Shocking Flexwatt development!

So I wired 11 4' pieces of flexwatt for my shelf, and taped it onto the shelf using foil tape. I test each piece to make sure it warms up, and also to test for conductivity. At one point I got the foil tape too close to the exposed solder and got shocked (oops, lesson learned)


So I wired everything up, soldered the wire to the expose flexwatt, and taped it all down, everything warmed up and was not shocking...


So now that I have it in the shelf, it was working fine for several days, no shocking, but tonight my wife said she was checking and got shocked when placing her hands over the foil tape.... not on one shelf, but on 10 of the 11 shelves!

What could be going wrong here? It worked fine at first, I used black tape on every exposed piece, and the foil tape is only touching the plastic covered portion.

We had left the humidifier running and the room was up to 50-60% humidity but I dont see that being the cause.

Any ideas? Im kinda confused as i dont see where the juice could be coming from

There has to be exposed metal somewhere. The foil tape is conducting the electricity.

nothing is grounded and when you touch the rack it sends volts through you(shocks). somewhere part of the flex is exposed or shorted. ckeck all your connections and ends tape them with quality electrical tape. tape around your wires and the bare ends of the flex. the foil tape is aluminium and can conduct electricity!



vaughn

Like Jaime wrote, there has to be some cut/loose end you left unchecked.

Quote:

---

Originally Posted by ssscales

Like Jaime wrote, there has to be some cut/loose end you left unchecked.

---

On every single shelf? I have black tape on everything, I am very confused.

Are you insulating the flexwatt edges as well as all the exposed ends and then taping it to the shelf or just taping it to the shelf with the aluminum tape?

What I didn't realize at first is that its 4" flex. Apparently that doesnt have the 1ft increment dotted lines that the 11" has (never worked with 4" myself). If that is the case I would bet anything that is where the current is coming from. Those cut ends.

somewhere voltage is coming into contact with the rack, this rack is wood right? wood can conduct volts also. how did you fasten down the flex?



vaughn

i always cover all the metal on mine with electrical tape, the contacts, the ends where i cut it, the solder everything, then i attach with the tape

Quote:

---

Originally Posted by shadraak

i always cover all the metal on mine with electrical tape, the contacts, the ends where i cut it, the solder everything, then i attach with the tape

---

Thats what I did. exactly.


I fastened it down with aluminum tape, but the tape is no where near the taped metal.

When you cut the heat tape to length, did you cover the cut edges on BOTH ends with electrical tape?

Quote:

---

Originally Posted by kavmon

somewhere voltage is coming into contact with the rack, this rack is wood right? wood can conduct volts also. how did you fasten down the flex?



vaughn

---

yes painted wood.

It is not a big shock, it barely tingles when she touches it... so it doesnt seem to be a direct leak.

Quote:

---

Originally Posted by Wild Bill

When you cut the heat tape to length, did you cover the cut edges on BOTH ends with electrical tape?

---

most definiitely

you could screw in a couple of ground wires to the rack. then wire this to an outlet ground in the room. if a breaker trips, you have a voltage short. grounding the rack will make it safer.


vaughn

Quote:

---

Originally Posted by kavmon

you could screw in a couple of ground wires to the rack. then wire this to an outlet ground in the room. if a breaker trips, you have a voltage short. grounding the rack will make it safer.


vaughn

---

Interesting, I didnt know I had to ground a wooden rack.. hrm


I should re-state that there isnt much of a shock coming from the aluminum tape, just a little tingle...

Im confused right now, I guess I will deal with it when I get home on thursday.

Thanks guys.

So I am now at home and have had time to play with it.....

Took off foil tape.

Double taped everything with black tape, including areas that were obviously not exposed, but i wanted to be safe.

Still getting a slight buzz from it, not like a shock but a tingle...

Still confused as all heck...

Quote:

---

Originally Posted by SnakeySnakeSnake

What could be going wrong here? It worked fine at first, I used black tape on every exposed piece, and the foil tape is only touching the plastic covered portion.

---

Are you sure it worked fine at first? If you were wearing rubber soled shoes, you may have insulated yourself from getting a shock right away. It definitely sounds like a ground fault. It may only be a tickle, but under the right circumstances (i.e a wet floor) it could be serious. I can't quite picture how you have this set up so bear with me: Are each of the 11 pieces wired together in series?

No, they are wired individually




~ 4 foot piece of flexwatt

1 end taped up in black tape

other end has an extension cord soldered on to it.

black tape all around the wire, the end of the flexwatt, completely covered


foil tape stretching down both sides of the length of the flexwatt


does it matter which side is facing up for flexwatt?

PS ++ for another chicago suburbs person :)

As far as I know, it doesn't matter which side is facing up. I am stumped. Are you positive there is no exposed contact on the flexwatt, and no exposed wiring on the cord? What about your rack? Is it in direct contact with the floor, or is it sitting on something that might be insulating it, like a rubber mat?

First, I have to say that wood is NOT a conductor.

Okay, as for the tingle, I'll bet that if you put one end of a voltmeter to the hot foil and the other end to the ground in the outlet, it would register 110VAC. The tingle is simply because the resistance in your body is great enough to prevent a serious shock. But don't press your luck.

So, is each tank on a seprate cord? If so, I'd unplug everything, and connect one side of an Ohmmeter to the foil, and then touch the other end to the prongs on each plug. This will at least tell you wich one is giving you a problem, and narrow your search down greatly.

If you don't have a digital multimeter, time to buy one. And I'd exercise some precautions for now while working on the shelf. Don't work on it alone - have a safety observer who can turn off the power if you get lit up.

And STOP TOUCHING THE METAL! A DMM is a much safer way to see if there is voltage present.

A good DMM (digital multimeter) will run about $130 at Home Depot. (Fluke brand) It will measure voltage, resistance, current, and a few other things. They even sell one with a temperature probe. But you can also get one for as low as $20 at Radio Shack. For this application, ensure it will measure voltages up to and over 120VAC. And don't take any current measurements unless you know what it means to measure a circuit in series as opposed to parallel. (improperly measuring current will result in a short circuit wich will manifest itself in the form of a few bright sparks before the circuit breaker trips (hopefully)

One last word of caution - the circuit breakers in your house won't save your life - they are rated at 15-20 amps. It takes about .02 amps to stop your heart.

i am friends with a high power lineman that got put into the hospital and suffered 3rd deg. burns and was in therapy for months when a tree( wooden) branch hit and crossed lines. his version of wood conducting will suffice for me. i also test live electrical circuits daily 24,120,240,480 single and 3 ph. some how his rack is "tingling" him.



ps. he was working on 19/9 lines these do differ from house wiring.

vaughn

I'm just very confused. Ive taped EVERYTHING that could be remotely considered conductive...

I have the cheapie voltmeter thingy i picked one up today... will go play with it ;-/

Quote:

---

Originally Posted by kavmon

i am friends with a high power lineman that got put into the hospital and suffered 3rd deg. burns and was in therapy for months when a tree( wooden) branch hit and crossed lines. his version of wood conducting will suffice for me. i also test live electrical circuits daily 24,120,240,480 single and 3 ph. some how his rack is "tingling" him.



ps. he was working on 19/9 lines these do differ from house wiring.

vaughn

---

He said that it's tingling when he touches the foil tape, not the rack.

As far as trees go, it's the sap and leaves that were conducting. But dry wood doesn't conduct. I've been in a couple electrical shops that keep wooden walking canes around (with the varnish stripped off) to pull people off live circuits if somebody hapens to get lit up.

Some types of paint can conduct electricity, even if the wood doesn't. I don't think the shelf is conducting though, or you would get a tingle when touching that too. I would think there is some spot on the conducting strip that is exposed, but on 10 of 11 pieces? Start with the ohmmeter and check resistance between the tape and each prong in the plug, like TraconSnake said. I would check multiple spots along the tape on each strip.

I mentioned this in passing, but I want to underline that you should never use an ohm-meter on a circuit wich has voltage present. Everything must be unplugged lest you fry your ohm-meter. (The way an Ohm Meter works is it introduces a very small voltage to the circuit and measures how much comes back in order to calculate circuit resistance. If power is applied, the meter will get back much more than it bargained for!)

Quote:

---

Originally Posted by TraconSnake

I mentioned this in passing, but I want to underline that you should never use an ohm-meter on a circuit wich has voltage present. Everything must be unplugged lest you fry your ohm-meter. (The way an Ohm Meter works is it introduces a very small voltage to the circuit and measures how much comes back in order to calculate circuit resistance. If power is applied, the meter will get back much more than it bargained for!)

---

I like you!!!!:) Want a Job..lol

1. Everything is taped up with black electrical tape (3m).

2. There are NO exposed pieces of metal touch the rack, the foil tape, or even the air...

3. I tested the foil tape with a multimeter, and it reads a spike of 3-9 volts when i first touch + and - to the two piece of foil tape running lengtwise down the heat tape. After that initial surge, it levels out at .1-.3 volts

4. I used the ohmeter and tested.... no circuit, no reading, from either prong of the cord, to either side of the foil tape (and remember, im only feeling the tingle when i touch both sides)

Is my foil tape somehow gaining a charge and acting as a capacitor through a slow trickle of ??inductive?? energy from running 4' down the length of a piece of 3" heat tape.

*confused* even more.

Was the meter set to read DCV or ACV? Sounds like it was set to read DCV if it was giving that sort of reading. Stick one end into the ground of the outlet and one end to the foil and see what that yields.

When you say you only feel a tingle, that's what I only felt when I was working on a computer with a hot chassis. (ground problem with the power supply) When I put a meter from the chassis to ground, I got 110VAC.

If there is 110 from the foil to ground, time to see if it's a dead short or not. What's the maximum amperage your multimeter will read? If it will read up to 20 amps, then put one end on ground, momentarily touch the other end to the foil. If it sparks, it's a dead short. (this may also trip the circuit breaker) If it doesn't, hold the lead to the foil and see how many amps you're getting. A dead short would read full current. If you're only getting something like a couple amps, then there is probably a portion of the flexwatt tape wich is exposed to the foil, wich would be a manufacturing defect in the tape.

I'm going to draw up a schematic. As soon as I'm done I'll post it. Let me know if it's accurate to how this setup is wired. Once we get a schematic established we'll better be able to troubleshoot the problem.

Okay, here's the schematic which I will revise as I get more information.

REV A
http://www.realmsoftracon.com/snake/rack1.jpg

Now, I know this is not accurate, so I need more information.

First, does each shelf have a strip of FlexWatt for each tub (as shown in the schematic) or one strip per shelf?

Second, does each shelf have an independant thermostat control, or is there just one main thermostat control for the whole thing?

Does each shelf have one long strip of foil tape (as shown) Actually, looks like in the picture there are two strips per shelf going the entire length. Is that correct?

Aything else on this schematic which needs to be corrected?

Once this schematic is correct, we can start getting some readings and both be on the same page.

-Dan

Quote:

---

Originally Posted by TraconSnake

Once this schematic is correct, we can start getting some readings and both be on the same page.

-Dan

---

It's true ... Dan really is "the man" ... sorry, couldn't resist. :colbert2:

triple E or work in the trade?

-adam

Quote:

---

Originally Posted by Adam_Wysocki

It's true ... Dan really is "the man" ... sorry, couldn't resist. :colbert2:

triple E or work in the trade?

-adam

---

If you mean Electronics Engineering Technology, yup, I took the course at ITT... though looking back I wish I took computer networking. I kinda sorta work in the trade, but hope to be back into a real electronics job in the future...

Well, no reply from SSS, so back to playing Oblivion!

Quote:

---

Originally Posted by TraconSnake

Okay, here's the schematic which I will revise as I get more information.

REV A


Now, I know this is not accurate, so I need more information.

First, does each shelf have a strip of FlexWatt for each tub (as shown in the schematic) or one strip per shelf?

Second, does each shelf have an independant thermostat control, or is there just one main thermostat control for the whole thing?

Does each shelf have one long strip of foil tape (as shown) Actually, looks like in the picture there are two strips per shelf going the entire length. Is that correct?

Aything else on this schematic which needs to be corrected?

Once this schematic is correct, we can start getting some readings and both be on the same page.

-Dan

---

I did a reading from ground (wall outlet) to the foil, and got about 4-5 volts each... (I was wrong before, I was going from foil to foil)

I have one strip of flexwatt per shelf, 4' long

I have one extension cord per shelf, attached to the far right end of flexwatt

I have two power strips. One is for the top 6 shelves, One is for the bottom 5 shelves.

I have one thermostat for the top power strip, and one thermostat for the bottom power strip.

The two places that have been cut on the flexwatt are diagonally on each end, with the direction of the heating element.

That leaves only two spots on each end exposed, the spot with the wire on the outsides... both have been taped thoroughly.

The foil tape goes from 2 inches in on each side, down the length of the flexwatt, covering about 1 inch each side, leaving maybe a 1 inche stretch of exposed flexwatt down the center (exposed plastic, not wire)

Thanks again for your help, I am VERY confused on what I thought was some simple wiring.

Okay, looks like editing is disabled once there have been replies. The picture is updated, but it still says Rev A on top. It is indeed Rev B.

Quote:

---

Originally Posted by SnakeySnakeSnake

I did a reading from ground (wall outlet) to the foil, and got about 4-5 volts each... (I was wrong before, I was going from foil to foil)

---

Okay, and this is a steady 4-5V AC? Hmmm.

Re-reading the first post, you said that this is occurring on just 10 of the 11 shelves. Which shelf is not "hot" (electrically speaking) The top shelf? Bottom shelf?

Induction may be what is going on, but I want to be certain first.

Okay, so, is there anything different about the one shelf that has no voltage? Any possible path to ground? Wired backwards from the other 10? Aligned with sunspots?

With the ten that are hot, unplug all but one. Do the 9 unplugged shelves still shock? Does the one plugged in shelf still shock?

Now, on an unplugged shelf that does shock, set the ohm-meter to it's highest setting, and measure between the foil and either side of the plug. Is there any resistance at all, or is it out of range?

Here's a possible solution based on some assumptions of what I expect the outcome to be.

PROVIDED the one good shelf is somehow grounded...
PROVIDED the shelves only shock when plugged in
PROVIDED there is infinite resistance between the cords and the foil

If the above three are all true, my fix would be to solder a wire to each foil strip, and connect that wire into the ground of the outlet.

You see, if the above is true, I think you were right in venturing that the voltage was being inducted. While the AC coming out of the wall is a very low frequency of 60Hz, it is still AC. As the voltage rises and falls, there is an electromagnetic field which is expanding and collapsing 60 times each second. Whenever a magnetic field is passed through a conductor, in our case the foil strips, a current is induced. Since these foil strips are not connected to ground, there is no way for this current to go anywhere. But when you touch it, the current finds you a good path to follow. Grounding all the foil strips will effectively rid us of this unwanted voltage.

This is why I suspect that the one good shelf is somehow grounded. Or possibly, you have a short in that shelf with the neutral side of the wire. But I'm more inclined to believe that it is somehow grounded.

Let us know what you find out!

MG: I couldn't find a site for the actual company that makes FlexWatt. I think it might be a good idea to call them and ask if they have heard from others about voltages being induced in the foil tape beneath long runs of Flexwatt. As far as the job goes, looks like the commute might be a little long... :confuzd:

Dan

Quote:

---

Originally Posted by TraconSnake

I couldn't find a site for the actual company that makes FlexWatt.

---

www.calorique.com

Many years ago, when I lived in MA I actually got a tour of their place ... it was wicked awesome. ;)

-adam

Quote:

---

Originally Posted by Adam_Wysocki

www.calorique.com

Many years ago, when I lived in MA I actually got a tour of their place ... it was wicked awesome. ;)

-adam

---

Thanks! I've E-mailed the following to their support team:

Quote:

---

Support,

I’m trying to help somebody resolve an issue with some flexible warming elements used to heat reptile cages. All the connections to the elements are insulated, however there is about 4-6V on the foil tape between the heating elements and the cages. I’m thinking this could be due to voltage being inductively induced into the foil strips.

Please refer to this forum thread for more detailed information:

http://www.ball-pythons.net/forums/showthread.php?p=340852

If you could provide us with some clues or a definite answer as to whether or not induction is the correct conclusion, I’d appreciate it.

Thanks!

Dan White (TraconSnake)

---

I wouldn't expect anything back until Monday. Perhaps we'll have this issue resolved ourselves by then - but at least this will give them a heads up to the possible issue.

Induction, huh? I guess that makes sense with all of the heating element involved. I really thought he was going to find a loose neutral someplace, or foil tape touching the contact strip on the end opposite the wiring. So tell me, not to hijack this thread or anything, but would one be better off making a rack out of metal, so that it could easily be grounded?

Going up to do the tests you asked..


Is there such thing as grounded flexwatt? I know my thermostats have a spot for ground, but id have to find extnesion cords with a ground wire

All 11 shelves shock, I was wrong to say only 10 did (I was going by feel at that point)

Both of the foil strips on all of the shelves has a charge.... it spikes when I first touch it, and then settles in the 1-5 range for the most part


Now here is the great part.... I unplugged everything, and the foil held a charge for one touch.... I would touch the other end of the multimeter to the foil and it would jump up to a few volts max, and then go down to 0.00 and stay there..

About half the shelves kept a charge until i touched them, unplugged, and then they stayed at 0....

Every shelf foil to plug = out of range on the highest resistance setting.

Quote:

---

Originally Posted by SnakeySnakeSnake

I have two power strips. One is for the top 6 shelves, One is for the bottom 5 shelves.

I have one thermostat for the top power strip, and one thermostat for the bottom power strip.

---

Okay, I am going to ask a stupid question here.... Most power strips have a three pronged plug with a ground, I know my t-stat doesn't have room for a ground plug, How is your power strip connected to the thermostat?

Quote:

---

Originally Posted by ErikH

Okay, I am going to ask a stupid question here.... Most power strips have a three pronged plug with a ground, I know my t-stat doesn't have room for a ground plug, How is your power strip connected to the thermostat?

---

Because my thermostat has room for a grounded plug


Helix Grounded , $5 more than the non grounded one.

Crap. I really gotta get a Helix. O.k., never mind, I thought I was on to something.....

Quote:

---

Originally Posted by ErikH

Crap. I really gotta get a Helix. O.k., never mind, I thought I was on to something.....

---

No problem! I appreciate any input.

The problem is my extension cords are only 2 pronged, so im not using that ground anyway (I only have 2 spots to hook wires too on the flexwatt anyway)... I suppose if i had an extension cord with a ground wire, I could split it and attach to the two piece of foil...

Im just wondering if the inducted current in the foil tape is worth worrying about, or if i should use some other kind of tape in the future.

Found an old post describing a mild electric shock


http://forum.kingsnake.com/caging/messages/13941.html



though he never responds back, he said that the seller told him that this is normal... wonder who the seller was.

Definitely sound like induction. The reason you get a shock even after unplugging is the flexwatt is acting like a giant capacitor. (a capacitor being two conductors separated by a thin strip of insulation) Technically speaking, even after the flexwatt is unplugged, there is either an excess or deficiency of electrons stored up on the foil tape which is released only when it finds a way to get to ground. Kinda like how static electricity works.

There is no way to ground the flexwatt itself - it just has two sides for voltage. Grounds are used on equipment where voltages can find their way into the chassis, such as a computer case, metal power tools, and some AV equipment. (really, ALL AV equipment should have a ground. We had a 60hz hum once that went away when we grounded the equipment)

Don't worry, you don't need to re-wire everything. Just take a piece of wire, connect all the foil strips together, and connect that wire to ground. The wire doesn't even have to be insulated. Just find a way to get a good solid connection to each strip of foil tape, and plug it into a ground somewhere. Either wire it into the cut off end of an extension cord with a grounding prong (it will be the green wire), or plug it straight into the ground receptacle of the outlet.

You could go to Radio Shack and get some of the microclips with the flat jaws, and just solder all those together, then put a bananna jack on the end of the wire to plug into the ground of the outlet. There's a lot of ways you can accomplish it. Just ground it all, and you should be good to go.

On an aside, my E-mail to Calorique bounced back to me undeliverable. But sounds like we got this under control.

Let us know how it turns out!

Dan

P.S. Here's a site that has a neat little JAVA applet that helps explain what's going on. The wire is like the foil. The magnet is like the AC current in the FlexWatt. Even though the foil is not coiled, there is enough of it that current is being induced into the foil by way of electromagnetic induction.

http://micro.magnet.fsu.edu/electromag/java/faraday2/

And a Wikipedia article:

http://en.wikipedia.org/wiki/Electromagnetic_induction

Thanks bud, I will try to get the ground setup wednesday.


Is there a reason why it doesnt have to be insulated? I understand its a ground but wont it have the juice running from the foil in it?

The ground wire prevents current from ever building up in the foil. It is acting like a lightning rod.

bryan, I don't know anything about this stuff at all but I did have the same thing happen to me. After called the Bean Farm(where I purchased the tape) they told me the provided instructions are not correct and you need to cut the tape in the clear band and not in the black band. I made this correction and my tingle problem disappeared. I have not idea if it was because I rewired everything or because I changed the cut point but it worked. I hope this helps. Awesome info from the forum smarties!

Quote:

---

Originally Posted by cueball

bryan, I don't know anything about this stuff at all but I did have the same thing happen to me. After called the Bean Farm(where I purchased the tape) they told me the provided instructions are not correct and you need to cut the tape in the clear band and not in the black band. I made this correction and my tingle problem disappeared. I have not idea if it was because I rewired everything or because I changed the cut point but it worked. I hope this helps. Awesome info from the forum smarties!

---

When you say the clear band versus the black band, what exactly are you referring to? (I haven't yet actually handled a piece of flexwatt) Isn't the black band the conductor?

If the conductor is cut as shown here:

http://www.mgreptiles.com/FLEXWIRING.html

Then Yes, if the edge is not taped, current could get to the foil. But SSS did affirm multiple times that all edges are insulated with electrical tape.


In reply to why the ground wire doesn't require insulation, the ground acts as an electrical short to ground, so all the current will follow the wire. The only way somebody could get shocked by touching a ground wire is if their body offered less resistance to the flow of current.

In reality, it's a lie that current follows the least path of resistance. Current follows ALL PATHS. But if you do the math, the resistance offered by the wire, which would be in the tenths of an ohm, is much less than the resistance offered by your body. So if you're grounding a charge of 6 volts, and there is 1 ohm of resistance in the wire, you'd have a 6 amp current flow in the wire. If you touched the wire, the resistance offered by your body is usually at least 100,000 ohms. So you'd get 60 micoramps (.00006A) worth of that current.

Now, while SSS was measuring upwards of 6V, there won't be 6A flowing through the wire as the charge won't have a chance to build up to that amount once the ground is applied. But it would be interesting to take a current reading between the wire and ground to see how much current is being bled off.

To do that, set the multimeter to measure AC Amps, disconnect the ground, and connect one wire to the ground wire, and the other end to the outlet ground. Turn everything on and you'll see how much current is being bled off. This might be a good thing to know as if you are getting significant current bleed off, you'll need a heavier gague wire to handle the increased load. If the wire gets warm, you need thicker wire. But I highly doubt this will be the case. Of course, we are grounding 11 strips...

The black band is the conductor and is listed in the instructions as the cut point. The clear portion seperates the black bands and was the logical cut point, I should have just listened to reason :P


I have the same basic setup. MDF rack, 4" flexwatt and Helix thermo

So, have you tried it out yet? Is there resolution?