24VAC current draw

[PaulD]

I need to determine the current draw for my 24VAC sprinkler valves to help me isolate some problems. I know what to do with a DC circuit but I am not sure how to measure current in a VAC circuit.

 

[WayneW]

Got a clamp-on ammeter? I don't know if they will read that low a voltage and current.

You can get a rough idea by using a Kill-a-watt meter on the primary side of the transformer. That would show a difference from one valve/solenoid to another, but won't tell you how much is going to the valve/solenoid itself and how much may be going to your irrigation controller (if any).

 

[TonyNo]

If you have a meter, just switch it to AC current and do the same thing as you would with DC.

 

[Sandpiper]

If you have a meter, just switch it to AC current and do the same thing as you would with DC.

Correct. But it depends on the meter. Some DVMs cannot read milliamps or amps. Some cannot read AC. Some have a different setting for these possibilities, and some have a different plug for the leads to access milliamps versus amps.

All depends on the meter. But, yes, a good DVM will read AC and DC, amps and milliamps.

 

[BraveSirRobbin]

HERE is a post (number 41 in that thread) that may be of interest to you as I actually show a multimeter measuring a sprinkler valve's current! :blush:

 

[PaulD]

Thanks all. I was concerned about the current draw on my irrigation valves because my controller (Rain8Net Pro) was kicking off after about 3-4 seconds. The Rain8Net is fused to shut off a zone if it draws more than 300ma. Turns out that the real problem was the default factory settings for the automatic shut off timers. The timers were apparently set for a few seconds. I reset them to 20 minutes and everything is OK.

BTW...I determined the way to use my DVM to measure current but never tried it after I discovered the timmer problem.

 

[icellama21]

Either get a meter that does AC current(RMS preferably) or AC voltage(monitor voltage across a resistor, Ohm's law doesn't work accurately on AC circuits due to issues I am sure most non-engineers don't care about, but you will see a difference between the current and no-current states.)

 

[Sandpiper]

Either get a meter that does AC current(RMS preferably) or AC voltage(monitor voltage across a resistor, Ohm's law doesn't work accurately on AC circuits due to issues I am sure most non-engineers don't care about, but you will see a difference between the current and no-current states.)

Not correct. Ohm's law works perfectly on DC or AC.

You are probably confusing resistance (which is commonly associated with DC circuits) with impedance (which is commomly associated with AC circuits). AC circuits have the extra complication of when capacatance and inductance affect the apparant resistance reading. At different frequencies, the "impedance" or apparant resistance, varies if inductors or capacitors are in the circuit.

But, AC or DC, low frequency or hi frequency, Ohm's Law still works. But there are factors on AC circuits which can change the apparant resistance, amperage, or voltage measurements versus what you would expect with a DC circuit. I think this is what you meant.