What a cool site! I ran across this site while researching a nagging electrical problem and decided to post this thread.

I have been having a problem with a dryer tripping a breaker. However, it only trips the breaker after it has run 5 - 10 minutes and I noticed that the breaker gets warm-to-hot to the touch when it trips. Plus the breaker won't reset for a couple of minutes until it cools back down. Not good.

In the course of working this problem I have replaced the breaker, the dryer (it was an old dryer with other issues so it was due any way), and the dryer outlet. When we replaced the breaker back around Thanksgiving the problem went away for a month or so but came back around Christmas. So Saturday we decided to replace the dryer and yesterday while digging deeper I took the outlet apart and noticed some arc marks on one of the contacts so I replaced it to no avail.

A little more background. The wiring in the house has some age in that the house was built in 1954. The dryer circuit is dedicated and has 3 wires running back to the breaker box: red, black, and white. The red and black wires connect to the bottom of a Square D 30 amp breaker and the white wire connects to the neutral bus in the box.

I am stumped as so what is going on. I suspect a problem in the breaker box since replacing the breaker did affect the problem positively. But I am skittish to dig into the box without having an understanding of what may be happening. The only other thing I haven't replaced is the dryer plug which would be an easy thing to do. But after researching last night and finding this site I thought I would seek some guidance before replacing any more parts.

Any ideas on what is going on? Thanks much in advance for your suggestions!!!!

kc

 

What you have described is the standard breaker trip due to overload. Overloads can sometimes be spoofed by excessive heat. Excessive heat can be caused by poor connections, ambient conditions, or too small of wire.

It is possible with a very old house that the dryer was originally wires to a 20-amp breaker with 12-gauge wire. Of course all modern dryers require 30-amp breakers, so somebody may have changed the breaker without changing the wire.

Can you verify the gauge of the wire? Is it copper? Did this setup work fine for years before the problem started? Are the adjacent breakers warm too?

 

Also, how secure is the breaker in the panel? Does it take some force to pull it out? Do you notice any scorch marks on the bus?

 

The setup in the house did work fine for years until this started happening. We have been in the house for 19 years and the 30 amp breaker was there at that time and we have had a dryer on the circuit the whole time with no problems until this fall. There is only one breaker adjacent to this one in that the original fuse box is still in place and these two breakers are on a sub-box from the main. I suspect that when a dryer was added way-back-when the sub-box was added to handle a 30 amp circuit and breaker. There are larger fuses for the range in the main box but everything else is 15 or 20 amp. However, I did not notice if the adjacent breaker warmed up as well.

It is original wiring though. The three wires are in flexible metal conduit like all of the other wiring in the house. As far as gauge goes I am not sure but it is either a 12 or 10 gauge solid copper wiring. I remember using 10 gauge on another circuit I did and it most resembles it (more difficult to bend) but I am not sure. What is the best way to confirm the gauge?

You mentioned this sounds like a typical overload and there is a facet to this saga I didn't relay in the original post. All was well until November when we had another dryer burn up. It literaly caught fire which we attributed to being a lint fire. But the wiring and other internals were damaged so I ditched that dryer and we got another used dryer from my brother-in-law which I referred to as the old dryer in the first post. The problem with tripping the breaker started with this replacment dryer and that's when my father-in-law suggested replacing the breaker which seemed to fix the breaker trips for a month or os. I wonder if the power requirements may have changed on the dryers with the switch. With that in mind should I consider measuring the draw on the circuit while it is in use to see if the load is excessive?

kc

 

If the breaker tripping started AFTER you replaced the dryer, then I'm more inclined to look at the dryer as the culprit, not the breaker/wires. How old is this 'old' replacement dryer you obtained? Is is a plug-in or direct-wire model? If it's a direct-wire model then perhaps recheck the connections. (with the power off of course) Otherwise you may be better to head over to the appliance forum on this site here and ask the folks there for an opinion.

Regards,

Savant

 

The "old" replacement dryer is 10 -15 years old and I was convinced it was the culprit last Saturday myself. Went out and bought a brand new Kenmore, came back, hooked it up, and tripped the breaker after 10 minutes of running. It is a plug-in model and Sunday I inspected the dryer outlet and noticed a couple of "arc" marks on one of the prongs so I replaced it to no avail. So far the only thing left not replaced is the dryer cord (I did to a continuity check on all three prongs which looked good), the circuit breaker box itself, and the wiring. I am thinking about the connections to the breaker in the box. There is an empty slot and for my next move I am going to try the breaker in the extra slot and redo all of the wire connections to the breaker. Beyond that I think it will be time to test the wires. Any ideas on how to test the wires end-to-end?

kc

 

Kcard,

If I read correctly, you say:

1. The dryer sub-panel is energized from the fused main service panel. What size fuses? Any other wires on those same fuses? What size and how many wires go between the main service panel and the sub-panel?

2. You say the sub panel has a second breaker in it so there is a 120 volt ckt supplying power to something? Any idea what? What size breaker? What size wire?

3. Inspect and verify for sure what size wire goes from the sub-panel 30 amp 2 pole breaker to the dryer plug. Verify it is indeed a 30 amp 2 pole breaker.

4. Where exactly is the sub-panel located? Anywhere near a heat source? Is it in a damp location? How far away is the dryer receptacle? Would it be easy to replace with #10 wire?

Maybe answering these step-at-a-time questions will reveal something....

 

Trs4594,

1. In the main panel there are a pair of 60 amp main fuses with another pair of 50 amp range fuses. Everything else is a 15 or 20 amp screw-in fuse. I don't see any other wires coming off of the main box except there is another separate breaker/switch for the water heater although I can't tell where it is fed from. The sub-panel is fed by three heavy gauge wires (I believe 6 gauge) -- red, black, and white which each feeds into their own bus strip.

2. The second breaker in the panel is a 20 amp circuit feeding my garage and a few additional outlets I added when I refinished my basement. The run feeding my garage is 10 gauge while the run feeding the outlets in the basement is 12 gauge. Each has 3 wires - white, black, and a copper ground. The white wires feed into the neutral bus, the black wires feed into the bottom of the breaker and the copper grounds are attached to the box.

3. Since my original post I have schooled myself in wire gauges. The wires feeding the dryer are 10 gauge albeit they may be 50 years old and the breaker is a square-D 2 pole 30 amp breaker.

4. The sub-panel is right next to the main panel -- about a foot away. Both are about 8 feet from the furnace located on the basement wall just below ground level. I do not sense any issues with heat or dampness other than when the breaker heats up after tripping. The dryer outlet is across the basement on the far-side wall. It is about 30 feet wall-to-wall but I am sure the run is several feet longer with the usual up-down-over. The dryer circuit wire could be replaced but it would be fun getting it in and through the walls and ceiling to hide it. If I did it I may have to just leave the wire exposed which I am sure my wife would love.

The thing that puzzles me the most about this is that none of this is new. We have been in the house 19 years and I did run a new garage circuit and added the outlets in the basement as mentioned above but both of these events happened over 10 years ago. We did have that dryer burn up back a couple of months ago which I feel could be related. It is also odd to me that the replacement dryer worked well for over a month when we replaced the original 30 amp breaker. Finally, the other thing I can't get over is that it takes time for the breaker to trip. It seems to heat up and it takes 5 to 10 minutes when first started. It takes less time to trip if I reset it and try again -- like it is already heated up and it takes less time to get there again. Maybe this is normal for an overload but it still puzzles me.

Thanks for the post and keeping the thoughts going...

kc

 

As noted, the heat you feel at the panel/breaker is common in an overload situation. For example, let's say you had a circuit that was rated to handle a load of 30 amps, but you put a 15 amp breaker on it. While the breaker would get hot (and eventually trip) from an overload, the wires at the actual device shouldn't get hot since they are rated to handle that load.

With that in mind, perhaps you can do a little test. Next time you use the dryer, get a stopwatch and time it. After 5 or so minutes, feel the dryer cord and outlet to see if they are hot. Keep the dryer going and as soon as the breaker trips, leave it OFF and feel the dryer cord, unplug the cord and feel the prongs, feel the outlet, and if you can work fast, open the dryer plug box and feel the wires connected to the receptacle. The cords and wires should be a bit warm but they shouldn't be hot.

In the meanwhile, I would suggest you don't run the dryer at full heat. Tripping the breaker repeatedly isn't safe, and it can cause premature failure of the breaker. Check your dryer manual for a reduced heat setting. (perhaps the 'gentle' cycle - depends on the model) On the reduced heat setting, try running the dryer again and see if it trips the breaker. If it doesn't, then it would strongly suggest a load issue and not a device issue. So long as a reduced heat setting doesn't trip the dryer, you can run it longer to dry your clothes in the meanwhile.

Since you have pretty well replaced everything, the only thing not replaced is the wire run back to the panel. What's possible is that when the old dryer failed, there was a significant overload that has damaged the integrity of the wire. This in turn could cause the device to draw more current to meet its normal demands. In this case replacing the entire run back to the panel is the only way to rectify this.

Regards,

Savant

 

kcard,

In trying to explain a problem, remember all that led up to it, and run a troubleshooting scheme it can become confusing. I always figured knowledge is power and by eliminating what it aint we should be able to narrow it down. Since the fuses in the main panel have held and the 120 volt ckt in the sub-panel has not tripped, we should be able to eliminate that area for now, right?

Now remember what John Nelson posted earlier on?

>>>>

If you are certain all the connections on the dryer ckt were snugged down so there were no loose conections anywhere, here is what I would do next: Unhook and move the dryer over near the sup-panel and/or buy a piece of 10-3 long enough to reach the dryer from the 30 amp 2 pole breaker in the sub-panel, and wire it into the new dryer receptacle you also bought. Make sure your connections are proper and snug and of course, be careful in the panel. Run the dryer for a bit until you are sure everything is jake. If the breaker trips, post back and we'll work another angle. But if it holds-and I think it will-you know what your problem is for sure...

 

We started off this evening checking the breaker and all looked visibly well. So next we moved the dryer over near the breaker box and rigged up a short run of wires to test from the outlet through the dryer and from the breaker out. It ran fine and the breaker did not heat up at all. All that's left is the wiring and it doesn't totally surprise me they are the culprit. With the age of the wires combined with the event where the dryer burned up I feel they must be damaged so it is time for a new run. Looking at it I don't think it will be too bad. We are going to run some surface mount wire moulding through the family room portion and thin wall in the utility room. Once again I appreciate everyone's help!!! Happy new year all!

kc