April 30th, 2020, 9:51 pm
May 1st, 2020, 8:39 am
May 1st, 2020, 8:40 am
Stuart Polansky wrote:Tom,
I've personally gone, to and heard from fellow employees who've gone on more, service calls for clothes dryers that spin, but don't heat. Problem is either failed heating elements or a 2-pole breaker which has only tripped on one phase. FPE is the usual culprit here and the issue is well documented with FPE breakers. I have never seen a dryer that didn't "need" the neutral connection. Haven't seen them all, nor even "most". Measured many a dryer load in a CBP, and always found greater load on one phase than the other, in addition to a neutral load.
I take your word for it that you've had experiences with dryers that do not have a neutral load.
So here's the deal: We must plan for the worst case. We don't know what dryer will be used, what future changes will occur when a new dryer is purchased, etc. So we always provide a neutral separated from ground, even if the present load doesn't need it. Exactly like the case with your pulsed xenon lighting. If we are installing a NEMA receptacle, we follow Code and Listing rules for that device, because ANYONE can come along after the installation and connect ANY appliance to the receptacle that has a matching cord cap. That person has every right to assume that conductors are connected correctly, not for one specific device.
A similar issue comes up with motor loads. We size wiring and overcurrent protection according to Code tables of motor loads. The ACTUAL motor used for the application will most likely have a lesser nameplate load. But that motor will eventually fail and be replaced with another (assuming same size to drive the same machine). The repair person may use the cheapest Dayton motor possible because his customer wants to spend the least money possible. That replacement motor will likely have a higher nameplate FLA than the original.
Again, we have to assume the worst. We supply the biggest circuit that an "X" horsepower motor could require. The overload protection is tailored to the specific motor nameplate information.
So I understand that it seems like the Code is "selling" you something you don't need, but the fact is, the installation is not designed for you, it's designed for you and whatever future owner/tenant comes along with whatever future requirements may exist.
May 1st, 2020, 8:51 am
May 1st, 2020, 9:29 am
tomp wrote:Stuart I totally agree with you on planning for future development. That is why I'm specifying a NEMA 14-50R receptacle in my garage for the electric car charger. It is a 4 wire connection even though many of the car chargers only have 3 wire plugs. Here are photos of the NEMA 10-30P plug on my current dryer which has largely been superseded and the newer NEMA 14-50R
May 1st, 2020, 9:38 am
tomp wrote:To further reinforce what Walt has said about fires it is interesting to note that the National Electrical code is produced by the National Fire Protection Association and is one of their many codes.
May 1st, 2020, 10:56 am
SoundMods wrote:I imagine that if you get enough electricians hauled away in a stretcher -- the requirements change.
May 1st, 2020, 12:05 pm
Stuart Polansky wrote:SoundMods wrote:I imagine that if you get enough electricians hauled away in a stretcher -- the requirements change.
Not just electricians on stretchers.
When Tom P. Walt and I were little kids, the standard used to ground an electrical service in a single family home was by connecting to the cold water pipe. No supplemental grounds were used. In that time frame, cold water pipes would have been galvanized pipe (with yummy lead inside) or copper tubing. So, the electrician installed a GEC (grounding electrode conductor) from the panel to the most convenient water pipe.
Three things happened. 1) A plumber repaired or replaced a section of pipe, maybe made a new tap for a new plumbing fixture. He shut off the water and cut the pipe in the basement ceiling over his head. He gets wet, and when he separates he pipe between his two hands, he becomes part of the service ground. Zap, one less plumber. 2) The connection was made to a hot water pipe and a new water heater was installed with non-metallic piping inside. No service ground in the house. Very bad for occupants. 3) That nasty old galvanized piping gets replaced.......with PVC or PEX. Again, no service ground in the house. Danger Will Robinson.
So, Code evolves, as Tom and Walt pointed out, due to dead plumbers and shocked, or worse occupants. Now we connect to cold water within 5' of the point of entry of piping to the house 250.68(C)(1). Where I work, we try very hard to make the connection closer to the point-of-entry than that. Also we try to connect ahead of the water shutoff whenever possible. AND we are required to use at least one ground rod (PG County requires two ground rods), so we minimize the chance of harming a plumber or homeowner working on household piping.
May 1st, 2020, 4:24 pm
May 1st, 2020, 6:43 pm