07-14-2005, 09:18 PM
Regarding your previous post:
“…I'm getting a quote for the 5 ton challenger unit that can be adjusted to run at 3 tons and increased if I need more. If it's not soooo much more, I'm going for it”
It sounds as though the 5 ton Challenger has a DBV rated at 2.0 tons, giving you a net 3.0 tons of cooling when the DBV is fully opened. Just make sure it is equipped with an anti-short cycling relay. Good luck……..once again friend.
John J. Dalton
07-14-2005, 11:55 PM
well, as the saying goes, you get what you pay for....I'm going to get the right equipment by paying the right amount of money. I don't know for sure, but I would guess that Liebert systems that are placed in server rooms for this type cooling scenarios would come standard with hot gas bypasses and anti-short cycle circuits.....btw, I don't remember if I wrote in the thread earlier, but when the lightning season started, I had to go to the office to save the server room from a thermal event , and from that experience, I found out that the anti-short cycle timer I had installed on the Trane unit was there, but it was set to 0 minutes, so even if I get it, I need to be careful.
I am begining to live like Fox Mulder, "Trust No One", If I go with that and add a bit of Star Wars, I'l trust no one but the Force, but in any even, one day soon I will be out of this mess.
A new question I have is how to utiize my Trane after the Liebert is installed....one thing I was told to do is set the rane to 73 degrees so if the Liebert stops cooling, it' automatically kick on when the room temp gets to 73, which it should never get to under normal operating circumstances.....does that sound like a good idea? Wil the system be able to turn on right away after being off for month and months at a time? Should I be sure to run the Trane unit for a few hours every month???
once again, thanks for heping me through this tough time.
07-19-2005, 08:29 PM
Hot gas bypass(DBV) may, or may not be standard on your particular system, so I would most diffidently ask before I bought it. The anti-short cycling relay should, and the key word here is should, be installed in the system, but again I would most diffidently ask before I bought it.
You’re correct in your assumption of making the Liebert mini-mate the 1st stage system and the Trane system your 2nd stage by adjusting the setpoint on the Trane system to 73 degrees F. This would automatically cycle on the Trane should there be an unscheduled shutdown of the Liebert system and the room temperature rose to 73 degrees F. I would also operate the Trane system for an hour twice(2X) a year just to keep the evaporative (indoor) and condensing (outdoor) motor bearings running periodically, everything else should be satisfactory.
Hope this helps, and as always, keep us informed………………..
John J. Dalton
07-19-2005, 11:48 PM
I will be sure to ask, and def inform you guys.
I believe the unit will be installed within 3 weeks
07-20-2005, 09:58 AM
The end of an era............
Originally posted by serverroomcooling
I believe the unit will be installed within 3 weeks
07-20-2005, 01:19 PM
is that optimism from Diceman....wow, I guess it really might be an end of an era
I'm going to be optimistic and say that I think this Challanger unit will actually end up getting installed....as far as time is concerned, what's the over/under on 3 weeks??
07-20-2005, 01:59 PM
I don’t think that is optimism on Diceman’s part, but rather wishful thinking. Three weeks………we’ll see my friend, we’ll see.
On another note, since we’re in the middle of summer and the outside temperature must be on the hot side, have you generated any cycle rates of the cooling mode on a typical hot Sunday afternoon when the building’s HVAC system is off? That would give us an approximate operating heat load under the outside conditions that it was obtained at.
John J. Dalton
07-21-2005, 04:23 PM
The Liebert Challenger will cycle its compressor to maintain room temperature. It's indoor air fan will run continuously to maintain air circulation in the room. You can get Challengers with hot gas bypass, and depending on which microprocessor you get, you may also get a compressor short-cycle alarm. My experience with Challengers is that room airflow restrictions and small room size cause more short cycling than light load does. In small rooms where I had problems with short-cycling, I just opened up the throttling range of the thermostat and that took care of the problem. If you have the advanced microprocessor, you can log compressor run hours once a week, or once a month and get a pretty good idea of the site cooling load by calculating compressor duty cycle. For example, if your compressor runs 84 hours per week, 84 divided by 168 (hours per week) gives you 50% duty cycle. If the unit is a BU071xxxxx (71 KBTUH nominal capacity), then your load would be about 35 KBTUH, although this won't indicate how much is latent heat and how much is sensible heat. If you are going to use another air conditioner as backup to the Challenger, I'd recommend that you wire in an alarm relay on that other unit so you get paged if it starts up. As a general statement on computer room environmental problems, the sooner you know about the problem, the more you can do about it before it becomes service affecting. If you put a programmable thermostat on the backup air conditioner, you could program it to change its setpoint to 50 degrees on Monday at 9:00 AM, and reset back to 80 degress or whatever your backup setpoint is, at 10:00 AM. This way it would start once a week or whatever you programmed it to, and you'd get a page when it ran, which would also verify that your notification system works.
Last, but not least, I recommend a stand-alone room high temperature alarm. The easiest way to achieve this is to install a seperate cooling thermostat, set at, say, 80 degrees. If the room temperature rises above 80 degrees, the thermostat will call for cooling, and you can tie that contact closure into your alarm system.
07-21-2005, 07:47 PM
How about dataaire, stulz, or Riedel?
This Liebert thing is over the top.
07-22-2005, 02:08 AM
I would say that all this talk about Liebert is decidedly not over the top.
I almost went into a long rant about product quality and all of my complaints about second tier manufacturers. I will state that in my opinion, Liebert is the Cadillac of Computer Room Air Conditioners, that they have earned that reputation the hard way (by proving it over the years), and that the majority of the other companies producing CRAC units are making sales by being low bidders.
I hope this sums up my thoughts: If you want to save on capital (engineering, construction, & installation) investments, plan on spending more on Operation & Maintenance costs in the future. If you want to save on future O&M costs, plan on spending more on your present capital investments. There is no free ride, unless your network availability/reliability aren't all that important.
The following is not a sop to engineers or contractors. Having managed capital construction projects and and also managed operations and maintenance (for technical facilities, computer rooms, server rooms, switchrooms, or what have you), I have had equal problems and equally positive results with both, or all three, if you consider architects to be a third breed. For the porposes of this discussion, I think architects are a legitimate third breed. They're all humans, so it depends on who you pick, how smart and inspired they are, and the quality of guidance you give them. I have to insert an admission here that occasionally I was the problem because I didn't know what I was talking about. Digressing to the first two, engineering to install something at your site is tough. Just figuring out what you (the customer) "really" want is tough. "Really" sometimes means differentiating what "you" want from what "you" can actually afford. The contractor will have the same problem. From the contractor/installer's point of view, installing something according to the instructions from someone (the engineer) who probably never installed anything like it in his life is also tough (I call it the "Ivory Tower Effect"). You, apparently the project manager, get the privilage of making all of this work. I don't know if it is the career/job you wanted, but I can tell you that it is entertaining.
More personal opinion:
Assuming you have found engineers that are well versed in the type of project you have, the best money you can spend is in the engineering phase of the project. Whatever money you spend in good engineering will come back in spades in the form of tighter and lower contractors' bids, less ambiguity in contractors' scope of work, and therefore fewer unknowns in your project scope, timeline, and budget. I mean this the best way. If you ask contractors to bid on some vague project, they will, of course, bid the way they think their competitors will: Cheap, with an unlimited timeline, and with no limit on change orders to clarify whatever the engineers missed. What else can they do? If the engineers say "match existing" for a door, for example, they all know that one of their competitors will walk around and find the cheapest door in the house and use that as the "existing". If you hire that guy on the basis of least capital outlay, and don't like his choice of doors, Change Order #1 is just the thing to fix it, and C/O #1 will also be the first bullet into your budget and timeline. The alternative is to end up with a bunch of doors that you hate and that you need to replace in a few years. Meanwhile, the other bidders know that offering "add-ins" like "if you select this door upgrade..." make them look greedy, in the owner's eyes. They'd really like to do it, for your benefit as much as their own, but they don't want their bids to look bad. So, the phrases "field verify" and "match existing" on engineering drawings should automatically make the hair on the back of your neck stand up.
Looking at it the other way, if your engineer(s) create a clear, practical, concise set of plans, then your contractors will know exactly what you want, and they will know that all the other contractors/bidders know exactly what you want, and then they will feel free to tell you exactly what it will cost to do what you want. It follows that if everyone knows exactly what you want, their bids to produce what you want will be pretty close, and there will be fewer change orders, since the engineers had already crossed the T's and dotted the I's. If you don't know the contractors, references are in order. I should have said so earlier, but the same goes for architects and engineers. As I stated earlier, it comes down to people and their performance. At this point, you can select a contractor that apparently knows what you want, and can produce the goods.
To recap, in the end, a good, clear engineering scope of work helps the contractor to give you a better bid.
p.s. "Design/builds" are a distinctly separate breed from what I have described and I wouldn't say that they are good or bad, but they are definitely outside of the scope of this email.
07-22-2005, 10:06 AM
Let's talk Liebert humidifiers... or maybe the benefits of using Nortec instead of Liebert.. wait... don't I see some Nortec in there now?
Name the parts Liebert uses that the other CRAC's couldn't/don't use.
Is Liebert designing their own motors?
07-22-2005, 04:42 PM
now way....not starting with the operation heat load again....that's a real dead end.....what I am doing is putting in a challanger that can pump out from 3-5 tons so I can adjust it is I find I really need 3.5 tons. Right now, I have been told that I am getting 1.5 net tons because of the load, out of the full 3 ton trane.....I can't go and demand heat load tests again, it just won't be fun, and I don't have the time.
as far as the unit is concerned.....I don't think I can go wrong with a Liebert, that's the bottom line, I could be wrong, but this is getting a bit crazy, and I need to know I'm in good cool hands
07-22-2005, 04:51 PM
I have two stand alone systems monitoring the temp of the server room. They both page me when there is a problem. This thread has testimony that the system worked. I was notified, and I got one of my employees to log in from home to shut down the non essential servers so that we would not have any thermal events. I got to the room when the temp reached about 88 and got the door opened and my backup fans on. The temp went back down to about 78 and I turned everything back on, got the AC back on, and everything went back to normal.
The problem was that when my short cycle switch was intsalled, it was set to 0 minutes. So much for a short cycle switch....always be sure that your installer finish their jobs!!! An Anti short cycle switch set to 0 minutes is worthless.