Electric Question 2

[pgrin]

First, Thanks to all for responses to Electric Question 1

Now this one is a little trickier.

I have a boat here in Phuket that was built in the US. The breaker panel for shore power is marked 120V. All of the electrics on the boat are 120V. How do I step down Thai 220V to allow me to use shore power? Step down transformer? How many watts? Where to buy? I asked 3 local marine shops and got 3 different/conlicting answers. Thanks again.

P

[chownah]

Step down transformer...yes!!!

Do you have anything which will not run on 50 Hz?....because that is what you are supplied with here in Thailand and the transformer will not change that at all...it will still be 50 Hz. Be aware that most stuff from the US is rated for 60 Hz.....but for many things (e.g. light and heat) it doesn't make any difference.

What size is the main breaker on the panel? If you got a transformer that supplied that many amps (plus some safety margin perhaps) then you would be sure to blow the breaker instead of the transformer. A useful fact here is that amps x volts = watts........so once you know the amperage you must supply (plus a safety margin perhaps) you mulitiply it by the voltage (in this case 120 V if that's what the transformere will be supplying) to give you the wattage that the tranformer must SUPPLY.....this is not the same as how much wattage the transformer will use...think of efficiency here.

If sizing your transformer to outperform your main breaker is too expensive then you could do a calculation as to what would be the maximum load you would ever conceivably draw and then size your transformer to that (plus some safety margin perhaps).

My advice is to get one that is too big rather than too small if you can afford it.....I guess this is obvious.

Of coures I'm just a rice farmer so you should consider that I'm luckless and clueless.

Chownah

Next.

[Crossy]

Chownah (the rice farmer) got there first and is 100% correct

Aim at getting a Tx that is too big rather than too small, reckon on it being about 90% efficient, so if you calculate your load at 1000 Watts get an 1100

Watt Tx

[Beardog]

Step down transformer...yes!!!

Do you have anything which will not run on 50 Hz?....because that is what you are supplied with here in Thailand and the transformer will not change that at all...it will still be 50 Hz. Be aware that most stuff from the US is rated for 60 Hz.....but for many things (e.g. light and heat) it doesn't make any difference.

What size is the main breaker on the panel? If you got a transformer that supplied that many amps (plus some safety margin perhaps) then you would be sure to blow the breaker instead of the transformer. A useful fact here is that amps x volts = watts........so once you know the amperage you must supply (plus a safety margin perhaps) you mulitiply it by the voltage (in this case 120 V if that's what the transformere will be supplying) to give you the wattage that the tranformer must SUPPLY.....this is not the same as how much wattage the transformer will use...think of efficiency here.

If sizing your transformer to outperform your main breaker is too expensive then you could do a calculation as to what would be the maximum load you would ever conceivably draw and then size your transformer to that (plus some safety margin perhaps).

My advice is to get one that is too big rather than too small if you can afford it.....I guess this is obvious.

Of coures I'm just a rice farmer so you should consider that I'm luckless and clueless.

Chownah

Next.

The best advise I ever got for a 110 voltage system to go up to 440 volt & break it to 4 legs at 110 saving a fortune in running air conditioners & other major appliances in the U.S. was from a friend that was a farmer!

Either a farmer or a sparky is always a good bet to listen to! Good call I always go a little over instead of under - that way you are never frettin over the age old cheap charlie failure. Thanks for the advice on the hertz difference I was not aware of that coming from the U.S.

Edited May 21, 2007 by Beardog

[lingling]

go up to 440 volt & break it to 4 legs at 110

uhhh....? (!)

[Crossy]

go up to 440 volt & break it to 4 legs at 110

uhhh....? (!)

Yeah, I know the US has an interesting supply system, not sure how this works though. To be honest, I can't be arsed to think about it.

[pgrin]

Update:

I got a quote from a marine supply company for a 1500w transformer, installed, for 50,000Baht. I then went to Keehin Electric and found a bear bones 1500w transformer for 2100baht.

I plan to put this in line between the 220v power supply on the dock and my shore power cord.

P

[Crossy]

Update:

I got a quote from a marine supply company for a 1500w transformer, installed, for 50,000Baht. I then went to Keehin Electric and found a bear bones 1500w transformer for 2100baht.

I plan to put this in line between the 220v power supply on the dock and my shore power cord.

P

WARNING, WARNING, Will Robinson !!!

If your Tx is exactly like that one, particularly the 220V inlet plug, PLEASE invest in the correct adaptor or remove the plug and fit a proper local 3-prong plug (obviously if the shore supply has matching Schuko outlets you can ignore this).

Look here - http://www.crossy.co.uk/wiring/plugs.html scroll down to the section on the 'Schuko' plug

Otherwise looks ideal

[Naam]

The best advise I ever got for a 110 voltage system to go up to 440 volt & break it to 4 legs at 110 saving a fortune in running air conditioners & other major appliances in the U.S. was from a friend that was a farmer!

that farmer must have been the chief engineer of the "Enterprise" in Startrek and your "savings" happened only during wet dreams of the future. am i right?

[chownah]

Pgrin,

How many volts on the output?....the picture looks like it says 130V but I can't tell for sure.

Chownah

[pgrin]

Thanks Crossy,

I am replacing the plugs with marine grade, its the only way to connect to shore power.

The input is 220v, output is 110v and is 1500 watts. I'm also considering an inline fuse, 20 amps?

P

[lingling]

Thanks Crossy,

I am replacing the plugs with marine grade, its the only way to connect to shore power.

The input is 220v, output is 110v and is 1500 watts. I'm also considering an inline fuse, 20 amps?

P

5A (6A) on the 220V side and 12A on the 110V side if you want to protect the transformer.

[Crossy]

Thanks Crossy,

I am replacing the plugs with marine grade, its the only way to connect to shore power.

The input is 220v, output is 110v and is 1500 watts. I'm also considering an inline fuse, 20 amps?

P

5A (6A) on the 220V side and 12A on the 110V side if you want to protect the transformer.

I'd be tempted to go for a 10A on the inlet side (inrush will be quite high and may pop a 6A), stick to 12-15A on the output as lingling suggests although fusing both is definately belt and braces