doughboyshredder wrote: I have been grabbed by 115 and held for over 5 seconds with the current going through my ass cheek in to wet soil. That sucked.
heh I got zapped the same type of way but got me in the back of the leg.
just dont grab with both hands or grab it and something else that will send the current across your chest!!!
The more i hear about this crap the more i just want to run a furnace and piping thru my molds/press
Though Dave is an electrician, i'm surprised this has never crossed his mind, maybe he's waiting for me to get knocked on my arse so he can have a good laugh.
knightsofnii wrote:just dont grab with both hands or grab it and something else that will send the current across your chest!!!
The more i hear about this crap the more i just want to run a furnace and piping thru my molds/press
Though Dave is an electrician, i'm surprised this has never crossed his mind, maybe he's waiting for me to get knocked on my arse so he can have a good laugh.
Start a poll to see how many people have gotten bit by their blankets.
I'm not trying to discount doughboy's or anyone elses experiences, but I have a feeling they are in the minority and something else might be going on with their setup. If everyone were getting zapped by "trace voltages" there would be a lot more threads about it.
I experienced the "trace voltage" doughboy described too tonight.
Blanket undamaged hiheat silicone type. Felt a fuzzy feeling when touching ungrounded cassette. It was worst near where the leads are and not evident right up the other end.
I will set up my ground system and hopefully that will get rid of it. I like the idea of a 1 hour pressing, but I don't know about this electricity business. A bit of a fad, I can't see it really catching on
I've been researching this too falls. My blankets should be here in a week or two. I'll definitely be grounding my press and alu layers. I really don't see a down side to doing this.
i have never been zapped by my blankets/alum.
the wiring on my press is very complex tho (relays, fuses, electrical everywhere).
220 isnt that bad, it hits you so hard you have the instant reaction to pull away (i always get shocked welding)
110 and higher than 220 have the option to really hurt because they will try and hold the connection with your body.
i worry more about burning myself badly on the alum if i am not paying attention.
will check wiring today for internal grounds (def nothing on cattrack, alum, etc)
Hi guys, thought I'd throw my thoughts in here for what its worth. I do have an electrical background experience and industry qualifcations so I can talk reasonably well on this.
My advice applies to NZ scenario, and any other country that follows the similar MEN multiple earth neutral system. Typical NZ we get 230VAC supply single or three phase.
First of all, make sure everything is well grounded to a common point. In my press I will be running some heavy earthing wires from the press frame members, and the cat track and the ali skins back to a common point. The resistance end to end back to earth lead where it terminates to the wall socket should be < 1ohm as a rule of thumb, hopefully less.
If you use an RCD then even better it will hopefully trip out before the earth wire even has a chance to conduct fault currents.
I am suprised any of you are getting shocks, I doubt very very much these are induced or trace voltages , and suspect this is simple electrical conductivity of the blanket material which sounds daft but I see no other possibility.....
Get the blankets tested properly with a megger or similar insulation testing device to test the insulation quality.
I don't really buy into any voltage being safe or otherwise to be shocked by, a high potential difference will allow a current to flow if you have sufficient conductivity, its all dangerous and uncontrolled so the best bet is to stop it happening alltogether - you shouldn't have any leakage at all or otherwise the blanket manufacturer is negligant in my opinion.
Any questions please fire them through, keen to help fellas.
At this stage I am the slowest press builder , my press is basically built and I have a great NZ company who is going to build my blanket, they build industrial silicone heat blankets all the time and are totally entheused about my project. So for whats its worth I have not built a single ski or board yet but I hope my electrical advise helps save you guys some nasty expereince.....
Great info thanks. what is an RCD? Are there guidelines on what gauge wire to use for this type of grounding system? I realize the NZ/US guidelines might be different.
RCD = residial current device. It compares the phase and neutral for any current difference, if there is then it must be leaking to earth. In a safe circuit phase and neutral should have the same current flowing of course. I'm not sure if RCD are used in the US or not.
Seriously get a sparkie in if youre in doubt. Insulation testers are common, and I suggest fix the issue thats causing the leakage as well as using earthing or RCD to protect against genuine faults like a cut blanket.
Hi, I would use similar or only slightly heavier than phase/neutral wires so you know it is not the weakest link. It does not need to be super heavy as its only carrying the same fault current that flows through phase/neutral and for long enough to blow the breaker which should be the weakest link eh! However since its possibly exposed earth wiring on the press a heavier wire looks nicer and is a bit more robust.........cheers
My controller will be ground separately from my press. Since my enclosure is metal I have a common ground post that grounds the case, main power switch and and outlets. Sine this is 220V wiring it takes #10 wire for everything. I plan on using #8 to ground the press frame and alu layers. I think for the Alu layers I'll use something like this to attach the wire to the sheets
I'll run those ground wires to a common point, maybe back to my breaker box ground bar. I'll have to check with my electrical guy on that part.
Well the electronics should hopefully have some good isolation from the mains through whatever low voltage power supply is in between, if you're worried about protecting your electronics from mains spikes? Any stray voltages generated within the press need to be nailed or you may have all kinds of other problems incl toasting your electronics...... I would take everything back to a common chassis earth myself and sort the stray voltages.
My press control system is becoming somewhat complex, as I have introduced accurate pressure control sensing and measurement and solenoid valves rather than "taps". This is possibly going to be more trouble than its worth but I am most of the way there now to get it going. The same controller that runs the pressure control will also kick the heating PID system in and out, so it controls the whole process.
I did have other concerns regarding the fragility ofthe electronics, as the pressure solenoid valves have a back EMF when turned off, so I am putting some diode snubbers on the solenoid terminals to suppress/conduct the back EMF, seems to work. Otherwise I might toast my little controller unit.
Why all this fancy stuff? Cause I can! Well actually I am aiming for a consistant pressure ramp up slowly in maybe 10psi increments over 10 minutes to get a more controlled squeeze out and less slipping/sliding, maybe????
