New Fine Woodworking magazin almost made me ill

[Rick]

If you really want the best of both worlds ...

You can have your electrician install a line-powered contactor in series with your shop sub-panel. The coil (110 VAC) is connected to your light switches (and optionally a key-lock switch) and the power to the sub-panel goes through the contactor. Thus, whenever you turn the lights out, the power goes off to all the tools. Bad side ... when you turn the lights back on, the tools could start again (if you left them in the "on" position).

For an improved version, wire up a start/stop switch to the array, so that in order to pull the contactor in, you need press the "Start" button (a normally open switch). Use an auxiliary contact ( a low current switch actuated by the armature) in parallel with the "Start" switch, and it will hold itself in (the Start and Stop buttons are momentary).

To shut the contactor off, the "Stop" button (normally closed) is wired in series with the contactor coil. When you press "Stop", it breaks the current path to the coil, the armature opens, and the auxiliary contact is no longer keeping the circuit energized.

PLUS ... should the power drop out, none of the machinery will automatically restart until you press the "Start" button again.

Going yet further, you could wire a series of emergency stop buttons around the shop ... push any button, and all power tools quit. You could also shut the lights off ... but that's not a "normal" emergency reaction, so I'm not recommending it.

If you can't follow these instructions, you'd better consult with an electrician.

HTH

Rick

All the ( ... ) indicate I've been writing WAY too much code lately. Time to smell the sawdust!

[Larry Jaques]

On Thu, 18 Nov 2004 20:11:56 GMT, "Mark Jerde" calmly ranted:

I dunno. Anyone who'd climb a frosty peak must have started in the IQ-65 mode at the bottom. And since they didn't have oxygen, they all -missed- the actual experience they meant to achieve by being in that dumb mode. How much bette would the trip have been if they had carried oxy? Ditto the pictures when NOT taken by a braindead guy?

Climbers' IQs just dropped in my estimation.

[Mike]

Good question. I've got two young children and sometimes have to evacuate the shop in a hurry to rescue SWMBO. I can just pull off the safety goggles and apron, and hit a switch on the way out the door. This makes sure my A/C, heater, fans, and radio all go off. That makes it a lot easier to come and go and not spend time prepping my workspace. Sometimes I leave the DC on, but it's not dangerous when it starts up.

-Mike

[Robert Bonomi]

"Not exactly".

Nitrogen, itself, is absolutely harmless. Good thing, too, because it makes up approximately 80% of what you're breathing _right_now_. It is an *inert* gas, totally non-reactive with _anything_.

That said, a 'near-total' nitrogen atmosphere *is* dangerous. Not so much _because_ of the Nitrogen presence, but because the levels of (a) Oxygen and (b) Carbon-Dioxide, are at unsafely _low_ levels -- 'driven out' by the excess Nitrogen.

Nitrogen is 'colorless, odorless, and tasteless' (good thing!, see above:), and, as such, you get no warning of the presence of a 'too nitrogen rich' environment.

The absence of CO2 means that the 'breathing reflex' is _not_ triggered, and you simply 'forget' to breathe. This _lack_ of CO2 is the 'real' killer -- you "don't know" you have a breathing problem, because you aren't "feeling the need, the need to breathe". Fairly quickly, this leads to oxygen depletion in the blood stream, which leads to cessation of many 'automatic' bodily functions. Unconsciousness follows. 3-5 minutes later, and you have irreversible brain-death due to lack of oxygen.

Catch the unconscious person promptly, remove them from the 'unhealthy' environment, and they will generally recover quite quickly. "Mouth-to-mouth" is actually the most effective 'direct' treatment -- it supplies the critical carbon-dioxide as well as the oxygen. Speed _is_ of the essence in getting breathing restored. Ephinepherine may also be beneficial -- it assists hemoglobin in binding to free oxygen.

[Robert Bonomi]

"FM 200" maybe? I can't find any apparently relevant on-line references to "FM1200"

FM 200 _is_ one of the closer substitutes, and the 'most commercially available'. It fails the 'drop-in' replacement test on at least a couple of points -- 1) tanks have to be kept in a controlled environment, HALON is ok, outside in the Arctic, or the tropics. 2) can't use it through long piping runs.

All the 'gory details', for anybody who is interested, at:

[Robert Bonomi]

*WOW*! I had _no_ idea what refills go for these days. That's 10-20 times what it would have cost for HALON, back in the 'bad old days'.

yeah. 12 large pays for a _lot_ of water damage.

[Robert Bonomi]

I'd regard _two_ circuits as the absolute minimum for a *safe* shop. One for lights (only), and 'everything else' on the other one. OR, as available, split the 'everything else' up on multiple breakers.

I entirely agree about the 'desirability' and 'convenience' of a "master kill" switch; *BUT* I don't want it to take out the lighting -- I need to be able to

*see* what those moving 'sharp bits' are doing, _at_least_ until they *stop* moving.

_Two_ switches -- the 'master kill', and the lights, is not an excessive burden. :)

BTW, this is a good reason to _not_ run the "lighting" circuit through a sub-panel, when you use a sub-panel for the shop. Pull the extra pair of wires. Then you can lock out the entire panel, without losing the lights. And, in that horror-of-horrors situation where you manage to overload the sub-panel feed, without overloading any -single- circuit, you'll *still* have the lights.

[Robert Bonomi]

That's the kind of environment where I'd make sure I had some battery-backed emergency lighting.

[Robert Bonomi]

You are *not* 'entirely wrong' in that premise.

As with everything else, everything depends on the details. :)

The 'typical' Nitrogen-pressurized HALON system uses HALON 1211, a sprayable liquid. The gas pressure is used to force the liquid out of the storage tank, through the pipes, and out into the 'protected' space.

It _is_ practical to install cut-off valves that pass the liquid flow, but shut themselves off when the gas starts going by. Doing so, however, _does_ add a fair amount of complexity, and _cost_, to the system.

You get into a _very_ complex set of trade-offs, regarding the size of the protected space, the layout, the number of people in it, how _quickly_ they can evacuate, given a warning, and the dollar cost of letting the fire burn 'without resistance' for that evacuation period.

One of the other HALON formulations (I don't have the number to hand) is built around a bromine atom. "Bromides" are _not_ 'people friendly'; this is the kind of a system where you absolutely *have* to evacuate before the dump goes.

[Robert Bonomi]

Theres an old B&W Hollywood movie featuring the U.S.A.F. that has a _very_ realistic scene in it of that pressure chamber testing. It's not 'Fail Safe'; not 12 O'Clock High setting _is_ in the United States; I don't think it's 'Strategic Air Command'; It _might_ be in the one (who's name escapes me) about training 'bombardiers', and how they deserve equal 'credit' with the pilots.

[Robert Bonomi]

The insidious thing is that you _don't_ experience shortness of breath. The CO2 is also driven out, and the breathing reflex doesn't cut in. You _don't_know_ you're in breathing trouble, because you've "forgotten" to breathe.

The 'hypoxia' suffered at high altitudes (mountain climbers, flyers) is _exactly_ the same thing.

It's similar to 'nitrogen narcosis' for SCUBA divers,

All of these things just 'sneak up on you' -- you don't know there's anything wrong.

With _mild_ hypoxia, *IF* you've had training to recognize the symptoms _in_yourself_, you *may*: (a) recognize that "you're *IN*TROUBLE*", (b) manage to remember 'what to do about it', (c) actually _do_ it.

Severe hypoxia can hit fast enough, and hard enough, that you _don't_ have any chance. You're unconscious before you're conscious (pun intended) that there's a problem.

[Robert Bonomi]

I'm told a job as a sex toy pays really well.

Sorry, couldn't resist.

When you leave the door _that_ wide open, *somebody* is going to drive the truck through it. I guess I'm "somebody" around here, today. :)

[Charlie Self]

Patriarch notes:

Yes. It makes me wonder how much it costs to set up one of those exit door floodlight kits you see in commercial buildings. But power outages around here aren't too much of a problem, usually hitting us at a time when sensible people are in the basement cowering under desks, or sitting in front of the woodstove speculating on when the snow/ice/rain will quit.

Charlie Self "Health nuts are going to feel stupid someday, lying in hospitals dying of nothing." Redd Foxx

[Charlie Self]

Robert Bonomi responds:

Yes. Today, I probably would. But back then, I never even thought about such a thing. That shop was a lot of fun, large (19' x 63'), and I spent over $1500 on lights, wiring and paint, plus a couple, three weeks getting it ready for tools. A lot of money for stuff that has to be left behind. The lease was a good one, the rent was low, the landlord helpful, and heat was free, so it was near ideal (except for a 7' 4" ceiling) at the time. But a battery pack of emergency lights would have made it handier. Who woulda thunk, though, that the blinking power company would be the one that created the problem.

Charlie Self "Health nuts are going to feel stupid someday, lying in hospitals dying of nothing." Redd Foxx

[Doug Miller]

"due to lack of oxygen".

Isn't that what I said?

I don't know if that's correct or not, but, like I said, nitrogen is *not* poisonous. Air is 78% +/- nitrogen.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.

[alexy]

Robert, I am not a medical professional, and Jr. high school biology was a long time ago, so I might be wrong, but aren't you ascribing to atmospheric CO2 what is really an issue with dissolved CO2 in the blood, or possibly CO2 build-up in the lungs? After all, this mechanism works when you are holding breath underwater, with no CO2 in the surrounding "atmosphere". Excessive CO2 buildup in the lungs is removed by breathing air with or without normal atmospheric levels of CO2.

[Doug Miller]

That is correct: the level of CO2 in the atmosphere is very, very low, approximately 0.035%, or only 350 ppm. The breathing reflex is triggered by the level of CO2 in lung tissue.

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.

[GregP]

Sorry, a typo, it is FM200. Our computer room fits the constraints: it's pretty small - about 10 X 17 - and it's got it's own cooling with backup. There are a bunch of alternatives, actually, but each has constraints that make it less ideal than Halon.

[Dave Hinz]

Yes.

Er, no. Plenty of nitrates, nitrites, and other nitrogen-containing compounds exist. It's not one of the noble (inert) gasses, those are the helium/neon/argon/krypton/xenon/radon column.

Yes, but that CO2 is in blood-chemistry, and is a result of cellular respiration rather than CO2 in the atmosphere.

I've been an EMT for a dozen years, and have never heard this theory. Can you provide a link I can read about it please? We provide 100% oxygen in situations like this, by bag/valve/mask in most cases. Mouth to mouth is only used until/unless we can get high-flow O2 on them, because exhaled breath has considerably _less_ than the 21% O2 that's in the atmosphere. It's certainly better than nothing, but nowhere near as good as pure O2. The breathing drive isn't needed at that time, because we're pushing it into them if they're not breathing well on their own.

At the EMT level of training, we use epi to raise blood pressure by constricting the blood vessels, and improve ventilation by opening up the air passages in the lungs. I am surprised to see that it has an effect on oxygenation of hemoglobin.

Dave Hinz

[Dave Hinz]

What ever happened to GHG-12? George Goble (spelling?) worked it up, blend of propane/butane/etc. Intended as a drop-in for R-12, for automotive use. People whined that it was flammable, but most cars have this whole fuel thing going on anyway, so...

Dave Hinz