I just got my Vulcan oven delivered today and was greeted to a giant arc flash and smoke when powering it on. A little post-mortem investigation shows that Langmuir is using screws that are WAY too long to install the DC power supply in the control box. See attached photos of where the screw went all the way in to the power supply PCB and created a hard short. What’s more is that none of the terminal strip bridges were installed in my electrical box when I received the machine (I have insulated terminal bridge strips on hand, so I took care of installing them). Knowing that they missed all on mine, someone could get a machine where they only missed the one on the ground connections and, as a result, have a machine that isn’t properly grounded. THIS IS A MAJOR ELECTROCUTION HAZARD THAT PEOPLE NEED TO BE AWARE OF AND LANGMUIR NEEDS TO ADDRESS IMMEDIATELY.
Perhaps my machine was the only screwup, but I encourage everyone to carefully check their machines for proper wiring and grounding as they are setting them up. Also, the three screws on the back side of the electrical panel which are used to mount the DC power supply should be removed one at a time and checked for length. None of them should be longer than about 3/16 of an inch.
For folks who have working ovens, I wouldn’t make an assumption yours is safe because it hasn’t blown up a power supply. There’s a piece of thin insulating plastic under that PCB and if a screw is poking at it, you’re on borrowed time. It doesn’t take a lot of effort to pop the electrical box and check the mounting screw length. Better to take a few minutes to do that than have a short and best case you just pop the supply, worst case someone gets electrocuted.
There is another major electrical problem I found with this oven and it’s a design flaw that violates electrical code. I was wondering why my circulation fan ran at turbine speed when I turned it on. It turns out it’s a 120v fan and when I was going through the assemble instructions, I thought the arrow for the spade connector on that wiring harness was pointing to the terminal block on the right because you aren’t allowed to use safety ground as a neutral, it violates code. Sure enough, a quick look at the curculating fan shows it’s 120v and they are telling you to hook up the neutral to the safety ground bar. Same situation with the light kit, they want you to get 120v by using safety ground as a neutral. That’s an electrical no-no because if you lose your safety ground, the machine frame floats and it’s another electrocution risk.
There are two ways to fix this.
Use a 220v circulating fan and bulbs in the lamps, common for both gets wired to the right side bus
The machine needs a 4 wire connection. L1, L2, neutral, safety ground.
Langmuir needs to address this. It’s not just some inconvenience thing, this is the sort of thing that should have a recall notice issued.
FWIW, I’m not trying to bash on Langmuir here. I like that they are putting things out that offer great value for the money. At the same time, the concerns I’m raising here are very real safety problems and not particularly costly to correct but they absolutely must be corrected for everyone that has bought one of these already and the design and QC need to be updated to ensure the mistakes aren’t repeated.
If langmuir doesn’t respond here early next week, I’ll post instructions on how to replace the cord and what wiring changes need to be made in order to get the machine to a safe operating configuration. Its about 30-45 minutes of work for anyone that is kinda handy.
I wired mine 4-wire with a neutral plug and saw the same issue. Regardless the machine chassis is still grounded. But I understand your point. My screws are short machine screws on the power supply. My machine was a prototype oven, and I was chasing a ground loop from the shielding of the thermocouples, touching the oven walls. I installed high-temperature shrink tubes on the thermocouple cables. I also installed ceramic insulators between the thermocouple brackets to isolate them from the stainless steel inner housing.
I believe that the thermocouple shielding was addressed prior to the release curing the ground loop issue.
With mine, the thermocouple standoff pieces had center holes that were oversized and they included some high temp plastic insulating washers. The thermocouple now have a fiberglass sleeve as well. One of mine is still kinda flaky and there isn’t any useful diagnostic info to tell me which one when it goes wonky.
I guess there is a third option for fixing the grounding / neutral issue that I left out. A small step-down transformer. Not what it would call the best solution, but it might be doable since we’re only talking about two halogen lamps ans a 50w fan motor. 150w would be more than adequate.
As I posted on the other thread, you can go to the top right of CureControl and tap on the page icon. You will be able to see the exact temperature of each one in real time. I turn off the scroll setting to monitor them. CureControl threshold is to tight during warm-up. Now if you are getting the alarm during curing then you might have a problem..
It does not violate any code. It has a grounded chassis. The machine is a 240-volt oven. Pull out your oven at home, and it will be the same way. Unless it has got clocks and 120-volt circuits. Which it does not.
How I read the post.. the machine is 240v. The fans are 120v. In order for the fans to get 120v the machine uses one hot leg and the earth. I have not seen the drawings but if that is correct it’s a no no. I design machines for a living and this is something you just dont to. If you lose the earth connection anywhere in that circuit, house, building etc the metal frame becomes live as it is connected to the motor. If you touch the frame you then become the neutral connection and being a neutral hurts even if you have an earth and it’s faulty. Your body may provide a lower resistance.
Again, I Havnt seen the drawings. That is just my understanding from reading this.
Having read it again. It’s only when connecting the fan and lights does it become an issue. The machine as is with no fan or lights is ok.
The Lights are 240 and so is the fan. The computer screen and Orange pi run off a 240v to 5 v power supply. Every contactor inside is 240v with 5v relays run from the Orange PI.
I can’t speak for every unit made, but what I received is absolutely not 240v fan or lights. It absolutely does violate code. The Only thing you can use ground for is chassis ground, period. You cannot use it as a neutral line.
Maybe your pre-production unut was, but the machine I received yesterday absolutely is 120v circulator fan and lights. Also, go have a look at the assembly guide and which terminal strips they have you hooking up to. Nothing except chassis grounding is allowed to go to that green safety ground terminal strip.
Mine are 240v. But this may have changed since production. The machine is still bonded regardless of the light and fan using it. The neutral and ground bond together in the panel box anyway.
Found it, I had to turn on the status logging, but now I see the average and two individual readings. I’d have to unhook one and see what happens to the readings to figure out which set of thermocouple inputs on the board maps to which field in the status line, but easy enough to do.
We’re not talking about a transformer here. There is no isolation that requires re-establishment of ground as a 0v reference, which is the reason you do that bonding with an isolation transformer (note that this is not the case with an auto transformer, as 0v reference is maintainined in such applications).
even if you have an earth and it’s faulty. Your body may provide a lower resistance.