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12v Fridge electrics


« MGVW | 12v Plug? »

 
 
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  #1 (permalink)  
Old June 28th 04, 07:35 PM posted to uk.rec.caravanning
John Deane
external usenet poster
 
Posts: 5
Default 12v Fridge electrics

I found on our last trip that the fridge wasn't working on the 12v when
we drove to Cornwall. I have just checked out the supply from the car
and that is 14.3v between pins 6 and 3 on the car side. There is
continuity to the fridge and the resistance at the socket end is 2ohms.
Anybody any ideas why I am not getting a cold fridge while driving? I
seem to recall a while ago that there was a comment about the resistance
having to be around 1.5ohms. Could the extra 0.5ohm be the cause, I
attributed that to the length of cable .

--
John Deane
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  #2 (permalink)  
Old June 29th 04, 10:52 PM posted to uk.rec.caravanning
Des
external usenet poster
 
Posts: 132
Default 12v Fridge electrics

Could it have been John Deane who typed:

|| I found on our last trip that the fridge wasn't working on the 12v
|| when we drove to Cornwall. I have just checked out the supply from
|| the car and that is 14.3v between pins 6 and 3 on the car side.
|| There is continuity to the fridge and the resistance at the socket
|| end is 2ohms. Anybody any ideas why I am not getting a cold fridge
|| while driving? I seem to recall a while ago that there was a comment
|| about the resistance having to be around 1.5ohms. Could the extra
|| 0.5ohm be the cause, I attributed that to the length of cable .
||
|| --
|| John Deane

But what is the voltage at the fridge when its connected to the car and
switched on?
you can have voltage and low resistance by a meter but as soon as you try
and draw the 8 amps or so the fridge needs the voltage collapses.

Des


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  #3 (permalink)  
Old June 30th 04, 12:04 AM posted to uk.rec.caravanning
John Deane
external usenet poster
 
Posts: 5
Default 12v Fridge electrics

Des,
I didn't appreciate that there could be a volt drop as you state. I was
hoping that I could avoid having to pull the fridge out again. Looks as
if it will have to be done after all. So I can measure the volts at the
fridge.
Thanks , John

In message , Des
writes
Could it have been John Deane who typed:

|| I found on our last trip that the fridge wasn't working on the 12v
|| when we drove to Cornwall. I have just checked out the supply from
|| the car and that is 14.3v between pins 6 and 3 on the car side.
|| There is continuity to the fridge and the resistance at the socket
|| end is 2ohms. Anybody any ideas why I am not getting a cold fridge
|| while driving? I seem to recall a while ago that there was a comment
|| about the resistance having to be around 1.5ohms. Could the extra
|| 0.5ohm be the cause, I attributed that to the length of cable .
||
|| --
|| John Deane

But what is the voltage at the fridge when its connected to the car and
switched on?
you can have voltage and low resistance by a meter but as soon as you try
and draw the 8 amps or so the fridge needs the voltage collapses.

Des


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.712 / Virus Database: 468 - Release Date: 27/06/2004



--
John Deane
  #4 (permalink)  
Old June 30th 04, 05:57 PM posted to uk.rec.caravanning
Tony Maris
external usenet poster
 
Posts: 161
Default 12v Fridge electrics

Hi John,

14.3 volts is about what I would expect without any load applied. What you
need to know is the voltage under load. What is your vehicle? Is the
supply fed directly from the battery or through another power source?

Fridges on 12 volt are not efficient at the best times, and certainly will
not cool from 'a standing start'. to have any chance of working, you need a
minimum of 11.5 volts AT THE FRIDGE. With current regulations (EN1648-1)
the caravan manufacturers are allowed up to 0.8 volts voltage drop through
the fixed wiring in the 'van. Add to that the voltage drop through the
vehicles installed wiring (often over 2 volts using manufacturers feeds),
through the relay itself (which could easily be 0.5 volts), through the 12S
cable on the car, the plug/socket interface, and the 12S wiring on the van,
and you will see that you are hard pressed to even get into double figures
at the fridge.

I have done extensive tests over the last 3 years on 12S installations,
including the work I do on the NTTA's training courses, and we can manage to
get in excess of 12 volts at the fridge from most towing vehicles, but on
every course we've run, we only manage it using a specific combination of
wiring and relays.

I now test the voltage drop on my towbar installations and when wired
directly to the battery, the voltage drop to the output side of the relay is
less than 0.6 volts with a 20 amp load applied. By adding links as
appropriate in the 12S plug, the drop is vastly reduced through the 12S
cables and plug/socket interface.

If you are local to Chesterfield, by all means pop in and we will test the
installation for you.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"John Deane" wrote in message
...
I found on our last trip that the fridge wasn't working on the 12v when
we drove to Cornwall. I have just checked out the supply from the car
and that is 14.3v between pins 6 and 3 on the car side. There is
continuity to the fridge and the resistance at the socket end is 2ohms.
Anybody any ideas why I am not getting a cold fridge while driving? I
seem to recall a while ago that there was a comment about the resistance
having to be around 1.5ohms. Could the extra 0.5ohm be the cause, I
attributed that to the length of cable .

--
John Deane



  #5 (permalink)  
Old June 30th 04, 08:08 PM posted to uk.rec.caravanning
Richard Green
external usenet poster
 
Posts: 11
Default 12v Fridge electrics

Tony,

My fridge has never worked on 12v although there is a power supply to it. I
want to wire a feed direct from the battery through the existing voltage
sensitive relay. What size cable, and fuse, would you recommend? The car is
a 1998 Citroen Xantia Estate 1.9TD.

Richard

"Tony Maris" wrote in message
...
Hi John,

14.3 volts is about what I would expect without any load applied. What

you
need to know is the voltage under load. What is your vehicle? Is the
supply fed directly from the battery or through another power source?



  #6 (permalink)  
Old June 30th 04, 08:26 PM posted to uk.rec.caravanning
Michael Leete
external usenet poster
 
Posts: 15
Default 12v Fridge electrics

Richard,

I will leave Tony to comment on the wiring inside the car.

As far as the van goes make sure its at least 4 sq mm with cable there and
back (don't use the chassis as a return). Use a 15 amp fuse.

Michael

"Richard Green" wrote in message
...
Tony,

My fridge has never worked on 12v although there is a power supply to it.

I
want to wire a feed direct from the battery through the existing voltage
sensitive relay. What size cable, and fuse, would you recommend? The car

is
a 1998 Citroen Xantia Estate 1.9TD.

Richard

"Tony Maris" wrote in message
...
Hi John,

14.3 volts is about what I would expect without any load applied. What

you
need to know is the voltage under load. What is your vehicle? Is the
supply fed directly from the battery or through another power source?





  #7 (permalink)  
Old June 30th 04, 09:51 PM posted to uk.rec.caravanning
John Deane
external usenet poster
 
Posts: 5
Default 12v Fridge electrics

Hi, Tony,
My vehicle is a Skoda Octavia 1.6. As far as I know the feed is
from the battery via the usual relay that comes in only when the
ignition is on and the engine running. As the 'van is a Sterkeman with
modified wiring to bring it to almost UK standard I rewired the 12v
circuit direct to the 12S plug using 7-core cable but with only the two
wires to the fridge connected to the socket. From what you say it
appears that I may need to do a couple of links to uprate the voltage
achieved at the fridge. I have the detail from one of your previous
posts. Looks as though the first job will be to pull the fridge and
check what volts are arriving at the fridge.
Thanks for the offer to check the wiring, but you are a bit too far
away. Thanks for the response, John.


In message , Tony Maris
writes
Hi John,

14.3 volts is about what I would expect without any load applied. What you
need to know is the voltage under load. What is your vehicle? Is the
supply fed directly from the battery or through another power source?

Fridges on 12 volt are not efficient at the best times, and certainly will
not cool from 'a standing start'. to have any chance of working, you need a
minimum of 11.5 volts AT THE FRIDGE. With current regulations (EN1648-1)
the caravan manufacturers are allowed up to 0.8 volts voltage drop through
the fixed wiring in the 'van. Add to that the voltage drop through the
vehicles installed wiring (often over 2 volts using manufacturers feeds),
through the relay itself (which could easily be 0.5 volts), through the 12S
cable on the car, the plug/socket interface, and the 12S wiring on the van,
and you will see that you are hard pressed to even get into double figures
at the fridge.

I have done extensive tests over the last 3 years on 12S installations,
including the work I do on the NTTA's training courses, and we can manage to
get in excess of 12 volts at the fridge from most towing vehicles, but on
every course we've run, we only manage it using a specific combination of
wiring and relays.

I now test the voltage drop on my towbar installations and when wired
directly to the battery, the voltage drop to the output side of the relay is
less than 0.6 volts with a 20 amp load applied. By adding links as
appropriate in the 12S plug, the drop is vastly reduced through the 12S
cables and plug/socket interface.

If you are local to Chesterfield, by all means pop in and we will test the
installation for you.

Regards


--
John Deane
  #8 (permalink)  
Old July 1st 04, 07:56 AM posted to uk.rec.caravanning
William Knott
external usenet poster
 
Posts: 5
Default 12v Fridge electrics

"Richard Green" wrote in message ...
Tony,

My fridge has never worked on 12v although there is a power supply to it. I
want to wire a feed direct from the battery through the existing voltage
sensitive relay. What size cable, and fuse, would you recommend? The car is
a 1998 Citroen Xantia Estate 1.9TD.

Richard

"Tony Maris" wrote in message
...
Hi John,

14.3 volts is about what I would expect without any load applied. What

you
need to know is the voltage under load. What is your vehicle? Is the
supply fed directly from the battery or through another power source?


To get adequate voltage at the fridge to run from 12vDC you have to
use a minimum of 6mm˛ cable with an Anderson type plug. I prefer to
use 2 x 6mm˛ twin sheathed cable (positive and negative). This also
charges my auxilliary battery correctly, as I have a manual switch to
disconnect my start battery.
  #9 (permalink)  
Old July 1st 04, 07:48 PM posted to uk.rec.caravanning
Tony Maris
external usenet poster
 
Posts: 161
Default 12v Fridge electrics

Hi Richard,

By coincidence, we use a Citroen Xantia Diesel as the test car on the
training courses. It proves consistently reliable in that we almost always
have 14.2 volts output at the battery when the alternator is charging, and
we are drawing 20 amps.

The best results are achieved by having a 6mm supply directly to the Voltage
Sensing Relay and I fuse with a good quality blade fuse holder and a 20 amp
fuse. The VSR's themselves suffer voltage drop through the circuit boards
and some can be subject to 'cycling' if the power feed is inadequate. In
practice, it is not normally possible to fit the 6mm CSA cable directly into
the terminal block on the VSR. I use a pin type connecter crimped with
ratchet crimpers.

The latest VSR's have been improved after feedback from our tests and now
have two 12 volt inputs and larger terminal blocks. This allows the use of
twin 44/0.30 cable which will fit in directly. This can be doubled up at
the fuse holder with a yellow spade terminal again crimped with ratchet
crimpers. Additionally, improvements to the circuit board have resulted in
much less voltage drop. The newest electronic VSR's are now comparable with
old fashioned normally open relays with regard to voltage drop.

To achieve in excess of 12 volts at the fridge, it is necessary to insert
the links I mentioned previously, in the caravan plug, (and earth the brown
wire [pin 5] in the car) but this should only be done if pins 2 and 5 in the
12S plug are vacant.

Hope this helps.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Richard Green" wrote in message
...
Tony,

My fridge has never worked on 12v although there is a power supply to it.

I
want to wire a feed direct from the battery through the existing voltage
sensitive relay. What size cable, and fuse, would you recommend? The car

is
a 1998 Citroen Xantia Estate 1.9TD.

Richard



  #10 (permalink)  
Old July 1st 04, 08:26 PM posted to uk.rec.caravanning
Richard Green
external usenet poster
 
Posts: 11
Default 12v Fridge electrics

Tony,

Thanks for the info. I should be able to remove the voltage drop across the
VSR if I used it's output to power the coil of a relay.

Where do you bring the feed into the interior of the car from the engine
bay? I have had a quick look and there are no obvious gaps. My current feed
is wired into the drivers side fuse box and runs down that side of the car.
I was hoping to use this wire as a guide and pull the new wire into place
with it. However knowing my luck it may end in tears!

Richard

"Tony Maris" wrote in message
...
Hi Richard,

By coincidence, we use a Citroen Xantia Diesel as the test car on the
training courses. It proves consistently reliable in that we almost

always
have 14.2 volts output at the battery when the alternator is charging, and
we are drawing 20 amps.

The best results are achieved by having a 6mm supply directly to the

Voltage
Sensing Relay and I fuse with a good quality blade fuse holder and a 20

amp
fuse. The VSR's themselves suffer voltage drop through the circuit boards
and some can be subject to 'cycling' if the power feed is inadequate. In
practice, it is not normally possible to fit the 6mm CSA cable directly

into
the terminal block on the VSR. I use a pin type connecter crimped with
ratchet crimpers.

The latest VSR's have been improved after feedback from our tests and now
have two 12 volt inputs and larger terminal blocks. This allows the use

of
twin 44/0.30 cable which will fit in directly. This can be doubled up at
the fuse holder with a yellow spade terminal again crimped with ratchet
crimpers. Additionally, improvements to the circuit board have resulted

in
much less voltage drop. The newest electronic VSR's are now comparable

with
old fashioned normally open relays with regard to voltage drop.

To achieve in excess of 12 volts at the fridge, it is necessary to insert
the links I mentioned previously, in the caravan plug, (and earth the

brown
wire [pin 5] in the car) but this should only be done if pins 2 and 5 in

the
12S plug are vacant.

Hope this helps.

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Richard Green" wrote in message
...
Tony,

My fridge has never worked on 12v although there is a power supply to

it.
I
want to wire a feed direct from the battery through the existing voltage
sensitive relay. What size cable, and fuse, would you recommend? The car

is
a 1998 Citroen Xantia Estate 1.9TD.

Richard





 


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