Frdige wiring question for Derek or those with first hand experience

Submitted: Saturday, Feb 02, 2008 at 19:07

ThreadID: 54157 Views:3590 Replies:7 FollowUps:15

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Cobes

Hi all,
I would like to get some advice from others regarding the wiring to my fridges.
I have a Nissan patrol with a Rotronics dual battery system (rdc12m). I currently run 4metres x 6mm wire to the rear of the wagon to run my 40litre and my 50 litre waeco. When running the waeco normally the voltage drop is about .2 of a volt. When running the Waeco on Turbo mode the voltage drop is near to .4 volts. I have not tested running both the Engel and Waeco together but assume the drop would be even greater.
The waeco usually shuts down just below 12 volts even when the battery protection switch is set to low. This greatly reduces my fridge running time when stationary.
I can only assume that the size of the wire needs to be increased?
If this is correct could you please recommend the type and size of wire that i should be using to reduce most or all of the voltage drop?
My current wiring from the aux battery runs via a relay which under load reduces the voltage by around .04 volts. (is this normal?).
Obviously the relay accepts a fairly small connector and if you were to recommend say 10mm square wire can you get a connector for this to connect to the relatively small relay?
Also what fuses do people recommend? I would be looking at around 30amps?

Thanks in advance
Chris.

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Reply By: MEMBER - Darian (SA) - Saturday, Feb 02, 2008 at 19:36

Saturday, Feb 02, 2008 at 19:36

Interested in the age and specific model of your Waeco - my CF60 has just been in for a warranty repair - playing up with low voltage response when voltage was ok - the techs here (I'm def. not one) may want to know exactly where you are measuring your voltages ?

AnswerID: 285189

Follow Up By: Cobes - Saturday, Feb 02, 2008 at 19:41

Saturday, Feb 02, 2008 at 19:41

Hi Darian,
My waeco is a cf50 Ac vera and about 2 years old.
I am measuring the voltage whils't under load from a junction box in the rear of the car that has three hella sockets on it?

Cheers
Chris.

FollowupID: 550004

Follow Up By: MEMBER - Darian (SA) - Saturday, Feb 02, 2008 at 20:05

Saturday, Feb 02, 2008 at 20:05

From my measurements with my budget meter, there is a sig voltage drop in the genuine Waeco 12V power lead too. So I check my voltage at the point where the lead plugs into the fridge, by spiking the sharp meter probes in through the cable insulation and contacting the copper strands inside - non destructive in my view, but tells the story (or seems to) while the fridge is running.

FollowupID: 550010

Follow Up By: franku - Saturday, Feb 02, 2008 at 22:37

Saturday, Feb 02, 2008 at 22:37

Darian,

I too have a CF60 which is about 9 months old.

There is a KNOWN FAULT with them - some of them - not all of them because a mate of mine with a 5 month old one did not have the issue have a problem with a special fuse which is soldered onto a board.

This $1 part neds to be replaced which is probably what you had done.

The symptom is that the "error light" will flash even with a fully charged battery with even zero voltage drop.

What actualy happen is that the compressor starts up - as soon as it winds up to 4.5AMP current draw it shuts off - so it cycles on and off constantly. This had about a 45% increase in amp hour draw over 24 hours on mine (monitored on a Xantrex Battery Monitor).

Also, Put it in Turbo mode and the compressor winds up to 7.5 AMPS and shuts down within 1 minute and wont stay on and the rror light comes on too.

Since it has been fixed with the new fuse, when in turbo mode, the compressor will stay on until it gets down to the set temperature.

If people out there have a CF60 - I suggest they check theirs before their next buig trip - it had a major impact on amp hour consumption.

FollowupID: 550044

Follow Up By: MEMBER - Darian (SA) - Sunday, Feb 03, 2008 at 10:58

Sunday, Feb 03, 2008 at 10:58

Yep - even with plenty of voltage in the supply, mine was continually moving to "low voltage error mode" - one flash - but only in hot weather (when you need it most) - cooler weather was fine. Following reports here, I spoke directly with Waeco and they referred me to an approved repairer in Adelaide - I have the fridge back and it seems to be happy, but I have not been posted the actual repairer's report yet. It has been suggested that the whole PC board has been replaced. Whatever - I'll find out soon I guess.

FollowupID: 550094

Follow Up By: Member - Frank U (QLD) - Sunday, Feb 03, 2008 at 17:52

Sunday, Feb 03, 2008 at 17:52

They may have replaced the whole board - the first repairer I called said that I did not know what I was talking about - there is no known faults and they would be replacing the board he thought depending on what they found when they look at it.

This would obviously fix it because the fuse is on that board.

The scond one - which I took it to, knew all about it and fixed it the same day because they just replaced that faulty componentrather than replacing the whole board...

Either way - I reckon yours will be fine now :)

FollowupID: 550237

Reply By: Derek from Affordable Batteries & Radiators - Saturday, Feb 02, 2008 at 20:14

Saturday, Feb 02, 2008 at 20:14

Hi Chris

If your wire is true 6mm2 core it would be fine but if it is 6mm automotive cable which is actually 4.58mm2 it would be too light for 2 fridges.

Here is a formula for voltage drop. Ideally we don't want more than 0.15V drop for a fridge.

Voltage drop equals (cable length (in metres) X current (in amps) X 0.017) divided by cable CROSS SECTION in mm.sq.

Lets take the 2 fridges running at the same time. Lets say 6 amps once they have started up. I would say your cable run is closer to 5m in a patrol.

5m x 6a x 0.017 / 6mm2 = 0.1v drop

using the same formula on 4.58mm2 (6mm Automotive cable) = 2.35V drop.

This could be your problem.

If your cable is true 6mm2 and not 6mm automotive then the relay or other joins / crimps / plugs are causeing the drop. Failing which have the fridge tested as some Waeco's need a modification done.

Regards

Derek.

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AnswerID: 285195

Follow Up By: Cobes - Saturday, Feb 02, 2008 at 20:17

Saturday, Feb 02, 2008 at 20:17

Hi Derek,
thank you for your answer.
Upon closer inspection the cable is labelled 10AWG??

Is this the same as 6mm?

Thanks
Chris.

FollowupID: 550014

Follow Up By: Member - Mike DID - Saturday, Feb 02, 2008 at 22:44

Saturday, Feb 02, 2008 at 22:44

Yes, 10AWG is pretty close to "6mm" although it depends on how cheap the manufacturer wants to get - 6mm outside insulation diameter tells you nothing about how much copper should be in it.

FollowupID: 550045

Follow Up By: Derek from Affordable Batteries & Radiators - Saturday, Feb 02, 2008 at 23:07

Saturday, Feb 02, 2008 at 23:07

10 AWG is 5.3mm2 and not suitable for your application.

Here is a link to a great calculator. Derek's Link to AGW

conductor size 10 AWG
area 5.261 mm^2 (square-mm)
area 10383 CM (circular mil)
diameter 117.7 mil (1)
diameter 2.989 mm (1)
DC-resistance 0.00334 Ohm/m
tensil strength 157.83 kgf (2)
weight 46.772 kg/km (Cu)
weight 14.205 kg/km (Al)

construction: stranded

Note: lay factor of stranded conductor is assumed 2 %.

Note:
1. diameter of stranded conductor is an approximation.
2. tensil strength of crimped terminal is about 60 % of conductor.

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FollowupID: 550048

Follow Up By: franku - Saturday, Feb 02, 2008 at 23:30

Saturday, Feb 02, 2008 at 23:30

Hi Derek,

Can you explain to me how you get 2.35V drop on 4.58mm2 wire in the above example?

I get this...

5m x 6a x 0.017 / 4.58mm2 = 0.11v drop ?

FollowupID: 550053