I allow it to run automatically with a thermostat controlling everything. It runs longer in terms of total running time since the first 5 minutes or so of running time doesn;t actually cool much. It generally kicks in every couple of hours for 15 minutes or so. This is supportting a 9 cu-ft freezer box and a 12 cu-ft fridge box in a spillover arrangement. The water pump draws a whopping half an amp I think. Another alternative I've seen, though it's a bit of an around-the-barn approach unless one is hooked up to shore power (recall from other discussions I really don't want to be running engines, whether propulsion or generator if I don't have to, and this would require an inverter). That's a washing machine or other similarly cheaply acquired motor with appropriately geared pulley driving the engine-driven compressor which has been set up with two/double pulleys and a means of quick-change on attitude so as to relieve the engine belt and engage the AC belt. You get the same output as with the engine but without running it. Ideal, perhaps for marina dwellers, but perhaps a bit of a kludge for everyday cruisers on the hook for days at a time, but not really long term. That, of course plus the accumulated draw with the inverter and pumps might be in the same ballpark as yours... That will work. Probably better to buy a small fridge at Home Depot if one is in a marina most of the time. L8R Skip -- Morgan 461 #2 SV Flying Pig http://tinyurl.com/384p2 "And then again, when you sit at the helm of your little ship on a clear night, and gaze at the countless stars overhead, and realize that you are quite alone on a great, wide sea, it is apt to occur to you that in the general scheme of things you are merely an insignificant speck on the surface of the ocean; and are not nearly so important or as self-sufficient as you thought you were. Which is an exceedingly wholesome thought, and one that may effect a permanent change in your deportment that will be greatly appreciated by your friends." - James S. Pitkin |
#10
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12V refrigeration
Skip:
Theoretical considerations aside, my advice would be to insulate your box to the hilt and then install one of the many DC driven Danfoss compressor systems with a direct evaporator coil, ie no holding plate. Alder Barbour and others make them. David |
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