mtwitty

The NEC states that the OCD is "not to exceed" 150% of the rated current. 422.11(E)(3) At 208 volts, that current would be 24.4 amps. The next standard size breaker is 25, which is the only one allowed in this scenario.

I don't like the double-tapped neutrals and the lack of handle ties on the MWBC's.

I think the primary function is binary. To gather all available pertinent information relating to the home. To accurately and clearly relay that information to the client.

Both 25 and 30 amp are compliant if the supply is 240 volts. If the supply is 208 volts, only a 25 amp breaker is allowed.

Cool micrometer. What brand is it?

Even if the mouse gets in, a trap is waiting for him.

#3 size are not allowed to be used in parallel. 1/0 AWG in the minimum size allowed for parallel feeds, per 310.10(H). For that reason alone, it's wrong.

The panel is a 200 amp, which in '92 allowed 40 breaker poles. The tandem is not allowed in that panel. The discoloration looks more like some type of chemical contamination than heat damage, but still may be a concern. There is some obvious paint overspray. I don't call out Challenger panels just because of their brand, particularly the newer ones like in your photo. There are many examples online of some failures of these panels. I have a pretty extensive photo library of failures on ITE, Siemens, Square D, Cutler Hammer, and others. The Square D breakers are not listed for use in that panel. AFCI breakers were not available in '92, so there really is no "listed" AFCI breaker for that panel that I know of......possibly Siemens, but doubtful. I think providing the AFCI protection is a positive safety upgrade that outweighs the non listed breaker issue.

KVA=apparent power=power before used. KW is power under load. (power consumed) So, to find actual KW usage, the power factor must be in the calculation. At least that is how I interpret it.

I defer to Marc. This falls in his wheelhouse and he is much more qualified to give you a quality answer.🙂

Hi Doug. to find the KW under the running load you would calculate: 208 x 600 x .8 x 1.732 =172,923/1000 =173 KW. if your generator is rated for 400 KW, you would be running at about 43% of full capacity. Is that what you are asking?

Hi Marc. It is under "Branch circuit, Multiwire" in article 100.

Hi Jim. Got to get picky here. Technically, any circuit that has two hots and share a neutral is a multi-wire circuit....even range and dryer circuits.....according to NEC definition. The main difference in requirement would be that if supplying a 240 volt appliance, a common trip would be required. That being said, I think what Johnny was asking was about multi-wire circuits that supply two 120 volt loads and how to identify. Your explanation totally covered his question. You know how nerdy I can get.

Tim, that circuit is most likely sharing a neutral with another circuit.....very common in older wiring installations. The imbalance of neutral current in the two circuits will cause the GFCI to trip, or as Marc said, there could actually be a ground fault on the circuit. If it is sharing a neutral with another circuit, your customer may just have to lose their affection for the old plates. Then you can use GFCI receptacles for the countertop receptacles, as long as you don't use the load terminals for other downstream outlets/receptacles.

It was a pleasure meeting you in NOLA, Marc.

Sounds like the unit 1 may have originally been a common area mechanical room, and was later converted to be used as a residence. Tell the property manager you will be getting the local building official involved. That may expedite a correction.

The LB is not really the issue...it's what's inside of it. The interior of a raceway (conduit) in a wet location is considered to be a wet location. NM cable is not allowed/rated for use in wet locations. NM cable can break down over time if subjected to water. If water gets in a conduit or conduit fitting, it can stay for a long time. I actually had a trouble call yrs. ago with an installation very similar to the one you posted. A breaker was tripping on a circuit. When I opened the LB, water ran out. The conduit was half full of water. The wire insulation probably had minor nicks or cracks that developed over time and caused a short. If I had not experienced this personally, I probably would think the likelihood of a problem would be rare; and in most cases, it would be, but for that reason, I always report NM in wet locations as a concern, particularly when it is in conduit. In your case, I would probably just explain the potential issues that could arise from the improper installation, recommend sealing the open end of the conduit in the crawl space, keeping a good gasket/seal on the LB cover, and carry on.

In that case, I'm assuming there is an LB to turn up to the bottom of the enclosure? If so, that puts the NM cables in a wet location, which is a violation and a larger concern than the overfill, in my opinion. LB fittings can be water holding reservoirs when the seals leak. It depends on how picky you want to be, but the installation is non-compliant on several fronts. 312.5(C) has 7 conditions that all must be met, and from what I can see and understand from your explanation, it fails to meet 5 of those. Also, non flexible raceways not less than 18 inches and not more than 10 feet in length with NM cables into enclosures are only allowed to enter from the top.

Charley, does the conduit attached to the panel? Looks like it comes in at the bottom.

I don't think so by looking at 312.5(C) exceptions. #7 exception still requires conductor fill requirements for conduit sleeves 18 inches to 10 ft. in length. Typically, sleeves are open on both ends, and do not have fill requirements. This exception allows a "sleeve" to be connected to the top of the enclosure and open on the other end, but still must meet fill requirements. Other violations in Charley's photo include no fastening of the cables on the outer end of the sleeve (exception #1), and no fitting on the end of the conduit, and/or plugging the outer end. (exceptions # 3 &4) I know I got rejected for this several years ago for "too many cables" in a nipple/sleeve connected to the top of the panel. I could be wrong (usually am) but that's how I interpret this.

Conduit nipples (24" or less) can be filled to 60%. Your photo appears to definitely exceed that. It is a common violation that is overlooked and accepted. It's usually not really a big concern.

Yep, the grounded conductors should be identified white or gray. They are not neutrals, but are required to be identified as current carrying grounded conductors.

Marc, no 120 volt is available in a 240 volt corner grounded delta configuration. 240 volts from each phase to the other, including the grounded phase.

Equipment grounding conductors in intentionally ungrounded systems are designed to actuate an alarm (ground detect devices). They do not cause overcurrent devices to open as they do in grounded systems. The purpose is to allow continuation of operation when one phase develops a ground fault. The grounded leg (fault) is at ground potential, so is not necessarily a shock hazard to personnel. The alarm should be addressed and the fault found and repaired ASAP. If a second phase develops a ground fault, this causes a line to line short and shuts down via the OCPD. Ground faults are common in industrial facilities and this ungrounded system is used to allow uninterrupted production until the fault is found. It's not the safest system, but is common. The "corner grounded" system like in the photo I posted intentionally grounds one phase leg and will open the OCPD if either of the other 2 ungrounded phase legs have a ground fault. (line to line short) An ungrounded system basically becomes a corner grounded system if one leg develops a ground fault. As far as single phase systems that are not grounded....that would be a faulted system and not by design. I know this is way over the top for residential and home inspection discussion but it is good to have a basic understanding of IMO. If you look at the photo I posted, at a glance, it looks like a single phase sub panel that we see everyday. Only giveaway is all 2 pole breakers and some blue wires. Although very uncommon, this could be present in an inspection of a commercial property. Hope this makes some sense and answers your question. I apologize for side-tracking this thread. Didn't mean to get so deep in this.

Good question Marc. Probably it was used to save the cost of the extra wire. Only need 3 as opposed to 4 for a "high leg". It also was considered safer than an ungrounded delta, that is often used in industrial installations. This link is to a good article on this subject. https://iaeimagazine.org/magazine/2002/01/16/installations-and-inspections-of-corner-grounded-systems/