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neonhomer
Dearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL

neonhomer to psiu

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to psiu

Re: [Electrical] "Retesticals"

As a HVAC controls and Building Automation tech, we get to interface with power monitors and such...

We had to run a Modbus cable from each of four "substations" back to our JACE to be able to monitor them. (Daisy chain). We submitted what we had to do to the customer, and they said okay, but flatly rejected our electricians... They wanted their electricians to do the panel penetrations... hot 480 3P panels.... yeah... we didn't argue with them.

What's got me worried now is here in a few months, we are going to be starting to retrofit their chiller plant to new controls... and their chillers run on 4160..... Now I'm afraid to go in there!

Lurch77
Premium Member
join:2001-11-22
Green Bay, WI

Lurch77

Premium Member

said by neonhomer:

Now I'm afraid to go in there!

No reason to be afraid. Just respect it. That sounds cheesy, but it is the truth. Here is one of the videos we watch for training. It walks you through what happened to a guy. It's pretty sobering.

»www.youtube.com/watch?v= ··· EuRA7-vo

sk1939
Premium Member
join:2010-10-23
Frederick, MD

sk1939

Premium Member

That's one depressing video.

zacron
Premium Member
join:2008-11-26
Frozen Hoth

zacron to Lurch77

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to Lurch77
I wish I had this video to teach a co-worker about safety... :/

neonhomer
Dearborn 5-2750
Premium Member
join:2004-01-27
Edgewater, FL

1 recommendation

neonhomer to Lurch77

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to Lurch77
I work with varying voltages throughout my job.... 24VAC, 120VAC, 240VAC, 277VAC, 480VAC... and maybe some in between there... On the higher stuff... 277 and 480, I've never worn any kind of special clothing, or really did anything out of the ordinary... mostly because I didn't know any better... I've never been trained on *proper* procedures for working with 480... For example...

My job requires me to work inside a 480V VFD. (I have to bring in 24VAC control circuits and wire them to the control board of the VFD.) I would consider the drive HOT... only because there is power going into the disconnect. (Even though the disconnect is off.) The electricians keep the panels locked, and the electrical rooms locked. So I would have to go to an electrician, and ask them to turn the circuit off.... and would promptly be laughed at for it. So I do what I can do... stay away from the bottom of the drive.

I know it doesn't make it right, but there is a small twinge in the back of my head that says "What is going to happen if I'm sitting in front of this drive, and something goes horribly wrong with this disconnect?" If anything, I have learned that when I turn something back on, I don't stand in front of it. I stand to the side, and try to do it at arm's length.... and have been laughed at for doing it.

I think as we move into this chiller plant, that before we do, I am going to push my company to do some training with working around higher voltages. We may not have to go into panels with 4160 in them... but I'd rather be trained and not need it, than to need the info and not know it. Hell... maybe it would be a good idea to forward my project manager and his boss the above video...

Lurch77
Premium Member
join:2001-11-22
Green Bay, WI

Lurch77

Premium Member

My employer's policy is to wear arc flash gear for anything 40 volts and above. I know that seems a bit over the top, but it is what it is. There are different rated clothing for different voltage. For example I don't have to wear the full space suit when working with 120v. But it still gets a few chuckles or comments of disbelief from some of my customers that don't care or sometimes don't even know what an arc flash is. I just tell them that's our company policy, and since I enjoy being employed I follow it. I've never had anyone give me more serious grief beyond that. If they did I would stop work and call our safety office for further direction.

We carry up to cat 2 on our trucks. I have yet to run into any equipment calling for anything more than cat 2, except for some 4160 motors. In those cases we work with a qualified electrician.



whizkid3
MVM
join:2002-02-21
Queens, NY

whizkid3

MVM

Click for full size
said by Lurch77:

There are different rated clothing for different voltage. For example I don't have to wear the full space suit when working with 120v.

Lurch, you should know that the level of PPE has no direct correlation with the voltage you are working at; although voltage is one characteristic. The only way to know what level of PPE is appropriate, is through the arc-flash sticker on the equipment, which would be there is an actual arc-flash study had been done. (Now a code requirement.) The arc-flash sticker will tell one what the arc-flash energy and boundaries are; and the PPE category.

When there is no label, then yes; one would have to take an educated guess. The level of energy is what dictates the PPE level. From a simple perspective, arc-flash incident energy = t x V x I

't' = time for the fuse to blow or breaker to trip
'V' = voltage
'I' = available fault current (3-phase bolted short circuit current)

Voltage is actually the least concern; although system design based on the voltage can have a large effect on the amount of energy. Some rules of thumb, assuming the over-current protection works and has an instantaneous setting; i.e. current-limiting fuse; thermal-magnetic breaker; etc. See below.

Warning, the following rules-of-thumb are estimates only. In all cases, one use the information on an arc-flash label; or consult with a professional engineer skilled in determining arc-flash incident energy levels.

- 208 or 120V on the secondary side of a transformer no larger than 75kVA = PPE 0 or 1

- up to 600V on the secondary side of a up transformer no greater than 500 kVA = PPE 3

- Any voltage from a utility 'grid-style' network (i.e. 208V utility in NYC) = PPE 4 or 'Dangerous' (meaning no level of protection will save you)

- Voltages over 1000V, from substation transformers 2MVA and larger = PPE 4 or 'Dangerous'

Personally, unless its 120/208V from a small transformer; if there are not labels on the equipment, I would use the highest level of PPE available. If the equipment has a 'maintenance' setting, that lowers energy levels (by reducing the amount of time for a breaker to trip), it should always be turned-on before servicing the equipment. These are not very common, except in new, high-end equipment.

Lurch77
Premium Member
join:2001-11-22
Green Bay, WI

Lurch77

Premium Member

Yes, I just left it simple. Voltage is usually the biggest factor in the equation from my experience. The higher the voltage, generally the higher the requirements. All the newer equipment I work on has the sticker, but most of the equipment I work on is not new.

enon
@66.87.81.x

1 recommendation

enon

Anon

Actually it has more to do with the available bolted fault current than anything else. Using voltage alone can be deceiving because the level of protection from the next upstream OCPD can vary wildly. This is exactly why the labels whizkid3 See Profile posted are now required.

neonhomer See Profile it sounds like you really might benefit from NFPA 70E training. If I were you, I'd follow up with your plant's safety officer not only about the training requirements for your job classification but also the safety culture being perpetrated by the maintenance electricians.

leibold
MVM
join:2002-07-09
Sunnyvale, CA
Netgear CG3000DCR
ZyXEL P-663HN-51

1 recommendation

leibold to Lurch77

MVM

to Lurch77
The best example for a high level of protection needed for low voltage systems are the bus bars from a 48V or 60V battery room. Whatever conductive material you drop on those bars will be instantly turned into a hot plasma cloud.

Low voltage does not mean safe, especially not if it can deliver a huge current.

pende_tim
Premium Member
join:2004-01-04
Selbyville, DE

pende_tim to neonhomer

Premium Member

to neonhomer
You are not doing anyone a favor working like that.

Ask your self this question: Who will take care of your loved ones when something goes wrong?

A a very bare minimum, LOTO and PPE will apply to any device you work on that has energy in it. It does not matter if you are a full time employee, a part time cleaner or contract worker: You are responsible for your safety. You must be in control the the energy available in and to the device you are maintaining.

Yes, you need to approach the company about this situation. It is not just for your benefit but point out to them that if something goes wrong and you have not been properly trained, the company is in deep dodo.

Lurch77
Premium Member
join:2001-11-22
Green Bay, WI

Lurch77 to leibold

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to leibold
said by leibold:

Low voltage does not mean safe, especially not if it can deliver a huge current.

I think you guys read too far into my admittedly over general comment. I'm speaking from my own experience in my field of work (industrial hvac). I have much experience with electricity and understand it fully.

I understand there is more to it than just voltage. But I stand by my comment that in my experience, in my field of work, voltage is a strong indicator of the level of protection needed. When I come across an unmarked piece of equipment I'm going to treat a 24v control box different from a 480v distribution box. That's not to say I won't respect 24v, but its just not the same.

chip89
Premium Member
join:2012-07-05
Columbia Station, OH

chip89 to Lurch77

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Wow 40V is common the outlet by me right now is 120v...

Lurch77
Premium Member
join:2001-11-22
Green Bay, WI

Lurch77

Premium Member

But you are not opening up and working on that outlet while it is live. People don't need to wear PPE just because they are near electricity. It is when they are working on it or near unprotected live electricity (opened boxes, exposed connections, etc).

chip89
Premium Member
join:2012-07-05
Columbia Station, OH

chip89

Premium Member

& This is way people need to be careful when resting circuit breakers at least don't stand in front of it incase it arcs.