help with dryer circuit please.

[zappy]

100207-1448 EST

zappy:

A typical digital voltmeter has a 10 megohm input resistance with a small amount of shunt capacitance.

A Simpson 260 or 270 on the 250 V range is 25,000*250 = 6.25 megohms.

One megohm = 1,000,000 ohms.

If the Wiggy was considered a pure resistance, which it is not, then 1000 ohms at 120 V would be 14,400/1000 = 14.4 W of power dissipation. That is a lot of power in a small space. Because the coil in the Wiggy has a substantial amount of inductance the dissipating resistance can be less than 1000 ohms while the circuit impedance could be 1000 ohms. My off hand guess is that if the AC impedance was reduced to 100 ohms there would be an excessive amount power dissipation.

I tried a Google search for a Wiggy impedance specification. SqD's page did not work. I did not find what I was looking for. But ran across the following that is sort of funny.

http://www.pumpsonline.com/electrical.htm

.

Thank you. I was wondering what's the 25000 stand for?

 

[mivey]

"I'm so confused!" ~ Vinnie Barbarino

"The Ladders" job search site.

 

[mivey]

Thank you. I was wondering what's the 25000 stand for?

ohms/volt .

 

[GeorgeB]

re: "I was wondering what's the 25000 stand for?"

ohms/volt

And indirectly an indication of the meter movement. The old "cheap" meters were 1 mA, 1000 ohms/volt. The "better" ones were 20 microamp, 50,000 ohms/volt. I don't remember what the construction that caused the AC and DC sensitivities to be different, but it may have been half-wave rectification.

Electronic (VTVM types) were constant load, often 10 megohms AC and 11 megohms DC ... I believe the 1 Meg resistor was in the probe ... still have one in the junk box and could check if there is areal question.

 

[don_resqcapt19]

100207-1718 EST

don:

Thanks.

That makes it about 4000 ohms impedance or thereabouts. Equivalent to a 3.5 W bulb load. However, the bulb maybe a better load for it has a lower resistance when cold.

This provides some useful values that may help many understand their instrument better.

.

Gar,
Doesn't a solenoid have a lower resistance until the steel plunger is pulled into the coil, making it act similar to the lamp?

 

[gar]

100208-1856 EST

Don:

Yes for about 1/2 cycle, and if there is not current to pull it in it will remain a lower impedance. This would be somewhere between the coil DC resistance and the 4000 ohm estimate from your estimate of 30 MA. Is it easy for you to make a DC resistance measurement on your Wiggy? Also could do an AC current measurement with various series resistances that do not move the plunger.

.

 

[LarryFine]

Also could do an AC current measurement with various series resistances that do not move the plunger.

If you want to really experiment, disassemble it and jam the plunger, and test with currents that would otherwise move it.

 

[don_resqcapt19]

100208-1856 EST

Don:

Yes for about 1/2 cycle, and if there is not current to pull it in it will remain a lower impedance. This would be somewhere between the coil DC resistance and the 4000 ohm estimate from your estimate of 30 MA. Is it easy for you to make a DC resistance measurement on your Wiggy? Also could do an AC current measurement with various series resistances that do not move the plunger.

.

I don't have it here at home. I will try to remember to bring it home tomorrow.

 

[gar]

100208-2156 EST

Larry:

It would be interesting to see what the locked plunger current is, but it can probably be calculated from a bridge measurement on the Wiggy. Another way is to measure the transient current when voltage is applied to the Wiggy. I expect it will be about a 1/2 cycle pulse. Very much like the transformer inrush current I have referenced in the past.

.

 

[hudsonvalleyelectrician]

Phase Check

Phase Check

Has anyone thought to tell him to check for power at the main. I saw a case once involving baseboard heaters where we had 220v at the heater, but once load was applied the heater would not heat, drove us nuts, turned out to be a lost phase at the breaker. It was passing enough voltage to be read by meters and wiggys but under load it failed to keep passing the voltage. A similar condition could occur if the phase is missing from the utility and you are reading through other 220v devices in your home, the 220v you are seeing at the dryer might not be a full 220v. I would look at the panel with the main off with wour wiggy to see if yo actually have 220v... then I would change the 2pole 30 dryer breaker just in case to rule it out.

 

[busman]

I've used the heat gun for a load before. It was on a dryer circuit and I just took a dryer cord and attached the load terminals to the screws on a duplex (split wired) and taped it up real good. Check one phase on the top. The other on the bottom.

Mark