Electical question...

BobE

BobE

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I get charged for the "units" I consume on a pontoon...
Units are, as I understand, Kilowatt hours.
When I check the consumption at a specific time on the boat I see from the electrical "gizmo" fitted in the system that I'm drawing say 4 amps with the fridge...
The boat system is about 12 1/2 v and as I remember V x A = watts So the draw is approx 50 watts ph which is 0.05 of a KwA...
This sounds wrong... I'm sure the difference between 12 V DC and 240 V AC must come into the calculation some where ...But Where?
/forums/images/graemlins/confused.gif
Cheers Bob E...
 
Bob

Your sums are broadly correct, assuming resistive loads. There will be an additional factor which is the efficiency of the battery charger, say 80%. Therefore you will be looking at say 0.06 kWh

In reality it will be less than this as the fridge will run with a low duty cycle at this time of year and the consumption (assuming no other devices connected) will be less than 1 kWh per day. This ties in broadly with our consumption, which is a little higher because we also run a de-humidifier
 
V x A = W is correct. As far as I am aware voltage does not make a difference but are you getting 12.5v at the fridge. If the cable is undersized voltage drop kicks in and at low voltage is critical.
 
Right Gents,
Thanks for that...
So is this how I calculate the (very approximate) cross rate from the Amp hours I'm using, (let's say 4) to the cost of electricity at Lymington Yacht Haven which is, I think, 15 pence per unit and 8 pence per unit at Priory Quay...
Very rough calcs....
4 amps = 0.05 Kwh @ 15 = 3/4 of a new penny per hour?? or at my summer berth
less than 1/2 a new penny per hour (0.4p)
Then one wonders whether the toy alternator fitted by Bukh is more economic!!
It's almost worth leaving the fridge on all the time in the summer!! /forums/images/graemlins/laugh.gif
Thanks again and Cheers Bob E....
 
<<our fridge is left on permanently>>
Have you bought another boat then, or has the disposal of the old one slipped your mind already?


Any road up: Bob, your leccy bill will not be reconcilable in any logical sense while useing and MDL metered lead, coupled with their broad brush KwH invoicing charge rates.
 
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