220V Electrical Question

[GaryM]

My electric dryer is triping the common trip 30A breakers that feed it. Dryer runs for about 3-4 minutes and then the breaker trips. Investigation reveals that one of the breakers get hot then they trip. The breaker on the other leg stays cool, other than perhaps some heat transfered by conduction from it's mate.

They are SquareD Homeline breakers Type TIPO.

As only one leg gets hot, I suspect a loose connection or a defective breaker. If they both got hot I'd suspect the dryer itself.

I do not have a amp meter to check actual current draw. New tool needed?

I'm going to pick up a new breaker set on the way home today. First I'll check for a loose connection, if the connection is tight, I'll swap out the breaker.

Any thing I'm missing here?

[Inspector507]

Gary,
Replacing the breaker is the simplest and cheapest attempt if your'e sure the breaker is making good connection on the buss. Also check the wire termination to see if it's tight. Don't just put a screwdriver to it, loosen the screw and visually inspect the wire for signs of an arc. Do the same with the breaker connection to the buss.
Could have a loose connection in the outlet or in the dryer as well.

[GaryM]

Inspector, I was hoping you'd appear, and here you are. Lucky me!

Only one of the breakers gets hot as I said. If it were the dryer or socket wouldn't it be more likely that both poles would get hot? I checked the plug on the dryer and it's pretty much room temperature. I'm pretty sure that the only unbalanced load, one leg to neutral, would be the motor and controls.

This dryer is one on the Maytag drying cabinets with the upper and lower units.

[GaryM]

I think I found the problem! [img]/forums/images/icons/shocked.gif[/img]

I cut both hot wires back about 1" to remove any heat damaged wire and insulation. Replaced the breaker too as it's was less than $8. Rather not be cheap now and sorry later!

Thanks for the advice! On the money as usual.

[Inspector507]

[img]/forums/images/icons/wink.gif[/img]

[Pat]

About that tool...

Gary, there are amp probes that replace the test leads of a high impedance volt meter or you can buy an amp probe, I.e. AKA AMP CLAMP.

The better ones handle both AC and DC. A while back the cheap ones were AC only. Since the clamp-on amp meter is essentially a one turn transformer, you can wrap the wire to be monitored around one of the jaws 2-3 or more times and then divide the reading by the number of wraps. This trick makes a cheaper less sensitive unit 2-3 or more times as sensitive as if you just clamped around a wire. Remember to clamp around just one conductor since the net current flow through both conductors (black and white...hot and neutral) is zero.

I will send the vector analysis for the field equations in a separate post.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[GaryM]

Pat,

Actually I thought about returning the meter as I didn't need it. I bought it incase the breaker showed no problems as the next step would have been to check current flow. But as most items you buy at the box store, it was sealed in a plastic package that has to be destroyed to get the product. So I decided to keep it rather than be hasseled about the package. Maybe the wrong choice, but there it is.

How do the DC units work? Wouldn't there only be one pluse as the circuit is closed?

[Pat]

Gary, Given the cost differential (It has been a while since I priced either or compared AC-DC prices to AC only prices) and the physical parameters, I'd guess there is a Hall effect device in the probe. Hall effect devices transduce magnetic fields (which always accompany a current flow) into voltages.

http://hyperphysics.phy-astr.gsu.edu...etic/hall.html

I used these devices in upper division physics lab classes and later to quantify magnetic fields. Since there is a known relationship between a DC curent and its magnetic field, you could calibrate a Hall effect device (Hall probe) to read in amps. I suspect you'd have to control the geometry within some reasonable limits.

It is entirely possible that the commercial DC amp clamps use other technology employing green Kryptonite or granular philosopher's stone or ... I don't know. They can be used for steady state readings not just transient pulse type inrush readings.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]