OHM'S LAW, same for AC and DC??

[new guy]

I am working on a 230vac circuit that keeps blowing a 1 amp fuse. To find the short without using too many fuses I want to use an ohmeter on the load side of the fuse. What is the minimum resistance I should measure, 230 ohms?? or higher. should I be measureing between the fuse holder and ground or between the fuse holder and neutral? Does OHMS LAW pertain to this as it would a DC circuit or is it different for AC??

[Robert Reed]

For the most part Ohms law applies to line voltage as DC. However, one more ingredient creeps in with AC voltage and that being reactance, which is not present in DC circuits. Reactance is a form of resistance that is known as impedance for AC circuits. It will not show up on your DC ohmmeter. Reactance also causes a property known as power factor in which the actual wattage could be vastly different than what a simple current and voltage measurement would indicate. It also is cause for motor reverse EMF which can cause a motor winding of very low ohmage to in reality be many times higher when factoring in impedance. For example, an induction motor may ohm out at 1- 2 ohms and yet only draw 5 amps from a 230 VAC source. What type of device is connected to your 240 circuit? This makes all the difference when beginning trouble shooting it. An electric heater (no fan involved) will draw the same current as a DC circuit and your ohmmeter would e reliable here, but almost anything else will have impedance and a power factor which your ohmmeter will not show.

[jwax]

You could connect a 230 Volt light bulb in place of the fuse, and apply power. Then isolate the location of the short by cutting branches. When you cut the branch with the short, the lamp will go dark.
What sort of device is this?

[dyarker]

... should I be measureing between the fuse holder and ground or between the fuse holder and neutral? Does OHMS LAW pertain to this as it would a DC circuit or is it different for AC??

Both! Fuse holder to ground should measure open, else you've found a problem.

Fuse holder to neutral will measure DC resistance. Expanding on what Robert said, the cold resistance of a heater will be less than hot resistance. DC resistance of transformer-rectifier-cap power supply is just the DC resistance of wire in primary winding, it will be lower than impedance when operating.

So question is still what type is the load?

Cheers,