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Old 15-06-2019, 08:43   #1
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Isotherm fridge/ BC35 controller setting question

Hello all.
This is my first post here seeking some information while debugging my Isotherm fridge.

In the Danfoss manual of the 1010N0210 controller, it says that the 'by default' setting for batterie protection is 10.4V (no resistor between C-P).

If I look at the chart, the lower the resistance is, the lower the voltage protection is. BUT, it also says 'if running on a wind generator without batteries the resistor should be 220K (9.6V cutoff).
That doesn't seem right to me. 9.6V is the lowest voltage acceptable for cutoff, so, it should be 0 ohms like it says in the chart (a jumper).

Is that chart right?

I just want to lower my protection from 10.4 to 9.6.

Here is the chart:
Thanks.
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Old 15-06-2019, 08:57   #2
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Re: Isotherm fridge/ BC35 controller setting question

Welcome to the forum.

This topic may have useful information.

Do not use the 220 Ohm resistor to change the 12V cutoff voltage from the default of 10.4V to the lowest of 9.6V, because it also eliminates the 17.0V maximum voltage.

Instead use the 0 Ohm R9 resistor (short circuit) to change the cutoff voltage while maintaining the maximum voltage limit.

Remember that the refrigerator will draw about 10% more current at the lower voltage.
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Old 15-06-2019, 09:04   #3
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Re: Isotherm fridge/ BC35 controller setting question

Quote:
Originally Posted by Wave34 View Post
This is my first post here seeking some information while debugging my Isotherm fridge.
What problems other than lower cutoff voltage are being debugged?
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Old 15-06-2019, 09:36   #4
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Re: Isotherm fridge/ BC35 controller setting question

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What problems other than lower cutoff voltage are being debugged?
My original problem was that it was not working on batteries but OK on 120VAC.

I found that the fridge 10A breaker was very resistive. So I replaced it and now it works on 12VDC.
BUT I still have about 1V of drop on the negative wire.
So, when the battery is 12V, the controller sees 11V, that means the cutoff will kick in earlier.

I am working on finding the bad connection for the ground (or pass a new wire), but in the mean time I was thinking that lowering the protection would let the fridge work a longer time before going into protection.

Thanks.
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Old 15-06-2019, 09:46   #5
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Re: Isotherm fridge/ BC35 controller setting question

Thanks for the info.

Location of the problem should be "easy" using a voltmeter.

Poke the sharp voltage meter leads onto the conductor and onto the terminal to locate the voltage drop at each connection to identify the problem.

Continue with your plan to fix the problem regardless.
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Old 15-06-2019, 09:53   #6
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Re: Isotherm fridge/ BC35 controller setting question

Quote:
Originally Posted by wingless View Post
Welcome to the forum.

This topic may have useful information.

Do not use the 220 Ohm resistor to change the 12V cutoff voltage from the default of 10.4V to the lowest of 9.6V, because it also eliminates the 17.0V maximum voltage.

Instead use the 0 Ohm R9 resistor (short circuit) to change the cutoff voltage while maintaining the maximum voltage limit.

Remember that the refrigerator will draw about 10% more current at the lower voltage.


wingless, this is where I am confused.
The chart lists 220K ohms for 9.6V (last line) but also list 0 ohms (jumper) as 9.6V (first line).

EDIT: Ok, the resistor is only a reference for the CPU telling what it should do. In the case of the last line, it selects 9.6V and ALSO removes the over voltage protection, while the 0 ohm or jumper selects the 9.6V BUT keeps the over voltage protection.
I will go with your suggestion and install a jumper for now, until I find the problem with the ground. Thanks.


Also, is the cooling fan supposed to run with the compressor or it kicks in only if the compressor becomes too hot?
While testing, the fridge was at room temperature when I started it, it ran for about 40 minutes then stopped when it reached the thermostat setpoint, but the fan never kicked in.
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Old 15-06-2019, 10:00   #7
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Re: Isotherm fridge/ BC35 controller setting question

Yes, look at that same table on page 5 of the first link in the linked topic, where the table isn't folded in half, it is much clearer. As was stated, use the 0 Ohm, not the 220 Ohm, if the voltage is lowered, so that the upper cutoff remains intact.

The fan should run whenever the thermostat calls for the compressor to run. Does the fan operate properly when connected directly to 12VDC?

A diagnostic LED is a terrific feature for this system. I added one that is visible through the vents from the front of the refrigerator. Remember to add a series resistor so that the current draw complies with the specified 10mA limit.
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Old 15-06-2019, 10:51   #8
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Re: Isotherm fridge/ BC35 controller setting question

CF is a great place for information, but personally, I'd spend my time replacing and/or repairing the known voltage drop instead of typing here about what's the best workaround.


It's like asking for advice on how to build an oil leak capture and scavenging system instead of replacing a seal or gasket to fix the leak.



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Old 15-06-2019, 12:56   #9
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Re: Isotherm fridge/ BC35 controller setting question

Quote:
Originally Posted by wingless View Post
Yes, look at that same table on page 5 of the first link in the linked topic, where the table isn't folded in half, it is much clearer. As was stated, use the 0 Ohm, not the 220 Ohm, if the voltage is lowered, so that the upper cutoff remains intact.

The fan should run whenever the thermostat calls for the compressor to run. Does the fan operate properly when connected directly to 12VDC?

A diagnostic LED is a terrific feature for this system. I added one that is visible through the vents from the front of the refrigerator. Remember to add a series resistor so that the current draw complies with the specified 10mA limit.
Coming back from doing more work.

I jumped the protection to 'C'.

I removed the fan to test it on a battery. I found that a blade was broken at it's base and blocking the rotation against it's casing.
I took my soldering iron and melted or fused the blade back taking care of having the same angle as the others.
Now the fan turns when the compressor starts. No vibration. I even tested the strength of my repair with my finger and it is like a new one, almost.

I put the fridge back in the hole since we are going for a 3-4 day trip next week end. I'm pretty sure it will work well. At the worst, I also have a Dometic cooler/freezer so I'm not 100% depending of the boat fridge.
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Old 15-06-2019, 13:06   #10
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Re: Isotherm fridge/ BC35 controller setting question

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Originally Posted by senormechanico View Post
CF is a great place for information, but personally, I'd spend my time replacing and/or repairing the known voltage drop instead of typing here about what's the best workaround.


It's like asking for advice on how to build an oil leak capture and scavenging system instead of replacing a seal or gasket to fix the leak.



senormechanico, no, I'm not trying to build an oil scavenging device. If you look at the 4th post, this is what I'm saying; 'I'm working on finding the problem'.
I try to find the path of the gnd cable and it's termination.

It is a cabin cruiser, with a whole interior so it is not easy, some disassembling is required.

I don't think I will have time to do the 'part 2' of the repair before our departure next Friday, that's why I was asking for the lower voltage protection setting.
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Old 15-06-2019, 13:12   #11
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Re: Isotherm fridge/ BC35 controller setting question

Thanks for the update.

Good work on the fan repair. That should be categorized as a temporary fix.

Plan on getting replacement fan(s) that satisfy the 500mA maximum continuous load, 1A peak load specification supplied by the F terminal.

An LED w/ series resistor is very handy to blink out fault codes.

Remember to have the refrigerator operating when looking for the voltage drop loss, so that the current load from the refrigerator will create the voltage drop at the problem point(s).

Have a nice trip.
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