Some cupped cuttings needed to be moved around this morning.  Half are in a humidity bin and half on a metal tray.  Both bin and tray share the same heating mat, an 11 x 24 Fast-Gro heating mat purchased from a seller on eBay.  Everything sits on wire metal shelving.  I removed the humidity bin and was pulling the heating mat from under the metal tray when sparks started flying around from under the mat.  I keep the electric for the heating mat, lights, etc. mounted high and quickly unplugged the heating mat from the thermostat.  When the smoke cleared I inspected the heating mat and found the connection of the wire to the mat was secured with a thin piece of black duct tape.  The tape ripped while pulling the mat across the wire shelving and made a tiny hole which caused an arc and the sparks to fly from under the mat.

   

Try using several layers of electrical tape to secure all the connections. I have about 4 layers on mine. Check out my propagation setup post.

Scarry stuff. I have looked into getting a few myself but may not now.

Good and timely information, I am sure several members are using mats at this time. I use electrical tape on several different problem items and also as a preventative measure for laptop computer power supply cords that I somehow keep fraying by bending them too many times. So my last new, after throwing away 3(slow learner), I taped the cord where it goes into the computer and presto, it should last forever. So Justin, preventative methods is the way to safety.

Tape is good.  Going to do that from now on.  I may also cover the wire shelves with some 1/4" plywood, just in case.  I also employ a multi-outlet GFI that plugs into the regular outlet.  It's great because the test/reset buttons on the outlet act as an on/off switch, too.  Can't be too careful!

Dave - Don't worry too much about it.  The quality of my rooting increased 1000% since I began using the heating mat.  Still dialing it in a little, but I can't think of using anything else now.  :)

I have a couple of their mats, I had a problem with one and they replaced it... the mats that are made where everything is sealed are more expensive but maybe worth it in the end.

Good Information, Thanks.  Glad you were there when sparks started flying.

I will say the 2 bins I have heat mats under have rooted and the roots are much more vigorous, at least 3 times faster than the 2 bins without heat mats.

Danny

You should have gone w Hydrofarm instead, I never had such a problem with them.

Hydrofarm heat mats conection point is secured and encased inside of hard molded plastic. That tape is a seriously cheap and possibly dangerous alternative.

For the life of the mat if you keep it, I would coat the expesed leads with liquid electrical tape. Then use a heavier duty tape over that to protect the coating from nicks.

I'm glad you caught it before something bad happen!

I rigged this mat with extra tape already.  The problem was dragging the mat across the metal bars of the shelving and not the mat itself.  Adding 1/4 plywood to the shelving will certainly help but I'm going to switch to the Hydrofarm heating mats.

I was in a house fire over a decade ago while staying with a friend. I discovered it at 1AM before it got too big and we all escaped. I have had a hard time using my fireplace ever since, freaks me out a little and I don't scare easily. Being in a fire will change your attitude. Don't ever say "it wont happen to me". I knew a kid growing up whose house caught fire twice. Use common sense and look for potential problems and learn from other peoples situations what went wrong.

yikes. Stuff like that can burn your house down

Thanks for the warning!  Glad you caught it before it caused a big problem.  Adding the extra tape is a good idea, but it seems that that thin plywood might not be a bad idea, either.

Thanks for the info.

Duct tape is an awful thing to use for isolation from 120vac.

You might also consider a plug in gfci like this one:

http:// http://www.homedepot.com/p/Tower-Manufacturing-Corporation-3-Wire-GFCI-Outlet-Adapter-30339005/202510242

This is the one that I currently use.  Works great as an on/off switch, too.

 

Wow - thanks for sharing that warning with us!

Danny,
Is that a gfci that you plug into an existing outlet? Did it trip when the wire on your heat mat arced?

Calvin - Yes, it is a GFCI that you plug into an existing outlet.  

The heating mat was temporarily moved to a different outlet at the time it arced.  I didn't even think about it until now but it was not plugged into the GFCI.  Going to have to buy another one.  Thanks.

I suggest using plywood on your shelf anyways since you will be directing much more of the heat generated to your pots.  I have one shelf heated with high quality professional Redi-Heat mats purchased used on eBay several years ago.  The others were purchased on Amazon after reading reviews carefully as several brands had various problems such as what you experienced.  I don't believe I have Hydrofarm as some problems were reported on theirs also, but don't remember what I actually bought for my other three shelves.

I also place some heavy black plastic sheeting over the top of the mats must in case any develop a crack so that water doesn't leak into it which was a problem reported by some folks.

If I'm buying something without a known history, I usually don't buy at eBay as it provides now way of knowing how well the product may last beyond the 60 day period a buyer may leave feedback.  Even if I don't buy at Amazon, I prefer checking there for reviews, if possible.