ECN Forum
Posted By: Trick440 200A Auto-transfer switches - 11/08/06 01:50 AM
Is there a cheaper way to do this?

We have a 12KW generator. The transfer switch I found is a 'Service Rated 200A auto- transfer switch' $900

They have a cheaper auto switch thats $700 but its not service rated. So I don't think I can use that one.

Any advice on doing this cheap or know a cheap place online I could order this?

The generator is a GE I think. The customer is gonna call and see what he can get. I know some generator transfer switches only work with certain generators.

[This message has been edited by Trick440 (edited 11-07-2006).]
Posted By: LarryC Re: 200A Auto-transfer switches - 11/08/06 03:30 AM
OK I'll bite.

What are you doing?

Standby generator for a house? A hospital? Your garage?

Is it for the whole structure? A sub panel? Vital loads?

Does switch need to be automatic? Is the genny auto or remote start?

Single phase or three phase?

Coffee, tea, or me? Whoops, sorry wrong question. [Linked Image]

Larry "SmartA**" C
Posted By: SteveFehr Re: 200A Auto-transfer switches - 11/08/06 12:01 PM
With a generator that small, I'm assuming this is for a house? At 240V, that's about 60A, which isn't a whole lot. Does it need to be automatic? You could find a manual transfer switch for much cheaper, I'm sure.

[This message has been edited by SteveFehr (edited 11-08-2006).]
Posted By: iwire Re: 200A Auto-transfer switches - 11/08/06 05:24 PM
I agree with Steve.

A 60 amp not service rated automatic or manual transfer switch and a 60 amp panel will be cheaper than the 200 amp service rated ATS alone.
Posted By: Trick440 Re: 200A Auto-transfer switches - 11/08/06 08:25 PM
Yes this is for a house.

It does need to be automatic. The generator is auto start.

It came to mind that the switch might need to be generator specific. As in, a Cutler Hammer switch will only work with CH generators... Or GE with GE , etc.

He wants the whole panel powered. He currently has a 12 circuit ATS... but like I said wants the whole panel powered.

Sounds to me if this guys wants his whole panel fired up automaticaly, then he needs the Service Rated, 200a ATS... and we might only be able to get it from the generator manufacturer.. if its generator specific.

Does that sound about right?


[This message has been edited by Trick440 (edited 11-08-2006).]
Posted By: Surfinsparky Re: 200A Auto-transfer switches - 11/08/06 11:57 PM
Going cheap on a transfer switch is a bad idea.Try kato light they have a big selection.Do they sell them on here?I prefer russellelectric myself.However that would be a huge overkill for a home.I have installed the generac switches in homes.Nothing automatic is going to be cheap price wise anyway.
Posted By: electure Re: 200A Auto-transfer switches - 11/09/06 12:50 AM
I don't think Cheap and Automatic Transfer belong in the same sentence.
You can't drive a Cadillac if all you want to pay for is a Yugo.

If Automatic, spend the money and get what you need to do a good, safe job..

If Cheap, Get manual switch, manual start, and warm coat.
Posted By: renosteinke Re: 200A Auto-transfer switches - 11/09/06 01:07 AM
I don't think I've ever installed a transfer switch that was made by the generator maker. probably the leader in this field is the company with the unlikely name of "Automatic Switch Company," or ASCO (Not to be confused with the valves of the same name).

Your supply house should be able to put you in touch with a rep. The switch company will help you select the switch, and could very well have someone there to inspect it before you power it up.

Even if you don't need to break a PoCo seal, you really need to get your PoCo 'in the loop.' They will make the appropriate notes, so as to limit the risk to their linemen.

The generator rep ought to also fill you in as to noise, and the regular exercising of the genny. My customers run theirs, weekly. Some transfer the load at this time, others have "load banks" (glorified toasters) that are used. And -trust me on this- noise is a BIG issue. Get the mufler kit!
Posted By: NJwirenut Re: 200A Auto-transfer switches - 11/09/06 01:44 AM
Quote
(Not to be confused with the valves of the same name)

While transfer switches and solenoid valves aren't exactly interchangeable, both of those product lines are made by the SAME company.
http://www.asco.com/
Posted By: e57 Re: 200A Auto-transfer switches - 11/09/06 07:57 AM
Why does it need to be service rated? are you transfering before, or in main equipment?
Posted By: Trick440 Re: 200A Auto-transfer switches - 11/09/06 12:05 PM
I would be removing the service cable from the current 200a panel and installing that into the ATS. (This cable comes from the meter.)

Then I would be comming out of the ATS with 4 conductor, back to the 200a panel which would now need to be phased out.

Would I need 'Service Rated' for this application?

Can someone clear this up when it would need to be 'Service Rated' and when it would not. Maybe an example or 2.

Thank you for the help so far,

[This message has been edited by Trick440 (edited 11-09-2006).]
Posted By: SteveFehr Re: 200A Auto-transfer switches - 11/09/06 12:27 PM
What exactly does "service rated" mean? It's not a term I hear a lot; I guess I have always just assumed things like 200A panels and disconnects were "service rated"?

NEC 100.1

Service Equipment. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constiture the main control and cutoff of the supply.

Sounds like if you cable this ATS directly to the meter, it's service equipment, but if you stick a disconnect switch/OCP between the meter and the switch, it's not. Would that save you $200 between materials and labor to stick an extra enclosed breaker in there?

[This message has been edited by SteveFehr (edited 11-09-2006).]
Posted By: renosteinke Re: 200A Auto-transfer switches - 11/09/06 03:43 PM
Equipment is "service rated" because there are different requirements. I believe the correct terminology is "Suitable for use as Service Equipment."

I think there is a higher interrupting rating (AIC) required. Things have to be mounted more securely. There are provisions for the neutral wire, and different grounding options.

In many cases, these differences are not readily visible.
Posted By: e57 Re: 200A Auto-transfer switches - 11/10/06 01:40 AM
Reno's got it - essencially it would need to be listed/rated as "Suitable for use as Service Equipment" if it is anywhere between the MCOP (Main CB) and the meter. And yep, if on the service conductors it opens another set of cans of worms involving the POCO. If say it were on a feeded to a panel only handling those loads (As they often are) then the POCO has no buisiness with you. As you would be on the protected side of the the main service breaker.

So now a question... A home that had a service calc that required 200A - only calc'ed 12KW as a "Connected Load" for the generator? How's that? I know the code offers alot of leeway in generator sizing for this application - but I don't think it would be a wise idea unless the owner had to manually swap over each load.
Quote
702.5 Capacity and Rating.
An optional standby system shall have adequate capacity and rating for the supply of all equipment intended to be operated at one time. Optional standby system equipment shall be suitable for the maximum available fault current at its terminals. The user of the optional standby system shall be permitted to select the load connected to the system.
If it say happened in peak use time you could be dropping POCO - then dropping in the generator on over-load. Say if an AC and Oven were on... Which is why often these are sized for either the whole house load - no call backs for over load drop. Or only for a few 'emergency' loads. (Refer, sump pumps a few lights and outlets here and there - but not the hot-tub, pool and entertainment center) If it takes on the whole house automaticly, the generator just might shut down right then and the owner might not know what to shut off. So in this case you have two options a bigger generator, or a ATS with an ammeter installed and instruction book about load shedding. Oh - or a load shedding shunt trip circuit.... It's not hard - but pricey. Use under-voltage trip shunts to drop all non-essential loads when POCO goes out, then the owner can turn them back on manualy after the generator connects. You would have to set it up with a momentary switch that would have to be flipped manually to latch a relay to re-power the shunts so the they could be reset only on generator power. But they would have to be re-set anyway even if the POCO came back on....

But an "Essential" panel, and "Non-essential" panel would be cheaper.

[This message has been edited by e57 (edited 11-09-2006).]
Posted By: Trick440 Re: 200A Auto-transfer switches - 11/10/06 03:05 AM
Sweet answers.

Thanks E57, for the insite about the huge power draw. We know its a small genny but didn't think about that.

Timne to talk this guy into a different route.
Posted By: e57 Re: 200A Auto-transfer switches - 11/10/06 04:13 AM
Well it depends on what he has as a load... If he has a 200a service for the sake of having a 200a, he may have a load demand that is far less. But it has all the bells and whistles and 100 amps of general lighting, and two 60a AC units - then no.

But the options of an essential and non-essential panel or larger gennie is a common method of doing it, and he should be informed of the options. Either way you get what you pay for. A few thousand more for seperation of the whole works, or simular amount of money more for a 30-50kW. Which the latter is enough to power him fully and a neighbor or two maybe? Depending on equipment loads? The only time I have ever seen a 200a service pull 200a is at X-mas during a catered party w/ 20kw in lights and caterers on hot plates.... I just questioned the size because powering 50A of an available 200 sounded odd. Often a service of that size will be that size due to something large as a load....
Posted By: Trick440 Re: 200A Auto-transfer switches - 11/10/06 04:26 AM
His service is actually 2, 200A panels. With most 220v devices in the other panel. So guess thats figured out.

I'll be pushing for putting the essential circuits into one panel and the non essentials in the other. Sounds like the best angle.

Thats why I made this post.... to become informed of my options. [Linked Image]
Posted By: e57 Re: 200A Auto-transfer switches - 11/10/06 08:22 AM
Ahhh.... So it's say a 320C/400A service? (2)200's in a meter/main combo w/ (2)200 lug panels, or a meter pan and (2)200 main panels?

Sounds as if one whole panel is general lights andrecept load? They may be lightly loaded, but the gennie should be sized for the load or in the very least a high demand of that load. Otherwise a small gennie would be defeating the purpose of being there when you need it if they are out there changing fuses, or flipping breakers. A generator salesman is going to give you the opinion that it needs to be sized a 100-150% of the load - but that is not nessesarily true...
http://www.generatorjoe.net/page.asp?id=40 http://www.dynagen.com/page.aspx?id=96259

Motor starting can drive it up a bit, but most are intermitant... IMO But you can guarantee that if everything else is off, what can be on - will be on.... So 100%+ is good. But my own opinion would be ~80% demand plus motor starting. Diesel likes a load.... Gas doesn't.

One of the nice things about an ATS, or more correctly certain ones. They can excercize the generator and load bank it on the house loads.

Another part of this is who gets to maintain it? It will need oil changes, and all things automotive, spare tire rotation. [Linked Image]
Posted By: jraef Re: 200A Auto-transfer switches - 11/10/06 10:36 PM
Just to further renosteinke's comment.
The SUSE labeling does in fact mean that the switch must be rated for whatever the PoCo's available fault current level is, you will need to find that out before you purchase it to be certain. For an industrial/commercial site that can be high compared to a residential site, that's why the price is higher. You probably will not need it to be that high, but even so you will still need that SUSE label if you connect it as you have indicated, and the ATS manufacturers (those that even offer SUSE labels because not all do) only make them for the larger market so you may be stuck with the spendier ones.
Posted By: JJM Re: 200A Auto-transfer switches - 11/11/06 12:26 AM
I've got a similar setup on my own home, 200A single phase service, 200A whole house ATS, and 12 Kw generator.

[Linked Image from mysite.verizon.net]

[Linked Image from mysite.verizon.net]

Since the ATS is not service entrance rated, a 200A main breaker is between the meter and ATS as shown below:

[Linked Image from mysite.verizon.net]

I know, I should've painted the walls before I put up the plywood, but I was excited with my new toys... you know how it is. In any event...

I can run the entire house no problem... 240V 18,000 BTU A/C, as well three smaller 120V A/C's a 5,000 BTU, 6,000 BTU, and 8,000 BTU, not to mention refrigerator, oil furnace, dehumidifier, attic exhaust fan, three computers, two televisions, toaster, dishwasher, microwave, and just about every single light in the house (mostly 75W cans) you name it... I really wanted to push it for the purposes of testing. At one point, I was reading a total of 50.6 amps on one leg, and 46.9 on the other leg with stable Hz. Had my wife turn on her 1,850 watt hairdryer and only then did the genny shut down on overload and Hz drop (50A genny breaker didn't trip).

I have oil heat and hot water, and natural gas for the stoves and dryer, so my electrical requirements aren't really that steep. If I had electric heat, hot water, stove and dryer, all bets would be off for this unit. Was fine with 100A 12 breaker panel before, but I wanted a 40 breaker panel for the rewire for lots of dedicated circuits.

Let's face it, few homes truly need 200A service... you get 200A for the number of dedicated circuits.

Joe


[This message has been edited by JJM (edited 11-10-2006).]

[This message has been edited by JJM (edited 11-10-2006).]
Posted By: Rewired Re: 200A Auto-transfer switches - 11/11/06 06:51 PM
Joe: Very nice install!


I just finished installing a 12 Kw "Briggs and Sratton" unit for a customer, He lives out in the sticks and at the very end of an unreliable primary line. We powered a handful of lights off the generator as well as a sump pump, sewage pump, water pump, furnace, microwave, and the GDO's and garage lights.. No problem whatsoever. Customer insisted his "Dry-O-Tron and pool motor be connected ( you know so the pool room doesn't get humid and the windows fog up, and we had problems. Unit started that mess once and had a hard time doing that, but would not again, it just shut down under the fault "Low Frequency". Guess he will have to deal with foggy windows. [Linked Image]

A.D
Posted By: iwire Re: 200A Auto-transfer switches - 11/11/06 07:13 PM
JJM Nice set up, glad you got it done under the existing rules.

It looks like that will be a violation in 2008 NEC.

For ATS installations the gen set will have to have a rating equal to the calculated load.
Posted By: ExpressQuote Re: 200A Auto-transfer switches - 11/12/06 05:46 AM
Before Y2K,

I spoke with many customers about installing transfer switches and genny's.

9 times out of 10, their original idea was to auto transfer ahead of the mains. However, once they learned of the expense of the the equipment and installation, due to the sizing requirements to handle the supply current, it was usually agreed that the better, and much less expensive option was to install a dedicated panel controlled by a transfer switch.

This dedicated panel only allowed the necessary loads to be operated by the genny, and ensured that the genny wasn't overloaded by accident.

[This message has been edited by ExpressQuote (edited 11-12-2006).]
Posted By: JJM Re: 200A Auto-transfer switches - 11/12/06 09:31 PM
Thanks guys! Truly an HONOR indeed to get the thumbs from you folks.

Much of the BX in those photos were temp, coming off the gang box (RH top) used to splice from the old panel... all gone now... that 200A panel has a lot more BX in it, almost full.

Rewired, how do you feel about Briggs units? I've only dealt with Onan, Generac and occasionally Kohler. I find Briggs' "Empower" load management interesting... allowing larger loads to be started if the genny has spare power:

[Linked Image from homegeneratorsystems.com]

Briggs & Stratton Transfer Switches

IWire, that's unreal. Unless the genny was used for life saving equipment, I can't understand why genny sizing would be of any concern for the NEC. As long as all safety aspects of wiring them are met, like cable sizing, grounding, bonding, disconnects, OPCD and so forth are met - and accordingly the installation is safe - what POSSIBLY could be the issue, other than sitting in the dark?

One thing I have found is that gennys are often grossly OVERSIZED - much like what you see with HVAC. It almost breaks my heart when I see a 45Kw genny in some of these McMansions powering only one of two 200A panels, when it's got more than enough juice to power both. I guess it's to be understood, genny dealers don't want to be in the position of not having a system guaranteed to work then have to deal with lawyers.

Two suppliers we buy gennys from told me my 12Kw application would NEVER work. I would need at least a 20Kw to 25Kw unit, and even still I should forget about central air - would have to go even bigger... on my humble little 1,100 SF home. To this day, I never mention anything about my set-up working perfectly. Generac recently started branding their gensets on how large of a central A/C unit they will start. Their 10 kW unit can supposedly "start a 3-ton AC with power to spare". That would be unheard of from a typical genny dealer. Briggs & Stratton is doing this too. Apparently all this fear about central A/C starting was way overblown.

It should also be noted that central A/C systems that normally won't start with a genny can often be "coaxed" into doing so with hard/soft start kits and staggered start-up of the condenser fan (lowering head pressure), compressor, then air handler.

I also wonder if this provision actually will go though with pressure from manufacturers. After all, what's gonna happen with all those larger capacity and likely higher margin ATS units?

Then there's also the practical issue of "calculated load" as a code requirement. That I'm sure is gonna spark fireworks with AHJ's and contractors. Oh, I can just see it know, "Fine, that panel says 200A so I want a 48Kw generator installed, period. Either pull that 30Kw unit out, or put in a dedicated 100A subpanel in or I'm gonna have the whole service red-tagged." Should be interesting...

Not arguing, code will be code I suppose... just venting because it doesn't make sense.

Joe
Posted By: iwire Re: 200A Auto-transfer switches - 11/12/06 10:16 PM
Joe I could not agree with you more.

I think many have lost sight of what the word optional means.

From what I understand it is the manufactures pushing the change.

If it's a manual transfer switch the rules are unchanged at least for 2008 NEC.
Posted By: iwire Re: 200A Auto-transfer switches - 11/12/06 10:20 PM
Check this thread out

Automatic Transfer Switch - Art 702
Posted By: Rewired Re: 200A Auto-transfer switches - 11/12/06 11:59 PM
Joe:

I found the Briggs unit not too bad to work with. Actually I found it a lot easier to install than the Generac my boss has at his house.
Only problem I noticed as well with the briggs is when I fired it up for the first time it did not seem to run right, sounded like it had a misfire and the voltage was fluctuating with a very light load. Maybe the mixture is off or something I am not sure but I am going to look into it Tuesday and see if there is a problem.
The unit we have installed does not have that "upgrade" to allow "control" of heavier loads, it just has a set of N.C contacts that will open and lock-out something when the transfer switch is transferred to "GEN".. Might have to use them to lockout the Dry-O-Tron compressor if I can't solve the problem by using a "kickstart" on the Dry-O-Tron.

I too have a back-up gennie, just a lil' "4500W continuous" Kodiak model.. I can run two refers, a freezer, my furnace and central A/C as well as a handful of lights with ease.. I used one of those "kickstart" hard starting devices and that helped bigtime. That and I wired a 2 min time delay into the A/C control, that way it gives the reefers and freezer a chance to start first.

A.D

[This message has been edited by Rewired (edited 11-12-2006).]
Posted By: renosteinke Re: 200A Auto-transfer switches - 11/13/06 12:53 AM
I just received an issue of the NFPA's magazine "NEC Digest." This article, IMO, glosses over the most important part of using ANY kind of back-up or supplimental power supply: the transfer switch.

Generator sizing is also a very important matter. This is one situation where 'bigger' is not always better! As a rule of thumb, a generator ought to be run at about 80% of it's capacity .... it's not really good for the genny to be massively oversized.

As for undersizing... well, that's usually something you can deal with- by pulling a few plugs, flipping a few breakers.

Another item often overlooked in genny installs is the regular 'exercising' of the equipment. The genny needs to operate, under load, at least once a month; weekly is better. The genny should operate under load; this can either be with an automatic transfer of power at the transfer switch, or by using a "load bank" to create an artificial load for the genny.

If one is not willing to 'do it right,' then I say they ought to stick to portable units and extension cords.
Posted By: e57 Re: 200A Auto-transfer switches - 11/13/06 08:07 AM
Reno, load banking would not be an issue with the many NG and Propane units out there now, but definately would for diesel. (Due to wet-stacking of the exaust) Otherwise excersizing is just to keep the battery charged and the oil moving on top of a good waste of fuel. [Linked Image]

Bob and Joe, I was looking at that proposal for 2008 I guess... It doesn't sound totaly unreasonable IMO
Quote
702.5 Capacity and Rating.
(A) Available Short Circuit Current. Optional standby system equipment shall be suitable for the maximum available fault short-circuit current at its terminals.
(B) System Capacity. The calculations of load on the standby source shall be made in accordance with Article 220 of by another method that is acceptable to the authority having jurisdiction.
(1) Manual Transfer Equipment. Where manual transfer equipment is used an optional standby system shall have adequate capacity and rating for the supply of all equipment intended to be operated at one time. The user of the optional standby system shall be permitted to select the load connected to the system.
(2) Automatic Transfer Equipment. Where automatic transfer equipment is used, an optional standby system comply with a or b.
(a) Full Load. The standby source shall be capable of supplying the full load that is transferred by the automatic transfer equipment.
(b) Load Management. Where a system is employed that will automatically manage the connected load, the standby source shall have a capacity sufficient to supply the maximum load that will be connected by the load management system.

Sounds more common sense than the current wording to me. Having worked on generators a lot in the past, I'll tell you that many of the safety devices are not immune to failure. And as we all know that breakers are the not the end all beat all of over-current protection. Many generators are equiped with the lowest bidder for breakers if at all, who knows maybe FPE or the like is that low bid? Why not be able to handle the load it is given? 'Cause none of us is going to camp out next to the panel to see what the capacity is for it when it turns on, and I don't think our customers are edjucated enough to do that either if they are even home or awake when it happens. Lets face it, we cant even get them to not over-lamp fixtures when they change bulbs.... Here in CA the black-outs seem to happen in peak use times in the summer, when the AC units are going, and usually at dusk. Several million people going home from work turning on the lights and AC... Then the under-sized neighborhood transformer fails. So in those situations one could easily expect full load when the ATS kicks over. What seems to be an over-sized unit will be getting the locked rotor amperage of at least an AC unit if not two on many of the homes these would be installed in.


[This message has been edited by e57 (edited 11-13-2006).]
Posted By: iwire Re: 200A Auto-transfer switches - 11/13/06 10:36 AM
I don't have much time now but I have to ask this.

If we can not trust breakers to do the job they are designed for we will have to stop installing multi-receptacle circuits.

Also note that that the change will still allow a homeowner to manually overload the circuit.

If it's not safe to let an Auto transfer switch overload the genset than it is not safe to let it be manually overloaded.

I think Joe's installation is perfect example of why we don't need this change.


Gotta go..Bob
Posted By: SteveFehr Re: 200A Auto-transfer switches - 11/13/06 03:27 PM
The only difference between an ATS and a MTS is the automatic action; if the ATS trips on overload, the ATS ceases to be automatic and becomes an MTS at that point, doesn't it? I wonder if any AHJs will buy into that explanation? [Linked Image]

It's common sense that if you want your generator to be automatic, you ensure it won't overload. If an overload is unlikely but possible and automatic operation is desired but not required- well, you're SOL in 2008...

[This message has been edited by SteveFehr (edited 11-13-2006).]
Posted By: seeks Re: 200A Auto-transfer switches - 11/13/06 04:40 PM
Lately, we have been specifying a disconnect on the side of the building, due to requirements of 700.12-B-6. We read this to mean that a shutdown switch INSIDE a generator enclosure is not readily accessible, so an additional disconnecting means is required. (I suppose this is so the firemen can disconnect the generator in an emergency). How do you read this, and have you seen this in your area?
Posted By: JJM Re: 200A Auto-transfer switches - 11/13/06 11:49 PM
IWire, I read the Automatic Transfer Switch - Art 702 link you noted with great interest... thanks. Looks like seems we think alike... wow... if you were a girl I'd marry you, LOL!

It looks like we're fighting a losing battle though; the duties the NEC is charged with is growing increasingly corrupted by manufacturers. Generators are protected and the associated wiring is protected not only by internal electronics (which are very sensitive) but by an OPCD. As was poined out in the thread, if you've got 40 20A breakers, do you need 800A service? And how many times are POCO service feeders sized way to small if they had to follow code? So if there service doesn't have to be upgraded, why should the genset?

Larry Fine makes a good point in that thread of using the aux contacts for load shedding (mine has them) but will that be enough to satisfy an AHJ under the proposed rules?

I do have a problem with the this part of the 702.5 Capacity and Rating for 2008:

(B) System Capacity. The calculations of load on the standby source shall be made in accordance with Article 220 of by another method that is acceptable to the authority having jurisdiction.

It the "another method that is acceptable to the authority having jurisdiction" I have a problem with. I can just see how that will go with the "right" types... though some AHJ's don't seem to give a hoot how or even if a genny is installed. My system passed without the genny in place! AHJ and POCO couldn't care less about what kind of generator I was using... they just wanted to see if the wiring was done to code, no interconnection, proper grounding and bonding, and gas piping was correct and holding 5 PSI when they got there. POCO even said we don't check "appliances". I've seen this on other jobs too - except for some reason when diesel is involved.

It should be pointed out that a genset with a dedicated panel can be overloaded just the same. A 10 Kw genset hooked up to an 8 breaker panel, with 5 15A and 3 20A breakers has a total load potential of 135A. Generator only produces 41.66A so we're in the same boat again. That genset can be overloaded.

As Reno pointed out, it's no good to have a massively oversized genset either. And what about physical space, there might not be enough room for such an oversized unit, not to mention the gas requirements of having such a huge genset. What if the POCO won't upgrade your gas service enough to feed an oversized beast (a 45Kw unit will burn over 500,000 BTU on average), then what happens?

Regarding disconnects really doesn't make a differnce in my opinion... you've got one of the best ones of all - the gas (or fuel) valve - turn it off and the genset stops producing power instantly. Fire department would probably do that anyway in an emergency.

Joe
Posted By: JJM Re: 200A Auto-transfer switches - 11/14/06 12:08 AM
Rewired, how's the gas pressure, both before and after the regulator? Some genny's require elevated gas pressure, so if you're running NG the typical 3-6" WC probably won't be enough. But there may be ways around that.

I've seen cases where gas pressure too low causes "flooding" since there's not enough pressure to "push" the diaphragm on the regulator and effect proper regulation, and gas pressure too high resulting in "starvation" because there's too much pressure on the diaphragm. Those cheezy regulators are not demand regulators by any means.

The output pressure depends on the spring installed in the regulator. They're usually rated in WC (Water Column) and have limited control range, say 1-3" or 3-6" or 12-15" and so forth. I sometimes pull the adjustment screw and spring out (no, you won't create a gas leak) and use my finger as the "spring" to adjust for the optimum engine performance (and electrical output) under all ranges. When it runs right, I record the output gas pressure and install the appropriate WC range spring, then make the final adjustment.

If you don't have a manometer, you can pretty much "make" one in a pinch if need be.

Many genny's are setup for natural gas, and if you're running propane, you usually have to install an orifice and lean out the carburetor.

Good luck!

Joe
Posted By: e57 Re: 200A Auto-transfer switches - 11/14/06 02:11 AM
Steve I think that says it all...
Quote
The only difference between an ATS and a MTS is the automatic action; if the ATS trips on overload, the ATS ceases to be automatic and becomes an MTS at that point, doesn't it? I wonder if any AHJs will buy into that explanation?
It's common sense that if you want your generator to be automatic, you ensure it won't overload. If an overload is unlikely but possible and automatic operation is desired but not required- well, you're SOL in 2008...

Bob on the OCP thing, most of the small sets have CB's that seem to be the cheapest item found, and larger sets will have a rarely used relay to drop out the load contacts. Granted most of the ones I have worked on were older Onan models with a circuit design that probhably hasn't changed since the 60's - but they would often hold all but a direct short, and some held direct shorts.... Anyway, my point was that there are 'certain' cb's we dont trust often - like zinsco, or FPE - why put your electrical design reliablity on a no name hench en mexico breaker? Or a raely used solid state circuits dependant on relays that are often exposed to the elements and harsh vibration? FYI my personal prefferance is a fused disco or fused transfer-switch...

I think Joe's example is not one the average HO should follow... Although Joe may have an average home, as a member of this forum he is not the average HO...
Quote
I really wanted to push it for the purposes of testing. At one point, I was reading a total of 50.6 amps on one leg, and 46.9 on the other leg with stable Hz. Had my wife turn on her 1,850 watt hairdryer and only then did the genny shut down on overload and Hz drop (50A genny breaker didn't trip).
On many gen sets over-load and under freq are optional items...

Maybe the NEC board took an electrically libertarian approach to design for the electricaly libertarian out there with manual transfer. [Linked Image] "It's mine, I'll over load it if I want to..."

Joe I have seen AC units that dim the nieghbors lights. [Linked Image] Some need all the HP they can muster to start a large motor without bogging down the Hz which is why some seem over-sized - just for FLA and LRA for motor starting. Try your experiment again and start the AC unit last....

But while on the NG subject... There has been an interesting Plumbing code development here. Often people who have been through the quakes here remember being without power for a few weeks - think about getting a generator and the plumber comes by to upgrade the NG main to accomadate the extra pressure and WC needed, and the mandatory (In some cities) siezmic cut-out valve. Most are manual ball/funnel rest type, and make the generator useless after a quake.


[This message has been edited by e57 (edited 11-13-2006).]
Posted By: JJM Re: 200A Auto-transfer switches - 11/14/06 05:24 AM
E57, regarding the OCPD issue, using my set-up as an example:

[Linked Image from mysite.verizon.net]

What if a 50A main breaker enclosure were installed in between the ATS and the genset disco, similar to the one shown below:

[Linked Image from foxelectricsupply.com]

Now the genset and wiring would be covered. I was considering such a configuration at first (you'll note I have room on my board) using a GE 70A enclosure with a 50A 2-pole breaker, but my friend who does lots of genset installs (mainly commercial) said my idea was "retarded" because the genset breaker and electronics provides protection. I could've also used a fused disco, but my supply house didn't have it in stock. Besides, like my friend said, why should I care about protecting less than 10' of cable; if anything, the genset wiring will burn up first long before the #4 in this app.

Funny you should mention disasters... ready for that too: If the natural gas goes out, I've got two 30# LP tanks and an adjustable regulator with a 3/4" connection for just such an emergency. That along with two 20# for the BBQ and I've got 10 hours of fuel minimum at full load (240,000 BTU) if my math is right. Granted, if there were such an emergency, the genset would be operated sporadicaly to conserve fuel.

One of the basic premises behind this discussion is if the genset overloads, and shuts down, the system is not truly automatic, hence not doing what it was designed to do. My question is why does EVERY fault have to result in shutdown and lockout? Why can't the manufacturers modify the firmware to automatically restart the genset say 2-3 times maximum after a brief delay if it's only a simple overload? Of course you'd want the genset to lockout on low oil, temp, or other serious issue... but for a momentary surge the genset? Doesn't make sense.

I think this simple change would go along way with the proposed 702.5, but obviously that won't do much to help the manufacturers bottom line, which I'm beginning to believe is the intent of the proposed changes.

Joe
Posted By: e57 Re: 200A Auto-transfer switches - 11/14/06 08:24 AM
If I were to get one, and I have been thinking about it.. I'd shoot for diesel for endurance and and the realities of the day I would need it, as it just might be a quake of 6.+ NG would be cut-off in different parts of the city just due to ruptures.

So Joe, you own one, would the breaker in it be one that you stock or would install? I've seen some I would give a second thought about seeing them on landscape lighting. Do you think it will operate in the tested 60hz 120'240 paramiters at ~30hz @ 60 volts? The fact that the safeties that are installed (Over-load, and under-freq) dropped the load before the breaker reaction time to me is pretty telling. Over-load protection circuits are there for protection of the engine, not the wiring or load the gennie is supplying. And some generators offer a by-pass button for that.... Under-freq is kind of a dual protection circuit that protects certain loads and offers some over-load and shortcircuit protection, because in those situations the windings slow down and even stop, but mainly for power quality. Depending on the circuit they may actually be the same 'over-load/under-freq' because the would act the same in effect. A loss in engine RPM.

I used to start 50HP motors with 60Kw generators (not that you would ever do that at home, but as an example) and it would temparalily stall the engine for a moment. From 60 to 10Hz due to in-rush current. The generator would physicaly shutter. This also drops the voltage for anything else on circuit... But do that on a 100Kw set, and you barely notice...

That proposed 702.5, for ATS would allow 2 options, full load, or load managment. Load management can be done in a number of ways, and still not exclude you from running the whole house as a connected load - just a managed load... A home like yours (Which has about 3X the load of mine at 1300sq') is a much smaller load than what I see install a 1/2 mile away from me in richer areas of town. Where as you could max yours out at 100+% and have to try to do it. Some of the homes I wire would stall a generator of that size - easy. Like dropping the clutch in your truck. But the diffence if that it doesn't just damage the engine, it creates other voltage and current problems on all the circuits connected to it. (Depending on the winding and regulator design.) A frequency controlled design would then just pump more fuel to compansate the loss in RPM/Hz - if it can... The reason they often wont auto-by-pass or reconnect is because this can be a dangerous electrical fault, and the idea not to self-destruct of cause damage. Would you connect to an under-voltage, 35Hz source? Or purposely over-load a transformer, or phase convertor? A generator is no different - IMO it has nothing to do with manufactures or thier bottom line. A generator is nothing more than a rotating transformer - in your case, a 12Kw transformer with an engine primary.

Really these types of residential units are kind of new in the grand sceme. I think the code is just playing catch up to the consumer protections and Darwin Award winning homeowners, but left some leeway for those facilities that still have qualified humans to operate these machines in reasonable methods, as opposed to the auto-connecting switch....
Posted By: SteveFehr Re: 200A Auto-transfer switches - 11/14/06 11:47 AM
Quote
I think Joe's example is not one the average HO should follow... Although Joe may have an average home, as a member of this forum he is not the average HO...
Quote
I really wanted to push it for the purposes of testing. At one point, I was reading a total of 50.6 amps on one leg, and 46.9 on the other leg with stable Hz. Had my wife turn on her 1,850 watt hairdryer and only then did the genny shut down on overload and Hz drop (50A genny breaker didn't trip).
On many gen sets over-load and under freq are optional items...

Thermal overload isn't going to do a very good job of preventing generator overload- the trip curves on those breakers are just far too lenient; I wouldn't expect a 12kW to put out 24kW long enough to trip! In cases like this, the generator really aught to have an electronic relay designed to trip before the engine stalls. Or maybe it's just not a big deal on engines this small, and at least saves on fuel if the engine just dies vice running unloaded...

I might be unique here in that I've only ever worked with the BIG gensets, 200kW, 400kW, 3MW etc, and we always have current transformers, PLC logic and servo-breakers with the luxury of sophisticated programming of the switchboards to do whatever we want. When you're talking about emergency power, sizing to avoid overload isn't just good practice, it's absolutely essential. What sort of brains do these small ATSs have? Is it just an atmel chip, a few lines of code on an EEPROM and a 2P contactor? That doesn't generally allow for reactive droop and closed transition back to utility power, does it?

On the big gennies, they're always rated for overload, and include internal protections to shut down if things are too out of whack for the engine to maintain proper rpm. I can go up to the panel on any of these and set what frequencies are acceptable, maximum current levels, etc, and adjust the trip settings on my breakers to match it. In-rush on startup is usually the worst; if the breakers can be timed to come back on one at a time, or not come back on at all if the generator is overloaded, it can allow a marginally sized generator to power a load it might otherwise stall or trip on. I can see how that might be cost probititive to a homeowner...

I'll just stick with my little manual-start 3.6kW that I bought a few years ago but have thankfully never had to use [Linked Image] It'll keep the fridge, TVs and lights on, and even run the A/C if I'm expedient with my load-shedding. As this forum shows up in a google search that laymen might find, I won't mention how I plug it in...



[This message has been edited by SteveFehr (edited 11-14-2006).]
Posted By: renosteinke Re: 200A Auto-transfer switches - 11/14/06 05:08 PM
On a side note, I have been following the latest craze in management circles.

When confronted by a crisis, such as a power failure, you should pause, take a deep breath, and ask:

"How would the ancient Egyptians solve this?"
Posted By: JJM Re: 200A Auto-transfer switches - 11/14/06 06:16 PM
E57, I hear you on CB quality on some gensets. I don't like pointing fingers, but a lot of the switchgear on Generac units in general leaves something to be desired. And the larger they seem to be, the worse they seem to get.

But in answer to your question about the CB in my particular unit, aside being from a French company (with the unoffical boycott and all) I'd use it... SquareD two pole, common trip... I believe QO series, not HomeLine if I remember right. That's why I like Onan. They're more expensive, but the quality seems to be much better.

If you're in CA I don't blame you for wanting to go diesel because of earthquake considerations (not to mention reliability and torque) but in NY that really isn't a major concern (although it's said we're due for one, but that's another issue). Cold weather is an issue though, diesels aren't too happy about being awoken in the cold.

Wow Steve... a 3Mw genset, now that must be fun! I don't think I've ever run into anything bigger than 200Kw, and that was for a large restaurant. And yes Steve, we know what a bad boy you are hooking up your own portable genny [Linked Image] [Linked Image] but considering the monsters you work with, I think we can make an exception. [Linked Image]

Joe
Posted By: SteveFehr Re: 200A Auto-transfer switches - 11/14/06 08:48 PM
From 200kW up through 1000kW, it gets a little bigger, but doesn't really change much- the gensets are a comparable size and appearance. Our 2-3MW gens, though... freaking locomotives! Low RPM, high torque, and just tons and tons of steel. It's all medium voltage at that point, too, which makes it even more (less) fun...


[This message has been edited by SteveFehr (edited 11-14-2006).]
Posted By: e57 Re: 200A Auto-transfer switches - 11/15/06 02:23 AM
I too used to work on a range of military generators from 10Kw - 2MW. But mostly on the 60-500 range as they are easily portable through muck, and by paraleling you could get as much as you want - so long as they were all equal size. Biggest farm of them I ever put together was 12 500's, 6 on, 6 off mostly. All open buss-work lug to lug, it was a sight to see. No OCP at all to over-head, and UG distribution. (Field expediant AKA no parts, and no time.) Biggest generators were 2MW, usually shipped in pairs for maintenance purposes. I was telling Reno that we used to load bank those against each other by paraleling them and gradualy taking them out of phase with each other. Like two train engines in an arm wrestling match. [Linked Image]

My specialty was "Electrical equipment repair" so my primary job was rescuing them from severe abuse after they came from the field and in/out of storage. As I mentioned before these are far less sofisticated units than what Steve has been working with - but built to take a severe beating. That said I have sent a few to the scrap yards too.

A lot of the ones I have worked on also had CT's and that dropped out the load contactor. (I haven't seen anything like that on some of the 'residential' marketed ones.) And one problem that happened on occasion was that that contactor was controlled/fed by a number of relays and contacts in series that would either drop the load, or shut the fuel off. (This also had a by-pass switch for for life or limb emergencies...) Problem was that the CT's fed an adjustable circuit that ended in an SCR that that controled the relay for over-current - it had IMO a design flaw, such that is if that circuit, SCR or relay failed there was no way of knowing, and you wouldn't know until the windings or the conductors it fed smoked. Which I have seen a few times. And smaller utility gen sets had a catch all safety circuit that operated via that dropped out at 40Hz to the fuel shut-off, with some crusty old used as a switch breaker that you could arch weld with. Which is why I have minor trust issues with over-load circuits, and shoot for fused discos. Not that I have a problem with quality thermal/magnetic breakers that we use all the time, but unlike other things - a weak link / cheap or abused breaker is often what keeps the circuit on... IMO a fused disco, or reliable breaker is the way to go.
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