Fridge problem

[brown]

Since I bought my boat a couple of months back the fridge hasn't worked, recently found out why, the previous owner had put a screw through the wires.

Anyway wires fixed on it went and after a couple of chirps and rattles, it worked fine. The genny was on charging the batteries at this time, batteries fully charged, genny off and within half an hour the fridge starts rattling and chirping going on and off. I've tried it a couple of times, I've only got 2 domestic bats 110mp/hour, the fridge is an inlander 12v. I thought the batteries may have been a bit duff, so I tried some new ones, result was the same. Any idea's guys? thx.

[Keeping Up]

It sounds like low voltage at the fridge. Are you able to measure it (with the fridge motor running)? You may be losing some volts in the cables, they may have been damaged where the screw went in, or the fuse holder or a connection may have been overheated.

 

If you can't measure the voltage, another way would be to take a battery to the fridge and see if it runs ok directly connected to it.

[Chris J W]

Have a quick read through my recent problem, too -12V Coolmatic problem - (Eventually solved by replacing the crappy continental style fuse.) You may get some info there.

[brown]

Should have done a search,

 

Plenty to think about there, Could well be the fuse as it's one one them continental types, was going to replace them anyway. I'll have a look tomorrow. cheers.

[steelaway]

Since I bought my boat a couple of months back the fridge hasn't worked, recently found out why, the previous owner had put a screw through the wires.

Anyway wires fixed on it went and after a couple of chirps and rattles, it worked fine. The genny was on charging the batteries at this time, batteries fully charged, genny off and within half an hour the fridge starts rattling and chirping going on and off. I've tried it a couple of times, I've only got 2 domestic bats 110mp/hour, the fridge is an inlander 12v. I thought the batteries may have been a bit duff, so I tried some new ones, result was the same. Any idea's guys? thx.

 

I also suspect voltage drop. if the fridge is more than 10 feet from the fuse you will need maybe 4 to 6 mm cable.

[brown]

The fuse is near the batteries and the fridge is about 7 metres away, also still wired through a switch on the wall near fridge and then a 240 domestic socket and plug behind fridge. Too many joints me thinks? Not sure how this wire thickness thing works, how thick would the internal cable need to be?

[steelaway]

The fuse is near the batteries and the fridge is about 7 metres away, also still wired through a switch on the wall near fridge and then a 240 domestic socket and plug behind fridge. Too many joints me thinks? Not sure how this wire thickness thing works, how thick would the internal cable need to be?

Sorry I did not realise it was a 240V fridge ignore everything about volts drop 1% at 12V is a lot more than at 240V

[Chris J W]

Sorry I did not realise it was a 240V fridge ignore everything about volts drop 1% at 12V is a lot more than at 240V

 

It is a 12V (check the OP - inlander 12v) so comment still valid. I think what he was trying to say is that a normal 240v is used as the on/off

[steelaway]

Since I bought my boat a couple of months back the fridge hasn't worked, recently found out why, the previous owner had put a screw through the wires.

Anyway wires fixed on it went and after a couple of chirps and rattles, it worked fine. The genny was on charging the batteries at this time, batteries fully charged, genny off and within half an hour the fridge starts rattling and chirping going on and off. I've tried it a couple of times, I've only got 2 domestic bats 110mp/hour, the fridge is an inlander 12v. I thought the batteries may have been a bit duff, so I tried some new ones, result was the same. Any idea's guys? thx.

 

I am sorry - got it completely wrong.

Any cable has its own internal resistance and a larger cable has less resistance. With a larger cable you will have more voltage arriving at the fridge. This will help the motor to start, also the more joints/connections you have can increase the resistance to the voltage.

If you have a standard domestic 13A socket plug you should consider changing it to a special 12V one to avoid confusion in the future.

[brown]

I am sorry - got it completely wrong.

Any cable has its own internal resistance and a larger cable has less resistance. With a larger cable you will have more voltage arriving at the fridge. This will help the motor to start, also the more joints/connections you have can increase the resistance to the voltage.

If you have a standard domestic 13A socket plug you should consider changing it to a special 12V one to avoid confusion in the future.

 

 

I was going to get rid of it all together, coz it's behind the fridge and I can't get to it normally anyway. Thanks guys I think a total rewire might be in order this week, I'll wire a battery direct to it first just to see if it works ok.

[Ray]

It is said by those wiser than me that the cable size for the fridge wiring has to be 1mm2 for every meter between fridge and batteries, so if your cable run is 7 metres there and 7 metres back, you'll need 7mm2 cable (if I remember correctly).

 

Certainly agree with removal of excess wiring and excess connections everywhere on any boat wiring as for each one that's at least one less connection to work lose.

 

Unless you definitely have no 240v circuits on the boat, please check that the 240v plug/socket behind the fridge isn't jut that - sorry, don't know if that model fridge is dual voltage or not.

[Peter R]

If it helps I have had similar problem that has been driving me up the wall! Basically, the volts at the fridge were fine, both with and without the motor running, but the motor kept dropping out on 'motor speed error'.

 

After trying everything else, I moved a battery next to the fridge and connected it direct and it works fine, so it must be the cable even though I was not getting any detectable volt drop. Fridge is about 8m from fuseboard, so i'm currently waiting for a mate to get me some new cable of at least 10mm (maybe 15mm to be on the safe side!).

 

Peter

[Radiomariner]

You mentioned "rattles" when the fridge started up, and again when it stopped. A little rattling noise is quite common as compressors start up and stop. However you did not mention any rattling noises when the fridge was running. When the fridge is running once it has reached the desired temperature the compressor should cut out (causing a rattle) when the temprature in the fridge rises two or three degrees the compressor should cut in again. The on/off ratio varies from fridge to fridge and according to setting, but normally I would expect 4mins on/20 mins off. Have you got the thermostat turned up all the way(For turned up. I mean turned to coldest possible) Set thus, the compressor would probably not cut out and your battery if not in the best of health could drain very rapidly indeed.

All the previous advice is valid, but also check that thermostat setting.

 

I fell foul of this when going out at New Year. I turned the fridge up to full when on shore power overnight, (batteries on charge). The idea being to get the fridge as cold as possible before starting out the next day when I would only be cruising for 1-1/2 hours, put it to its normal setting before setting out therefore delaying the time necessary before the compressor cut in again thus saving a little drain from the batteries. Unfortunately, I forgot to reduce the fridge setting. Mooring in the stretch above Grove Lock the wind for the next few days was fierce and I deemed it prudent to remain moored. I got a shock after the second night away that the battery voltage had dropped to 11.8V. The fridge compressor was cutting out and in, but at a ratio more like 20 mins on 4 mins off!

 

As the voltage drops, the compressor uses more current to keep running, it is no longer running efficiently, fridge does not reach temperature so compressor does not cut out. When the voltage drops to a point when the compressor does not run the drain on the batteries can be phenonimal. (Some compressors cut out to prevent this). There is something to be said about the gas fridge in spite of its so called dangerous pilot light!

[brown]

Put a battery direct to it and it ran all night, so I just need to sort the wiring out, Cheers guys.

[chris w]

If it helps I have had similar problem that has been driving me up the wall! Basically, the volts at the fridge were fine, both with and without the motor running, but the motor kept dropping out on 'motor speed error'.

 

After trying everything else, I moved a battery next to the fridge and connected it direct and it works fine, so it must be the cable even though I was not getting any detectable volt drop. Fridge is about 8m from fuseboard, so i'm currently waiting for a mate to get me some new cable of at least 10mm (maybe 15mm to be on the safe side!).

 

Peter

 

Running the maths for a 16m run of cable and 6A current, a cable area of 6mm² will be sufficient so 10mm² will be great. (This assumes the batteries are very close to the fuseboard) What cable do you have at the moment?

 

Chris

 

PS: a 3% volts drop (~0.4v) is the max recommended. That's what I used in the calculation

Edited January 22, 2008 by chris w

[brown]

Running the maths for a 16m run of cable and 6A current, a cable area of 6mm² will be sufficient so 10mm² will be great. (This assumes the batteries are very close to the fuseboard) What cable do you have at the moment?

 

Chris

 

PS: a 3% volts drop (~0.4v) is the max recommended. That's what I used in the calculation

 

 

I have no idea how you measure thickness of wire, but it's got to many joins it it anyway.

[chris w]

I have no idea how you measure thickness of wire, but it's got to many joins it it anyway.

 

The wire dimensions used in my calculations are not wire thickness but cross-sectional AREA (in mm²). That's how cable is traditionally sold, by area not diameter.

 

If you can measure the diameter (using say a vernier) then the cross-sectional area (from basic maths) will be 0.8 x d² where d is the diameter of the cable.

 

If you can't get through the insulation anywhere, then a reasonable guess would be the outside diameter (ie: including the insulation) less about 2-3mm for the insulation wall thickness in total. Thus. if the overall outside diameter is about 6mm, the cable inside will be about 3.5mm in diameter, which means the cross-sectional area will be 10mm².

 

Chris

[Peter R]

Running the maths for a 16m run of cable and 6A current, a cable area of 6mm² will be sufficient so 10mm² will be great. (This assumes the batteries are very close to the fuseboard) What cable do you have at the moment?

 

Chris

 

PS: a 3% volts drop (~0.4v) is the max recommended. That's what I used in the calculation

 

Chris

 

connection from battery to fuseboard is about 2-3m, currently 2 x 6mm cables in parallel - may get upgraded to something bigger at some point. Yes, I know the maths says 6mm for the fridge connection should be fine, but if I am buying new cable I would rather get something too big than find out the hard way that it isn't big enough. Existing cable is 6mm (but to be fair it is about 15 years old).

 

Peter

[chris w]

Chris

 

connection from battery to fuseboard is about 2-3m, currently 2 x 6mm cables in parallel - may get upgraded to something bigger at some point. Yes, I know the maths says 6mm for the fridge connection should be fine, but if I am buying new cable I would rather get something too big than find out the hard way that it isn't big enough. Existing cable is 6mm (but to be fair it is about 15 years old).

 

Peter

you can't go wrong with bigger (10mm²)

 

Chris