Originally Posted by s/v Jedi
How can your fridge pull 7A at 230V? Mine only at maximum pulls 5% of that; 7A at 12V and most of the time not half of that.
Also, you can switch the water heater so count it as a controlled load. My 18kBTU air conditioner pulls 7A at 240V... how big are your two units? You always need to run the two of them? You must be running 40-50 kBTU at that 4.6 kW draw!
The battery charger is also a controlled load like you write. I must admit that I don't know how big your boat is but I always thought that we used a lot of power on our 64' boat with all the gadgets and A/C and washer/drier etc. but you more than double it :-)
Part of the problem is older equipment
which is not nearly as efficient as modern equipment. The Air conditioners run about 1.8KW when in air conditioning
mode (18,000 btu units) but pull about 2.1KW each when in heat mode and then there is the water pump which pulls another 200 ish watts. Unfortunately the startup surge for these units is very high.
The vessel is an Oyster
55 and with the very large windows in the saloon
and originally teak
decks the heat load on the boat in the tropics was substantial. However, since the boat was setup for two independent AC systems I can't just run one and keep the temperature consistent through the boat. One unit caries half of the saloon
, the galley
, aft stateroom, aft head
. The other unit caries half of the saloon, the forward stateroom the forward bunk cabin
, and the forward head
. Because the vessel is so heavy (55,000lbs) all of the bulkheads, cabinetry, etc provide a significant thermal load so if I come home and it is very cold or very hot I turn on both units and it will take them about an hour to pull the boat down to the point where they start cycling. Perhaps newer units would be more efficient.
The fridge / freezer
is an old holding plate system with a single
16,000 btu compressor
pulling down two huge freezer
plates and a single
fridge plate. It does not run very much (about an hour per day) so the average power use is about 1/20th of the running power but the nominal running load is rather large.
The boat was originally setup based upon running a generator
for an hour in the morning and a hour in the evening to keep the fridge / freezer cold and at the same time charge the batteries / run the microwave, etc.
For example the current
charger consumes about 5 amps ( 1150 watts) peak is 7A (1600 watts) to output 30amps @ 26V (780 watts) which is less than 70% efficient! (The peak is at 29V just before the amperage drops).
I have definitely thought about putting a "load sensor" on the input line and if the input load exceeds XXX watts (pick a number) open a relay for the hot water heater to shed the load. But, like your house, I generally don't turn the hot water heater on and off but just let it cycle on it's own.
She is definitely an "old school" boat from 1990.
There are times I wonder if it would be simplier to rip everything out and start over with more efficient / different systems.
For example, I could easily go to 24V constant cycling fridge compressors and evaporator plates rather than the holding plate system. More modern AC units would be nice (although try to find AC units now that can handle 50hz and 60hz in the states! The claim [which I don't know that I believe] is that when everyone jumped to the new refrigerants they made them in 60hz only and 50hz only not combined frequency for the hermetic compressors)
Luckily the average power draw of the equpment is not too bad, I normally run about a $40 - $60 / month electric
bill which in southern CA (high electric
costs) is not terrible.
Interestingly the boat was setup with dual shore power
inputs when the boat was in europe
, each was a 32A line at 230V. All of the GFIs in the power panel are rated at 64A. It's interesting, there are 3 GFIs in the main panel, Generator
, Shore 1, Shore 2.
This has been the most "interesting" jigsaw puzzle of the boat since I bought it. I had thought that the mastervolt mass GI multitap 7.0 was going to be along shortly and I would buy one, if it was not enough I would parallel a second.
Several of these boats have been retrofitted with an A/Sea system which takes in 10KVA of anything and outputs 9KVA of whatever you program it to output. The 10% loss I can stand, the $18,000 cost for the box which is not a battery charger or an inverter
just the converter is a bit steep and it weights about what the charles isolation transformer does (220lbs).
I did find another isolation transformer company in the states who I am contacting that makes a toroidal marine
isolation transformer in 2KVA, 3.6KVA, 6KVA, 9KVA, and 12 KVA sizes. Weight for the 9KVA unit is about 100 lbs and can take either 120V or 240V, 50 or 60hz and output 240V power. I have a call into them about if there could be a 208V tap added since they wind
them semi-custom. I could run it off the 120V circuit but that would limit me to 50A of input so the 6KVA unit would be the largest. The 9KVA unit would draw about 75A at 120, I would rather run it off of 208 which would draw about 43A...
I wish there had been more standardization of the US docks, the 208 vs 240V issue makes everything a bit of a mess!
Have a wonderful weekend!