Electrical/Electrician work with PM

I know this has been covered before (I've read a few topics) but I just wanted to share my experience.

Shortly after my pacemaker implant (100% dependant - my former doc accidentally ablated my AV node... another story for another time) I got a new job. It started out as a desk/IT job. Any electrical work was low-voltate or data/signal cabling. Once my boss realized I know electrical, he asked me if I would take the test to be a licensed electrician (Lake County, IN) and... I am in the process. Meanwhile I'm being sent to wire up outlets and lighting in office buildings where you *can't* just start throwing circuit breakers (killing computers and other vital equipment).

At first I was afraid to work on a hot circuit. My EP (new doctor) said my Medtronic device is rated and can handle a shock of up to 250V before it's a problem. However, I hadn't considered the EMI thing.

So we're doing a restaurant remodel that's inside a truck stop. We were upstairs in the electrical room, talking about our next step in this rewire when I started feeling really dizzy. Turns out the metal box I was leaning on was a 1200 AMP transformer! Naturally next time I saw my EP he asked what the heck I was doing on that date...

But here's the part that I don't get. Today I was installing a new outlet in an office, where I had to tie into an existing outlet box, hot. I'm always careful, I wrap tape around the sides of the outlet as soon as I pull it out of the live box... but while fishing the new BX cable into the 1/2" knockout and pushing wires out of the way my hand came into contact with the black wire... It's been so long since I've been zapped with 120V I forgot what it felt like. Naturally my first thought was check my pulse (make sure it's still there!) but this incident didn't make me dizzy or anything at all.

Likely it's because the shock was pretty much limited to my right hand (didn't travel through my chest).... but I suppose my point is that EMI is much more dangerous than an actually current flow through the skin. I've gotten dizzy near the welder at our shop, and once wiring up a 12V winch we (the other guy!) mixed up a wire, and on hitting the button the selenoid dead-shorted a 1000 amp car battery, and the cable actually curled up due to the EM force (and/or heat)... and I immediately got a dizzy spell. DC can be just as bad (worse than?) AC...

I used to work in radio, and now won't go near a transmitter site... but I feel perfectly comfortable working in a live breaker box or even tying into a live outlet/switch box (after verifying no continuity between hot/neutral/ground on the new wiring)... because a simple electric shock doesn't seem to affect the device. But being around an invisible field you may not even realize is there... it's a scary thought that the thing I first feared isn't a big deal, but the things I hadn't considered are a considerable risk.

FYI my PM was installed in 2015, had a lead slip and had it extracted/replaced shortly after, then developed afib, had ablation for that ... 5 surgeries in and the afib is still acting up. And I'm 42 and otherwise healthy...

Sorry for the long rant but I'd love to hear any updated stories from electricians or others who work with moderate (residential/commercial 120/240 or 120/208 3-phase) voltage (I won't go near high-voltage at all, and I think I have good reason lol)...

I'd also love to hear from anyone who works near RF transmitters and what kind of experiences you've had there - near the transmitter, antenna, transmission cable etc...



by AgentX86 - 2018-06-13 22:48:39

The issue isn't electricity or the PM's pulse generator.  The issue is the PM's sensing leads picking up EMI from strong magnetic fields.  It's not at all surprising that the 1200A transformer or a welder caused problems. The signals the PM's lookg for are in the millivolts.  Any inductive pickup from the high magnetic fields can cause a voltage on the leads, confusing the PM. 

Smaller fields or a shock shouldn't cause a problem, at least any shocks that aren't very dangerous in themselves.  Since I'm 100% dependent, too (AV ablation), my EP is really paranoid about large magnetic fields.  I haven't had any trouble yet but I give the X-Ray machine at work a wide birth and I don't mow my lawn anymore (at my EP's, and wife's  insistence).

Great post...

by donr - 2018-06-14 01:20:30

...but you forgot one intsie, weensie point - A steADY MAGNETIC FIELD - LIKE FROM A 1000 aMP BATTERY CANNOT INDUCE A current in anythying unless that thing or the mag field is MOVING.  Now moving can be the PM host walking through the steady mag field or the field building up or collapsing when the battery is energiged or disconnected. Then  without the presence of an inductor to slow the current, hence the mag field, buildup, you would just have a sudden pulse of current in the target leads.  Sounds more like the mag switch in the PM was opened/closed to change its mode of operatiion.

The difference between a field & a current in the human body is that he field is EVERYWHERE; the current rushes along the shortest path to get t its oppposite pole & escape.  I've taken a boatload of 120 jolt shocks along many paths - rt hand to left hand; rt hand to rt foot; rt hand to lt foot.  You name it.  None of them have ever affected my PM one bit.  Even tried one finger to another on same hand.  That's no big deal!  Hand to foot on same side is no big deal.  Hand to hand could be - but - the PM is sealed in a Ti case, a conductor, BTW, so very little if any current goes through the cxase - it all travels over the surface, protecting the electronic guts from harm.  As to antennae - I'd almost hazard a guess that you would have to hug the output horn on a multi-megawatt radar antenna before you would reach field strengths strong enough to do any damage to your PM.  I'm probably exaggerating a bit, but the case is enouigh of a conductor that very little RF would get through it.  The leads are probably too long to act as antennae to bring any RF into the case.  Your eyeballs would probably congeal like an egg white before the PM would be affected.  In short, the pM is tougher than we are!  OP is correct that the strong mag field is the most troublesome threat to us. 


I feel brighter

by Gotrhythm - 2018-06-14 15:10:01

Don't know how much of this discussion I really understood, but I felt smarter just reading it!

Thanks to all for sharing.


by jm4n69 - 2018-06-16 09:07:17

Thanks everyone for the input, it has put my mind a bit more at ease. I know what to avoid (transformers, or anything that might have a high-output transformer like welders or (automotive) battery chargers) and what's no big deal (120V shock). I'll be pursuing my Electrician work, doing small commercial stuff like I've been doing (I hate doing residential) and no more fear whatsoever about wiring into a hot circuit :)

In a weird way, that shock the other day was a good thing... it confirmed what my EP said, that (in his opinion) a shock up to about 250V won't hurt the PM. I'll still be extremely careful as always but I don't have to be afraid to pull the live wires/wire nuts out of a box and tap in.

need a coil

by dwelch - 2018-06-21 01:26:10

Individual wires, even a circuit breaker box is not the kind of thing that should generate the EMI fields of concern.  Transformers, generators, things like this with big coils will throw off a field.  I worked where we had a shake table, this was 20 years ago or so and the pacer vendor was perhaps less worried about lawsuits.  Long story short my device would have to be within 6 inches while running, I would literally have to hug it.  Sure the high powered lines, single wire could throw out a field if the current is high enough, but...you hug one of those you are not going to be happy pacer or not.  

I was worried about even static zaps, as well as 120V and other shocks, 30 years ago was told not to worry about those things it is protected.

The devices today have storage capabilities and one would hope could record such events (hugging transformers).  So it sounds like when you were in a field near the transformer the device did record an event?  Something to point out the person who just asked about working in a power plant.

I dont personally know how powerful various types of radio towers are, but would assume the field there or more likely the equipment that drives the antenna is something you want to not hug either.  I imagine you could make it a safe hobby if you kept your distance when using the radio, and had it off when working on the radio/tower/etc...

BTW was told at the time that the field would confuse the device, the device would stop pacing and i would go back to natural rythm, depending on the patients condition that could mean passing out, but being moved away from the field the device would start pacing again.  I did later go in the shaker room once myself and the lab manager talked to the pacer vendor and took some measurements.  Didnt have any ill effects, the only thing that was really long term is they put a red and white sign on the wall stating that implanted electronic medical devices could be affected.  So they put the sign up for me basically...Now that I think about this, they closed that facility a few years ago I should have asked someone still there to take the sign and send it to me...

You know you're wired when...

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