[C320-list] Fridge Usage

[Warren Updike]

Re: voltage drop, from Nigel Calder, the proper way to measure voltage drop
is to test each leg (neg then pos,) separately by placing one probe on a
battery TERMINAL, not the connector, and the other probe on the end of the
circuit (compressor, in your case,) while there is a load on the circuit.
The drop can be different for the different legs because the corrosion at
terminals and connections can be different.  
It is total resistance in the circuit that causes the drop.  The resistance
is the total of the natural resistance in the wire and the resistance added
by connections.  Using a sub-standard connector with a cheap crimper allows
the connection to degrade over time.  If you have more than 3% voltage drop
and you're sure the wire is sized correctly, look for degraded connectors
and connections.  If in doubt, cut them off and replace them.  There's lots
of good info on the net re. using crimped connectors.  Make sure you are
following advice for marine installations.
Warren

-----Original Message-----
From: Colin Evans [mailto:twosailors at bigpond.com] 
Sent: Tuesday, December 13, 2011 11:47 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Fridge Usage

 Yesterday I made a bit of an error.  I have just spent a couple of hours
taking readings with the fridge running, and not running.  Thr first thing I
did was to turn off the shore power and leave thing for a while.
Fridge on  12.34v at fridge, 12.48 at Battery
Fridge off  12.15 at switch board 12.74 at battery  That`s the one I can`t
understand as other items on the switch board were reading around 12.72
Fridge running, 11.97 at the fridge 12.51 at battery and a reading of 0.7 at
the switchboard.  I don`t know what that means
I took several readings all about the same, but the last was with the fridge
switched off on the board I got 12.5 across the switch. 
Now I am completely confused.

Ignoring the first reading, generally there seems to be 0.5v difference
between fridge and battery when running and 0.02v (not 0.2 as stated
yesterday)when stopped.  But I don`t understand the readings at the switch.
I also shifted the fridge connection on the switchboard to an un-used
position and got the same sort of readings.
I`ve tried wriggling connections.  The switch board connections look clean,
as do the connections into the Adler Barbour unit.
*************************
Regards
Colin Evans
Watermark #774
Lake Macquarie, Australia
 



 

-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Stephen Cox
Sent: Wednesday, 14 December 2011 12:17 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Fridge Usage


> 
> OK. Lets assume Catalina used 8 gauge wire and the path is to 
> the breaker panel then out to the compressor near the stern 
> or 20' one-way from the battery.
> Using this tool to solve for a load that would result in a 
> 0.2 vDC drop
> (http://genuinedealz.com/voltage-drop.html)
> I get 7.7 amps!!!!
> 
> I assume you are measuring at the compressor and not at the 
> breaker (although I'd like to have the breaker reading also).
> 
> So, no, a 0.2 VDC drop does not seem correct when the fridge 
> is not cycling.
> 

I would try wriggling the connectors at each end of all the wires involved
before panicking.  The push on connectors do build up corrosion over time in
a salt water environment and could be causing the difference.

Stephen Cox
Tegwen #1141