A Kiwi couple's cruising adventures on America's Great Loop and around the coast of New Zealand

Monday, 17 June 2013

Power to the people

Or Loopy Kiwi anyway!

If you've been reading earlier postings, you will know that in the pre-Loop days I did a lot of research into the power supply to Loopy Kiwi to make her behave more like a New Zealand based boat as far as travelling and anchoring out were concerned. This resulted in the installation of a 3kW inverter, which was enough to run some of the appliances without having to resort to using the genset - particularly refrigeration - but certainly not the whole shebang. When we made the decision to bring LK home, the biggest issue was always going to the supply of shore power to make things work. Now, for those technophobes reading, forgive me for some of the content of this posting as it can't help but contain stuff that you will find frightfully boring, but it may be useful to those who are contemplating bringing a US boat to New Zealand, or somewhere else that has a similar power system to us - Europe, for example.

In New Zealand, the typical AC (alternating current) shore power supply is 240 V (volts) 50 Hz (hertz)  16A(amps). In the US, there are a variety of differing supplies but the most common these days is 240/115V  60Hz  50A. So....contrary to popular belief in NZ, you will notice that the USA does, in fact, have 240V like we do. However that voltage is where all similarity stops, because their 240V is a strange 240V indeed. Ours is a 3 wire, single phase system and theirs is a 4 wire system comprising 2 "hot" wires (L1 and L2 - sometimes referred to as "two phase") a neutral (L0) and an earth. Here is a drawing of the two differing systems:
Our system provides 240V between the phase and neutral wires. The US system provides 115V between either "hot" wire and the neutral (L0), and 240V between both "hot wires". This is how you can have a boat with both 240V for the airconditioning and 115V for other appliances - as Loopy Kiwi does. One important point, though, is that the two hot wires must have waveforms that are 180 degrees apart from one another, or it just doesn't work. This is why you have to be careful when connecting a 240V 50A boat to 2 x 115V 30A supplies using a Y adapter as, if they are from the same source, you don't get 240V. You may recall earlier posts where I talked about a "smart Y" adapter that I had purchased (and later sold). They are designed to make sure the hot wires are out of phase to protect the 240V equipment on the boat.

The next problem is just the electrical appetite of US boats. Loopy Kiwi, in common with many American craft, is very hungry electrically as she expects to have 50A of supply in most situations. Even then, if all the appliances were turned on simultaneously, there would be enough load to exceed this limit by some considerable margin (not that anybody ever turns everything on at once!). So here we are now faced with trying to make everything go on a measly 16A supply which, according to the laws of Physics, can't be done. What we end up with, is the ability to have roughly 3.6kW of energy, which is not a lot more than we get from the inverter. We have achieved this by installing 2 x 2kW, 240V to 115V transformers (these were off the shelf items and were cheaper than having 1 x 3.6kW one specially made). They are also wound in such a way that we get the "out of phase" hot wires necessary to give us 240V for LK's aircon - not that we will be using it much as each unit draws around 7A. Ultimately I will change the electric hotplate to gas as it, alone, uses 15A when all 3 are on (and I hate how slow electric cooking is compared with gas!).

The final issue is the difference in frequency - NZ's 50Hz vs USA's 60Hz. This does not effect things like heating elements in water heaters or ovens, but will make motors, such as those in refrigerators run slower and hotter. Prior to my retirement, my Company was involved in importing specialised fans from the USA and in the 20 years of doing so we had no problems with running them on NZ frequencies using transformers. Since we modified LK, all the appliances that contain electric motors seem to be running fine.

Loopy Kiwi came to us fitted with a "Cablemaster" deployment and storage system for the 2 x 50A shore power cables (did I mention that LK actually has TWO of these 50A supplies - although the second was dedicated entirely to the aircon for the sundeck and flybridge, and we never used that). These even had remote controls so you could easily deploy or retrieve the bulky cables with one person, usually with much envy from fellow boaters. When I told the Admiral that we were removing them she was bitterly disappointed, but they had no further purpose and took up a lot of space behind the headboard of the master stateroom, making access to some of the serviceable items quite difficult to impossible. Here's a few before, during and after pix, so you'll see what I mean:

These are shots looking up to where the vacuflush unit for the aft head is located. How you would have got to it before the Cablemasters were removed is anybody's guess!

The old power cords were 55ft long, around 1" in diameter and contained 4 cables, each with wire 16mm2 in cross sectional diameter. They have been replaced by a single cord about 3/8" in diameter and containing 3 wires each with a cross sectional diameter of 2.5mm2 each, Some difference!!!
And here's everything that came out - anyone want to buy a couple of Cablemasters c/w 55ft 50A cables??
We have made allowance for the 240V 50Hz system to be extended to the rest of the boat, particularly to replace 115V appliances if or when they fail. Fortunately, Silverton had the sense to build their boats with cabling suitable to run 240V appliances - probably because they had a reasonable export market to countries where 240V is the norm - which is not always the case in some US manufactured boats.

The next project is a liftout, bottom paint and Propspeed. We will probably give her a bit of a clean and polish at the same time to remove the rust stains etc from the shipment to NZ. The weather is pretty dismal here right now for doing this kind of work - hopefully it will improve in the next few weeks

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