Help! Need to understand Transfer Switch
Thanks in advance for your input.
The background: I’m installing a new, 200A 3-wire 240/120 V service entrance in a shop to be fed with underground cable from an existing, on-site, 100 KVA, pad-mounted Transformer with Central Metering system (to serve 3 buildings ultimately.) I want to incorporate a manual transfer switch for a possible standby generator &/or alternate energy use in the future in just this building only. I’m having dificulty selecting the transfer switch. (I have a bonded neutral generator now.)
My problem🙁Should I select a 2 or a 3 pole double throw switch?
This outbuilding is a shop with welding, machine tool, stationary compressor & assorted motor loads as well as general lighting loads planned. My existing generator is 12KVA, however I’ll be able to get a 100KVA Diesel Generator for the cost of hauling it. I’m in a rural area where power outages are far from uncommon, especially in the whiter months! I believe the 3 pole is what I need to match my existing gen. however I’ll replace ithe gen. if I deem another plan to be safer &/or more flexible.
Some generators have a bonded neutral, some don’t. I want the system to be as safe & flexible as possible, however, I’m not entirely comfortable with switching my main service neutral trhough the transfer switch. (I plan on a 200A fused disconnect as the main service entrance wherein the incoming neutral connects to the main grounding electrode. I’ll use a 200A splitter box (down line of the transfer switch) to supply the load center, welder- breaker box/receptacle, motor load boxes etc.
I’m especially concerned about the ramifications of the grounding/bonding issues due to the switching of the neutral. As I understand it, the generator will be grounded with its own electrode. Any thoughts or opinions jump out at you? (It appears to me that a 2 pole switch would leave the main service neutral connected all the time regardless of the transfer switch lever position, NO?)
Your thoughts, experiences or what you’ve seen done in the field are all valuable, if you have had the time to wade through all the foregoing & are still with me, that is!
Sincerely,
STAINLESS
Replies
I've put in a couple of whole-house standby systems, though they were much smaller than your: 20 KVa, and also a few largish manually-switched generators (along with many small ones).
I've never used a 3-pole transfer switch on a single-phase system, even with bonded-neutral gensets. The gensets were NOT separately grounded via a rod, but they were grounded back through the building grounding electrode system.
(It appears to me that a 2 pole switch would leave the main service neutral connected all the time regardless of the transfer switch lever position, NO?)
That is true.
I don't know enough to know when there would be a need to install what's called an separately derived system, which requires you break the neutral. The utility co's don't have any problem with the permanant neutral connection. There's little or no chance for any power to get back into their line through the neutral. And any ground-loop created is restricted to the feeder between the genset and the service equipment.
The NEC doesn't seem to require you break the neutral (Article 702 and sections of Art.250 ) . I would guess you don't need to do it.
Ed
Thanks for the reply, edlee.
I feel more comfortable with the 2-pole switch myself if ESA (our local inspection body) and the pow. co. people are OK with that setup. Now that I've got my permit pulled, I'll be putting a call (or multiples most likely!) into the inspector to get his take on this. (Until you've got the permit in hand ESA won't give you the time of day.)
Unfortunately, trying to reach the inspector in the field is a bit of a c##p shoot. The office suggested the only time to reach him in the office is before 08:00. After that, just to keep dialing his cell until you get lucky. And "no there was no one in the office at the time who had technical knowledge to help me at this time!" when I asked.
When I asked what time does he start, I got a chuckle: he comes in at 07:45! so me and 10,000 other guys will be trying to call this guy within the same 15 min. window!
Thanks for the insight,
Sincerely,
STAINLESS
Edited 10/13/2007 11:42 am ET by STAINLESS
3 pole= Pro: every situation's covered; Cons: may not need third leg.
2 pole= Pro: cheaper; Cons: may have to replace with 3 pole.
SamT
SamT, I normally like the belt + suspenders approach when it comes to elec.
The incremental cost doesn't phase me, (pardon the pun), I am concerned at the time & cost to tear out & redo if I guess wrong on this one.
I'm also trying to go over the possible scenario's regarding safety in the event of an accident. A few years back during some foundation work the incoming neutral only was severed on the u'ground service supply line by accident. It was momentarily shorted to one of the hot supplies but didn't trip the pole fuse or any of the service breakers. The upshot was multiple 120 V appliances failures due to over voltage. A Computer power supply, microwave oven PC card , kitchen oven control card, stereo, GFI receptacle and a television were all casualties as they were all connected and although not functioning at the time they were drawing those phantom loads that "sleep mode" assures.
I'm struggling with all the permutations & combinations of things that could go wrong after my new install has been safely in operation for many years to point out the weakness in planning that I'm specifically trying to avoid right now before I commit to a system plan.
Admittedly; severing just the neutral of an underground cable doesn't happen but once in a blue moon, but with my luck I'd have to say that Murphy was an optimist!
Thanks for the input,
Sincerely,
STAINLESS
A few general observations .... I'd like to highlight a few areas where folks typically screw up their generator (or other 'alternative power') arrangements.
The first is sizing. Have you measured just how much electricity you're using under normal conditions? Or, with everything running? There is absolutely no need to 'match' the size of the PoCo service .... indeed, doing so may be a bad idea.
I like to open the neutral when the transfer is made. This makes things a lot simpler ... especially if there are any problems to troubleshoot.
Not to worry ... even with the neutral 'switched,' the grounds remain connected. This means that there is still an INDIRECT neutral connection. (Then generator grounding electrode MUST be connected to the household grounding system).
In the simplest terms, electricity tries to go 'home' - back to where it was made. Electricity made by your generator should have no other place to go, but back to that generator. There is no reason to keep a neutral connection with the utility neutral.
A generator should be sized NO MORE than 15% larger than the load it will be expected to supply. For example, if you measure your home as actually using 10kva .... you want a 10kva generator.
Smaller than that, and you'll have to choose what to run.
Larger than that, and the generator will not operate correctly. "Wet stacking" and other maintenance issues arise. Bigger is NOT better ... even if free.
Generators need to be operated, at load, regularly. This 'exercising' is accomplished by one of two ways.
If you have an automatic transfer switch, an 'exerciser' can actually switch your home over to generator power at regular intervals.
With a manual transfer switch, the generator will need a 'load bank' to simulate the load of the house. A 'load bank' is nothing more than an enormous toaster.
With any generator, noise is a major issue- especially as they get larger.
hello renosteinke,
Don't believe I've had the pleasure before this. Thank you for the reply.
I have done a detailed calculation for "worst case scenario" power draw. Sits @ approx. 40 KVA. Mostly balanced due to large 240V loads. Compressor is 7.5HP & can come on at any time due to press. control switch. General lighting load is approx. 4KVA, Welder has a demand of approx. 10KVA @ the normal current I weld at (with a capability of 80% duty cycle) but has an output capability of almost 17KVA @ peak output & 10% duty cycle. Assorted other connected and auto-start loads and provision for a few helpers in the shop running the larger draw machine tools add up to the worst case .
Rather than permanently pick and choose which loads I'll have to live with during gen. operation I'll switch the entire service and then load match to gen. capacity based on what I want to do at that time, shutting off the loads that exceed my gen. capacity. Granted I'll probably never need the worst case on gen. operation, however, that is the determinant for the entry service sizing.
Although I have the capability to measure actual current draw (up to 600A with present instrument) unfortunately no service yet exists to do so. Once I can establish a "normal" operational load through actual measurement I'll be able to fine tune the gen. capacity requirement. Until then I'll presume that the 12KVA gen. will be a good 1st approximation, with the 100KVA bad boy a possibility if it is still available when (or if) I may want it.
I'm still unclear as to the ramifications of switching the neutral, however. If it is bonded in the fusible entry service switch then it will indeed still be connected through the building ground electrode regardless of the transfer switch position. I question what has been accomplished by this.
My inclination is to follow the inspector's direction on this and I suspect he will have a very good explanation supporting his opinion on this, however, I am still interested in the ramifications for future safety during unanticipated situations, such as the severed neutral that wreaked so much havoc before.
Thanks again!
Sincerely,
STAINLESS
I'm glad you took my reply with grace; since this is a public forum, I try to give answers that will make sense to the casual reader - or address other issues that you may have already considered. Now, looking at some of your specifics: As a rule, I always have the transfer switch break the neutral. To not do so seems to only create another opportunity for trouble. The genny and the PoCo should be kept as separate as possible. Just my perspective. No, for another word about load calculations ..... Sizing a service and sizing a generator are two different matters. There are a few important things that simple load calculations fail to take into consideration. Looking at a machine's nameplate is a good starting point - but that's all it is - a starting point. There are a few other matters to consider.
The first of these is to recognize that the machine will probably never run at anything near "full load amps." That 3hp pump is likely only using 2hp for the water it's pumping. Then there is the matter of starting current. There used to be a 'rule of thumb' that said you should consider the starting current to be 6 times the full load amps. Today, one can no longer apply that rule across the board. With the advent of variable speed drives and 'soft start' technology, the starting current may actually be lower than the full load current. This is especially true if the machine starts without a load on it (as a table saw would).
This current surge, in any event, will almost certainly be 'lost' in the overall load the genny is supplying. Simply having magnetic starters for your equipment will ensure that you will never have every machine start at once, either. That's why I said you should turn it all on, and actually measure the current you're drawing ....and base the genny selection on that. If you measure 40 amps, than 40 amps is what you need. If you are concerned about several large machines starting at once, then the solution is a capacitor bank - not a larger genny. If you go ahead and get a larger genny, you will definitely need a load bank. Load banks typically have controls that adjust how much load they add, depending upon the current being used. So, during your weekly (or maybe monthly) "exercising" of the genny, it is possible that the load bank will only draw half the load it can. Running a 100kw genny with a 40 amp load is less than 1/10 of the capacity of that generator. This means that you will need to 'waste' 80% of the power it makes. Running a big genny to provide for a small load is a very bad idea. It is also likely that the used genny was neither cared for, nor operated properly. Generators are not cheap to fix, or maintain. The associated equipment - transfer switch, exerciser, load bank - can often cost as much as the new generator itself. Some brands - Generac comes to mind - seem to be specifically designed to operate only with brand-specific, unreliable parts. Some bargain! I am seeing many, many 'bargain' generators these days. In every case, the application was doomed from the start. The generator was over sized. Costs were saved on the installation by failing to have the proper associated equipment. Maintenance and exercising were neglected - many times because the unit came with the standard muffler, rather than the optional 'noise package.' Noisy generators annoy you and piss off the neighbors.
since this is a public forum, I try to give answers that will make sense to the casual reader -
Hello!
Or maybe not so casual, as I have a 25KW PTO generator already. Way more than the house needs, particularly with no active heating/cooling systems. Load bank I'd not before heard about.
My application is similar. Large occasional loads from large machinery. Currently only get 17KW as my sole PTO tractor is small, but I use it all when I plane wood. The welder is much lower draw. As I'm typically at capacity (on the rare occasions I use the generator), I did measure draw. Dull those planer knives and my tractor doesn't quite keep up. Good-sized planer obviously.
I tuned in to find out what neither my poco, nor my licensed electrician friends could tell me: exactly how the transfer switch was wired. My confusion was the relatively low rating for the switches I've seen advertised, compared to my 200A service. As you point out, I'm never drawing 200A. The 2 vs 3 pole switching never occured to me. Presumably you're aware that this isn't very common information you're sharing.
Cost is a larger factor to me than stainless and when I priced 200A disconnect switches I got sticker shock. But as you point out, buying an insufficient bargain is no bargain at all.
My plan is to take hydraulic power from a larger tractor (2 available, without PTO) for powering the generator. Losses are obvious, but I've already got the machinery. Then I'll have all the current I can use. No neighbors, noise not an issue with the tractor down the mountain a ways. I already maintain the tractors, for other uses.
Have you got a recommendation you'd like to share for a load bank? Assuming that my generator has the same low-load risk you're talking about. Rare that we lose grid power for very long, but I've been idly prospecting the possibility of going off-grid.
Much appreciate your sharing your knowledge.PAHS Designer/Builder- Bury it!
Grew up around Amish that often put hydraulics on their formerly electric power tools. Just a thought, but if your only large load is the planer maybe you could replace the electric motor with hydraulic hooked to a larger tractor and bypass the energy loss on the generator. A smaller generator could still service welder, etc.
Afraid I can't offer any more specifics, just some food for thought.
-Nate
Very interesting idea. Planer actually has 2 motors, drive and feed. Plus a third one for the blade grinder. Weighs 4500 lbs.
What I didn't mention was the 3 drum 42" sander waiting to be hooked up. 4 motors on it. Don't now have the electric capacity, but will with the Cat hydraulics and 540 rpm hydraulic motor. Never dreamed I'd have such tools when I was setting up here. In fact, had to build another building after I bought the sander at auction- for $50.
Most expensive 50 bucks I ever spent.PAHS Designer/Builder- Bury it!
Found this on a google search:
http://books.google.com/books?id=fDJ16aCKRecC&pg=PA116&lpg=PA116&dq=amish+hydraulic+motor+tools&source=web&ots=6uzVuQgfd1&sig=n3vxrkp0siExpNBVyQEoDE3Y9zw#PPA118,M1
page 115
-Nate
That was interesting. Mennonites around here.
Line shafts I knew about. Arranged to get a wood planer originally powered that way for my machinist, converted to a jack shaft.
Surplus Center http://surpluscenter.com/home.asp?UID=2007101421303519 is a good source for hydraulic motors. Techs are knowledgeable.
Lots of non-functional earthmovers available. Many with working enginges/hydraulics if you can figure out how to get them into position. Plenty of flow. Considered buying one from a buddy just to use as a vehicle lift. Good for 8 tons. Would have been interesting getting it up here.PAHS Designer/Builder- Bury it!
The main point about exercising a generator is to keep the engine in good running condition, but since you have a PTO setup that's not really an issue - I assume you use the tractor for other purposes so it's getting the exercise it needs.
The load bank is for exercising the generator without engaging the transfer switch. I'd say you can get by without one, as long as periodically flipping the transfer switch and running your normal loads off the generator isn't an inconvenience. Also, I believe many automatic transfer switches (at least the ones I've worked with) have exerciser circuitry built in.
As far as the size of the auto transfer switch goes, if it's set up to switch the entire service it has to have at least the same ampacity of the service. On the other hand, if you have the emergency loads all connected to a sub-panel that is fed from a branch circuit from the main panel, and the auto transfer switch is in between the main panel and subpanel, it only needs to have the same ampacity as the branch circuit feeding the sub-panel.
As far as the size of the auto transfer switch goes, if it's set up to switch the entire service it has to have at least the same ampacity of the service.
That was my original assumption. Not a small issue with a 200A service. Sub-panel I understand and appears a better option. 3 wires between the house and there, but no inspections.
I misunderstood the point of the load bank, thank you. My generator's currently used 3-4 times/yr. If I start accepting commissions again, more often. You're correct, the tractors have other duties and are exercised often, one of my attractions to a PTO generator. Less required maintenance is better.
PAHS Designer/Builder- Bury it!
Transfer switches are both the simplest and most complex of devices. The electrician need only where each of the three sets of wires go, and take pains to make sure that the different sources are "in sequence" with each other. It's when you try to design a transfer switch that things get hairy. This is because, in a fight between the PoCo generator and your's something is going to go BOOM .... and it probably won't be the PoCo plant! Engineers have figured this out to the point where there exist transfer switches that make the change-over without any noticeable dip in power to you. Because that's what a transfer switch does: it disconnects your panel from the PoCo service, and hooks it up to the generator. Your generator supplier is the best source for the accessories appropriate to your generator. See them for transfer switches, noise reduction, exercisers, and load banks. Indeed, I strongly suggest that anyone wanting a generator work with the supplier in the selection and design of their system. A distant second choice is a QUALIFIED engineer. I have a customer who has had me install two generators ... a 400kw and a 250kw. These two are good examples of what's involved.
In common, both have automatic transfer switches and exercisers. That's where the similarity ends. The 400kw unit is set up to automatically switch the establishment over to generator power for two hours every Tuesday. Timing was selected to assure the greatest chance of the generator operating at full load. The 260kw unit has automatic start, and transfer, in the event of a power failure. Otherwise, it also is exercised weekly - but without the load transfer. Instead, there is a load bank "giant toaster" mounted on the generator. This provides the load that the generator serves during exercising. Both of these units have the 'standard' mufflers ... which means that they are loud enough you cannot speak while standing next to them. Contrast this to another customer, who paid for the optional 'noise package' when they ordered the generator. This unit operates at about 67 decibels, right next to the unit. Inside the building (30 ft. away) you don't even hear it start up. Onan, Cumins, and Cat all have loads of great info on their web sites. Use it. On the other hand, I would shy away from Generac; they seem too heavily focused on their marketing plan. For those planning on a different source of power, most generator principles apply. The simplest, best solution is to separate your system from the PoCo when you are supplying your own power. If you're going to make the transfer manually, you MUST turn everything OFF before you make the transfer. Then turn the loads back on again. You do NOT want to operate that switch under load .... even if it's rated for the load. It's not unusual for even an electrical contractor to have had little direct experience with generator installs. Again, your local generator dealer ought to be able to tell you who he has worked with in the past.
Thanks, but my generator's apparently an orphan. Third owner, second one couldn't figure out which two legs would give 240v (3 phase generator, what I wanted). Fried a couple of expensive cash registers and sold it to me cheap. $2.99 spent at Harbor Freight could have prevented that. Web search for the mfg. netted a phone number that didn't return the call. No web site.
I was surprised that neither the poco, nor the electricians who hunt here (several of them) had any idea. Not anything they'd ever done. Poco's a coop.
The poco install guys mentioned that they love to find a backfeeding generator. Find it highly amusing to blow one up.
How to wire seems straightforward. Which hardware, considerably more difficult.
We live in an underground house, 700' away from where the generator lives, behind another concrete building. Noise from the tractor isn't an issue. Cat's very good about specific issues. My generator isn't. I'll look.PAHS Designer/Builder- Bury it!
'Lo there VaTom! Long time no see, so to speak.
Haven't yet got any response from my Request For Quotation re: the 200A TXFR Switch. I am NOT anticipating it will be inexpensive, however! (Aside: I've been hunting for a long time for one of these suckers at distress pricing with absolutely no luck, so I'm afraid I'll just have to bite the bullet!)
Just priced the RWU-90 XLPE copper 3-0 service conductors @ 21.75 CAD per meter, need 3 wires on my 31 meter run. The numbers get serious in hurry!
I've also seen many generator panels with very limited TXFR switch capacity, say 30-60 AMPS; probably very applicable to a carefully anticipated & chosen residential load where the emergency loads of select lighting, HVAC, refrigeration & water pumping will get one through a blackout without serious disruption to a way of life.
Both our needs/desires seem similar to each other & possibly quite different from such a residential application, I suspect. I am willing to switch manually & load match my gen. output based on what I want to do that particular day. A seamless switch over more appropriate perhaps to a financial, or medical facility for example is not what I am after.
I'll be running on Gen. power only what it can handle & what I consider to be the priority at that time. Rather than tie myself down to a set of predetermined emergency loads that can be sized in advance to utilize the optimum gen. capacity, I want the flexibility of selecting from any of my loads the gen. can handle and running them based on what is my priority.
I won't want to be sitting in a standby minimalist power consumption mode until the power co. gets back up; when I can be running my show instead, however. I clearly understand that this will not be inexpensive & hope to defray a good portion of the costs by doing the grunt work myself.
Just got the Ford 4500 TLB all tricked out with new Rear Axle oil & a top up on the HYD. Package. fluid & filter. A 31 meter trench should be some good exercise for both me & the machine! (I'm sort of looking forward to that part once I can get through all the interior wiring, service entrance setup & fussy elec. stuff!)
renosteinke makes some excellent points with respect to gen. sizing and periodic exercising, noise, & maintenance, I think.
Wiring of the actual TXFR switch shouldn't be too much of a bear I believe. From the schematics that I've looked at from the offerings of Eaton/Cutler-Hammer for manual switches if you imagine each pole of the switch to be a large knife switch on a center pivot with contacts at each end of the "throw" you can get a picture in your head. The load goes to the center pivot, each of your different sources of supply go to each opposite end of the "throw" of the switch. The center Knife portion can connect to only one of the ends at a time. The ends of the "throw"can never connect to each other. The switch is a break-before-make type and although rated for switching at full load I would echo reno's suggestion to disconnect all loads before switching off grid to gen. operation.& vice versa. Each of the poles are wired similarly: both the black hot conductors & possibly the white neutral (jury still out on this one for me I'm afraid) The switches I looked at can also be wired differently to transfer from a single source of supply to either of 2 loads.
My original purpose of the post was to get a feeling for 2 pole vs. 3 pole switches & I think I've persuaded myself that I still like 3-pole,wired as a 2 pole however I'll leave that determination to the ESA inspector if/when I reach her/him!
Sincerely,
STAINLESS
Edited 10/14/2007 11:22 pm ET by STAINLESS
And hello to you. Hope you didn't mind the mild diversion from your thread. Related, as you point out. If not exactly normal HO related.
I'm not thinking to buy a 200A transfer switch. We have no problem running the whole house on 50A. Only V, no H_AC here. That's 700' from the generator (speaking of trenches). My, and presumably your, major elec draw is for large tools. 25KW is sufficient for me, paid $1k for my generator, already had the tractors.
Freedom from maintaining yet another engine (for the generator) is adequate for me to put up with manual switching. More than switching, I have to move a tractor and hook up the generator. Thought about doing a Junkhound approach with a surplus gas 3 L V6 and decided against it.
Wiring isn't much of a challenge, other than heavy wire, once I figure out exactly what hardware I need. I generally jump on heavy switches when they come up at auction. Unfortunately, it's clear I should have been more attentive.
A hundred years ago I actually received an electronics tech education, spent some university time (sometimes) studying for EE, mostly forgotten now. Hey, at one time I was the only guy in town who could repair the new car radios. The ones with transistors. LOL
I'm long accustomed to 3 phase, use a home-made phase convertor for the smaller tools. Thought about it for the larger ones but didn't have adequate current to do so until I added another poco service at that outbuilding. 3 phase generation made perfect sense. And now I'm rethinking my options for the whole property, 3 buildings so far. Woodgas (producer gas) is interesting.
Better to do what you're doing, plan it all out ahead. I never dreamed I'd ever own such large tools when I decided that 50A would be adequate for my shop. That's all I ever had in Denver for all those professional years. Was close, but it worked.
No longer. So I'm muddling through the revision now. Possibly the last one.
Glad you brought up the subject. It was in my future.
PAHS Designer/Builder- Bury it!
Hi Tom.
No unkind thoughts at this end regarding diversions! The're the stuff of knowledge.
Can't say I've ever categorized you or myself as normal HOs. H*ll, distinctly abnormal is how I think of myself these days.!
Re: the 700' trench. You may want to be on the lookout for a pair of suitable transformers, say 12KVA & up that step down from 480V to 240V. If you think about the tremendous voltage drop associated with such a transmission line length as you are contemplating; stepping up from 240 to 480 at the gen. and back down to 240 at the house makes some sense given the insane copper pricing these days. "Suitable" contemplates a price tag of zero, it would be far cheaper to buy the proper wire than to actually part with coin for the TXFRMRS!
SPECIAL NOTE AND GENERAL DISCLAIMER: THE FOREGOING DISCUSSION IS MEANT TO BE NOTHING MORE THAN A MENTAL EXERCISE AND CONCEPTUALIZES IDEAS THAT WOULD BE ILLEGAL AND POTENTIALLY VERY DANGEROUS TO IMPLEMENT. PLEASE DO NOT ATTEMPT TO TRY THESE THINGS UNLESS YOU ARE EMINENTLY QUALIFIED TO DO SO AND HAVE THE FULL PERMISSION AND INSPECTION OF YOUR LOCAL ELECTRICAL SAFETY AUTHORITY.
I would love nothing more than 600V 3phase on our concession, alas to run the line up from the highway is much more than I am willing to pay. (I am in the process of collecting the necessaries for a good sized (10 HP) rotary myself).
The service transformer I have on the property is 100KVA and draws only 20A from the 4.8KV line it is being fed from. Although it cost me plenty at the time to share its cost with the local hydro supplier, they own it and maintain it. Since it is a Central Metering system, I can add buildings to the service as I see fit with no extra costs from the local hydro people to do the hookups. Only 1 meter to read and only one service to the property, all neat on one bill.
You just never know what stuff you come across on this site. Glad the timing of my query was good for you.
Sincerely,
STAINLESS
Re: the 700' trench. You may want to be on the lookout for a pair of suitable transformers, say 12KVA & up that step down from 480V to 240V.
That trench happened 13 yrs ago. Unfortunately I followed the best advice at the time (electrician and building inspector). Aluminum wire, direct burial. Worked great for the first decade.
I got the second poco service in lieu of new (larger) wire. Was promised a minimal monthly billing of $7. The first bill minimum was $35, they'd changed their procedure. Pay considerably more for the meter sitting there than I do for the electricity. Both the shop and house.
Hindsight, the new wire and re-digging the trench would have been a bargain. So I'm looking at Plan 3. Independence from the grid, and poco whims, has large appeal. Which would still require replacing the wire.
Don't have much idea of the quality of 3 phase I'm generating, but my planer likes it. No extra planer power to waste, so a phase convertor would be problematic (and huge). That 17KW generated is consumed by the planer and chip blower. Sander, not yet online, needs more for its 4 motors. Hence, larger power plant, just a matter of plumbing the Cat.
PAHS Designer/Builder- Bury it!
I'm a huge fan of 3phase myself, I can appreciate the logic you've thought through.
Is your 3phase 480V? If/when you get around to replacing the existing trench line, you may not have too much sticker shock (pun intended!) if you lay a 3phase 480V line in the trench.
I'm curious about the comment re. "Aluminum direct burial cable working fine for the 1st decade." What about the install has given pause? The wire itself, the interconnects?
I'm a fan of copper, even to the extent of sucking up the price differential. I've always though it somewhat ominous that the Electrical Code I follow demands COPPER ONLY for arguably the most important part of my electrical installation, THE GROUNDING & BONDING. I've had it explained to me that Aluminum is fine with the larger dia. conductors, however, the service ground wire required for the 200AMP service I am installing is a #3 bare copper, not exactly a small conductor. No aluminum is welcome here apparently.
(I also like not having to deal with the anti-ox compound and the compression type lugs.)
Sincerely,
STAINLESS
No 480v here. And no need for 3 phase in the house. Generator lives in one of the outbuildings. Guy who sold it to me only used single phase for his country store. Unfortunately, his "electrician" apparently didn't own a meter. Fried a couple of very expensive cash registers by hooking them up to the wrong legs.
The problem with aluminum direct burial is small cracking in the insulation, resulting in major degradation of the aluminum. Aluminum direct burial remains the standard here. Inside conduit, or pvc water line-anything, and I'd have been blissfully ignorant of the problem.
My new poco service is aluminum direct burial to the meter. But it's not my wire. They're refunding me 2 yrs of elec billing toward the $650 installation cost (me providing the trench). So I'm running the house off that meter (in addition to the two outbuildings) for the period. At which point I'll have decided if we can comfortably go off-grid, making things here all that more "interesting".
First discovered the wire problem when the water system failed. OK, measure voltage in the outbuilding where the switch lives. Oops, only 124v- the other leg open. I knew where to look fortunately, had a guy working for me put in a water line check valve. Dug there and found that he'd nicked the elec line. Took several yrs to become a problem.
Since then I've found another (repaired) failure, and one I have yet to locate even though someone from BT was kind enough to explain (privately) how to do it. Both unrelated to the check valve installation.
My systems are a mishmash here, hope you do better. For instance, I have a 50 psi pressure drop from the well switch (which shouldn't have been located where it is) to the house. Again, followed expert bad advice. From folks who do nothing but supply hardware to well drillers, and sold me 2 submersible pumps that were inappropriate for my installation. After spending a half hour calculating, while I patiently waited. "I don't know" doesn't seem to be part of their vocabulary. 2 minutes on the phone with the pump mfg got the problem straightened out. Design still sucks, but it works.
The pump has no problem operating 80/100 psi (necessary to get a shower in the house). As I can't buy that pressure switch locally, keep a spare on hand. Plus, the higher pressure reduces the effective size of the pressure tank. It's huge.
DW takes very good care of me. Understands that it might be difficult for a stranger to sort it out. <G> PAHS Designer/Builder- Bury it!
Update on 2-pole vs. 3-pole transfer switch for gen. connection.
Finally got to converse with the ESA inspector for my area this AM after a few false starts with calls to his office & messages on his cell, etc., etc.
Seems that the code requires a 3-pole switch on bonded neutral generators and doesn't on un-bonded neutral generators. He has no problem with my plan to install a 200AMP, 3-pole, double throw safety switch from Cutler-Hammer as my Transfer Switch and wire it as a 2-pole switch or as a 3-pole to suit whatever generator I decide to connect. The only caution he had was to clear that application with Cutler-Hammer 1st.
Now have a call into a Cutler-Hammer product specialist re: use of a 3-pole switch for either 2-pole or 3-pole use, both as approved usages for the same switch?
As a strange aside: I have still not received my quotation from the Cutler-Hammer distributor regarding the price on such a beast! (Admittedly I have 11 line items on my RFQ, 3 of the items are for copper wire I guesstimate at over $2200 CAD). You might think that 3-4K$ in materials would warrant a bit more alacrity, however, I suppose in the overall scheme of things I'm still a very small fish swimming in a huge pond!
Sincerely,
STAINLESS
Morning VaTom!
Pardon me for not making myself too clear. I was thinking that if you wanted to go off-grid & use your 3phase genny to run the house you would save on conductor costs if you could bury a 3-phase 480V line to the house and transform it there to the 120-240V you use residentially.
All kinds of single phase 120-240V applications are routinely run on 3phase commercial services as I'm sure you know, it all revolves around the transformer inside the building which is supplied with 3phase. I think they are referred to as "lighting transformers."
GENERAL CAVEAT: Again I must apologize if I offend anyone with this caution. The foregoing discussion is nothing more than a mental exercise. The concepts presented may be illegal &/OR dangerous to implement without the express approval & inspection from your local Electrical Safety Authority & the implementation from a person trained/capable in such work.
Glad to hear that your DW is cognizant of the valuable piece of work you ar... ahem, cough that is ..piece of work you can accomplish around the homestead. It is good to have sinecure.
Regards,
STAINLESS
Final Update re: 2-pole vs 3-pole 200AMP Transfer Switch
Reached the product specialist @ Cutler-Hammer re: my plan to install a 3-pole Double Throw Safety Switch for use as a 200AMP Transfer switch, and wire it as either a 2-pole or as a 3-pole, based on whether the generator is a neutral un-bonded or neutral bonded configuration.
The 3-pole switch is also approved for use as 2-pole transfer switch (by leaving one set of contacts unused), by adding a neutral bus kit and a ground kit.
The price to the distributor for the 2-pole switch vs. the 3-pole switch from Cutler-Hammer is the same according to the product specialist. No I can't purchase directly from Cutler-Hammer, (of course not you fool Stainless! you're not part of the club!) The pricing from my local distributor for the 3-pole is about $850.00 CAD TNIP (tax not included price) now that my RFQ has been finally answered. It would be interesting to find out their pricing to me on the 2-pole just to see how honest they are, however, I might be better off not knowing & tainting a relationship of many years!
OUCH!! I guess I'll just have to go non-local & shop this sucker! At least I know what I need now.
Hope this thread has been helpful to someone other than just me!.
Sincerely,
STAINLESS
Hope this thread has been helpful to someone other than just me!.
Well, me of course. And future (lucky) search function users seeking similar info.
I've occasionally been shocked at something mentioned much after a thread ended. You never know who's been reading.
Happy shopping. Something I find a PITA, but often well-rewarded. PAHS Designer/Builder- Bury it!
Stainless,
I can't answer your question any better than the other posters. I have however come across on the web, several times, on the sites of various power companys, their requirements for the arraingment your wondering about. I would go 3 pole , but I'm pretty uptight.
Harry
Thanks for the web search comment, That's an avenue I had overlooked.
I'm tending more toward the 3pole option myself as time goes by and will suggest that I would be willing to install the 3pole and wire only 2 of the poles (leaving the neutral unswitched) if the inspector prefers unswitched. This way I can always go to the switched mode if a future code change or po.co. demand requires it. He may not be happy with that option, however, so I'll let him/her make the call.
I have been around long enough to witness 180* about-face changes in the code as new information and actual field experiences point out weaknesses and limitations of current (no pun intended!) practices. I have become well aware that the electrical safety code is a living document.
(I could also be forced to admit to more than a touch of obssessive-compulsive behaviour myself when it comes to elec. work that will ultimately be passed /failed by the personal discretionary judgement of a single individual that I may never see again!)
Sincerely,
STAINLESS