For the 6' cord limitation, the best I can remember is the branch circuit requirement in Article 210-52 for dwellings; I can't find the Article 422 reference for cord length for "general appliances." The length is sometimes referred to as 6', sometimes 2m.
Per NEC Article 305-3 (1996), Temporary use is considered during periods of construction, 90 days, or during emergencies and tests.
Article 400 provides information on flexible cords and connections, including permissable uses. It specifically states that flexible cords shall not be used as a substitute for fixed wiring of a structure. It also provides ampacities for such cords.
The UL listing for your 50', #16 AWG cable is going to be for temporary wiring, outdoor wiring, or for a maximum of 12A, despite the fact that it has a 15A plug... similar to what you are saying about the equipment pulling the power it wants to.
For something "permanent," the cord would need to be an "appliance cord." The only exception to the 6' appliance cord limitation that I am aware of is if the room is classified as a computer room (which requires extra protective measures, including an Emergency Power Off).
YMMV. If there is zero chance of an electrical inspector or fire marshal walking into the office, and safety isn't really a concern, what the heck?
The biggest obvious problem with this technology is the fact that you can no longer have universal power supplies, since the voltage ratio is a function of distance.
Nice to remove the inductors and other compensating components, but it seems like there is still a HUGE trade-off.
I'm a strong proponent of a messenger bag with a laptop sleeve inside. The laptop sleeve is more efficient than a laptop bag, and keeps your bag flexible.
The sleeve I have also straps nicely onto a rollerboard's hook thing, making airport security check-in a breeze!
If you really want some thing that will stand up to impact, Timbuk2 makes a laptop sleeve that has 1/2" padding. Wrong application, but... it works. I still prefer the Eagle Creek!
...aaah, now the "stripes" thing makes sense! Any color stripes you want, as long as it is blue on the top, white in the middle, and red on the bottom!
If my memory serves me, you get into the oil-filled cables around 80-100kV. These lines are comparable to major transmission lines. Great for places like Hong Kong, were there just isn't enough space to get power around otherwise.
Also, if I recall correctly, the cost of these cables is around US$1,000 per linear foot! Compare that with $70/ft for overhead cables, and you get a sense of the cost to put things underground.
Still worth it in my book, but... you have to understand the impact.
My biggest problem with online statements is that they are only kept online for six months. Between doing taxes and reconciling business expenses, that isn't nearly long enough! It doesn't seem logical for that sort of limit.
Anybody know a credit card company that keeps records for at least 18 months? Citibank is killing me!
Technically, this doesn't meet code in most jurisdictions. You can end up needing to put in an EPO system (big red button that makes the room quiet) if you go that route.
First, extension cords are limited to 6' by the National Electrical Code and UL. If the cord is longer than 6', it is supposed to have larger wire than what is normally provided (#14 for 15A vs. #16/18 typical extension cord). Outlet strips are generally considered "temporary" wiring, and is a code violation. YMMV
Running cables along the floor is a bad idea both because of the tripping hazard, and the potential to short out the wires.
Get an electrician out there and have him move the circuits to the racks. I would recommend having a about 3' of slack (LFMC conduit), and attach the outlet box to the rack via "temporary" means.
(If you are in CA, you don't want to make a permanant connection to the racks, as supplemental seismic bracing may be required.)
The thing missing in the discussion...
on
Pre-Fab Homes?
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· Score: 1
...is if a home should be unique, or something coming out of an assembly line. Also, what intrinsic compromises must be made if the building is shipped to site? Weight, dimensions, interconnections must all be considered.
Personally, I like some mass to a house, and organic free-flowing nature. I know there are benefits to assembly-line construction, but... there are also things to be said for something unique. Cost will always go to the assembly line, though.
As an engieer, I take exception to hiring an architect first. Find someone that has enough of an architectural background to know when you might need two exits, but focuses more on HVAC and electrical design-- someone that really has a good idea of the underlying engineering. Unfortunately, architects like being in charge all the time, and in specific cases like this they might overshadow an engineer's advice.
One example would be the floor loading stated by the parent. Generally, the only things that are a concern in an office building are the UPS system and the batteries. The solution is generally just to spread out the load. (Actually, almost all density-related problems (structural, cooling, or electrical) are best solved with this approach.)
Rackmounted UPS systems are OK, but going overboard with them doesn't help things. They need maintenance, batteries only last a few years, and most importantly, they are fire hazards.
Using rule-of-thumb numbers, for 50 servers I would guess between a 10-15 kVA UPS. Generally, 15 minutes of battery is a good number, but if you don't have a generator backing it up, all it will give you is orderly shutdown. That may be good enough for your needs... much of it depends on how good the utility is.
15 kVA is small enough that you can add some batteries and go for 30 minutes, but a generator isn't really cost effective. If you have redundant power supplies, the money is better spent getting two systems each with 15 minutes. At half load, you will get almost 30 minutes on each. Going longer than 30 minutes is going to be a push on the AC; you start to need a generator. Generators don't make much sense smaller than 100kW, or 50 kVA of UPS load. If you are in a high rise, try to negotiate for generator backup power... a few 30A circuits can go a long way.
Also, make sure that your UPS has an EXTERNAL bypass.
Actually, adding fans can cause a lot of problems. You are going to increase air mixing, which means that the computers never get really cold air. Not much of a problem if you only have a couple servers in a cabinet, but when your density gets higher it won't work as well.
The first thing to do is hire someone that knows what they are doing. You are talking about a fairly small computer room-- they are often the ones with the most problems.
Some quick pointers: -A single rack can be at about 2 kW with overhead air conditioning. Underfloor AC will get you closer to 3 kW. Much more than that, and you get in trouble. If you guess a real demand of 150W/server, you can fit about twelve servers in a single cabinet before you start to get into trouble. Plan for 5kW per rack on your UPS system and distribution - 2x20A outlets or 1x30A, 208V per cabinet (non-redundant)-- double for redundant cords. -The back of the racks should be hot. That isn't a problem, in and of itself. Good data center design is based on hot and cold aisles for just this reason. To see if you have a problem with the air conditioning, check and see what the return air temperature is-- if that is too low (close to the cold aisle temperature), you are going to get stuck. -If the backs of the racks are hot, make sure you have blank covers over all the open spaces on the racks. That keeps the hot air from mixing with the cold air on the front. -If you have raised floors with AC, try putting a tile or two on the hot aisle to induce flow and make it more comfortable. That should help some of the hot air get back to the AC units. -Have an engineer look at it. If you can, hire someone that specializes in data center design. Plan for at least $1,000/day of their time, $2k minimum-- just for looking at it and giving you a report. It's money well spent! You can bolt on a number of fixes for a problem, but it won't fix the root cause. Maybe that is good enough. -Be careful of the breadbox UPS vendors. They want to bypass the engineers and the contractors. They don't always tell you what you need to know.
{shameless plug}I work for a company called Syska-- there's plenty of other companies that do this type of work though. {/shameless plug} Find someone close to you that can help.
Current solar cell technology takes a big performance hit based on temperature. If the back of the cell is in the conditioned space, you should see efficiency well above 20%.
There are PV cells on the market now that double as water heaters; the water is used to maintain the cell temperature, and improve efficiency.
The idea isn't that different from Fritted Glass, where you have ceramic paint on the window to reflect some light and reduce the solar heat load (or just for privacy). Any glare on the screen is bad, and makes it difficult to focus; the pattern might make it slightly more manageable.
I think the scale of the cells shown in the renderings is a bit off; you would actually get more usuable surface area with "dots" rather than "small panels", and it would be MUCH less obtrusive.
The problem with all of these "services" that will help protect your identity is that you are paying the very people that have if not created, made the problem worse than it would have otherwise been.
Credit card companies have systems to look for fraud on an account-basis in place; it is in their own best interests. But, if you were looking at wide-spread fraud involving hundreds of thousands of different people, who would stop it?
The reporting agencies don't do anything, even if they do notice a spike in requests.
Hopefully, Identity Theft will render all the credit databases useless in a few years. That's the only way for the problem to get back to the source. The question then becomes what happens to the banking industry?!
Not all ports should be blocked on a constant basis, but port filtering should be dynamic based on threat assessments.
The ISP's job is to make sure that their other customers quality of service is not compromised beyond an acceptable time frame based on what is happening on one other customer's link. An automatic (adaptive) response is the most logical.
Think of recent virus attacks. Being able to stop them on all levels limits their opportunities to spread. It's a firewall throughout the link.
If you should happen to need that port that has been compromised on a network level, you have a problem. Logically, you would be able to tunnel that traffic across a VPN link, which would pass through the filters. If that isn't possible, then create "safe" vlans and "open" vlans at the ISP level. Do what you can for as many customers as possible, and have a way-out for the others.
It isn't likely that the SCADA or management systems themselves are running on a windows box, but the front end will be. You do see a lot more of ModBus-over-Ethernet these days, which I understand can coexist with TCP/IP. Although this would be a bad design, I can picture how you would end up with a single ethernet backbone, and have multiple protocols and devices running on it.
If the critical system is on the same physical network as workstations other than the head-end, that could be a problem. Technician plugs his infected laptop into the networ for diagnostics or downloading data, and the network traffic kills the ability for the SCADA nodes to interact.
This is an easy mistake to make; all it takes is having multiple people need to share the same information, and a lack of money to provide dedicated physical layers for each function and proper gateways between the layers.
It's more like you installed AutoCAD, outgrew it, and then passed it on. Maybe when you bought a new computer, you upgraded to a new version of AutoCAD. To do this, you must "turn in" your old license, and then you can install the new verson.
If the application isn't removed from the old computer, you are in violation. If you haven't upgraded the computer, just purchased the upgraded software, you are in violation unless you uninstall the old version.
Many companies fall into one of these two categories-- either dealing with hand-me-downs or making sure they don't break compatibility.
They were ignorant, as most companies are. The computer would work as-is for clerical staff, so they didn't uninstall software. It's situation normal for small businesses! Many companies don't buy new PCs for clerical staff, when they have a 2-year upgrade cycle for engineering machines and a 4-year cycle for clerical.
Even big companies often mirror a "standard install" for all the PC's. Maybe there are a few extra applications here and there, but it saves them effort and total cost of ownership. If the BSA targets this type of activity, their own arguments for the merits of their software can rightly be called into question.
If the reliability of the utility is not sufficient for your needs, provide a means of backup. If you are most worried about a lot of short "hits", buy a UPS. If you are worried about outages longer than 10-15 minutes, buy a generator.
You ask for five nines. In data center terms, that is a 2N system. Imagine what the national power grid would look like (and more importantly COST) if it was designed like a proper data center!
Deregulation creates a dis-incentive to have "spinning reserve." Spinning reserve is generators running without load, to compensate for failure of a power circuit or generation station.
In California prior to de-regulation, spinning reserve was kept at the size of the largest plant on the grid. With 1GW of nuke power on the system, that means you need a lot of gas-fired plants to be idling.
Spinning reserve increases cost without the opportunity for increased revenue, so economically you must be forced to maintain a high ratio.
As for "failing safe," the switching systems have about 8 milliseconds to determine if there is a problem, and then it will take 50 ms to actually open a switch. A fault has enough energy to vaporize things... you must fail safe! The restore process is just a function of electrical equipment... motors and transformers need 6-10x initial current to energize the magnetic field, and that will overload upstream supplies if everything happens at once.
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For the 6' cord limitation, the best I can remember is the branch circuit requirement in Article 210-52 for dwellings; I can't find the Article 422 reference for cord length for "general appliances." The length is sometimes referred to as 6', sometimes 2m.
Per NEC Article 305-3 (1996), Temporary use is considered during periods of construction, 90 days, or during emergencies and tests.
Article 400 provides information on flexible cords and connections, including permissable uses. It specifically states that flexible cords shall not be used as a substitute for fixed wiring of a structure. It also provides ampacities for such cords.
The UL listing for your 50', #16 AWG cable is going to be for temporary wiring, outdoor wiring, or for a maximum of 12A, despite the fact that it has a 15A plug... similar to what you are saying about the equipment pulling the power it wants to.
For something "permanent," the cord would need to be an "appliance cord." The only exception to the 6' appliance cord limitation that I am aware of is if the room is classified as a computer room (which requires extra protective measures, including an Emergency Power Off).
YMMV. If there is zero chance of an electrical inspector or fire marshal walking into the office, and safety isn't really a concern, what the heck?
The biggest obvious problem with this technology is the fact that you can no longer have universal power supplies, since the voltage ratio is a function of distance.
Nice to remove the inductors and other compensating components, but it seems like there is still a HUGE trade-off.
Go for a Pelican Box! You can even take it underwater. Can even survive a motorcycle crash... with a little luck.
The 1490 case is pretty good size, hard case. Not sure if it can hold a 17" Powerbook, but whatever is inside is pretty damn secure
I'm a strong proponent of a messenger bag with a laptop sleeve inside. The laptop sleeve is more efficient than a laptop bag, and keeps your bag flexible.
The sleeve I have also straps nicely onto a rollerboard's hook thing, making airport security check-in a breeze!
If you really want some thing that will stand up to impact, Timbuk2 makes a laptop sleeve that has 1/2" padding. Wrong application, but... it works. I still prefer the Eagle Creek!
...aaah, now the "stripes" thing makes sense! Any color stripes you want, as long as it is blue on the top, white in the middle, and red on the bottom!
If my memory serves me, you get into the oil-filled cables around 80-100kV. These lines are comparable to major transmission lines. Great for places like Hong Kong, were there just isn't enough space to get power around otherwise.
Also, if I recall correctly, the cost of these cables is around US$1,000 per linear foot! Compare that with $70/ft for overhead cables, and you get a sense of the cost to put things underground.
Still worth it in my book, but... you have to understand the impact.
For a story on interface design, it is a little ironic that they have the trolling scroll bar problem that /. has long since fixed.
My biggest problem with online statements is that they are only kept online for six months. Between doing taxes and reconciling business expenses, that isn't nearly long enough! It doesn't seem logical for that sort of limit.
Anybody know a credit card company that keeps records for at least 18 months? Citibank is killing me!
Technically, this doesn't meet code in most jurisdictions. You can end up needing to put in an EPO system (big red button that makes the room quiet) if you go that route.
First, extension cords are limited to 6' by the National Electrical Code and UL. If the cord is longer than 6', it is supposed to have larger wire than what is normally provided (#14 for 15A vs. #16/18 typical extension cord). Outlet strips are generally considered "temporary" wiring, and is a code violation. YMMV
Running cables along the floor is a bad idea both because of the tripping hazard, and the potential to short out the wires.
Get an electrician out there and have him move the circuits to the racks. I would recommend having a about 3' of slack (LFMC conduit), and attach the outlet box to the rack via "temporary" means.
(If you are in CA, you don't want to make a permanant connection to the racks, as supplemental seismic bracing may be required.)
...is if a home should be unique, or something coming out of an assembly line. Also, what intrinsic compromises must be made if the building is shipped to site? Weight, dimensions, interconnections must all be considered.
Personally, I like some mass to a house, and organic free-flowing nature. I know there are benefits to assembly-line construction, but... there are also things to be said for something unique. Cost will always go to the assembly line, though.
As an engieer, I take exception to hiring an architect first. Find someone that has enough of an architectural background to know when you might need two exits, but focuses more on HVAC and electrical design-- someone that really has a good idea of the underlying engineering. Unfortunately, architects like being in charge all the time, and in specific cases like this they might overshadow an engineer's advice.
One example would be the floor loading stated by the parent. Generally, the only things that are a concern in an office building are the UPS system and the batteries. The solution is generally just to spread out the load. (Actually, almost all density-related problems (structural, cooling, or electrical) are best solved with this approach.)
Rackmounted UPS systems are OK, but going overboard with them doesn't help things. They need maintenance, batteries only last a few years, and most importantly, they are fire hazards.
Using rule-of-thumb numbers, for 50 servers I would guess between a 10-15 kVA UPS. Generally, 15 minutes of battery is a good number, but if you don't have a generator backing it up, all it will give you is orderly shutdown. That may be good enough for your needs... much of it depends on how good the utility is.
15 kVA is small enough that you can add some batteries and go for 30 minutes, but a generator isn't really cost effective. If you have redundant power supplies, the money is better spent getting two systems each with 15 minutes. At half load, you will get almost 30 minutes on each. Going longer than 30 minutes is going to be a push on the AC; you start to need a generator. Generators don't make much sense smaller than 100kW, or 50 kVA of UPS load. If you are in a high rise, try to negotiate for generator backup power... a few 30A circuits can go a long way.
Also, make sure that your UPS has an EXTERNAL bypass.
Actually, adding fans can cause a lot of problems. You are going to increase air mixing, which means that the computers never get really cold air. Not much of a problem if you only have a couple servers in a cabinet, but when your density gets higher it won't work as well.
The first thing to do is hire someone that knows what they are doing. You are talking about a fairly small computer room-- they are often the ones with the most problems.
Some quick pointers:
-A single rack can be at about 2 kW with overhead air conditioning. Underfloor AC will get you closer to 3 kW. Much more than that, and you get in trouble. If you guess a real demand of 150W/server, you can fit about twelve servers in a single cabinet before you start to get into trouble. Plan for 5kW per rack on your UPS system and distribution - 2x20A outlets or 1x30A, 208V per cabinet (non-redundant)-- double for redundant cords.
-The back of the racks should be hot. That isn't a problem, in and of itself. Good data center design is based on hot and cold aisles for just this reason. To see if you have a problem with the air conditioning, check and see what the return air temperature is-- if that is too low (close to the cold aisle temperature), you are going to get stuck.
-If the backs of the racks are hot, make sure you have blank covers over all the open spaces on the racks. That keeps the hot air from mixing with the cold air on the front.
-If you have raised floors with AC, try putting a tile or two on the hot aisle to induce flow and make it more comfortable. That should help some of the hot air get back to the AC units.
-Have an engineer look at it. If you can, hire someone that specializes in data center design. Plan for at least $1,000/day of their time, $2k minimum-- just for looking at it and giving you a report. It's money well spent! You can bolt on a number of fixes for a problem, but it won't fix the root cause. Maybe that is good enough.
-Be careful of the breadbox UPS vendors. They want to bypass the engineers and the contractors. They don't always tell you what you need to know.
{shameless plug}I work for a company called Syska-- there's plenty of other companies that do this type of work though. {/shameless plug} Find someone close to you that can help.
Current solar cell technology takes a big performance hit based on temperature. If the back of the cell is in the conditioned space, you should see efficiency well above 20%.
There are PV cells on the market now that double as water heaters; the water is used to maintain the cell temperature, and improve efficiency.
The idea isn't that different from Fritted Glass, where you have ceramic paint on the window to reflect some light and reduce the solar heat load (or just for privacy). Any glare on the screen is bad, and makes it difficult to focus; the pattern might make it slightly more manageable.
I think the scale of the cells shown in the renderings is a bit off; you would actually get more usuable surface area with "dots" rather than "small panels", and it would be MUCH less obtrusive.
The problem with all of these "services" that will help protect your identity is that you are paying the very people that have if not created, made the problem worse than it would have otherwise been.
Credit card companies have systems to look for fraud on an account-basis in place; it is in their own best interests. But, if you were looking at wide-spread fraud involving hundreds of thousands of different people, who would stop it?
The reporting agencies don't do anything, even if they do notice a spike in requests.
Hopefully, Identity Theft will render all the credit databases useless in a few years. That's the only way for the problem to get back to the source. The question then becomes what happens to the banking industry?!
OPEC isn't a problem; we have a contingency plan for this. We invade a major oil-producing country, and liberate their oil.
Not all ports should be blocked on a constant basis, but port filtering should be dynamic based on threat assessments.
The ISP's job is to make sure that their other customers quality of service is not compromised beyond an acceptable time frame based on what is happening on one other customer's link. An automatic (adaptive) response is the most logical.
Think of recent virus attacks. Being able to stop them on all levels limits their opportunities to spread. It's a firewall throughout the link.
If you should happen to need that port that has been compromised on a network level, you have a problem. Logically, you would be able to tunnel that traffic across a VPN link, which would pass through the filters. If that isn't possible, then create "safe" vlans and "open" vlans at the ISP level. Do what you can for as many customers as possible, and have a way-out for the others.
It isn't likely that the SCADA or management systems themselves are running on a windows box, but the front end will be. You do see a lot more of ModBus-over-Ethernet these days, which I understand can coexist with TCP/IP. Although this would be a bad design, I can picture how you would end up with a single ethernet backbone, and have multiple protocols and devices running on it.
If the critical system is on the same physical network as workstations other than the head-end, that could be a problem. Technician plugs his infected laptop into the networ for diagnostics or downloading data, and the network traffic kills the ability for the SCADA nodes to interact.
This is an easy mistake to make; all it takes is having multiple people need to share the same information, and a lack of money to provide dedicated physical layers for each function and proper gateways between the layers.
It's more like you installed AutoCAD, outgrew it, and then passed it on. Maybe when you bought a new computer, you upgraded to a new version of AutoCAD. To do this, you must "turn in" your old license, and then you can install the new verson.
If the application isn't removed from the old computer, you are in violation. If you haven't upgraded the computer, just purchased the upgraded software, you are in violation unless you uninstall the old version.
Many companies fall into one of these two categories-- either dealing with hand-me-downs or making sure they don't break compatibility.
They were ignorant, as most companies are. The computer would work as-is for clerical staff, so they didn't uninstall software. It's situation normal for small businesses! Many companies don't buy new PCs for clerical staff, when they have a 2-year upgrade cycle for engineering machines and a 4-year cycle for clerical.
Even big companies often mirror a "standard install" for all the PC's. Maybe there are a few extra applications here and there, but it saves them effort and total cost of ownership. If the BSA targets this type of activity, their own arguments for the merits of their software can rightly be called into question.
If the reliability of the utility is not sufficient for your needs, provide a means of backup. If you are most worried about a lot of short "hits", buy a UPS. If you are worried about outages longer than 10-15 minutes, buy a generator.
You ask for five nines. In data center terms, that is a 2N system. Imagine what the national power grid would look like (and more importantly COST) if it was designed like a proper data center!
Deregulation creates a dis-incentive to have "spinning reserve." Spinning reserve is generators running without load, to compensate for failure of a power circuit or generation station.
In California prior to de-regulation, spinning reserve was kept at the size of the largest plant on the grid. With 1GW of nuke power on the system, that means you need a lot of gas-fired plants to be idling.
Spinning reserve increases cost without the opportunity for increased revenue, so economically you must be forced to maintain a high ratio.
As for "failing safe," the switching systems have about 8 milliseconds to determine if there is a problem, and then it will take 50 ms to actually open a switch. A fault has enough energy to vaporize things... you must fail safe! The restore process is just a function of electrical equipment... motors and transformers need 6-10x initial current to energize the magnetic field, and that will overload upstream supplies if everything happens at once.