Got shocked - Please help figure out my electrical safety issue

[eyedoctodd]

Hi all, I wired up an STC-1000 according to this thread:https://www.homebrewtalk.com/f51/stc-1000-wiring-diagram-question-362214/

(I broke off the tab from the hot side to give the top receptacle for the heating stage and the bottom for cooling - I didn't break the neutral side as the original poster in that thread did).

Plugged it in and it seemed good to go. I tested it by plugging in this immersion heater:
http://www.amazon.com/dp/B00FO8FY68/?tag=skimlinks_replacement-20 and setting the temp to 60C, with the temp sensor and heater submerged in a plastic bucket of water in my plastic laundry tub.

It was happily heating along so I decided to take a hydrometer sample on a fermenting batch, and when I was done, I went to rinse off the hydrometer by dunking it in the bucket of water.

I instantly got a shock and the GFCI tripped off.

Obviously I am concerned. My intended use of this controller and heater is to have the immersion heater in my stainless hot liquor tank to heat mash water to a set point.
Is the problem that the heater has just a 2-prong (I'm guessing that means ungrounded) cord? I was careful to wire things properly in the STC-1000 but does this symptom maybe sound like I possibly screwed something up in that? The temp probe for the STC-1000 is supposed to be waterproof and submersible, any chance I got one with a small break in the insulation? Do you think if I just plug that heater directly into a GFCI outlet and test it the same way, bypassing the controller, that it will still trip the GFCI? Is that a stupid way to troubleshoot? All I got was a small jolt, but I don't want to keep putting my life in the hands of a $10 GFCI.

Will my HLT be energized if I don't change anything? Is there a way to properly ground the heater or kettle to resolve this? I use a Blichmann toptier, for what it's worth - I don't know if the aluminum mast can be employed some way in grounding this.

Any help is appreciated. Cheers!


Sent from my iPad using Home Brew

 

[Bobb25]

First I would try to protect the micro-electronics in the STC1000 by not using it until the source of the problem is found. I suspect that there is a problem with the immersion heater. If you have a mutimeter, check between each lead and the case. If you are concerned about more shocks while you troubleshoot, put one hand in your back pocket, and only touch things with one hand. Also you could wire the GFCI through a switch with an insulated toggle. Remember safety first, and to paraphrase Nathan Hale, you only have one asto-risk for your beer.

 

[wilserbrewer]

How far submerged was the immersion heater, was the the cord or black plastic top of the immersion heater submerged, or just the metal heating element? I have wondered how well the cord to element is waterproofed on these heaters.

FWIW I dont think the temp probe is the issue...

 

[raouliii]

I suspect you have the controller wired correctly and the problem is in the immersion heater. It is likely allowing water to contact internal current carrying components. It is energizing the water and since the bucket nor the water was grounded, the gfci did not trip until your hand created a path to ground. Since the immersion heater is of an un-grounded type, I would recommend making sure your stainless HLT is grounded. Of course with the fault in the heater, the gfci should constantly trip until the problem is resolved.

BTW, that 1350watt/110v heater is drawing a current over the 10amp rating of the STC1000. You might get away with it for a while, maybe not.

 

[BadNewsBrewery]

You definitely have a grounding issue and a current leakage issue. Fixing the grounding issue will keep you from getting shocked again. Fixing the current leakage issue will keep your system from tripping.

If you plan to use this in a SS kettle, definitely run a separate ground line from the kettle to a common ground, either at your panel or at the house's main ground bar. If the top of the heater near the plastic doesn't get hot (I imagine it doesn't on account of the plastic) then you could solder a ground lug to that maybe.

As for the current leakage - I'm definitely thinking it had to do with the cord or black plastic part being submerged or partially submerged. If it wasn't, then you likely have a bad heater that has an exposed wire somewhere.

Lastly - you are drawing 12+ amps with that heater, which as has been pointed out, is outside the working range of your temp controller. That's not the cause of your problems, but it will be a potential cause for problems in the future.

-Kevin

 

[eyedoctodd]

Thank you all for the help so far. A couple of follow-ups:

1. I was under the impression that the STC-1000 was rated at 10 amps on a 220V circuit, and 15A on a 110. See this thread:
https://www.homebrewtalk.com/f51/stc-1000-ebay-temperature-controller-build-330427/index3.html

2. Some of you asked - I definitely did not have that heater any deeper than half way up the prongs. I definitely did not submerge the plastic housing or cord, though it's possibly some drips got on them. Anyway, for grounding it, could I cut off the 2-prong plug end, splice the existing 2 wires into a 3-prong plug and then run a copper wire to the ground connection on that plug from the coil itself? Would wrapping it around several times suffice or would I need to solder it on? Could I use a hose clamp or something to secure it?

Still digesting the rest if the info... Thank you all again, I really appreciate it.

 

[BadNewsBrewery]

I can't speak to the amp rating. I can't say I've ever seen anything rated at various amperages for various voltages, but maybe I've just never paid attention enough. Either way, I really can't see it being the cause of your shock.

Grounding to the actual element may solve the shock issue, but still won't solve the "why is there an opportunity for me to get shocked in the first place" issue. If you do go the route you've mentioned, I would make sure it was electrically bonded to the element, IE soldered or attached via a screw and ring terminal. Just wrapping the wire around the element or using a hose clamp is not a guaranteed method of ensuring electrical conductivity.

But to the original issue - you need to figure out how the stray voltage is getting into your bucket to begin with. There's something wrong with your element... Can you return it and get a new one?

 

[eyedoctodd]

I had bought two of those elements from Amazon and only used one, but I think I'll just return them both. I don't like the idea of it being ungrounded, and of course, having been shocked, there hopefully shouldn't be any argument about the return.

The reasons I bought two were: A) they were cheap, and B) The previous immersible heater I had (a grounded, stainless, 1000W model that pulled only 8.3A) died after a year of use and I wanted a backup, especially if cheap.

For now it sounds like the input received mostly points to a faulty heater, so I'm going to replace that first and see if I get any similar problems with a different one.

Back to the amperage rating on the STC-1000's relays... This particular heater was rated 1350W at 120V (on the packaging, 110V on Amazon), which is 11.25A. Clearly 11.25 > 10, but what exactly is the risk if that's exceeded? I melt down the STC-1000, ruin an extension cord, or does this burn down my house? Hypothetical question since I'm replacing the heater, but I would like to know what dies first in such circumstances.

Thanks to all for your input!