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Post by saxofon on Aug 8, 2016 5:50:19 GMT
Agree... you need to be a real viking to appreciate these temperatures... But somehow we seem have to left off the original thread context...
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Post by sailbleu on Aug 8, 2016 6:49:56 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. As I feel responsable for the off topic deviation I'll set the example. I have done the same years ago David , bypassed the old thermostat , added a digital temp. controller and also installed 2 relais ( plus & minus) which are commanded by the panel switch. I also disabled the old wiring from my panel to the compressor because of the voltage drop due to relatively long and thin leads from panel to compressor. That resulted in compressor shut down even at 11,5 volts on the meter when the macerator of my electrical toilet drew the required 20 amps . The drop to let's say 10.5 volts for a few seconds was enough for the danfoss compressor to go in safety mode ( save battery from getting sulfatized ) , and In my case there is no automatic reset when the voltage rises above the 10,5 volts again. Now I have thick leads straight from the battery ( fused of course) to the compressor , the relais are activated by the original circuitbreaker on the panel and old wiring , and the make contact in the digital controller does the on/off for the compressor depending the temp setting of the digital controller. Considering the way these fridges are built in there are no options for easy additional insulation I would think. We had this topic before , and will give you the same answer / suggestion , add another solarpanel to compensate the loss of cold due to poor insulation , less work and worries than breaking down the furniture . Regards
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oasis36i
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Post by oasis36i on Aug 8, 2016 20:28:17 GMT
I have now installed the digital thermostat mentioned in other posts. It is a really neat unit. I chose to wire it into the power supply (as mentioned by David). I cut a hole between the compressor space and the sink cupboard, pulled the wires through, cut them and took power to the thermostat and then from the thermostat back to the compressor. I elected to pull the probe into the fridge through the same hole as the existing thermostat. This is just plugged with putty so was easy to unplug and re plug. Here's the finished job, temporarily stuck under the sink. I will make a small plywood box as a better mounting. I chose to leave the existing thermostat in place and in use. The early results are interesting. With the electronic thermostat set to 5 degrees with a 1 degree delta (turn on at 6 degrees and off at 5 degrees), the fridge achieved 5 degrees easily in the morning and the electronic thermostat was turning on and off. However, by the evening the original evaporator plate thermostat was turning on and off and it was struggling to reach 5 degrees. It does suggest that heat build up means that the fridge is fighting to achieve the temperature demanded (and consuming lots of power). My next test is to set gradually increasing temperatures on the digital thermostat and see what the 24 hour Ah rate is like at different settings. £10 well spent for a bit of control and potential Ah saving.
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oasis36i
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Post by oasis36i on Aug 8, 2016 20:29:05 GMT
The finished job.
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Post by ForGrinsToo on Aug 8, 2016 22:34:39 GMT
Ian, Is that black grill a muffin fan? I have milled-in slots in that panel.
Sailbleu, did you wire this so that the panel enables the relays as well as the digital controller? Did you also set the Danfoss thermostat to max?
Geoff
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oasis36i
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Post by oasis36i on Aug 8, 2016 22:46:16 GMT
Geoff
Assuming you mean the black item bottom right in the last photo, this is the intake to the condenser fan as supplied. It is a basic plastic cowl that fits in a hole through the wooden access panel.
Ian
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Post by ForGrinsToo on Aug 9, 2016 0:34:18 GMT
Yes, I have milled-in sots in that panel. Your cowl would seem almost ready-made for a muffin fan to bring cooler air into that compartment.
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oasis36i
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Post by oasis36i on Aug 9, 2016 8:29:07 GMT
The cowl is for a fan that already draws air into the compartment over the condenser. The problem with the design is that the compartment simply gets warm as there is no simple exhaust route for the hot air.
I had a good rummage around last night and think my plan of fitting a fan and exhaust hose running vertically up to the space next to the cupboard is what I will try. All other routes have problems. The saloon seating is full of hot water tank. The other way is the oven.
An extra fan would draw a tiny current but would potentially save a few degrees.
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Post by sailbleu on Aug 9, 2016 9:06:12 GMT
If I understand correctly you have used the relai contact inside the controller to replace the old thermostat . Right ? Where did you put the sensor , I might of missed that part in one of your previous posts. Mine is completely underneath , near the bottom of the fridge . If I would do it again I would not position it there again.
Regards
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Post by vasko on Aug 9, 2016 14:04:14 GMT
I have now installed the digital thermostat mentioned in other posts. It is a really neat unit. I chose to wire it into the power supply (as mentioned by David). I cut a hole between the compressor space and the sink cupboard, pulled the wires through, cut them and took power to the thermostat and then from the thermostat back to the compressor. I elected to pull the probe into the fridge through the same hole as the existing thermostat. This is just plugged with putty so was easy to unplug and re plug. Here's the finished job, temporarily stuck under the sink. I will make a small plywood box as a better mounting. I chose to leave the existing thermostat in place and in use. The early results are interesting. With the electronic thermostat set to 5 degrees with a 1 degree delta (turn on at 6 degrees and off at 5 degrees), the fridge achieved 5 degrees easily in the morning and the electronic thermostat was turning on and off. However, by the evening the original evaporator plate thermostat was turning on and off and it was struggling to reach 5 degrees. It does suggest that heat build up means that the fridge is fighting to achieve the temperature demanded (and consuming lots of power). My next test is to set gradually increasing temperatures on the digital thermostat and see what the 24 hour Ah rate is like at different settings. £10 well spent for a bit of control and potential Ah saving. The best settings are : 5 degree OFF - 7 degree ON - this what is suggested by the pro fridge engineers and I use it and I'm very happy - btw - I would expect the gauge to be somewhere near to the top of the fridge about 5-10 cm lower then the top - at least this is the place where I found it works best... and I have ice cubes for the whisky and in the same time nothing is frozen from the food...
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oasis36i
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Post by oasis36i on Aug 9, 2016 16:28:02 GMT
I actually wired the new thermostat I to the power circuit. My hand drawn diagram is below. I cut the red and black main power to the Danfoss and took these to the new thermostat and then back to the Danfoss.
The original mechanical thermostat is still in place and in use. For now, I have just turned it to maximum cold so, in effect, it is permanently on. In due course I will just unplug it and put a jumper wire where it used to be.
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oasis36i
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Post by oasis36i on Aug 9, 2016 16:28:30 GMT
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Post by oasis36i on Aug 9, 2016 16:32:55 GMT
Ps I put the sensor probe just under the wire tray attached to the shelf so that it is out of the way and measuring roughly half way down the fridge.
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oasis36i
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Post by oasis36i on Aug 10, 2016 22:41:47 GMT
The final results. It is worth remembering my original aim. As delivered I had 2 x 70 Ah house with a fridge consuming about 60 Ah per day. I always start on shore power but wanted to be able to have long weekends off grid.
I now have 2 x 135 Ah after moving the engine start battery (see separate post). I also have a fridge consuming around 40 Ah per day so have achieved my long weekend aim.
The task with the fridge was to achieve the temperature I want as efficiently as possible - turning the compressor on and off to maintain this temperature. The original thermostat ran the fridge slightly too cold even on the warmest setting and seemed to be switching on and off very frequently. The thermostat on the evaporator plate simply did not seem well matched to the rate of heat transfer.
The digital thermostat shows me that it takes about 7 mins to cool from 7 deg to 6 deg drawing 5 amps, and about 20 to 30 mins (depending on ambient temp) to warm up from 6 deg to 7 deg. So the duty cycle is improved whilst giving more accurate control.
I made on extra change - removed the resistor in the original thermostat circuit. The Danfoss BD35 is well documented on the inter web. One feature is the placing of a resistor in this circuit. The resistor as delivered 690 ohms caused the Danfoss to run at 3000 rpm. Removing this causes the Danfoss to run at 2000 rpm. This reduces the rate of cooling, but in doing so reduces the rate of heat build up and allows the compressor to be more efficient. There are smart controllers out there that can automatically vary the speed. I think I am happy just to run at 2000 rpm as the digital thermostat showed me that it only took 9 mins to cool from 7 deg to 6 deg drawing 3.5 amps. A longer run time, but a net gain in amps. After a few hours, this gave a slight further efficiency of about 10%.
So the total cost was the old plywood for the battery box, the longer leads for the engine battery, the £10 thermostat and zero cost for removing a resistor.
I will still look into improving the air flow to the condenser, but that is for another day. I think this may be more difficult than I thought as the best efficiency would be to draw air from outside the boat.
Ian Oasis36i
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Post by vasko on Aug 11, 2016 8:19:46 GMT
FYI: Kitchen towel on top of the fridge opening help's also in the warm med also ...
in my case my compressor is quite old ( still working like a sharm) - 1990 and the saving that I got was about 30%-50% from switching to electronic control 5 to 7 degree
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Post by sailbleu on Aug 14, 2016 20:45:09 GMT
Ian, Is that black grill a muffin fan? I have milled-in slots in that panel. Sailbleu, did you wire this so that the panel enables the relays as well as the digital controller? Did you also set the Danfoss thermostat to max? Geoff Yes on both accounts. The panel switch enables the relays aswell as the controller. The make- contact inside the controller works like , or replaces , the old thermostat. Only one setback for placing the sensor on the bottom of the fridge , if or whenever you put some frozen ( or very cold) stuff down there the sensor is being misguided and the fridge will stop cooling untill that frozen stuff is not frozen anymore. Higher up in the fridge things will be alot warmer as a result. Regards
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Post by so32foot on Sept 13, 2017 9:36:06 GMT
I want to install a digital temperature control on my SO 32 too. The link here above is not available anymore, so could you please let me know the type you bought? I found few options but these controllers are using 3 Watt, I assume 24 hours continuously, which is quite a bit if I'm sailing 5 - 7 days in the Sweden, without entering harbours and little motor usage.
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Post by vasko on Sept 13, 2017 9:55:17 GMT
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Post by so32foot on Sept 13, 2017 11:19:50 GMT
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Post by so32foot on Nov 6, 2017 18:28:49 GMT
Vasko, I bought the same controller through Alexpress and it's supplied in the meantime and I can start to install it. Where in the fridge did you install teh sensor?
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Post by vasko on Nov 6, 2017 20:00:25 GMT
Vasko, I bought the same controller through Alexpress and it's supplied in the meantime and I can start to install it. Where in the fridge did you install teh sensor? In my case the sensor is on the wall on the closest side of the camera(coolong element/ice box) - the wall have a channel with rubber band and I stick the gauge in the rubber band and used the rubber band to hide the cable behind it/on the side of it. The whole thing just simulate the default sensor of the original fridge - e.g I used the cables of the old sensor and did not put new cables. The settings that I found to work best is 5-7 degreece celsius - start at 7 stop at 5
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Post by so32foot on Nov 7, 2017 11:03:35 GMT
Vasko, I bought the same controller through Alexpress and it's supplied in the meantime and I can start to install it. Where in the fridge did you install teh sensor? In my case the sensor is on the wall on the closest side of the camera(coolong element/ice box) - the wall have a channel with rubber band and I stick the gauge in the rubber band and used the rubber band to hide the cable behind it/on the side of it. The whole thing just simulate the default sensor of the original fridge - e.g I used the cables of the old sensor and did not put new cables. The settings that I found to work best is 5-7 degreece celsius - start at 7 stop at 5 Many thanx, Vasko. I assume that you refer to a picture, however it's not clear to me which picture. Anyhow, in a SO 32 the fridge might be different. In the SO 32 the cooling element is installed on the left side in the top of the fridge. My plan is to install the sensor not straight under the element, but more to the right side: under the element at the bottom the temperature is mostly few degrees lower than at other places. that's a good place for meat. But other stuff I like to keep at the 5 - 7 degrees C. So I want the adjust the controller at this temperature, as you mentioned, and put the sensor just above the stuff I want to have at that temperature. Or is it better to have the sensor at the top of the fridge same as Jeanneau has done with the original controller?
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Post by MalcolmP on Nov 7, 2017 15:35:27 GMT
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Post by so32foot on Nov 7, 2017 16:45:30 GMT
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Post by so36idavid on Nov 8, 2017 6:34:29 GMT
I've found that I need different temperature setpoints depending on how full the fridge is. At the beginning of a trip if it's too cold then the stuff nearest the cooling plate is going to freeze if I set it too cold. The bottom of the fridge is warmer than the top because it takes a long time to get the energy out of there. As the fridge empties there's more airflow inside the fridge and the setpoint needs to come down a degree or two because the temperature is more uniform. Bottom line is that it doesn't really matter where you put the thermostat as long as you adjust the setpoint accordingly. You're going to have to play with it to learn what keeps the milk from going bad while not freezing the lettuce .
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