For R.C.

[wtdoor67]

If your company puts copper leads in each pots, what are the 3 factors that must be considered when choosing a lead?


If your fusing factor is 2.3 X the full load current what size fuse would a 37 1/2 KVA take? 2400/4160 voltage pot.

Had a single phase Kyle lock out once. Had about 4 laterals. Opened them and the Kyle would hold and hold. Close the laterals and it would lock out. What's your guess?


Here's one of my favorites. You have a 3 pot Wye/Delta bank with the usual lineman hookup. No let's make it different. The 2 outside pots use the H1 bushings and the middle pot uses the H2. Hook the secondary as you wish.

2 spans away you have the same hookup bank but it faces the opposite direction. It has to be hooked to parallel the first. How do you wire it?

Gotta get off this Limbaugh stuff. Anyway if you have stuff like this Swimp never comments.

Lotta these things have been up before, hopefully the old hands will leave off until R.C. has time to comment.

You need to rig a handline as high as you can on a pole. There is no becky on the line. You're sent up a steel choker and the handline. How do you rig?

There's open wire 120/240 volt secondary on the pole. Also a 3 pot 120/208 bank. It's desired to change out the bank to the next larger size pots. How do you do it without a kill?


Which would require larger secondary leads, a single phase 480 pot or a 240 volt pot?

Could you use a 240/480 pot in a 120/240 delta bank at all?

Could you hook up a corner grounded delta secondary with triplex?

[rcdallas]

If your company puts copper leads in each pots, what are the 3 factors that must be considered when choosing a lead?

Not too sure on this one, we'll use a TLS lug or CU hy lugs, no aluminum connectors like popsicle sticks...help me out on this one.




If your fusing factor is 2.3 X the full load current what size fuse would a 37 1/2 KVA take? 2400/4160 voltage pot.

20 amp fuse closer to 21, but 20 seems more realistic size for a fuse...though I could be wrong. 37500 / 4160 x 2.3 = 20.73 also since that's a delta I'm just guessing I'd go by 4160 instead of 2400 based on the fact I seen DTE Energy use a single cutout. Again I could be wrong.


**EDIT** since the pot is labeled 2400/4160 It'd be a WYE connection on the high side 37500/2400x2.3=35.93 -- I'd go with a 35 amp fuse. I'm pretty sure if it's a delta pot it would just say 4160 on the label. I've never seen anything less then 7200...2400/4160 I'm sure it could exist.





Had a single phase Kyle lock out once. Had about 4 laterals. Opened them and the Kyle would hold and hold. Close the laterals and it would lock out. What's your guess?


To me that's kind of a broad question, could be a cold load pickup issue... if that's the case close one lateral at a time wait a few minutes then close the next.

Or it could just be too much load now and it's locking it out.



Here's one of my favorites. You have a 3 pot Wye/Delta bank with the usual lineman hookup. No let's make it different. The 2 outside pots use the H1 bushings and the middle pot uses the H2. Hook the secondary as you wish.

Ok... see my attached.


2 spans away you have the same hookup bank but it faces the opposite direction. It has to be hooked to parallel the first. How do you wire it?

Never paralleled a bank, but I'll stab at it with build it the same, mirror all your phasing high side along with your secondary and before actually connecting the secondary to each other check for 0 volts.



Gotta get off this Limbaugh stuff. Anyway if you have stuff like this Swimp never comments.

Lotta these things have been up before, hopefully the old hands will leave off until R.C. has time to comment.

Lucky I had time...WAS on my way to hurricane alex but found myself turned around.


You need to rig a handline as high as you can on a pole. There is no becky on the line. You're sent up a steel choker and the handline. How do you rig?

I'd take that steel choker and throw it back down and pull the eye nut I keep in my ditty and put it on the ridge pin bolt, problem solved. :) How would you use it, if you had to? I really don't know, screw driver maybe?


There's open wire 120/240 volt secondary on the pole. Also a 3 pot 120/208 bank. It's desired to change out the bank to the next larger size pots. How do you do it without a kill?

Ummm.... that's a thinker, I suppose you could temporarily install two more pots (cutover or not don't matter 120/240 you just loose half kva if not paralled) on one of the inline poles, just quarter them in there, on the wye bank you'd want to make sure you'd mark the legs of the service for each one and pay attention to what primary phase each one of those secondary legs are in and basically bust onto the service with your temp pots and the secondary pots, again paying **** good attention to your phasing, use your voltmeter and look for 0 volts. Then cut the existing service near the secondary bushings, tape it all up in the clear and get after it.




Which would require larger secondary leads, a single phase 480 pot or a 240 volt pot?

240 volt pot, the higher the voltage the lower the current thus smaller AWG wire.


Could you use a 240/480 pot in a 120/240 delta bank at all?

Yes sir, take a 7200/12470 120/240 w/ a 14400/24900 240/480... I'd put a smaller lightning arrestor on the 14.4 pot though.


Could you hook up a corner grounded delta secondary with triplex?

You *could* use the grounded leg on the neutral. Here we use quad and just bust the service neutral onto the system neutral for safety.

[wtdoor67]

You're pretty well on for the most part. On a lead wire in a pot there are basically 3 things you look for. Resilency, Insulation and Current capacity.

Resilency, well it's got to be large enough it doesn't break in the wind etc.
Insulation, usually 600 volt wire I think.
Current capacity, got to go along with your fusing factor. If it's 2.3, then it's gotta exceed the full load secondary current of the pot by 2.3. Most places just have a chart you go by. It's what most people go by but I wondered how they came up with it. Lotta places use #2 cu. for 25's and below simply for resilency. Current capacity is much more than the fusing factor, but it won't break easily.

The little popsicle, firecracker things. I think they're actually copper. Someone will correct me if wrong. Got some kind of coating so they'll go with Alum.

Yeah you caught yourself on the fuse sizing. Most people just memorize the chart but I wanted to know why.

2400/4160? Common as flies. Still a lot of it around. Pots labeled like that will work in a 2400 Delta system or 4160 Wye.

The Kyle that wouldn't hold? Nothing exotic, just a bad Kyle. Thought at first someone had slugged a lateral but I just bypassed it and it was okay. Took it down and repaired it later. Saw one once that was tripping on overload. It would hold about 30 minutes and then trip. Later put in a higher amp Kyle.

Paralleling a bank? Used to do it a lot. You're right. Mirror image. Long as the polarities are the same, pretty simple. You run across people that don't know though.

Sorry on the choker rigging. I should have specified a bare pole. Transmission thing I guess. Just choke the steel sling around the pole near the top and drape the other end over the center of the top and adjust it until you have the snap of the handline just over the pole top and laying horizonal on the top of the pole. Kapesh?

On the pot changeout I said there was open wire secondary on the pole. If it's 120/240 half the coils will parallel with your 208 paralleled pots. Just make sure the 120/240 pot is on the same primary as the one you're changing out. Used to do this is Saudi all the time.

You didn't fall for that lead thing on the 240 or 480 pot did you?

What I was referring to on using a 480 pot in a bank was just using it as a power pot and paralleling the coils or using just half of the coils.

Your method would work though, however if you ever had the other pot fuse open it would backfeed 14.4. Not good.

I've seen that triplex on the corner grounded secondary a few times. Guy told me he opened the messenger once on one of those and it lit him up.

Overall though, good job buddy. Keep your rubbers on and your feet out of the grounds.

[MI-Lineman]

You're pretty well on for the most part. On a lead wire in a pot there are basically 3 things you look for. Resilency, Insulation and Current capacity.

Resilency, well it's got to be large enough it doesn't break in the wind etc.
Insulation, usually 600 volt wire I think.
Current capacity, got to go along with your fusing factor. If it's 2.3, then it's gotta exceed the full load secondary current of the pot by 2.3. Most places just have a chart you go by. It's what most people go by but I wondered how they came up with it. Lotta places use #2 cu. for 25's and below simply for resilency. Current capacity is much more than the fusing factor, but it won't break easily.

The little popsicle, firecracker things. I think they're actually copper. Someone will correct me if wrong. Got some kind of coating so they'll go with Alum.

Yeah you caught yourself on the fuse sizing. Most people just memorize the chart but I wanted to know why.

2400/4160? Common as flies. Still a lot of it around. Pots labeled like that will work in a 2400 Delta system or 4160 Wye.

The Kyle that wouldn't hold? Nothing exotic, just a bad Kyle. Thought at first someone had slugged a lateral but I just bypassed it and it was okay. Took it down and repaired it later. Saw one once that was tripping on overload. It would hold about 30 minutes and then trip. Later put in a higher amp Kyle.

Paralleling a bank? Used to do it a lot. You're right. Mirror image. Long as the polarities are the same, pretty simple. You run across people that don't know though.
Sorry on the choker rigging. I should have specified a bare pole. Transmission thing I guess. Just choke the steel sling around the pole near the top and drape the other end over the center of the top and adjust it until you have the snap of the handline just over the pole top and laying horizonal on the top of the pole. Kapesh?

On the pot changeout I said there was open wire secondary on the pole. If it's 120/240 half the coils will parallel with your 208 paralleled pots. Just make sure the 120/240 pot is on the same primary as the one you're changing out. Used to do this is Saudi all the time.

You didn't fall for that lead thing on the 240 or 480 pot did you?

What I was referring to on using a 480 pot in a bank was just using it as a power pot and paralleling the coils or using just half of the coils.

Your method would work though, however if you ever had the other pot fuse open it would backfeed 14.4. Not good.

I've seen that triplex on the corner grounded secondary a few times. Guy told me he opened the messenger once on one of those and it lit him up.

Overall though, good job buddy. Keep your rubbers on and your feet out of the grounds.

THAT USE TO DRIVE ME NUTS IN DETROIT WITH ALL THE BANKED TUBS! Guys from out of town always would argue you had to flip flop the phasing!:rolleyes: I use to tell them forget about lookin at the **** tub and just follow the phasing from high side to low! Like you said a mirror!

[topgroove]

we still have a ton of 240 delta banks that use #2 triplex. :D

[rcdallas]

I gotcha on the open secondary to use with the wye bank, I just missed a few words typing in the 30 minutes it took me to reply and quote and stuff... I said I'd hang two temp pots, just didn't mention grabbing a hot leg off the secondary.

Let me ask you this... how do you fuse a single phase pot on a delta system?

MI Lineman just loves it one I say the one cutout, so you would double the fuse size on a deal like that, or leave it in half?

As far as the recloser goes, that's a new one... when I was with the coop there was just a couple of times when I was on the service truck where we had checked for a recloser, my old lineman would tell me to take off the load side (all where on hot taps) and when you close it in if you heard a loud thump it was a bad recloser. (that is if I remember right)

[Pootnaigle]

Ummmm as far as yer fusing goes an amp is an amp no matter if its tween a hot anda ground era hot anda hot so to answer yer question ya fuse that bad boy for sactley what yer fuse chart sez . when one side blows the transformer coil is no longer energized.

[rcdallas]

Ok... now then if you have a single phase pot on a delta with TWO cutouts, you would then still fuse both cutouts the same as if you would if you hand only one cutout?

It just seems in my little world if you have two cutouts essentially half the load is coming from one phase and the other half is coming from the other, and you'd only want to fuse half.

[LEAFMAN]

We use 3/0 copper leads on all of our trans banks.

[Pootnaigle]

Ummmmm the amp flow is tween the 2 phases it dont meet inna middle n go away dude............. So yes you wud fuse em bof wif whatever yer fuse chart sez.
If'n ya stop fera second n think onnit sum........ how would half yer current come frum one phase n the other half cum from the other.... Jus aint possible. Ittsa same as if yer dealin wif a wye system....... all of the current flows thru the coil.

[wtdoor67]

According to the fusing factors I've worked under you would be wasting copper on some pots and would not have enough size on others.

For example a 100 KVA 120/240 pot would have a full load secondary current of about 418 amps. If the fusing factor was just 200 % then you'd want wire that would withstand 836 Amps. Ain't no way 3/0 would hack that. In a general sort of way I think a lot of companies intend for typical house pots to be overloaded about 1 1/2 their full load for perhaps a couple of hours during peak times. Even then you'd want wire on a 100 KVA to withstand a little over 600 Amps.

I used to have a foreman who would routinely wire up a 480 bank with 15 KVA pots with 4/0 Cu. Now why would you need 480 Amp wire in a pot that was about 30 Amps at 100%? Just stupid. A waste of wire.

I've seen some guys wire a pot with only leads sufficient to handle the load that was then attached. Later on someone would add an additional service until the pot leads became overload necessitating someone to go out and kill the bank and put on bigger leads. Best to just put the max. wire needed in on the first installation and then the servicemen can just add services as needed. Sometimes I think subjects such as this ought to be addressed in apprenticeships, but I never knew of it.

[Pootnaigle]

Along with that Ive seen many installations on large single phase transformers where someone used big copper in the secondary bushings and very small copper in the neutral.I spoze if the load is balanced it'll work but if that load aint balanced and its unbalanced enough thats a prollem waitin to happen.

[MI-Lineman]

Ummmmm the amp flow is tween the 2 phases it dont meet inna middle n go away dude............. So yes you wud fuse em bof wif whatever yer fuse chart sez.
If'n ya stop fera second n think onnit sum........ how would half yer current come frum one phase n the other half cum from the other.... Jus aint possible. Ittsa same as if yer dealin wif a wye system....... all of the current flows thru the coil.

HEY RC I Think what he means is you're gonna have a certain amount of draw through both the cutouts together but at anyone time again one phase could have more draw than the other! Anyways we fused our 50kva's (we used mostly 50's) at 40kva! Yep! Fused the sh!t out of that overloaded crap!:D

OH YEAH....4800 BTW!

[wtdoor67]

The fuses on a Delta connected pot would probably be at least the same size as a Wye connected pot, like a 2400 Delta pot or a 2400 pot on a 4160 Wye. You'd have to check your co's fusing scheme. I'm sure they got some in some of your specs or standards. Cart home some of those spec books. They have some interesting stuff sometimes.

What Poontangle says about the fusing etc. makes sense when you think of the full load of a pot. Do you know how to tell if a pot is overloaded by just a read on an amp meter? Lotta people don't.

The one usually given for example is a 120/240 pot of 25 KVA size. Do you total the read of the neut. and the 2 phases or what, to decide if it's overloaded? You may know already, I don't know.

[rcdallas]

I have a half baked idea on what I came up with in my head to tell if a pot is overloaded or not. Maybe there is a easier way...

For example:

25kva = 25,000 watts

50 amps on one leg 60 amps on another = 110 amps total, in that case there I should see 10 amps on the neutral, however I don't read the neutral, just the hot legs.

Using ohm's law I*E=P (Current X voltage = Watts)

110 x 120 = 13,200 watts

I should be able to get a total of 208 amps (104 each leg) out of a 25kva pot running at exactly 120 volts.

As far as the fusing charts go, honestly I never looked at one. Tomorrow I'll go through my standards books and see what I find. Predominately almost everything we have in my area is 7200/12470, they all say just 1/4 the kva and stick that in there. I've brought up on different primary voltages that's not right for a couple of other subs we have... I just do what they tell me on that. Kinda goes back to the open wye delta with leading and lagging phases along with a counter clock wise rotation 55 degrees vs 60 degrees.

I'll have to think on the delta fusing part a bit to get it to click.

[wtdoor67]

It's not something a lineman absolutely needs to know cause I've worked with plenty who didn't. But the more you learn about electrical stuff the better off you are.

I used to know a rule of thumb for an open Delta bank but I've forgotten it.
On the pot lead thing, most co's have a chart you can select your transformer size and pot lead size.

Took me a while before I discovered that wire sizes varied although they were listed as the same.

When do you top out?

[rcdallas]

It's not something a lineman absolutely needs to know cause I've worked with plenty who didn't. But the more you learn about electrical stuff the better off you are.

I used to know a rule of thumb for an open Delta bank but I've forgotten it.
On the pot lead thing, most co's have a chart you can select your transformer size and pot lead size.

Took me a while before I discovered that wire sizes varied although they were listed as the same.

When do you top out?

Now when it comes to calculating for a bank, I'll have to rip open one of my intermediate books for that... see if you can remember how to calculate, I know it got more involved then a single phase pot.

I top out in just over a year... then maybe after about another 5-10 years I'll be worth a ****. :D

[rcdallas]

If you can find an easier way, or rule of thumb or something easier then this... too much. :confused:



Here's what I have for 3 phase open delta bank example.

An open delta 120/240 4 wire bank has the following values:

I1 = 230A
I2 = 260A
Ihi = 110A
In = 30A

3 phase KVA = (1.73) x (240 / 1000) X 110 = 45.7 KVA

1 phase KVA = (240 / 1000) x (260 - 110) = 36 KVA

KVA on Power XFMR = (.577) x (45.7) = 26.4 KVA

KVA on lighting XFMR = (36) + (.577 x 45.7) = 62.4kva

----

Here's another example:

Open wye-Open delta 480v 3 wire 3 phase

[wtdoor67]

Bud what I was referring to was the max load for a 2 pot bank. I think it was about 20 to 25 horse. Anything more required a closed bank.

[rcdallas]

Bud what I was referring to was the max load for a 2 pot bank. I think it was about 20 to 25 horse. Anything more required a closed bank.

Oh... ite.

746 watts in a horse @ 25 horse = 18.6kva

In an open delta I don't think I ever built anything more then a 25 on the lighter and 15 on the power.

Something about a open delta where the pots are 57% efficient vs a closed.

Closed delta biggest I built was 3 333's, 7200/12470 down to 2400/4160, big ******* that was.

[Pootnaigle]

Ummmm they make a full load current chart and if you read it you will find that a single phase 240 volt 25 kva transformer is considered fully loaded at 113 amps.( I are using my memory here and its gettin rusty like everthin else I have)
It always struck me as kinda strange that a customer with a 200 amp service was required to have a minimum of 2/0 cu in the weatherhead yet the company would serve em with a 25 Kva pot that was overloaded past 113 amps. Not only that but they may have a couple of 200 amp services on that same 25 kva pot.
In any case the chart is purdy handy for figuring not only the secondary current max but also for figureing the primary fusing since it also tells full load current on a 25 kva at different primary voltages.Many Transformer manufacturers make a booklet containing the full load current charts for single phase as well as 3 phase transformers. Failing that Theres one in every UGLY'S book.

[wtdoor67]

Oh... ite.

746 watts in a horse @ 25 horse = 18.6kva

In an open delta I don't think I ever built anything more then a 25 on the lighter and 15 on the power.

Something about a open delta where the pots are 57% efficient vs a closed.

Closed delta biggest I built was 3 333's, 7200/12470 down to 2400/4160, big ******* that was.


333 is the biggest pots I've ever hung. I think for awhile a 333 was the largest polemounted pots you could get but I understand now they make an even bigger one.

The 20 HP rule I think is fairly general. However if you ever been around a Muni. you will find they have their own rules.