Feeder calculations in Iraq

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CAPTMIKE

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I am in Iraq and have written in before about water heaters,now it is window A/C units.I have about 20 buildings and each has window units for cooling/heating.I am unsure if these can be demanded as an appliance and I am trying to size a generator.Now each building has 20-25 units,so if there is a demand I can use,will it apply to each building or only to the main service?? I know they cannot be damanded twice if they can be at all,but hopefully I have expressed this clearly.Each building has a panel fed from a MDP.
Now second question,this is powered by large prime power diesel generators with an efficiency of .8,so where does this go in the equation,I think to add up KW,then divide by .8 = KVA ?? Thanks for the help as over here I really need it.
 
There would be no way to apply a demand factor to window shaker units without knowing how they were sized and how the space will be used. You absolutely cannot apply a demand factor to these air conditioners, in my opinion. The units may cycle on and off, but put a batch of people in there on a hot day, and they might run flat-out, all day.
 
CAPTMIKE said:
I am in Iraq and have written in before about water heaters,now it is window A/C units.I have about 20 buildings and each has window units for cooling/heating.I am unsure if these can be demanded as an appliance and I am trying to size a generator.Now each building has 20-25 units,so if there is a demand I can use,will it apply to each building or only to the main service?? I know they cannot be damanded twice if they can be at all,but hopefully I have expressed this clearly.Each building has a panel fed from a MDP.
Now second question,this is powered by large prime power diesel generators with an efficiency of .8,so where does this go in the equation,I think to add up KW,then divide by .8 = KVA ?? Thanks for the help as over here I really need it.
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Hi,
When you say efficiency of 0.8 do you mean the same thing as a power factor of 0.8? I am just trying to understand this part of your question. If that is the case, you are right to go with KVA = KW / PF.
 
mdshunk said:
There would be no way to apply a demand factor to window shaker units without knowing how they were sized and how the space will be used. You absolutely cannot apply a demand factor to these air conditioners, in my opinion. The units may cycle on and off, but put a batch of people in there on a hot day, and they might run flat-out, all day.
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Great answer Marc... May I add as hot as it can get over there, the real question may be: "How many should be totaled as 125%",????
 
captaincrab55 said:
Great answer Marc... May I add as hot as it can get over there, the real question may be: "How many should be totaled as 125%",????
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I don't see where you have a choice but to total all of them since you're running off a generator. Functionally, if the generator stops for some reason, when it restarts, all of the a/c's are going to fire up. Not sure if we're following a code here or just talking about what works.
 
Iraq

Iraq

Thanks so much for the comments as they are exactly what I had figured as well.I am working for a contractor who prematurely ordered gensets,1.5megawatt size and wanted me to stay within them but I saw no way to do that.We have an ambient temp here over 50 celcius.I have been in country since 2004 and dealt with the same sort of issues.My thinking was also that the generators do cut off and once back on then you have everything coming on at one time...Big loads..For example if someone will calculate what I am dealing with on one building..24window units@2400watts each,100 receptacles@360va ea(I did demand them as a commercial building per NEC),4-36KW water heaters,75-2 lamp 36 watt fluorescent lights.Voltage here is 400/230 3phase 50hz. PF .8.....Thanks
 
You can always get some loadshed equipment if you must use that genset. Maybe something as crude as an undervoltage release main in the a/c panel, and bring the breakers for the a/c back on manually. Use your imagination.
 
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even make a sectional #'s of subpanels so you can manually reengerized after you get the generator back on line.

most generators i useally dealt they are designed to take 70~100% of load in one step depending on type of prime mover itself and check the surge capaitcty as well because the window shaker is the biggest load when they get back on line and it can put a stress on it so kinda designed along the way to see what is crictal load to pick up first like lighting system which i know is the first thing to be back on line then chose the next one then others along the way.

Merci, Marc
 
Iraq

Iraq

I agree with you and the only issue is actually finding NEC articles to substantiate what I do when applicable.The work has to be done in accordance with NEC and thats where some of the issues are arising,such as applying demands to as much as possible.I again appreciate any and all help .
 
CAPTMIKE said:
I agree with you and the only issue is actually finding NEC articles to substantiate what I do when applicable.The work has to be done in accordance with NEC and thats where some of the issues are arising,such as applying demands to as much as possible.I again appreciate any and all help .
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When I was in the Marines it was strictly "Field Expedient".... No NEC at all..... And if you're in the s'i'ck - the NEC does not apply to you... Contractor?????

A quote from my past:
"OCP is for pussies!" :mad: :rolleyes: The only OCP was the generator.... On a few occasions wire lost the battle.

Anyway - since you have been there since 04 - you may have realized that certain military politics and etiquette will dictate who and what is on any load shedding or outage program. You'll want distribution to these at the generator.

Also - one must assume worst case scenario that all AC's are on all the time continuous.... (the areas they serve my never reach temp personnel set them for...) Not to mention rapid growth of load by add-on's down the line... IMO - go big on load, and parallel for the gennies. IMO a number of smaller paralleled sets are best - you can take some out for maintenance when necessary, and bring them back one line when needed. Also easier to link up multiples of similar sized sets. And similarly with the load - you will need to "walk on" the load bit by bit if you ever go completely off. So breaking it up as much as possible right at the gen farm is best. While most sets will handle the in-rush - if it doesn't you have big problems. You'll have to go around shutting things off to get re-started.

What voltage are you going to be distributing? Transformers? Over-head or under ground?

IMO med voltage is out of the question for the environment and safety of personnel. 480Y and transformers sized for, and at each building would be good if you have them available. Calc the load at 100%, and divide that across 4 gen sets of 6 available. And manage the load @ 80% capacity. i.e. when demand is low - take one gen set off line to keep from wet stacking the sets. (Clear dry exaust)

But reading your 2nd to last post and have ordered gen sets already.....:rolleyes:

400/230 50Hz - non-US? Or dealing with available shipped equipment? Are the recepticals 230 at 360va? Normal NEC calc'ed values would be 180 per yoke at 120v for GP recepticals.... 230 would be like 60va... Considering the circumstances (which have no equal in the NEC) the AC units would need to be no demand factor applied, as well as lighting - the only fudge area you have is hot water heaters - and from experiance they too should have no demand factor applied - everyone seems to shower at the same time....

Sorry to say there is no way to apply a demand factor to your application. At dusk all the lights will go on, the AC/heater units cranked and everyone is going to shower and shave till the lights go out.
 
Iraq

Iraq

This stuff is actually being built for the Iraqi Army but by US contractors.Now the issue is they are famous for pluggin in a bunch of stuff,I mean multi outlet into multi..real fire hazard.Anyway I know the NEC allows for 180va per outlet on a service calc,if you add these all up are they then demanded,or is that only if you square foot the load.In other words the amount of receptacles are known,does that amount get demanded or is it taken at the full 180va each and then just totaled up?The 360 actually came from a Turkish engineering company??? The problem is I am trying to get as real of a load as possible,the gensets were bought long before the load was known...Any help is again really appreciated..
 
Out of curiosity, what is driving the design to the NEC? Is it just because the US contractors are most familiar with this code? Wondering if it wouldn't make more sense to use UK or EU electrical standards that are more targeted at a 230v consumer use system.

CAPTMIKE, you've been over there since 2004... WOW! Thank you for your service!!!
 
Everything built now especially for the Iraqi Army is actually being inspected and approved according to the NEC,I cant figure the reasons.All of the stuff installed is from the UK,Turkey and who knows where.This has been an ongoing battle from the beginning..Anyway thanks for the advice..Capt Mike
 
e57 said:
400/230 50Hz - non-US? Or dealing with available shipped equipment? Are the recepticals 230 at 360va? Normal NEC calc'ed values would be 180 per yoke at 120v for GP recepticals.... 230 would be like 60va...
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Nah - the wattage stays the same irrespective of voltage, but the current is about halved for 240V supplies.

Captain Mike - what sort of sockets are you fitting? As in what country style? I'm assuming it cant be Edisons, as they're the wrong voltage...

And yeah, it would be "unwise" to have less than the full capaicty for the AC plant - one day it will be needed. One little note; the NEC wibbles on about not loading stuff to more than 80% on continuous loads; European stuff is able to handle 100% continuous loads.
 
Iraq

Iraq

We are using Eastern style devices,standard 13amp outlets for general purpose and 15amp for appliable a/c units,window type.I have added the a/c units in at 100% as I am sure they will run constantly in the summer,not being cleaned after dust storms etc.So I will use the 180va each per the NEC as they state that is a minimum for feeder calcs.The de-rating allowed on receptacles in 220-44(NEC 2005) is that only if you va/square meter calc the outlets or can I use it also if I am counting outlets that are on the plans?.Thanks
 
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