DIY - 30 Amp 3-wire Dryer Outlet Replacement. Does this look damaged?

[Mech20]

Hi all. DIY here. Electric Dryer (Kenmore Dryer - 796.61552.610) had been tripping the breaker sporadically over the past few months. Recently the dryer has stopped heating though it does still continues to spin and blow air.



Using a multimeter, I checked the double pole 30 amp breaker's voltage and it is fine. I checked for continuity (and ohms) on various dryer parts such as the high limit thermostats, thermister and heating coils. All seem fine.



I then checked the voltage on the 30-amp 3-wire surface mount outlet. The black side (left in the picture) read 123 while the red side (right in picture) read 2. Both together read 124. I did the same readings on the dry terminals with the same results.



I'm assuming the outlet is bad. I opened it up, removed all of the dust balls that were inside the outlet and took this photo. Is it possible for an outlet to malfunction without some sort of obvious looking issue? Or perhaps there is something obvious there that I'm not aware of. I'm not sure why the electrician (would have been around 20 years ago) taped the red wire. I'm assuming the dryer issue is actually an outlet issue but I don't want to change the outlet if I've overlooked something.



Thank you for any advice.

 

[Lucien Nunes]

The hot and neutral screw terminals are a little corroded which can lead to high-resistance connections, but that probably isn't the case here otherwise they would likely also show signs of overheating. Obviously check the terminal tightness just in case the terminal is not in contact with the wire, but OTOH there's nothing that suggests a short-circuit that would trip a breaker. There are two separate symptoms, one hot wire dead (open-circuit) and a tripping breaker (probably short-circuit) which are probably from the same cause (a nail through the cable?) but not guaranteed to be.

If the connections are tight at the panel and the outlet, there's probably some cable damage somewhere between the two. I would disconnect all four conductors at the panel end, join them in a wirenut and test for continuity between them at the outlet. The hot that is showing 2V at the outlet should also show no continuity or high resistance between the two ends. If the continuity shows as OK, test back the other way from the panel, and then separate the wires and test between each and each other at both ends for shorts. If anything is wrong, you might have to follow the cable along its route to locate the damage. If it's hidden, there are gadgets to measure the distance to the fault but they are not cheap.

I am in the UK and my knowledge of the USA's NEC is sometimes patchy, but IMO that receptacle is not correctly wired. The middle prong of a 10-30 is technically a neutral, not a ground, and should be connected to the white wire, not the bare copper one. The 10-30 was intended for dual-voltage circuits - 120/240 - two hots and a neutral, but without a ground. That hookup would be correct for a 6-30 type which is for single-voltage 240V circuits - two hots, ground, but without a neutral. As I understand it, the confusion arises because for 30 years after the 1966 edition of the NEC, it was permitted to connect the dryer chassis to neutral instead of ground, as the risk of the chassis becoming energised through a broken neutral connection was reckoned to be small. However, that grandfathered rule was deleted in 1995 because it had caused accidents, and now it is not permitted to install a dryer outlet without a ground, so a 14-30 4-prong type is required for a new 120/240 dryer circuit.

Obviously that NM cable is 3+G so once the fault is repaired, the neutral could potentially be connected at the panel and the outlet upgraded to a 14-30 without replacing the wiring. I would say that the situation you have - a suspected break in the cable from the panel - is actually one of the few that can cause the dryer chassis to become energised and create a risk of shock. OK, your break appears to be in the hot not the neutral, but we don't actually know yet what has happened. If possible, I would look at it as an opportunity to upgrade to a 4-prong outlet and remove that potential hazard.

 

[Mech20]

Hi Lucien Nunes. Thank you for the information. I should note that the breaker didn't always trip. It was every often but did become more frequent. As of now the dryer doesn't even turn on (though the dryer door light flickers when opened). It did run and blow when the heat stopped. I'm not sure if testing it again or running it again has caused it to not turn on or if the board has blown or it's even more underpowered or what.

I removed the tape on the red wire that's in the outlet box and noticed that the insulation was perhaps inadvertently partially stripped when installed....just a guess, not sure. In the photo attached (outlet and both conduit boxes) you'll see the exposed wire with what I assume is green oxidation (white arrow pointing to it). Could that be the issue?

The wiring from the breaker box to the dryer outlet goes under ground for some of the way. I have noticed that it is being pushed above ground at one point likely because of roots. I opened the conduit box that leads into the ground and the other one that comes out of the ground (which then leads to the dryer). The first one was caked with dirt. I tried to remove as much as possible without messing around too much in it. I didn't see any obvious signs of issues with the wiring in those boxes but I'm just a diy'er. I'm wondering if those wires should be tested at each box?

Thank you for any tips and/or ideas.

 

[Lucien Nunes]

My best guess is that the roots have damaged the UF cable and if you test that section it will have one leg open circuit, very low insulation, and all sorts of nasty arc damage and generally look like a train wreck. The boxes don't look so great either. The wirenuts are probably not the cause of the bad connection as otherwise I would expect to see signs of burnout. The green corrosion inside the wire at the outlet is probably a reaction between the copper and the insulation, that actually stretches all the way along the cable. It was a problem in some UK-made cables too in the 1960s/70s, when they tried a new formula of plastic compound which attacked the copper. We call it 'green goo.' Alternatively, water might be wicking along inside the cable if this run goes outside.

I would say that a dryer circuit feeing a 10-30 outlet is the last place you want suspect cables and connectors, for the reason I mentioned earlier that there is no ground and the dryer ground has to be tied into the neutral prong. A failed neutral connection can cause the whole chassis to become live, and a damaged underground cable with possibly rusted-out connections is a sure way to encourage an open-circuit neutral. This is exactly the scenario that led to electric shock accidents and made the NEC withdraw the grandfathered use of no-ground circuit.

Without any further thought, I would disconnect this at the breaker. Inspect and test the underground cable and repair or replace as required, and overhaul the connections at all junction boxes (if that twisted bare ground doesn't have a wirenut, that's literally shocking because it's also the neutral.) I would want to see insulation resistance tests for all the cables before pronouncing them safe and good to re-connect. If at all possible, reconnect this as a 3+G circuit with separate neutral and ground and upgrade the outlet and plug to a 14-30. Then, if the cable is damaged, either the dryer will stop working or worst case you lose the ground, but you will avoid the nasty outcome of 120V on the dryer body occurring with a single bad connection or broken conductor.