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Post by so36idavid on Apr 21, 2015 5:46:18 GMT
I've been working through becoming more efficient in the way my boat uses and produces electricity. The elephant in the room is the fridge's electricity consumption. Our climate is not terribly hot yet my fridge still uses 60-80 Ah/day which is by far the greatest power consumer. Based on what I can see, the design and installation of the fridge is less than stellar. The compressor is under the edge of the fridge, in a very poorly vented compartment that opens into a cabinet. i.e. the heat from the compressor is basically channeled up to the bottom of the fridge. What's more, the fridge itself doesn't appear to be much more than a thin, polyethylene shell. I don't see anything that suggests quality insulation.
So the obvious solutions are to add insulation to the fridge and improve ventilation to the compressor. I have a good idea how to do the latter but getting access to the fridge seems very problematic. The only path that I see would be to cut an access panel in the plywood panel that covers the front of the fridge, and possibly another in the panel that separates the fridge from the stove in order to get access to the outer face of the fridge. This seems highly intrusive and could possibly compromise the structural integrity of the galley itself. The fridge and stove can add up to considerable weight and I don't particularly want to open those panels up if I don't have to.
Has anyone done any work on a 36i in this direction? If I could squeeze some quality cryogel or vacuum panels in there I think I could make a big dent in the amount of work the compressor has to do. I suppose I could blast in some spray insulation and hope for the best but I'd rather do it right.
Thx David
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Post by vasko on Apr 21, 2015 7:39:01 GMT
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Post by rene460 on Apr 21, 2015 11:26:13 GMT
Hi David,
Don't have a 36i and my 30i seems to have a useful degree of insulation, so that fridge power consumption is around 30 - 35 amp hours per day, admittedly it is probably a smaller fridge. Similar access problems to what you describe discourage me from trying to add more insulation. If there was none, I would definitely be making the effort to add some.
My previous boat used an Indel portable fridge which was obviously intended for installation in a truck with now power limits, as it had no insulation and ran almost continually. I installed it in a box big enough to allow 50 mm styrofoam layer under the fridge and 40 - 50 around the sides which were tapered. My wife made a quilted cover for the lid and power consumption came down to what could be supplied with a 55 watt panel in reasonable weather, though we lost ground on cloudy days. Insulation is definitely the place to start.
I used styrofoam, though polyurethane is better from the fire risk point of view. I filled the gaps at the corners with expanding foam from a can which, from memory, tended to stick like glue, so tended to seal it up. In that case I started with a polythene sheet to prevent the foam sticking to the fridge in case it ever needed service. I had occassion to remove it after some years and there was no evidence of water condensation, so my vapour sealing was adequate. Do not use the porous foam rubber which belongs in cushions and draught seals.
Do you have enough access to push strips of polyurethane foam up from underneath? Perhaps with beads of expanding foam used like brickies mortar and to glue them onto the plastic casing? Main issue is to fill gaps and make a complete vapour seal to prevent water condensation on the outside of the plastic. But always make sure there is room for the foam to expand, because it will regardless. Up to 100 mm is useful though this may only be practical for the bottom. Finally, ideally stick Al foil on the outside of your outer layer to reflect back radiant heat from the surrounding woodwork.
But also definitely worth working on the airflow to the compressor and condenser. Computer fans selected for low noise and air flow at suitable vents will easily justify their low power consumption. Exhaust the air to the cabin and let air from the bilges, cooled by the sea, replace the vented air. Everything that is in the right direction will help. Definitely worth trying.
rene460
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Post by mikebz on Apr 21, 2015 20:30:18 GMT
So the obvious solutions are to add insulation to the fridge and improve ventilation to the compressor. I have a good idea how to do the latter but getting access to the fridge seems very problematic. The only path that I see would be to cut an access panel in the plywood panel that covers the front of the fridge, and possibly another in the panel that separates the fridge from the stove in order to get access to the outer face of the fridge. I've been pondering the same issue with our SO32. I'd like to insulate the fridge box with Celotex but short of cutting a hole in the panel in front of the fridge I'm stumped. I suppose with sufficient skills a large rectangle could be cut out and the replaced with some beading or trim covering the join. Not a job I could do without it looking a complete dog's dinner.
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Post by Tafika II on Apr 22, 2015 19:10:36 GMT
This is one of my next projects. I'm adding a 12VDC computer fan at the condenser compartment to help exit the heat. Not sure what I'm going to do about the insulation yet, but I'll be following this thread and post my progress when I get finished.
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Post by dbostrom on Apr 26, 2015 17:15:45 GMT
It's probably something you've already nailed, but our boat was missing the fridge drain plug when we bought it, meaning that cold air was continuously draining out of the bottom and as well the fridge had an icing problem. A $0.30 cork saves many AH/day and ended the icing problem.
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Post by ForGrinsToo on Apr 27, 2015 18:08:20 GMT
This is one of my next projects. I'm adding a 12VDC computer fan at the condenser compartment to help exit the heat. Not sure what I'm going to do about the insulation yet, but I'll be following this thread and post my progress when I get finished. I'll be especially interested to see if you find a good location for the fan. Should I assume you would wire it across the compressor motor terminals? We have found that it is quite helpful to keep the under-sink door open to improve compressor cooling. It is kind of amazing that the cabinets trap heat close to the thing you're trying to cool. Geoff
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debenboy
Full Member
Posts: 46
Country: UK
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Post by debenboy on Apr 27, 2015 20:44:37 GMT
As you say the fridge is the real problem when it comes to reducing power cinsumption. All the LEDs in the world only scratch the surface of reducing daily consumption compared to the fridge. There are a number of problems: Fridge too big
Possibly poorly insulated
Compressor in less than ideal position with integral inefficiencies as well as possibly contributing to fridge warming.
For a couple of years I reduced the effective volume of the fridge by installing rolls of bubble wrap in the bottom and sides, although I remain unconvinced by the efficacy of this. I also,installed a 69 W solar panel which has been a great success.
I also,pondered installing a keel cooled unit similar to one I had on my old Sunshine 38.
However eventually I decided that the cheapest way forward was to increase the battery capacity substantially, achieved by moving the engine start battery to the "hole" in the shed beyond the shower, and installing 2x125Ah in the compartment under the starboard double berth.
Last summer that seemed to work fine, although I do turn up the fridge cooling when motoring, and turn it off over night( more to,avoid the compressor noise than to save amps)!
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Post by so36idavid on Apr 28, 2015 1:05:21 GMT
Debenboy,
Where did you mount the solar panel and how many Ah/day do you get out of it? I guess it would help to know roughly where in the world you're sailing too. There's a post in the hints and tips section in which a guy put a solar panel on the cabin top under the boom, forward of the dodger, which seems ok. Alternately I was thinking of putting a couple of smaller panels on the top of the dodger.
Generally I think it's better to save Ah than to add more capacity or generation power. But as you say a little bit of each is a decent compromise.
Thx David
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debenboy
Full Member
Posts: 46
Country: UK
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Post by debenboy on Apr 28, 2015 6:19:55 GMT
Hi David, Until last year I was based on the Deben, but now at Brixham. Not Wanting to reinvent the wheel I followed the lead of our cousin with his SO36i and installed a Sunware on the hatch garage.
Debenboy
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Post by rene460 on Apr 28, 2015 11:25:24 GMT
Hi debenboy,
The load on the fridge consists of heat in leak through the insulation plus the heat necessary to cool fresh stores added. Heat in leak is determined by the thickness and quality of the insulation and the external surface area. Your bubble wrap idea will only help to the extent that it is well enough placed against the walls of the fridge that it increases the effective insulation. Air gaps around the bubble wrap mould minimise its effect. Reducing the internal volume does not alone reduce the power demand. A larger fridge has a larger external surface area, hence more heat inflow. It can always in principal be compensated by extra thickness, but in practice sufficient extra is rarely provided. I would just enjoy the extra volume and fill it with your choice, all cooled down while the mains power is connected.
I must update my earlier figures on the consumption of the fridge in my SO30i as I now have more data. The more repeatable figures are around 60 amp hours/day with a temperature of 26 to 27C in the condenser compartment. (There was a calibration problem in my earlier records which I have now adjusted. But it is still a rough estimate. I may have to have a closer look at the insulation. We are having a cool end to Autumn, so there will be no more interesting readings 'til winter is over, when I will try and get some data on the solar panel.
rene460
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Post by zofiasailing on Apr 29, 2015 10:55:06 GMT
Rene460 We have done the same as Vasko. A digital thermostat with led display. Has helped optimise fridge temp Vs amp usage. A tiny cost for big improvement and we haven't even done anything about extra insulation etc. yet. Zofiasailing
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Post by Trevor on Apr 29, 2015 11:20:36 GMT
Hello gents,
The fridge on my SO42DS already has a thermostat at the back of the fridge so I can set the temperature within reason to whatever I like. I understand that it doesn't have a digital readout but I guess I could put a digital thermometer in the fridge to set the temperature. Apart from being able to set the temperature very accurately, what is the advantage of the digital thermostat? Doesn't the fridge have exactly the same thermal characteristics after the new thermostat is installed as it had before?
I like the idea of the digital thermostat but cannot see how it could make the fridge more efficient.
Regards,
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oasis36i
Full Member
SO 36i Oasis
Posts: 39
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Post by oasis36i on Aug 1, 2016 6:56:38 GMT
I am now going to tackle reducing the fridge consumption. Even at its warmest setting, the fridge runs very cold and more accuracy sounds a good plan. Could anyone who has installed a more accurate and controllable (digital) thermostat give a few more details? I have pasted below an image of the connections to the Danfoss unit on my SO36i. I believe brown and blue are the thermostat connections according to a downloaded Danfoss guide with a resistor that sets the motor speed. Does a new thermostat simply connect to these connections in place of the existing thermostat?
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Post by vasko on Aug 1, 2016 7:20:24 GMT
I am now going to tackle reducing the fridge consumption. Even at its warmest setting, the fridge runs very cold and more accuracy sounds a good plan. Could anyone who has installed a more accurate and controllable (digital) thermostat give a few more details? I have pasted below an image of the connections to the Danfoss unit on my SO36i. I believe brown and blue are the thermostat connections according to a downloaded Danfoss guide with a resistor that sets the motor speed. Does a new thermostat simply connect to these connections in place of the existing thermostat? my installation of the new electronic control does exactly that - install the new gauge using the already existing cables from the old thermostat connection to inside the fridge, connect 12v to the electronic unit from the fridge fuse, and connect the output for fridge from the unit to the old place where the thermostat has been attached....
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oasis36i
Full Member
SO 36i Oasis
Posts: 39
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Post by oasis36i on Aug 1, 2016 8:10:16 GMT
Vasko - thanks for the super quick reply. All - another point made earlier in this thread relates to needless heat build up in the compressor compartment. It strikes me that better ventilation here could make a real difference. Has anyone implemented any solutions? My current thinking is to make a basic extraction "hood" over the compressor and take a length of ducting upwards. A low power, quiet fan could provide the extraction. I have identified the cupboard above the fridge as a useful place to output the air. This has ventilation grilles above it and is generally leaky. The duct would run in the small space to the left of the cupboard (image below). Any thoughts? Ian
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Post by so36idavid on Aug 3, 2016 20:05:43 GMT
Ian,
On the advice of a fridge mechanic I put a jumper across the thermostat and then wired the digital thermostat into the 12v circuit. I don't know why that is "better" than hard wiring in 12v and then putting the digital thermostat inline, but I did it and it seems to work quite well.
I'm working on a heat extraction solution myself. I bought an inexpensive 3" muffin fan and duct from McMaster Carr. The fan is wired into the same 12v circuit that is turning the fridge on, and it only draws 50 mA.
My original plan was to vent the duct to the salon outboard of the settee. But I'm concerned about noise. I have temporarily routed it into the HVAC duct that opens out in the compartment next to the bilge pump. This is a trivial mod that requires no new holes. I think it will work well but I haven't had a chance to test it.
Let me know if you have a better idea, I'd love to hear it!
David
P.S. I've taken a close look and I'm pretty sure that there's no hope of improving the insulation on the fridge. Maybe you could squeeze some in around the compressor but there's no way to properly insulate that fridge, short of major carpentry on the galley.
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oasis36i
Full Member
SO 36i Oasis
Posts: 39
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Post by oasis36i on Aug 3, 2016 22:20:52 GMT
David, thanks for the advice on the wiring. I hadn't thought of wiring it that way, but I can hazard a guess at why. The existing thermostat is a simple mechanical switch and the Danfoss controller is expecting either an on or off (with a resistor in the circuit). If the new thermostat behaves differently (such as having any internal resistance) it might change the operation of the compressor. I doubt it makes any real difference.
I suspect you are ahead of me in planning the ventilation, but my thinking is: - run any vent hose as vertically as possible to assist flow - avoid cutting any very visible bits of wood
The small gap just to the left of cupboard over the fridge caught my eye as being a suitable place to run a hose vertically from near the compressor below. I would then cut some holes into the cupboard so that the air is vented into the cupboard (which has air vents at the top and a gap at the back and so would vent freely to the saloon). It would ventilate my plates too.
I though of venting into the space under the saloon berth, but this is a warm space itself (calorifier) and not particularly leaky.
Let me know if you make any progress. My thermostat arrived today and I plan to do this first at the end of the month.
Ian
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Post by saxofon on Aug 5, 2016 18:12:19 GMT
Here is my attempts in same area. The original compressor did draw way too much. Tried to vent a bit more around it: That helped a bit but a bit later the electronic failed. With the "while I'm anyway at it..." attitude I upgraded the box from a small evaporator to much larger, covering three sides of the wall, got a new compressor cooled via the pentry sink outlet (special thruhull as can be seen below) and finally down to very little energy consumption. It runs for like 4-5 min two to three times an hour at 5.5A. Next is to lower it to very little... so will probably add a electronic regulator as made by people in this thread. Probably also adding a vertical tube inside the box with openings at the bottom, a small fan inside and outlet at top so that the air is circulated inside the box for better temp all in all.
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Post by sailbleu on Aug 6, 2016 7:15:28 GMT
What does the manufacturer of that pentry sink outlet claim about the clogging of that thru-hull ? I would think it takes one season to be completely encapsuled no ? As I often clean my thru-hulls with a toothbrush ( copper hairs type) to get the barnacles out , this outlet will be even harder to keep clean. Would love to read your review on it next year.
Regards
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Post by saxofon on Aug 6, 2016 7:38:38 GMT
Sailbleu, I actually did the montage for the 2012 season (the holes for the old compressor was the season before...) and it have worked splendid so far. I sail around in the Stockholm archipelago so I'm a bit lucky the barnacles aren't so aggressive here. Never had any problems with such and not any problem with whatever stuff we throw in the pentry to stick around in the thruhull. The backdraw is that the thruhull needs to be constant open (since I have the fridge constant on) for optimal result. The small movements the boat makes is enough to recircle the water for better cooling. (in the extent, the more I cool the fridge the more I heat up my big swimming pool ;-) )
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Post by sailbleu on Aug 7, 2016 6:30:28 GMT
Well Saxofon , my swimming pool doesn't need heating up any further , 32°C in the Greek Ionian waters. The heat and humidity is killing us , I run my genset and AC wherever and whenever I can , provided I don't disturb others with the noise that is. Currently on the quay at the island Zakinthos , which in our view is a dissaster with the ferries' swell in here. No water , no electric , and at the highest rate sofar here in Greece. 20 € to get swept on and off due to the ferries every 20 minutes or so. Sheer rip off .
Sorry for the off topic.
Regards
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Post by vasko on Aug 7, 2016 11:07:28 GMT
Well Saxofon , my swimming pool doesn't need heating up any further , 32°C in the Greek Ionian waters. The heat and humidity is killing us , I run my genset and AC wherever and whenever I can , provided I don't disturb others with the noise that is. Currently on the quay at the island Zakinthos , which in our view is a dissaster with the ferries' swell in here. No water , no electric , and at the highest rate sofar here in Greece. 20 € to get swept on and off due to the ferries every 20 minutes or so. Sheer rip off . Sorry for the off topic. Regards Zakinthos : Know-How main town : if you ever go there - refuse going to the paid part ( right of the entrance) go instead opposite to entrance and the paid side - moor side-to with fenders and plank - close to the water and electricity box - when asking do you need water or electricity - replay firm NO and state that you will go and visit the port police yourself and sort the documents e.g. you do not need any help! after that never go to the port police - if they want they will come about and visit you ! and after sunset use water and electricity how much you want - no one will stop you best place to go on Zakinthos: ship wreck beach: during the day and anchor overnight at Vroma bay ( about 10 minutes south) - very deep and very safe bay - achor in about 15-20m and take 2 lines ashore bay on the south-west side - opposite the protected area - there is a small marina for local boats - anchor off the marina where depth suits you - interesting island to visit there blue -caves : little bit over estimated according to my opinion - anchor overnight at Ag Nikolaos but is swell from the sea - anchor behind the small island instead going to the quay as the key gets all the swell AND DO NOT BE LIKE EVERY USUAL LAZY BASTARD - and go and visit on Kefalonia west side : Argostolli - nice huge harbour with space for everyone for free and you can actually see the Kareta-Kareta turtles, Luxory and DEFINITELY Assos - Assos can be little bit choppy if there is swell from the north BUT YOU WILL LOVE THE PLACE ! - I'm always amazed how everyone is scared from the west part of Kefalonia - but the west part is the best one ! and also do not forget about the hidden jam - Palairos opposite Nidri main land and also Kioni on Ithaka ....
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Post by hoppy on Aug 8, 2016 3:50:13 GMT
Well Saxofon , my swimming pool doesn't need heating up any further , 32°C in the Greek Ionian waters. The heat and humidity is killing us , I run my genset and AC wherever and whenever I can , provided I don't disturb others with the noise that is. Currently on the quay at the island Zakinthos , which in our view is a dissaster with the ferries' swell in here. No water , no electric , and at the highest rate sofar here in Greece. 20 € to get swept on and off due to the ferries every 20 minutes or so. Sheer rip off . Sorry for the off topic. Regards Better to be in the Aegean in July. The meltemi keeps the heat away. I stayed in the main port on Zakinthos last year, on the pier that sticks out. I got water there. The tap was hidden away and I only found it because someone was using it. Happily don't need water now.
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Post by hoppy on Aug 8, 2016 3:54:37 GMT
(in the extent, the more I cool the fridge the more I heat up my big swimming pool ;-) ) I had a boat in Stockholm for a couple of summers and never once swam in the archipelago, just too d**n cold in the water. In Mälaren I could find suitably warm water 3 or 4 days a year. I sold my boat after two seasons and bought my Jeanneau in Greece
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