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Off Grid Building
2

Off Grid Building

Off Grid Building

(OP)
So I'm designing a co-gen power system for an off grid remote research building. I'm not really sure where to begin- I need a few pointers/guidance on where to start...

Does this look like a good design? Should I get creative with how the gensets are interconnected?



Or just keep things really basic?



Anything I've missed? Go/no go? Or am I way off?


Power is normally produced by natural gas and solar with onsite diesel tanks to meet the requirements of article 700.

https://files.engineering.com/getfile.aspx?folder=...

https://files.engineering.com/getfile.aspx?folder=...

RE: Off Grid Building

Just my 2 cents, but if you are wanting reliability I would go with a breaker and a half bus arrangement.
That maybe harder to do with lower voltages. Or maybe not cost effective.

RE: Off Grid Building

(OP)
I've never seen breaker and a half used on LV, nor have I thought about it... it would make for some interesting operation and relaying though.

Ultimately I don't want to be running these gens in parallel, hence the ATS approach seen here.

RE: Off Grid Building

Why do you not want to operate the units in parallel? Typically mixed units plants operating in island mode are all working thru a paralleling arrangement of some kind for lots of reasons.

One of your biggest problems will be restoring after an outage and bringing the plant back up on diesel, then trying to transition over to the gas engine driven units. Been down that path several times, I think you will find your end user won't like it.

Woodward has added solar integration to the EasyGen line of controls, you may want to talk with them as it is likely a solution that best fits your plant and generator sizing.

Attached is a product guide to the new Solar integration.

MikeL.

RE: Off Grid Building

(OP)
Paralleling adds cost, complexity, and common failure modes that I would like to avoid. Most can service an ATS during an emergency, but if the gear fails in particular the logic good luck.

The gas units have automatic electric starters that get the engine up to speed (and voltage) within 30 seconds. Some models are listed as capable of accepting full load in one step.

RE: Off Grid Building

The ATSs are the weakest link, single point of failure. Breaker based paralleling gear can be designed to be more reliable. What's an hour of no power to part or all of the facility worth? Is not paralleling really cheaper?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

(OP)
Can't ATSs be designed more reliable? Gear with computers seems far more complex with more parts to them. I've never understood that one.

RE: Off Grid Building

(OP)
@David: I notice you've brought up ATSs before. With all the well earned experience on your tool belt, I've take it you've seen a fair share of ATSs failures?

RE: Off Grid Building

I agree with catserveng, if this is really an islanded application with no grid connection, make it capable of running in parallel to start with.
As catserveng has mentioned, Woodward has a decent range of products to support this, so does ComAp.

Paralleling allows:
1. Choice of the most cost effective generation for the load at the time, without the penalty of having to go black to change generation sources.
2. Transparent transition between generation sources without affecting consumers.

There is the consideration of equipment ratings for the required switchboards, but its not insurmountable and probably no worse than multiple ATSs to feed different sections of plant.

EDMS Australia

RE: Off Grid Building

(OP)
How much extra are you spending on paralleling gear?

I just can't see a compelling need for it.

RE: Off Grid Building

(OP)
Ok, so I came up with a bit of a compromise.

Size both gas gens to 100% of the switch gear load (general lighting and power + emergency circuits).

Combine feeders under 400 amps.

Include a tie between both switch gears so that either gas gen can be serviced during light load periods ie when cooling is not needed.




Still got ATS in series, though why not?

RE: Off Grid Building

You can feed from either side with the 1000 kW generators by opening one generator breaker and closing the tie (assuming an open transition is okay) using electrically-operated breakers, essentially created a breaker-based transfer scheme, so you don't need the first set of ATSs.

Also, please reduce the clutter by breaking this up into several diagrams. There's way too much on this drawing.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Off Grid Building

I know the feeling Mbrooke. I like to see everything in my mind which multiple pages screws-over. My old boss insisted you always use "17" x 24" artist pads or you will cramp your thinking". He was a prodigious inventor of the highest order.

Alas, I can only get about 11 x 17 to work for me.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Off Grid Building

(OP)
@Xnuke: I like your idea, but the PLC will also need to shed the chiller mains (and perhaps some load) on one side. The 1000kw rating is 100% of the normal load on one side of the gear.

Originally I was thinking 50% loading and more gens.


Here is "zoomed in" version without all the extras.


RE: Off Grid Building

(OP)
@Its smoked: Thanks :) Multiple pages are like a train derailment for me, I lose track of the bigger picture. At the same time I've gotten used to re-drawing it all on a single sheet of paper so I can make sense of it all. Sometimes I forget that not everyone is like me.


Anyway, to be fair, the drawings are pretty bad by my standards.

Right now this project is all napkin drawings, trying to find what "looks good".

RE: Off Grid Building

At least some of the more modern equipment that handles load sharing and synchronising can also handle load shedding of certain loads without the need to resort to a PLC and all the customisation that goes along with it.

Another factor, sizing of generators has a number of requirements, often competing, in terms of what your operation can handle. Paralleling of sets makes for much easier starting of larger loads, and once running excess sets can be dropped off without any penalty. Attempting to do this with what I presume are open-transition ATSs would likely result in the need to oversize the sets to be able to start large loads, including the associated fuel efficiency penalties.

EDMS Australia

RE: Off Grid Building

(OP)
Yes, open transition ATSs. You make a good point, the generators do have to take inrush and motors into account.

The heat from the gas units has a high probability of being reclaimed from the engine jacket and exhaust.

However I'm figuring out you get the most bang from fuel when the generator is 60-90% loaded. so 50/50 loading will probably be abandoned.

RE: Off Grid Building

You could seriously mitigate big load starting with soft starters or VFDs even if they have a slight efficiency loss as compared to added more generators or having to oversize them (large efficiency loss).

Keith Cress
kcress - http://www.flaminsystems.com

RE: Off Grid Building

itsmoked, that's true for loads that can be started by a VFD or softstarter. Probably not so relevant for dumping the load onto a set via an ATS, at least not without a complicated staging arrangement to get everything back on.
However, in this case the money spent on such equipment could just as easily cover the cost of decent Generator equipment and motorised breakers which allow for paralleling, and whilst it won't solve all the cold load pickup issues, it'll certainly be better equipped to handle it than a bunch of open transition ATSs.

MBrooke, have you actually asked the client how they feel about having to go black every time there's an issue, a set needs to be serviced or they need to change sets?
I've never met a client that is happy about having to turn the power off if there are other viable options.

RE: Off Grid Building

Carrying on from FreddyNurk's comment above, whats is your estimated genset availability? Say its 90%, 8760 hours in a year, so the set could be down for 876 hours, that's 36.5 days!

95% gives you 18 days and so on...

Admittedly, some of this will be planned maintenance (oil changes, tappets etc) which could be scheduled at weekends - if this site does not operate at weekends. Breakdowns can occur randomly.

Next, what is the load profile? The gas engines I worked with would shut down if the load fell below 30% for more than a few minutes, and this could not be overridden.

I would just run them in parallel with N + 1 or N + 2,

Parallelling this type of set is a mature technology, changing from ATS to parallel later will not be easy!

I wold look at the load profile to determine the rating of the sets.

RE: Off Grid Building

(OP)
Power will be out for only cycles, UPS for what really can't handle it.

Motors are an issue, I'm thinking a delayed transition ATS to demagnetize the motors before re-energizing them.

RE: Off Grid Building

(OP)
@Hoxton: The hope is that the another gas gen-set or a diesel genset will take over for maintenance and failure of the main set. Letting the diesel run during scheduled outages will allow the genset to warm up without having to load bank thus preventing wet stacking.

What gensets did you have that shut down on low load?

During the summer with cooling the load will be steady, perhaps near full load for 12 hours a day. Other things like lighting, refrigeration, computers, lab equipment, ect will present a steady load.

There might be absorption cooling using the gen's waste heat if that helps.

RE: Off Grid Building

There are packages for diesel set that provide cooling from the rejected heat.

Just saying.

RE: Off Grid Building

The sets were MWM (Now CAT)

I think other high tech engine control systems had a similar feature. The problem is lube oil carry over at low loads / low turbo pressure causing knocking and spark plug fouling.

RE: Off Grid Building

(OP)
I hope CAT isn't the same today. I plan on **auto correct messed up here** CAT and ONAN gen sets as they seem to be the most reliable.

Do smaller units have the same issue?

RE: Off Grid Building

Suing?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

(OP)
LOL- auto correct strikes again! lol

I plan on using USING CAT and ONAN sets.

My bad.

RE: Off Grid Building

Just so you know there are no more Onan generators they were bought by Cummins in 92 and for a while were called Cummins-Onan generators when they were Cummins prime-movered. Now they seem to have dropped the Onan with the exception of residential and RV where they do still call them Cummins-Onan probably riding on past consumer memory. They seem to have stuck with the Onan pukey green though.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Off Grid Building

(OP)
And thats why I think of them as ONAN bigsmile (from the green color).

CAT and Cummins seems to be the best, Ive seen to many Kohler units fail as the worst times.

RE: Off Grid Building

(OP)
I'm nearing on something like this- 3 gas units 3 diesel units:




I hear smaller ATS are more reliable than large ATSs.

Debating whether I should rotate the feeders around that the total load served by any gas unit has leads to more than one diesel unit but I can't see any technical need for that.

Still not 100% set on number of units or ther size- ie keep all the gas units the same size or have different sizes.

Or if I should combine any of the diesel units since they are physically smaller (and more inrush tolerant).

RE: Off Grid Building

Gotta say from a user's perspective I don't like any of this at all. I'd not like any of these proposed non-solutions. If you're going to power off-grid a facility then I'd expect power reliability and operational freedom like the grid supplies. This should be N+1 straight-up. You run the number of generators needed paralleled as more are added or dropped. An extra there for maintenance.

If you use what I'm seeing you will have management cursing you and coming to spit on your grave after they have you bumped-off. Operations does not want pieces of the plant dead nor does maintenance want all these confusing disjointed circuits with double and triple the conduits running everywhere, machines next to each other with one that can work and one that can't. Truly an operational nightmare other companies they compete with won't have and at greater expense.

If you have N+1 there is no logical reason you can't have endless reliable power. Entire towns run this way. This gas/diesel thing is crazy too. If you really can't get a single fuel to do the job then use bi-fuel engines. I live next door to UCSC where they have on-site generation that is a 2.5MW diesel generator that they normally run on 5% diesel 95% NG. If they have NG problems it goes to 100% diesel. Do the same thing. Having a set of diesel and a separate set of NG generators is bonkers!! They'll always run the NG generators and eventually you'll have a bazillion gallons of aged-out crap diesel they'll have to deal with. <shudder>

Just saying.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Off Grid Building

(OP)
Uhhh... there is N+1. Thats what the ATSs are for. If the gas gen fails or need to be taken out for maintenance the diesel unit starts and load transfers over in cycle to seconds. The diesel fuel gets burned off and the gen is fully loaded preventing wet stack. Because the gas unit needs to cool down, checked over, oil changed, ect you are looking at least 96 hours on the diesel unit.

There are no double or tripple conduits*. 2000 amps will require parellel sets no matter what, so you could either combine all of them into a single circuit or multiple smaller circuits totaling 2000amp. You'll have more panelboards and gear, I'll give you that, but at the same time I'd rather use smaller ATSs than one big ATSs. Also a bigger breaker is less likely to trip before the gen stalls out.

*Some parts of the facility will have extra conduit via normal power besides life safety, COPs and so forth. The idea is that if the COPs goes down, equipment can be unplugged from the red outlets and plugged into the white ones like done in a hospital. Same with the stairwells, life safety runs up the shaft, but a normal conduit from each floor hits another supplementary luminary on the landing. All electrical rooms and critical areas have two switches, a lighted toggle off the life safety branch running 50% illumination a white toggle off the normal branch running the other 50%. Gen rooms, e;electrical rooms, telephone closets, tunnels, ect may also have bug eyes or a Bodine on the fixtures fed from the life safety/critical operations circuit.

RE: Off Grid Building

So I'm curious, what alternators have the OEMs advised that you can use for your proposed voltage and power ratings?
Whilst I'm on the other side of the world with different voltage and frequency, I've not seen a datasheet from the alternator OEMs that provides the power level you've shown with the current capability on your drawings.



EDMS Australia

RE: Off Grid Building

(OP)
Here is a "standard" 1000kw diesel data sheet:

http://resources.kohler.com/power/kohler/industria...




I can get up to 3470 amps at 120/208Y, at 125% that gives me 4337 amps rounding up to a 5000 amp breaker.

127/220Y, 139/240Y, and 230/400Y for anything international. 277/480 if needed.

A gen set in a prime power application may take the amp rating for that instead of the standby rating.

This why gen's breaker may appear slightly undersized or grossly over sized relative to the kw rating.

For anything none standard or exotic I can turn to Stamford alternators:

https://files.engineering.com/getfile.aspx?folder=...

https://files.engineering.com/getfile.aspx?folder=...

RE: Off Grid Building

Have you actually been to an island mode cogeneration site in the size range you're looking at? When you add heat recovery and the associated systems then you have to manage engine loads to that all the balance of plant works like its supposed to. So along with many of the issues already raised, what about factors like environmental, such as ambient temperatures, humidity, sea air, etc. Also will these units be operating in an area with air quality regulations?

What kinds of loads? You said research facility somewhere in your post, so where at, what kind of research? You looking at something like an agricultural research station in a fairly friendly climate, or like an arctic research station?

Mixed engine plants aren't all that uncommon, especially in systems like mining and oil and gas sites, sizing and operation depends on a lot of factors, like cost of liquid fuel, quality of gas fuel, operating cycles and so on.

Bi-fuel engines can be a good solution depending on sizing, load factor and fuel quality. And designs range from units like Keith mentions with very high replacement rates, to more common systems that use lower replacement rates but are usually bolt on additions to existing diesel engines.

Not sure what really is your heartache with a paralleling system for what you're proposing, ATS's have their place, but in trying to use them as you've described you may need to spec "dual prime" switches, as the typically have more robust contacts and controllers.

You also mentioned at some integrating solar, which could be fairly simple or a real PIA depending on a number of factors, so unless you can provide a lot more info about what you are really trying to you.

If nothing else, this post has been quite entertaining for me, good luck in your venture.

MikeL.

RE: Off Grid Building

Thanks Mbrooke for putting up with my pained sensibilities.

I'm still saying you don't really have N+1 capacity it seems more like N+3, too many excess generators.
You're still working the emergency generators, COPs (whatever they are), and life safety. The whole premise; its operational and cost complexity, can be dumped if you have a flat N+1 deployment.

There is no need for emergency stuff in this case because the system isn't hooked to a POCO grid that they have no control over and can be lost for whatever reason. As an OFF-Grid facility there is no reason to ever have it all go down unexpectedly. You have hot standby that can come online faster than an emergency generator. Hence no emergency circuits, no life safety, no COP.

I hear your concern about gear size, but. Every other non-off grid place has one incoming buss from the POC and it gets distributed in the standard every-one-does-it way. They wouldn't have a butt-load of ATS, Probably not a single one.
This place should be built the same way. Plan it like the power is from a POCO then build a power plant and connect it to the standard industrial structure.

Doing this allows complete freedom in the future to supply power anyway they want it. Co-Gen, solar, wind, walkaway nuke, maybe the grid even shows up. It all comes in thru the same portal. The existing generation can augment whatever's available. Maybe solar can supply 70% during the day. Drop off 2 prime-movers. Add one when the sun goes down. Maximum flexibility from the get-go. Consider these contingencies in your N+3 design, they'd be so painful as to be non-starters.

Having a flat design means you could have one generator running at 3am. The above design can never have less than 3 generators running 24 hours a day. That can't be as cost effective.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Off Grid Building

(OP)

Quote:

Have you actually been to an island mode cogeneration site in the size range you're looking at?

Honestly- I have not been or ever seen an off grid system of such size in person.

Quote:

When you add heat recovery and the associated systems then you have to manage engine loads to that all the balance of plant works like its supposed to. So along with many of the issues already raised, what about factors like environmental, such as ambient temperatures, humidity, sea air, etc. Also will these units be operating in an area with air quality regulations?

I agree, however power will take priority. If absorption, heating or domestic hot water calls for less heat than the engine is outputing the extra heat is released outside.

Quote:

What kinds of loads? You said research facility somewhere in your post, so where at, what kind of research? You looking at something like an agricultural research station in a fairly friendly climate, or like an arctic research station?

Computers, server room, office equipment, lab equipment, things of that nature.

Quote:

Mixed engine plants aren't all that uncommon, especially in systems like mining and oil and gas sites, sizing and operation depends on a lot of factors, like cost of liquid fuel, quality of gas fuel, operating cycles and so on.

Bi-fuel engines can be a good solution depending on sizing, load factor and fuel quality. And designs range from units like Keith mentions with very high replacement rates, to more common systems that use lower replacement rates but are usually bolt on additions to existing diesel engines.

I guess this is a moment of learning for me. How are Bi-fuel engines better? Are they more efficient? Do they last longer?



Quote:

Not sure what really is your heartache with a paralleling system for what you're proposing, ATS's have their place, but in trying to use them as you've described you may need to spec "dual prime" switches, as the typically have more robust contacts and controllers.


Paralleling has multiple single failure points and presents knowledge/experienced based complexity that not every technician has or understands. Second it tends to force all the gen sets into one room vs diversity of sources- typically this will never be a problem until fire or some other disaster makes itself known. Further it is difficult if not impossible to parallel a mobile unit should one or more end up being brought in to feed the gear during an emergency. I can get just about any mobile unit of any size on wheels, but what guarantee do I have that the paralleling gear will connect to it control circuit wise, recognize it, and be of identical parameters to the existing onsite sets or the other mobile sets?


Quote:

You also mentioned at some integrating solar, which could be fairly simple or a real PIA depending on a number of factors, so unless you can provide a lot more info about what you are really trying to you.

If nothing else, this post has been quite entertaining for me, good luck in your venture.

Why is this entertaining if I may ask? What do you see me doing wrong here?

RE: Off Grid Building

(OP)

Quote:

Thanks Mbrooke for putting up with my pained sensibilities.

Nahh- I need someone to put this through the wringer so to speak. More minds are better than one :)


Quote:

I'm still saying you don't really have N+1 capacity it seems more like N+3, too many excess generators.

KW capacity wise there is a lot more excess than if the gens were paralleled and of the duel fuel type. Sure. I will recognize this part.

Quote:

You're still working the emergency generators, COPs (whatever they are), and life safety. The whole premise; its operational and cost complexity, can be dumped if you have a flat N+1 deployment.

Critical Operations Power System- see NEC article 708:

https://ewh.ieee.org/r3/atlanta/ias/Article%20708%...

Quote:

There is no need for emergency stuff in this case because the system isn't hooked to a POCO grid that they have no control over and can be lost for whatever reason.

Huh!?! shocked Honestly, its statements like this which make me question the knowledge/experience/understanding of engineering in some of the members posting here. I only make this rebuttal on the basis that another member said I was entertaining- so I figure the discussion is open for tit for tat on both sides going both ways smile tongue

But, I'm glad you said this. I think this where a lot of the disputes in this thread are originating from. A lack of understanding in regards to code, critical power and not having all your eggs in one basket.

There is very much a need for emergency stuff:

1. Article 700 of the NEC (along with NFPA 101 and driven by pother applicable building codes / AHJs) still require life safety systems in buildings even when supplied by an off grid system.

2. The Normal source of power can fail for a variety of reasons, in a variety of ways even when fed from a co-gen.

3. Article 700 requires separate circuits reasonably protected from fire in regards to emergency egress lighting where as normal power does not have this requirement.

Granted in remote construction or government project you might be able to pick and chose what codes apply, if any, but do you really want to put people at risk? Do you really want a fire taking out the normal power system leaving an 8 story building pitch black to the point people can't find stairwells let alone be able to walk down them to get out?

Quote:

As an OFF-Grid facility there is no reason to ever have it all go down unexpectedly.

Not when you are paralleling everything into a single piece of gear.


Quote:

You have hot standby that can come online faster than an emergency generator. Hence no emergency circuits, no life safety, no COP.

I know plenty of places with parallel power production that can take over when the utility drops out without so much as a blink. Does that mean hospitals in these cases can ditch all the extra conduit, wiring, runs, isolation, dedicated rooms, dedicated shafts, panels, ATSs, ect for the separate branches? Required by code as a means to create redundant diversity and so a fault on one branch does not take out the other?



Quote:

I hear your concern about gear size, but. Every other non-off grid place has one incoming buss from the POC and it gets distributed in the standard every-one-does-it way. They wouldn't have a butt-load of ATS, Probably not a single one.

So based on what you said:

Quote:

...there is no reason to ever have it all go down unexpectedly.

The main bus will never fault? And be protected from fire? As well as all the other unprotected runs through out the facility?


Quote:

This place should be built the same way. Plan it like the power is from a POCO then build a power plant and connect it to the standard industrial structure.

Ummm- if I was to plan this as if from the POCO I still need at least 3 ATS for life safety, legally required and COPs load.

Re-read what you wrote, at first you said I would need emergency circuits if only fed from a POCO, but are now telling me to design as coming from a POCO.

Quote:

Doing this allows complete freedom in the future to supply power anyway they want it. Co-Gen, solar, wind, walkaway nuke, maybe the grid even shows up. It all comes in thru the same portal. The existing generation can augment whatever's available. Maybe solar can supply 70% during the day. Drop off 2 prime-movers. Add one when the sun goes down. Maximum flexibility from the get-go. Consider these contingencies in your N+3 design, they'd be so painful as to be non-starters.

Having a flat design means you could have one generator running at 3am. The above design can never have less than 3 generators running 24 hours a day. That can't be as cost effective.

I'll give you that- the gas units will see low load levels at night during cool weather periods. This is where I need to really think about paralleling or just accept poor fuel economy.

RE: Off Grid Building

Yes on emergency generation. And it should have sufficient capacity to provide what ever blackstart resources the main power plant needs. One ATS for the whole kit and kaboodle. Enough paralleled generation in the main power plant to allow any single unit to be out of service at any given time and paralleled so that the building occupants never know that generation sources have been redispatched.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

Quote (Mbrooke)

Honestly- I have not been or ever seen an off grid system of such size in person.

Quote (Mbrooke)

Honestly, its statements like this which make me question the knowledge/experience/understanding of engineering in some of the members posting here. I only make this rebuttal on the basis that another member said I was entertaining- so I figure the discussion is open for tit for tat on both sides going both ways
Not really, the reason for the pushback is that its obvious that the first statement is correct, and the assertions that people who do have experience in such off-grid facilities aren't following code are not likely to be accurate.

Paralleling equipment does not require everything to be in a single switchboard, or a single point of failure. Its done on maritime installations with paralleling to shore (grid...) as well as multiple sets and the capability to have additional emergency sets all the time.

There's no forcing all generators into a single room to allow for paralleling, nor is it impossible to parallel mobile or rental sets, politely, you're inventing reasons that do not exist as an argument to continue your designated solution.

As for the code compliance, what loads are designated as emergency? If there's secondary fire pump systems or the like, then they can be treated appropriately. If there's other critical loads then the overall design can cater for that as well, whether it be by a dual distribution system with an intertie arrangement or similar.


RE: Off Grid Building

(OP)
@David- I'm confused. Code would require at least 3 ATSs for emergency as I interpret NFPA 70.

RE: Off Grid Building

Admittedly it’s been 15+ years since I had to follow every in and out of all of the code changes. But, at least once, not a hospital meant that a facility with life safety needs required one ATS. If you triggered other requirements there could be more. Regardless, normal power should come from a power plant that feeds the whole thing. Physically segregated as necessary to limit the impact of single events.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

(OP)
@FreddyNurk: I've never seen a large scale co-gen in person, however at the same time I know that code requires emergency power along with dedicated branches for life safety, cops, legally required ect where the AHJ determines so. Saying co-generation lets you skip article 700 due to a lack of utility power is without basis.

So yes, either these folks are not following the code or are simply dealing with buildings where emergency requirements do not go past bug-eyes.

Right, paralleling can be done with more than one gear, in separate rooms, however cost and complexity goes up (in addition) now that you need to worry about fault protection between tie conduits.

The system still has a central computer which can fail, stuck breaker which will not open, ect.

Right, mobile sets can be paralleled- those which have the capability and are compatible with each other. However there is no guarantee compatible sets can be scored in an emergency. While this facility has the ability to to say "hey, send me 3 vagabonds, 208-240Y, 60Hz, 400-600kw range", there is no guarantee these units will be identical or have paralleling abilities. The genset stash is a one size fits all comprised of various units of varying ages, makes and alternators.

Even if I do parellel via redundant normal systems, I will still need an emergency set, 3 ATSs, and separate branches.


RE: Off Grid Building

(OP)
@David: If you have just life safety (egress lighting) than one ATS is enough. However COPs requires its own ATS. Ditto for legally required. Fire pumps adds a forth. Optional might even push you to five ATSs.

Here is what is typical today:





Some design standards (like those for VA hospitals) don't like large ATSs (ie over 800amps) so high capacity emergency branches often result in additional ATSs over the code minimum.

RE: Off Grid Building

So, what the heck is the facility? What’s even relevant? For an off-grid building I’d use an engine driven fire pump located in its own outbuilding separate from everything else.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

(OP)
Think of this as any other municipal or low rise office type building. Just off grid.

Engine driven fire pump would work as well in this scenario.

RE: Off Grid Building

At low-rise how do you get beyond the need for a life safety system?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

(OP)
You don't. You still need emergency lighting in the corridors, basement, stair wells and alcoves. Shelter in place or evacuate, both require occupants leave the fire floor.

FWIW, if I was to go the parallel route, my system would look something like this- minus the utility of course:





RE: Off Grid Building

What drives the need for either Critical or Equipment? Not every installation that needs an emergency generator needs more than Life Safety.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

(OP)
COPs comes from the fact this building could be used for continuity of government during times of need- hence meeting the requirements of article 708. When the building is not needed for emergency operations or command, its still nice to have a dedicated, protected branch for the computers and sensitive lab equipment. Legally required comes again from article 700 of the NEC- loads that while essential can not share the life safety ATS.

Regarding an equipment ATS Elevators and essential motors need delayed transition in order to demagnetize. Not doing so can cause inrush high enough to trip OCPDs and even damage elevator equipment. The elevator cab lights are on the life safety circuit, no one notices when the elevator stops for a few seconds and then restarts.

RE: Off Grid Building

(OP)
From the 2020 NEC:

RE: Off Grid Building

Are you confusing “shall be permitted to” with “shall”? You still haven’t defined a use that goes beyond egress lighting. Any facility with a legitimate “continuity of government” function certainly wouldn’t go for a 1001 ATS fantasy system.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: Off Grid Building

(OP)
David, do you have a code 2014, 2017 or 2020 book on hand? I think excerpts from the code may help in conveying my point of view-









If this building ever takes the roll of emergency management during a disaster, the power system aiding in the efforts (computers, radio devices, hard wired phones, liaison devices, meeting room lighting, projection screens, ect) is considered essential and thus those having jurisdiction of (or over) this building have the discretion to require (or at least ask for) a COPs system.

The cops system itself must be seperate from all other electrical, including life safety, so that alone will require at least one ATS or an independent piece of gear with two sources of power.

A COPs system isn't unique, some local police and fire departments might have them, 911 centers, municipal buildings, financial institutions, ect all the way up to military sites and nuclear research faculties.

Think of it exactly as the critical branch in a hospital, but instead of medical equipment you've got a computer plugged in tracking a hurricane or taking emergency dispatch reports. Nothing more special than that.


Here is a slide share going more in depth-

https://www.slideshare.net/michaeljmack/cops-an-ar...

RE: Off Grid Building

(OP)
Earlier I made a claim that some standards either require, force, increase, or limit the size of ATSs in addition to what is already required by the NEC.

Here is an example from Department of Veterans Affairs Design Guide for Hospitals, Laboratories and Animal Research Facilities:



Paralleling of gens is permitted, however an emergency system totally separate from the normal system is still required with a minimum of two EM feeders. ATSs are shown despite motorized breakers, and both the normal and emergency branches are limited to 800 amps maximum.



Thus a large facility may have upwards of 56 or more ATSs.

Just to be fair I'm not trying to "rub" anyone or prove them wrong, rather referencing like standards which are influencing or dictating my designs.

VA design doc:

https://files.engineering.com/getfile.aspx?folder=...

800 amp ATS limit:

https://files.engineering.com/getfile.aspx?folder=...

"Ultimate" Generic Design:

https://files.engineering.com/getfile.aspx?folder=...

It may seem silly, but smaller subdivided equipment is more reliable day to day. In an emergency it is easier to deal with small 225 amp ATS than a 4000 amp behemoth.

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