Metal grow cabinet shocks while HPS is starting up.

[HowardWCampbell]

I'm trying to help out a friend with a pretty serious problem, but I am totally stumped. I'll try to explain this as best I can.

He has a metal cabinet with a 400w hps light. A couple weeks ago, the bulb wouldn't come on. He went out, bought a new bulb, and it still wouldn't turn on. So he bought a new starter. He installed it, and everything worked fine for a day. The next day, he heard his bulb trying to start. When he touched the cabinet he got a small shock. As soon as he got the cabinet open, the bulb came on and stayed on. The cabinet only shocks you while the bulb is trying to start.

He has disassembled the ballast and checked the wiring three times. Once by himself, and again with two different people. Nobody saw anything wrong with any connections, or any of the wiring. There are no wires running anywhere near the doors that could be pinched by opening or closing the cabinet.

Every time it has been taken apart and checked, it would work normally once. After that, it's back to the same old routine. If anyone has any input at all it would be greatly appreciated. Even a link to a detailed explanation of HPS operation would be very helpful.

I haven't gone to look at it myself yet, but I don't really know what else I should look for at this point. I'm fairly confident that the 3 people who have inspected it already would catch the more obvious stuff.

Any ideas? +rep will be freely given for anything helpful

 

[joker152]

well part of it sounds like a ballast problem, how old is the ballast thats used in the system? is the light an in ballast or external ballast? i would have to say that the shock from the cabinet is just coincidental and most likely static, if a wire was being pinched and passing electricity to the cabinet from a 400w ballast your friend would have felt more than a small shock

 

[HowardWCampbell]

well part of it sounds like a ballast problem, how old is the ballast thats used in the system? is the light an in ballast or external ballast? i would have to say that the shock from the cabinet is just coincidental and most likely static, if a wire was being pinched and passing electricity to the cabinet from a 400w ballast your friend would have felt more than a small shock

I'm not sure the exact age of the light, but it's at least 4+ years old. It's an internal ballast.

He says it's quite a painful shock if barefoot, but pretty minor with shoes on. He also says he can see electricity arc if he holds his hand near the cabinet. Once the light comes on, the cabinet no longer shocks.

Thanks for the quick reply. +rep

 

[Arrid]

I'd recommend either changing the light or replacing the grow chamber with another material.

The cheapest would probably be to change the light.

If this continues it could lead to a real problem, try getting it sorted asap.

 

[luv2grow]

check the way its mounted in the cabniet.... the ground is probably shorting to the casing. Easy fix...new ballast or he could try rubber grommets on the mounting surface. Probably not the safest thing but its worth a look.

 

[HowardWCampbell]

check the way its mounted in the cabniet.... the ground is probably shorting to the casing. Easy fix...new ballast or he could try rubber grommets on the mounting surface. Probably not the safest thing but its worth a look.

I forgot to add in my original post that the light is not grounded. It came with a three wire plug, but the ground was cut off to fit into the ungrounded timer.The light is hung by a chain, suspended from top of the cabinet. This was done by the original owner of the cabinet. My friend acquired it from him, and used it as is. The light is hung by a chain, suspended from top of the cabinet.

If he were to insulate the light from the cabinet with some rubber grommets or something similar, then the cabinet itself would no longer shock you. But the light itself still would if you touched it. Am I understanding that correctly? Would grounding the light stop him from getting shocked at all?

As I understand it, voltage going to ground is indicative of a problem. Since the problem only occurs when the light is starting up, that makes me think it's the starter. Although maybe a capacitor shorting out to ground could do this as well?

I just don't understand why it always works properly the first time after its been removed from the cabinet and checked out.

I realize it would be quicker/easier to get a new light. My buddy and I are just cheap stoners that like taking shit apart and trying to fix it. I appreciate all the advice so far, please keep it coming.

 

[DirtyCanuck]

"I forgot to add in my original post that the light is not grounded. It came with a three wire plug, but the ground was cut off to fit into the ungrounded timer"

Rewire it with a ground, splurge on a 15$ grounded plug from walmart. I would bet my left testicle that is the problem

 

[HowardWCampbell]

Rewire it with a ground, splurge on a 15$ grounded plug from walmart. I would bet my left testicle that is the problem

He was supposed to have done that last week, but for whatever reason it has not happened yet.

But as I understand it, voltage should not be going to ground at all. It worked exactly as is for years without shocking anybody. That leads me to believe that there is a problem with a component of the ballast.

When I go over there next week, I won't leave until he grounds his light. But I think the shocks are a symptom, not the real problem.

If I am totally misunderstanding the theory behind grounding, someone please correct me. Thanks for all the help so far, you've all given me some things to think about.

 

[fat sam]

you answered your own question... the ground was cut off to fit the timer, that 3rd wire for the ground is there to catch stray electricity and keep it from doing just whats happening

 

[danksmoker77]

Question asked question answered I love RIU. I am an electrical angineer and I will tell you that 99% of the time this conditioner is caused by an improperly grounded circuit. The ground wire ARE there for a purpose. They are there for a purpose!!! Especially around a grow enviorment where water and moisture are always present. The humidity in the air alone can act as a conductor. If the system is ungrounded the current travels through the air, to the metal case, and through your partner to the ground. Add a ground wire and give the electricity another path to follow.

 

[HowardWCampbell]

I am an electrical angineer

Just the kind of person I was hoping would stop by. I hope you don't mind if I ask you a few questions.

In a properly functioning light, should there be any current going to ground?

If he grounds the light, I'm thinking there is a good chance that the GFCI will begin to trip anytime the light turns on. Is this a likely scenario?

I talked to my buddy and he's got a new grounded cord to install on the light, but he still has not bought a grounded timer.

If we were to get a little creative (cheap?), and use some scrap wire to ground the light directly to the ground plug on his power strip, could he continue to use the timer he already has?

 

[danksmoker77]

to answer your first question, No there should be no current running through the ground. If he does hook a ground up and it trips the breaker then you should look at the other possible causes of the problem. You have already stated that you have checked all wires. Ensure all connections are secure. Loose wires causes fires. If all wires are secure and your light is still not working properly, then I would consider the transformer might be shorting internally, but this is not very likely. Since your cabinet is metal I would also ground this. Just run a wire from your ground terminal and connect it to the cabinet somewhere. Have you tried using the light without the timer. Some times the contacts inside these timers fail and cause problems. Troubleshooting a problem like this is fairly easy if you understand how to use a volt meter. Voltmeters have a setting for continuity. You could use this to test for a short circuit condition. you should never have continuity between your different wires, meaning you shouldnt have continuity between ground and any power wires. Also you should have continuity between all grounded components. First things first thuogh hook up the grounds and see what you get. Troubleshooting is step by step. and the cheapest steps are always first.

 

[danksmoker77]

and yes he could run the ground from the light and bypass aroound the timer. good question.

 

[danksmoker77]

and I should also say there should be no constant current to ground. You may have small amounts at certain times due to static discharge and humidity in the air. Grounds are for protection not to constantly carry current.

 

[HowardWCampbell]

danksmoker,

kiss-ass

Thank you for your detailed response. He has tried disconnecting the timer, it did not help.

So my gameplan for when I go over there next week should be to ground the light and cabinet, then check for continuity from the various ballast components to ground (w/ power off of course)?

Once again, kiss-ass Thanks. I really appreciate you taking the time to share a bit of your knowledge with me.

 

[HowardWCampbell]

and I should also say there should be no constant current to ground. You may have small amounts at certain times due to static discharge and humidity in the air. Grounds are for protection not to constantly carry current.

So that means that the shocks are the symptom of a failed device/wire/connection and grounding it would hide the symptom, but not cure the problem?

Sorry to ask so many questions, I'm just eager to learn about how this all works.

 

[danksmoker77]

the shocks are most likely static electricity. the ground wire gives this static electricity a path to travel. It is called a ground cause thats exactly where it goes into the ground. there is always electricity in the air in small amounts. when no ground is connected this stray electricity has no place to go so its easiest path with least resistance is from the air, to the metal cabinet, to your partner and then to the ground. This is common problem in industrial applications. Ungrounded circuits will cause havoc for a technician. I have troubleshot systems for days to find out the culprit was a bad/missing ground. Anything metal should be grounded. I have gotten small shocks flipping switces that werent grounded. the current doesnt only run through the wire it kind runs all around the wire. electricity dosent need a wire to flow. think of it as putting two wires close together. the current will travel even if there is a gap. the air is the conductor. Yes, test for continuity between all grounded metal parts of the circuit(cabinet, wires, outlet boxes, etc.). you gotta give the stray electricity a place to go. Also make sure there is NO continuity between ground and power wires. If the circuit is grounded, and there are no short circuits(continuity between ground and power) then work your way back wards to the ballast. Kinda like eliminating possible causes. (bulb, socket, wire connections to the socket, wires from ballast to socket, etc.) always work your way backwards thats how you troubleshoot. If I am correct you said the light works fine as long as it is outside the cabinet. This would mean the problem most likely lies with the cab. Good Luck and feel free to ask more questions. I will check back. And be sure to lemme know if you get the prob. solved.

 

[madcow]

ground the cabinet.wouldn't that solve the problem?

 

[danksmoker77]

to answer that last question the shocks probably arent caused by anything faulty. The cause is theres no ground. Grounding dosent hide the problem. Not being grounded is creating the problem.

AHHHHHH I see said the blind man.

Grounded outlets and receptacles were designed for this very reason, stray electricity causin problems.

 

[HowardWCampbell]

I think I'll be heading over there to check it out on monday, I'll let you know how it goes. I really appreciate all the help, especially you danksmoker.

So the likely reason that the bulb works only after the cabinet is opened is because the built up static electricity is discharged when you get shocked? And this built up static charge is preventing normal operation of the light?

I'm just trying to make sure I'm really understanding what is going on here. I'm having fun learning about this. Thanks to everyone who has contributed so far.