I agree that using a financial incentive is a better way to go, and there are several reasons why breakers are a problem:
- They don't actually trip at the rated current. Breakers have a profile, and will trip quickly if you draw significantly more than their rated current, but may sit at (or even somewhat above) their rated current for quite some time. - Breakers also get weak if tripped frequently or run near their limits for a long time. This can take a few years to happen, but it *will* happen eventually, and your customers will get unhappy if they can no longer run up to their rated current. Breakers are not meant to be run at-or-near their rated current continuously. - Breakers are not precision-trip devices. They are designed for protection, not metering, so they have some variability in rating. If you actually want to shut down the circuit based on current limit, you could use a monitored power bar that also has controlled shutdown for each circuit, but the cost may exceed your business model. The advantage to this is that if you can use larger (even 30A) circuits to feed the power bar, and can choose to warn/charge $ if the customer exceeds their limit, but not actually shut them down unless the entire circuit is at risk. Another reason that breakers are undesirable - you actually have to go to them and switch them on after they trip. I don't know if this is an inconvenience for you or not. What kind of gear are you planning to let your customers install that will vary in power requirements this much? You might solve the problem by putting a 'Kill-a-Watt' on their gear and getting them to run the equipment full-out. Once you know the maximum current requirement, charge them based on the maximum power usage, and distribute the equipment on circuits accordingly. (Monitored power bars could also do this, but the Kill-a-Watt costs about $20.) This is less convenient if there are frequent equipment changes, but if most customers drop it in and forget it, it might be practical. (You could have a fee for gear change, to cover the overhead of doing the power profile.) - Richard Brian Mathis wrote: > You need to think like a businessman, not a techie. The techie wants > to figure out a technical solution to prevent people from doing > something, while the businessman charges a penalty fee if someone uses > more than they're supposed to. > > Using a fee has a bunch of advantages: > - You get more money if people go over > - It costs you almost nothing in time or effort to implement (as far > as engineering a solution). You just need to have the monitoring > system setup. > - It places the burden on your customers to stay in line, instead of you > - It allows you to make more efficient use of your power resources > since you don't have to rigidly divide them up among customers. > - We live in a capitalist society. Capitalism is not about greed, > it's about using financial incentives/disincentives to steer people in > the direction you want them to go, instead of forcing them. > > It does put you at some risk, and the amount of the overage fee should > be proportional to that risk. > > You're running a business, so be the businessman. > > > On Thu, Jul 15, 2010 at 7:57 PM, Luke S Crawford <[email protected]> wrote: > >> so here is the problem: I am exploring the idea of getting >> back into the co-location business. Now, for this to work for me >> and my market, it's got to fit several things. >> >> 1. It's got to be cheap. There is a place for selling expensive >> co-lo... but my entire business is built around selling less expensive >> stuff to people willing to skimp on certain features (and on skimping on >> the right features for that group.) >> >> this means I probably want to sell half-racks, or even quarter racks. >> >> 2. it's got to be low-calorie on my part. if I've got to go re-negotiate >> with a customer every time they exceed their power allowance, or argue >> about if 75% or 85% utilization is acceptable, I'm going to want to charge >> more than my market is willing to bear. Negotiation is fine in many >> markets, but in my market, it would raise costs an unacceptable amount. >> >> 3. there has to be good isolation. It's fine if there are sharp edges; >> my customers are willing to tolerate it if it's easy for them to break their >> own stuff. But if their neighbor's mistakes or my mistakes take them down? >> that is not acceptable. >> >> So, here is what I was thinking. what if I split every 15a circuit into >> two 7.5a circuits. put a breaker on each that blew at 7.5 amps. >> the idea is to make things 'fire and forget' - if you exceed 7.5 amps, >> well, your shit breaks. No negotiation. >> >> (this also removes the possibility of me or one of my people 'going easy' on >> one customer eating more than their share for a few days and then the >> other customer sharing that circuit suddenly having a spike and killing off >> both users.) >> >> Anyhow, uh, is anyone else doing this? is it an absolutely stupid idea? >> should I go looking for a PDU that simulates this behavior? or writing >> a perl script hitting a PDU to simulate this? or is it better to have an >> electrician wire such a thing up with real breakers. would such a thing >> even be possible? (I mean, ultimately, I'd like a breaker that goes >> at 3.75amps, 4 to the 15 amp circuit.) >> _______________________________________________ >> Tech mailing list >> [email protected] >> http://lopsa.org/cgi-bin/mailman/listinfo/tech >> This list provided by the League of Professional System Administrators >> http://lopsa.org/ >> >> > > _______________________________________________ > Tech mailing list > [email protected] > http://lopsa.org/cgi-bin/mailman/listinfo/tech > This list provided by the League of Professional System Administrators > http://lopsa.org/ > _______________________________________________ Tech mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
