Shock from kiln

[theanimallover]

I have had my hotstart kiln for a few years.

Today I shuffled over to it in my slippers, bent down and got quite a shock (to my head!) from the kiln catch. Could this be a static shock? I unplugged the kiln, then touched it again but didn't get a shock. I also noticed when I plugged the kiln in a few sparks inside the socket, but you often see that inside of socket don't you?

Thanks,
K

[Bert Weiss]

It sounds like there is a contact between power and ground. Maybe a loose one or an arc. Look closely at all the connections and elements. Remember that ground could be any metal that attaches to the frame. If you have an ammeter, and access to a single ground wire, you can check to see if there is power going in to ground.

You will also get a shock if you touch an element and ground when the kiln is plugged in but not turned on. That is supposed to happen. There is a way to wire a kiln so this does not happen, but I have rarely seen it used.

[tonyroberts]

Wow, Bert, really?

You will also get a shock if you touch an element and ground when the kiln is plugged in but not turned on. That is supposed to happen. There is a way to wire a kiln so this does not happen, but I have rarely seen it used.

It sure doesn't happen over here in the UK. We must use a safer type of electricity!

Tony

PS - I'd treat your kiln as dangerous, K, and isolate it before someone else touches it. And get it fixed...

[Bert Weiss]

Wow, Bert, really?

You will also get a shock if you touch an element and ground when the kiln is plugged in but not turned on. That is supposed to happen. There is a way to wire a kiln so this does not happen, but I have rarely seen it used.

It sure doesn't happen over here in the UK. We must use a safer type of electricity!

Tony

PS - I'd treat your kiln as dangerous, K, and isolate it before someone else touches it. And get it fixed...

Tony, I think you are right. Our power comes in 120v per leg with 2 legs available. UK may well have higher voltage on one leg. In this case, that might be safer, but in most cases, it will give you twice the shock if you connect power to ground.

[tonyroberts]

You're right, bert. We have 220V on one line - called 'live' - and zero on the other - called 'neutral'. But this isn't relevant from a safety point of view, as both lines are normally disconnected when the kiln is switched off. Although there should be no current on the neutral line, there often is in practice.

Tony

[DonMcClennen]

This getting a shock from a kiln when it is turned off sounds to me like it's not correctly wired. We in Canada have the same basic system as the US. There is no way you can get a shock from a properly wired (which includes grounded) turned off kiln!!! Better get it checked!
Don

[Lauri Levanto]

here we have live, zero and ground. The kiln exterior must be connected to the ground. My own kiln has three phase wiring (Three live plus ground).

There is also an extra relay in line that before the working relays. The purpose is to cut off all live lines when the kiln is opened. It is triggered by a lid switch.

Bert mentioned that the elements may have voltage when the kiln is off. I guess this is a property of solid state relays.
-lauri

[Bert Weiss]

Lauri, the circuit wiring has nothing to do with solid state relays. In the USA, most kilns are turned on and off by breaking one leg of the circuit. This will turn the element off. If you take the probes of a voltmeter, touch one side to ground and the other to an element that is off, it will read 120v. If you were to wire the kiln with a double pole relay, this would not happen.

Lauri, you are right about SCR solid state relays. They can have their gain setting such that power leaks in to the element. A SSR is only all off or all on. Both are solid state relays.

My preferred way to wire a kiln is with a high temp limit circuit, that includes a hitemp limit controller, a thermocouple, and double pole mechanical relays for each zone. The controller is wired with a light switch. When you take power away from the controller, the mechanical relays open, which removes 100% of the power. This provides safety on various levels.

[Lauri Levanto]

My preferred way to wire a kiln is with a high temp limit circuit, that includes a hitemp limit controller, a thermocouple, and double pole mechanical relays for each zone. The controller is wired with a light switch. When you take power away from the controller, the mechanical relays open, which removes 100% of the power. This provides safety on various levels.

Sounds very similar to European safety rules. The major difference is that the high temp limit here makes use of the same thermocouple as working relays.

[Bert Weiss]

My preferred way to wire a kiln is with a high temp limit circuit, that includes a hitemp limit controller, a thermocouple, and double pole mechanical relays for each zone. The controller is wired with a light switch. When you take power away from the controller, the mechanical relays open, which removes 100% of the power. This provides safety on various levels.

Sounds very similar to European safety rules. The major difference is that the high temp limit here makes use of the same thermocouple as working relays.

I was taught this system with redundant controller and thermocouple by an industrial temperature control engineer. He has always told me that this exact system is required in industrial codes. I don't think I have ever seen it in used in any kilns I have observed in use, in either large industry or small. I may not have always looked deep enough to see it was in place. I am thinking about 2 Italian manufactured industrial style kilns, and I don't recall such a system being in place in either. One, I do recall had it's lone process thermocouple in the strangest place, it was in an upper corner, protruding a quarter inch, sitting 2" away from a quartz tube with element coil.

[Marty]

Start with the socket and plug- worn insulation? loose connections? bent blades? bad socket (GFIs go bad occasionally)?

[Rick Wilton]

I really doubt you'd mistake a real electrical shock to the head with static. I would bet it was static and it just felt worse because it was to a sensitive part of the body. (trust me I got a static shock the other day from my sandblaster to the rather sensitive area) An electrical shock to the head would be a real wake up call. Have you ever had a true 110 or 220v shock before? Like you said the slippers generated the static and you grounded yourself once your head touched the kiln. That released the static through your melon.

[theanimallover]

Wow, I really have stirred up some electrical debate! Thanks everyone for your electrical input...Sorry I started a conversation, then got ill and haven't had time to look and respond.

After all that I think that Rick is right, it was just a very sharp static shock as I got similar yesterday with a light switch. It was pretty hard though and when I saw the sparks in the socket I thought there might be an electrical fault.

Completely irrelevant to everyone perhaps, but...I have had a cough for 3 weeks now and I went on the internet to find out how to get rid of it. I read that too little humidity in the air can irritate a cough. Also, too little humidity can cause static electricity in a house. So I started to put cups of water on the radiators, drinking more and getting more moisture in the house - it seems to be working My cough is going and I haven't had a shock!

[JestersBaubles]

I really doubt you'd mistake a real electrical shock to the head with static. I would bet it was static and it just felt worse because it was to a sensitive part of the body. (trust me I got a static shock the other day from my sandblaster to the rather sensitive area) An electrical shock to the head would be a real wake up call. Have you ever had a true 110 or 220v shock before? Like you said the slippers generated the static and you grounded yourself once your head touched the kiln. That released the static through your melon.

That, and a static shock is a "pop" and an electrical shock is a buzz. I've had both (which could explain a few things... ).

Dana W.

[theanimallover]

It was a pop...then an ow...

[jolly]

Yes, a static shock is a quick snapping type and when I have grabbed a live wire (120 volt) it is a buzz (just did it the other day while fixing a broken light bulb that the person said was off).

[theanimallover]

Ouch, don't trust them again!