help with dryer circuit please.

Merry Christmas
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gar

Senior Member
100207-0939 EST

Charlie Bob:

My following comments may seem harsh, but treat your problem as a learning experience.

You have been instructed correctly above to use a large load to test a circuit for problems with poor connections.

Your customer was perfectly correct in telling you to solve the problem at your expense. Your customer went to the extra expense to buy a new dryer because you probably incorrectly diagnosed the problem.

A question without an answer yet --- did the new dryer come with a new cord and plug? This might be critical as to whether the misdiagnose was all your problem. Note: you could have done a resistance check on the neutral conductor in the cord.

Your following statement from the first post is not at all clear:
I check for continuity, everything is OK. I pluged the cord, and check the connections at the dryer, 245V L1-L2, and 65V L1-n, 178V L2-N. Loose nuetral or broken neutral in cord. Idisconnect the neutral from the cord at dryer connection.I get 245, 110, and 117V at the cord, when i check at the dryer is showing open neutral though.
I think you were saying --- I disconnected the neutral wire of the cord from the neutral terminal in the dryer. Then I read 245 line to line, 110 from one line to the cord neutral, and 117 from the other line to the cord neutral.

Note: 110 +117 = 227 is not 245. This should be a red flag.

I have no idea what you meant by " when i check at the dryer is showing open neutral". Checked what, and open neutral where?

Your problem is a good illustration of why an understanding of electrical theory, and how various instruments work is important.

I favor using a high impedance voltmeter and when needed adding a shunt load like a 1500 W heater to check for a high impedance source. But I am not an electrician and a Wiggy as an only tool would be more convenient.

You could have a poor connection, assume 5 ohms, in the neutral. I do not know the impedance of a Wiggy, but I will guess at 1000 ohms. A change of 5 ohms in 1000 ohms at 120 V only produces a voltage change of 120*5/1000 = 0.6 V. By comparison a 1500 W heater when hot is about 10 ohms. A 120 V source with a 5 ohm and 10 resistor in series as the load will produce about 120*10/15 = 80 V across the 10 ohm (heater) load.

Using a modern high end high impedance digital voltmeter should give you 0.1 V resolution on a range reading 120 V. One can not realistically put a continuous 1500 W resistor for 120 V in this meter. You can do a lot of useful troubleshooting or circuit tracing with a meter with 0.1 V resolution, and an external 1500 W load.

.
 

AV ELECTRIC

Senior Member
Make up a 3 wire drop cord, lug it into the orignal dryer breaker and plug the dryer in. If the dryer functions properly then something is wrong with the orignal circ. from the panel to the dryer plug. If it doesn't function properly then it should be something in the panel. Could be as simple as a bad breaker. Since you did not mention anything else going wrong other than the dryer chances are you can rule out a bad poco neutral.

I agree Ive done this before and saves a lot of time .
 

brantmacga

Señor Member
Location
Georgia
Occupation
Electrical Monke
They now called me all worked out, they want me back and the guy even told me that it's got to work this time since they already paid me. Hell of a nerve.

I can't say I blame him. You gave the wrong diagnosis; so off that the customer went and purchased a new appliance when that was never the problem.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I didn't suggest a dummy load since the OP has a perfectly good one: the dryer not working and the voltage imbalance showing up.

All he has to do is narrow down the point where the imbalance starts, geographically speaking, by testing at the accessible places.

I've seen people buy new dryers when the old one ran but didn't heat. Of course, the supplying only the heater element was open.
 

zappy

Senior Member
Location
CA.
To add, what I meant is that a low-impedance load (such as a solenoid tester, a 100w bulb, or a dryer's line-to-neutral loads) will expose the voltage differences, while a high-impedance meter won't.

The voltages must remain balanced (within a small range) under load for the load to function properly with line-to-neutral loads. Line-to-line-only loads have no 120v components.


Any ol' time. :)

There's my answer, again. Maybe i should read more and type less:roll:
 

zappy

Senior Member
Location
CA.
I'm confused

I'm confused

100207-0939 EST

Charlie Bob:

My following comments may seem harsh, but treat your problem as a learning experience.

You have been instructed correctly above to use a large load to test a circuit for problems with poor connections.

Your customer was perfectly correct in telling you to solve the problem at your expense. Your customer went to the extra expense to buy a new dryer because you probably incorrectly diagnosed the problem.

A question without an answer yet --- did the new dryer come with a new cord and plug? This might be critical as to whether the misdiagnose was all your problem. Note: you could have done a resistance check on the neutral conductor in the cord.

Your following statement from the first post is not at all clear:

I think you were saying --- I disconnected the neutral wire of the cord from the neutral terminal in the dryer. Then I read 245 line to line, 110 from one line to the cord neutral, and 117 from the other line to the cord neutral.

Note: 110 +117 = 227 is not 245. This should be a red flag.

I have no idea what you meant by " when i check at the dryer is showing open neutral". Checked what, and open neutral where?

Your problem is a good illustration of why an understanding of electrical theory, and how various instruments work is important.

I favor using a high impedance voltmeter and when needed adding a shunt load like a 1500 W heater to check for a high impedance source. But I am not an electrician and a Wiggy as an only tool would be more convenient.

You could have a poor connection, assume 5 ohms, in the neutral. I do not know the impedance of a Wiggy, but I will guess at 1000 ohms. A change of 5 ohms in 1000 ohms at 120 V only produces a voltage change of 120*5/1000 = 0.6 V. By comparison a 1500 W heater when hot is about 10 ohms. A 120 V source with a 5 ohm and 10 resistor in series as the load will produce about 120*10/15 = 80 V across the 10 ohm (heater) load.

Using a modern high end high impedance digital voltmeter should give you 0.1 V resolution on a range reading 120 V. One can not realistically put a continuous 1500 W resistor for 120 V in this meter. You can do a lot of useful troubleshooting or circuit tracing with a meter with 0.1 V resolution, and an external 1500 W load.

.

A "wiggy" is around 1000 ohms? And that's a low impedance? Sounds high to me? What is a DMM a 100000 ohms??
 

gar

Senior Member
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

.
 

rich000

Senior Member
I am not sure if you mentioned it or not, but did you check the connections in the panel? i.e. are they all tightened down?

My shotgun internet response is a loose connection at the panel or at the receptacle.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Gar,
My guess is that a wiggy draws about 30 mA at 120 volts. This is based on that fact that it sometimes trips a 30 mA ground fault breaker and other times it doesn't. I have never hooked a meter up to find out for sure.
 

gar

Senior Member
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.

.
 

Ohmy

Senior Member
Location
Atlanta, GA
I have a short test cord with alligator clips on one end and a 15 amp connector on the other. I would connect this to the circuit in question and plug in my electric heat gun to put a 1500 watt load on the circuit. If there is a connection issue somewhere on the circuit it will show itself fairly quick with that kind of a load on it.


This is how we do it. Works like a charm. The old wiggies are great too but sometimes that do not put enough load on the circuit.
 
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