Temporary power tap KCP&L & upgrade

[Torque1st]

Does anyone know what KCP&L supplies in the KC area for a temporary power tap while upgrading a service?

I am upgrading my electrical service from a 100A FPE panel to a 200A Siemens panel. The power company, KCP&L, is providing a "temporary power tap" while I am doing the work. I can find their definitions of a "construction tap" which consists of a pole, meter, and a couple 120VAC outlets. What I think I need is a meter with a couple outlets AND a 30-40A breaker with a SO cord of some type that I can use to power my circuits temporarily in several configurations while I work. It is freezing cold outside!!! I could turn the 30-40A breaker on and off as required while I work. A lockout box would be nice.

I have about 40' of triplex from the pole to the mast. I am planning on using a 2" rigid conduit mast and weatherhead. #2/0 copper power conductors with a #4 copper grounded conductor. I need 18" of clearance over my roof overhang so I figure 30" of conduit above the roof will do the job with drip loop etc. I have #6 solid copper wire running to my water pipe. I also have a #6 solid copper wire to my 10-12' long 1/2" diameter copper clad supplemental electrode driven below the meter box itself. The supplemental electrode is connected to ground in the meter box at the moment. KCP&L now says they do not allow that. Could I clamp it to the #4 copper grounded conductor in the LB below the meter before the conduit enters the house? I would like to have as close to a straight shot to ground as I can get for lightning transients.

I will probably use PVC ENT for the run from the meter box to the panel just for ease of fabrication. It is close to being a straight drop from the meter to the main panel in the basement. Three LB's will probably do the job.

There is another ground rod placed by the telephone company about 20' away from the meter and maybe 35' from the water line. Do I need to bond to that ground rod also?

The transformer at the pole is only 15KVA and serves two dwellings with 100A service. If my calculations are close that is only about 60A, or 30A per residence. I have a welder, kiln, lathe, mill, and a real 3HP compressor. I can see needing 130A for several minutes at a time. I have been getting by by running around and making sure stuff is off. The ex messed me up while welding by turning on the oven once. Will KCP&L upgrade the transformer at the same time? I don't want to fry the transformer and put me and my neighbor out of power when it is 105°F outside.

Am I doing it correctly?

Thanks for your help. I can design and build machine controls and large motor control centers for use in the US, Europe, or elsewhere, but residential NEC conditions are confusing.

The KCP&L electric service manual:
http://www.kcpl.com/newconst/ess.html

 

[Torque1st]

The answer on the temporary power tap turned out to be unfastening the meter box from the wall, pulling the load side SE cable out, and installing three 2' long wires out of the meter can. Those wires were then bolted to the original SE cable with split bolts and tape. The meter was then plugged back in. So I am left with working the wires hot. They used to provide a setup with breakers like I described above but apparently the lawyers got to thinking, which is ALWAYS bad, and did away with the safer option in favor of live wires.

It also looks like I will just have to burn up the transformer to get it changed. I will call my service planner and see if I can avoid that situation.

Any answers or help on the conduit & wire size?

 

[Gigfy]

"Any answers or help on the conduit & wire size?"



I've read some of your old posts and you probably know a lot more about a lot of electrical than I do. If you're like me, you're pretty sure you already know how to do it, but bouncing it off the collective knowledge of a board may catch details one has overlooked. Here are my thoughts:

Years ago when I laid conduit, I used 2" for 4/0 aluminum triplex and there was plenty of room (These were feeds for 200 amp boxes.)

If you want something a little more authoritative you could examine conduit fill charts, if you could find one for Triplex.

Here is one for THWN and THHN:

http://www.jhlarson.com/ind_tables/fill/pvcfill.htm

As I understand it, in this instance the cross sectional area of the cables needs to equal 40% of the cross sectional area of the conduit.

In terms of wire size, as I mentioned we used 4/0 for 200 amp. I notice 2/0 copper carries a little less than 4/0 aluminum, so I don't have much of a comment about that, other than to reference the charts for wire size. 40' of triplex doesn't sound like a very long run, so I doubt voltage drop will come into play.

I'm not sure I understand your whole layout, but you seem to be running part of your run underground. If so, make sure where the cable exits the conduit, there are no sharp edges to eventually cut through the insulation of the cable. (I was once told the number one "call back" for cable repairs was where the cable entered the conduit below grade, and there was no elbow to prevent the conduit from cutting the insulation.) And remember to treat the Triplex like your baby (no scratches or nicks). And don't forget to have a good set of cutters on hand.

 

[Torque1st]

Thanks for the reply.

I am trying to bounce it off the "collective" to see if I have missed anything. I am a firm believer in "two heads are better than one". My electrical experience has been with machine design, industrial controls, motor control centers, microprocessors, and repairs around the home. I have rewired entire houses but I have never set a new meter or service.

The NEC is a mystery to me. I have a PDF copy of the 2002 code and paper copies of previous years. Finding anything in the NEC is frustrating. I am usually working to machine tool codes, UL, CSA, international codes, IEC, or the old VDE.

This service is entirely above ground. The meter box is on the side of the house directly below the mast. The main panel is in the basement just slightly offset from directly below the meter. The short run from the meter box to the main panel will be PVC through the rim joist.

I fixed up a temporary panel for myself from some old equipment I have. It is an old split bus FPE box from a garage sale which will work just fine for a temporary panel to allow me to turn on/off power during the actual upgrade. I will be installing it in a few minutes. I am backfeeding a 50A breaker and providing 2 ea 20A breakers to duplex outlets and a 50A breaker for the service to the old panel or a pigtail as required. That way I will always have power for droplights etc. The temporary outlets won't be GFI but oh well... I used what I had in the junk box. I lived without GFI for 30 years.

 

[foolishpride]

I found this, and it looks like 2" conduit is fine for your service mast. I know some power companies require 2 1/2" conduit.

www.kcpl.com/newconst/ess2007.pdf

You mentioned running 2/0 copper for your conductors. I think this is adequate, but some inspectors will require the next size larger. You mentioned a #4 Grounded Conductor. This term actually refers to the neutral, and must be sized at 2/0, to match your two hot conductors. You probably meant to say Grounding Electrode Conductor.

The old code books had an exception in them, to allow a #6 ground to your ground rod, or rods. I'm not up on current code, like I was years ago, but I believe the #4 should go to your water pipe. The other ends of these need to go to your panel, and bonded together I believe.

Are you sure the transformer is only 15 KVA? Yes, this is definately undersized.

Maybe mrb can chime in with anymore help you may need.

 

[Gigfy]

"This term actually refers to the neutral, and must be sized at 2/0, to match your two hot conductors."

As I recall, the old Triplex was sized with the neutral 2 sizes down from the lead conductors. Has this changed over the years?

 

[Torque1st]

I used this table for my service entrance conductors:

Table 310.15(B)(6) Conductor Types and Sizes
for 120/240-Volt, 3-Wire, Single-Phase Dwelling
Services and Feeders.

Conductor (AWG or kcmil)
Copper		        Aluminum or		Service or
			Copper-Clad		Feeder Rating
			Aluminum			(Amperes)

4			 2 				100
3 			1 				110
2 			1/0 				125
1 			2/0 				150
1/0 			3/0 				175
2/0 			4/0 				200
3/0 			250 				225
4/0 			300 				250
250 			350 				300
350 			500 				350
400 			600 				400

I believe this table gives the grounded (neutral) service entrance conductor size as referenced several places in the code. The service entrance is a center tapped transformer circuit so the neutral only carries the unbalanced part of the load. I believe that it does not need to be as heavy as the ungrounded conductors.

Table 250.66 Grounding Electrode Conductor for
Alternating-Current Systems

Size of Largest Ungrounded		Size of Grounding
Service-Entrance Conductor		Electrode Conductor
or Equivalent Area for			(AWG/kcmil)
Parallel Conductorsa
(AWG/kcmil)
						
Copper              Aluminum or      Copper         Aluminum or
                       Copper-Clad                         Copper-Clad
                       Aluminum                            Aluminum
				
2 or smaller       1/0 or smaller     8                6
1 or 1/0 		2/0 or 3/0 		6                4
2/0 or 3/0 		4/0 or 250 		4                2

Sorry about the jumbled table spacing, tab stops etc do not translate well.

I believe that this section of code references the size of conductors to the ground rod and water pipe:

250.66 Size of Alternating-Current Grounding Electrode
Conductor. The size of the grounding electrode conductor
of a grounded or ungrounded ac system shall not be
less than given in Table 250.66, except as permitted in
250.66(A) through (C).
FPN: See 250.24(B) for size of ac system conductor
brought to service equipment.
(A) Connections to Rod, Pipe, or Plate Electrodes.
Where the grounding electrode conductor is connected to
rod, pipe, or plate electrodes as permitted in 250.52(A)(5)
or 250.52(A)(6), that portion of the conductor that is the
sole connection to the grounding electrode shall not be
required to be larger than 6 AWG copper wire or 4 AWG
aluminum wire.

I have looked through the code but I may have missed some requirement in all the jumps back and forth in the NEC. What a nightmare! I am hoping some of the code guru's will check my "assumptions". Like I mentioned, I only have the 2002 code. In my city we are on the 2005 code.

 

[Torque1st]

By the way-

Installation of the temporary power tap panel went smoothly. The only problem I had was that one of the tap conductors pulled out of the meter box connection. I had the meter out so I did not have to work live. Working live with those heavy conductors would have been very difficult. Now I can shut off power as necessary.

 

[foolishpride]

I used this table for my service entrance conductors:

Table 310.15(B)(6) Conductor Types and Sizes
for 120/240-Volt, 3-Wire, Single-Phase Dwelling
Services and Feeders.

Conductor (AWG or kcmil)
Copper		        Aluminum or		Service or
			Copper-Clad		Feeder Rating
			Aluminum			(Amperes)

4			 2 				100
3 			1 				110
2 			1/0 				125
1 			2/0 				150
1/0 			3/0 				175
2/0 			4/0 				200
3/0 			250 				225
4/0 			300 				250
250 			350 				300
350 			500 				350
400 			600 				400

I believe this table gives the grounded (neutral) service entrance conductor size as referenced several places in the code. The service entrance is a center tapped transformer circuit so the neutral only carries the unbalanced part of the load. I believe that it does not need to be as heavy as the ungrounded conductors.

Table 250.66 [B]Grounding [/B]Electrode Conductor for
Alternating-Current Systems

Size of Largest Ungrounded		Size of Grounding
Service-Entrance Conductor		Electrode Conductor
or Equivalent Area for			(AWG/kcmil)
Parallel Conductorsa
(AWG/kcmil)
						
Copper              Aluminum or      Copper         Aluminum or
                       Copper-Clad                         Copper-Clad
                       Aluminum                            Aluminum
				
2 or smaller       1/0 or smaller     8                6
1 or 1/0 		2/0 or 3/0 		6                4
2/0 or 3/0 		4/0 or 250 		4                2

Sorry about the jumbled table spacing, tab stops etc do not translate well.

I believe that this section of code references the size of conductors to the ground rod and water pipe:



I have looked through the code but I may have missed some requirement in all the jumps back and forth in the NEC. What a nightmare! I am hoping some of the code guru's will check my "assumptions". Like I mentioned, I only have the 2002 code. In my city we are on the 2005 code.

According to Table 310.15 you referenced, 2/0 should be fine for your service entrance.

I think you're getting the terms Grounded Conductor, and Grounding Electrode Conductor mixed up. I know, it is confusing. The Grounded Conductor is the Neutral. The Grounding Conductor is your wires to your ground rods and/or water pipe.

Table 250.66 you referenced, is the wire size that must be ran to your ground rods and water pipe. That's not for sizing the neutral.

I'm pretty certain the Neutral must be sized like your two Hot Service Entrance Conductors. But I don't have access to any modern Code Books.

 

[Torque1st]

This is what I found when studying the NEC:

From:

310.15 Ampacities for Conductors Rated 0–2000 Volts.

...

(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services
and Feeders. For dwelling units, conductors, as listed
in Table 310.15(B)(6), shall be permitted as 120/240-volt,
3-wire, single-phase service-entrance conductors, service
lateral conductors, and feeder conductors that serve as the
main power feeder to a dwelling unit and are installed in
raceway or cable with or without an equipment grounding
conductor. For application of this section, the main power
feeder shall be the feeder(s) between the main disconnect
and the lighting and appliance branch-circuit panelboard(s).
The feeder conductors to a dwelling unit shall not be required
to be larger than their service-entrance conductors.
The grounded conductor shall be permitted to be smaller
than the ungrounded conductors, provided the requirements
of 215.2, 220.22, and 230.42 are met.

-Which basically refers back to: Table 250.66

Thanks for all the ideas guys. Keep them coming! They provide checks against what I have surmised from the nightmare code.

 

[oleguy]

art.250 only applies to grounds and grounding conductors.neutrals are grounded conductors.also in your code book,go to the back of book to annex D.the examples will tell you how to do a load calc.read all of example d1a.

 

[foolishpride]

This is what I found when studying the NEC:

From:


-Which basically refers back to: Table 250.66

Thanks for all the ideas guys. Keep them coming! They provide checks against what I have surmised from the nightmare code.

I believe Article 215.2 and 220.22 refer to Feeders only, and don't apply to your Service. Damn, I need a Code Book to look at.

 

[fefarms]

As other posters have mentioned, 250.66 refers only to grounding electrode conductors and has nothing to do with grounded conductors (neutral).

The neutral is sized according to the maximum unbalanced load. You do a load calculation similar to that used to pick the service conductor rating. You can rely on a certain degree of load diversity. There are formulas for this. The code used to specify that, regardless of calculated load, the neutral be no more than 2 wire sizes below the service entrance conductors, but this has been rescinded, and you can shrink it as much as you think you can justify from load calculations. As a practical matter, going with 2 wire sizes smaller for the neutral is reasonably economical and would be a conservative choice from a safety point of view in all but an especially pathological situatuin.

With regard to that 15KVA transformer, be aware that utility companies operate under different rules than the NEC. Transformers are sized based on maximum continuous load over a 3 hour period. It is expected that multiple dwellings would exhibit load diversity and further that maximum loads would not be sustained for 3 hours. A typical single family dwelling with a 200 amp service is supplied by a 25 KVA transformer. This is only half of what the naive calculation would call for, and yet it works fine because houses don't draw the 200 amps for hours at a time.

 

[Torque1st]

I am aware that the utility operates under their own rules under the "engineering supervision" exemptions in the code. That is why I used to have a 10KVA transformer feeding TWO houses with 100 Amp services with little #6 aluminum overhead conductors. My friends that work for the utilities tell me they accept a 150% overload on transformers etc. Basically because the loads are not continuous. A 15KVA transformer will supply about 60A continuous or 90A overloaded to the two houses. With my calculated loads and duty cycles I figure a 25KVA transformer will probably serve the two houses. I just don't want to find out the 15KVA transformer is inadequate on some hot August afternoon. Otherwise I can just turn on all my stuff and fry that 15KVA transformer when the weather is nice. An emergency repair is never as efficient as a planned replacement regardless of the fact that it destroys a perfectly good transformer and the under voltage and transients may harm my equipment.


I have been through the load calculations, For the life of me I cannot figure out what load a 240V appliance puts on the neutral except for small ancillary loads like controls and lights, a few watts at most so why the 70% BS in the code??? Most of my heavy loads and the reason I am upgrading the service are all 240V loads that place no load on the neutral whatsoever.

Compressor 3HP 17A = 4.1KVA
Table saw 5HP 27A = 6.5KVA
Lathe 7.5HP 39A = 9.4KVA
Mill 1.5HP 10A = 2.4KVA
Welder 50A (30A) = 7.2KVA (duty cycle applies)
Kiln 27A = 6.5KVA (this is a continuous load for hours)

The above tools will not be used all at once. The major loads that might be on all at once are the kiln, lathe, and compressor plus the normal house load. I normally operate only one tool at a time. My multi-tasking ability has weakened with age.


My house load is lighter than most.

My appliances:
Electric oven 240V 5.6KW (rarely used)
Air conditioning 240V 3KVA
Blower 7A 120V

Most of the below loads are insignificant due to the duty cycle.
Electric dishwasher ?A
Microwave 1.6KW (5-10 minutes/day)
Refrigerator ?A
Disposer ?A
Washing machine
Lights (even these are well balanced on 4 circuits & mostly CFLs)
TV, stereo, computer small tools and appliances.

Gas: cook top, heat, water heater, dryer.

The above loads (minus tools) operate on the original 100A service rarely exceeding 40A per leg and the neutral load rarely goes above 10A. I have watched with my meters. All of my calculations and observations would indicate I could probably use a 12AWG grounded conductor with capacity to spare. -hehe

Even a #4AWG grounded conductor will accommodate a 100A service current. With a 200A service it takes a hell of a lot of imbalance in the 120V loads to generate 100A of neutral load. If I switched every 120V load I have to operate on one leg and turned them all ON I don't think I could develop a 100A load on the neutral.

Sometimes the codes give outrageous solutions to nonexistent problems. That is also why they have those notes about "engineering supervision" in most codes.

 

[Torque1st]

As I see it the key is:

230.42 Minimum Size and Rating.
(A) General. The ampacity of the service-entrance conductors
before the application of any adjustment or correction
factors shall not be less than either (1) or (2). Loads
shall be determined in accordance with Article 220. Ampacity
shall be determined from 310.15. The maximum allowable
current of busways shall be that value for which
the busway has been listed or labeled.
(1) The sum of the noncontinuous loads plus 125 percent
of continuous loads
(2) The sum of the noncontinuous load plus the continuous
load if the service-entrance conductors terminate in an
overcurrent device where both the overcurrent device
and its assembly are listed for operation at 100 percent
of their rating
(B) Specific Installations. In addition to the requirements
of 230.42(A), the minimum ampacity for ungrounded conductors
for specific installations shall not be less than the
rating of the service disconnecting means specified in
230.79(A) through (D).
(C) Grounded Conductors. The grounded conductor shall
not be less than the minimum size as required by
250.24(B).

The applicable part of 250.24 seems to be:

(B) Grounded Conductor Brought to Service Equipment.
Where an ac system operating at less than 1000 volts is
grounded at any point, the grounded conductor(s) shall be
run to each service disconnecting means and shall be
bonded to each disconnecting means enclosure. The
grounded conductor(s) shall be installed in accordance with
250.24(B)(1) through (B)(3).
Exception: Where more than one service disconnecting
means are located in an assembly listed for use as service
equipment, it shall be permitted to run the grounded conductor(
s) to the assembly, and the conductor(s) shall be
bonded to the assembly enclosure.
(1) Routing and Sizing. This conductor shall be routed
with the phase conductors and shall not be smaller than the
required grounding electrode conductor specified in Table
250.66 but shall not be required to be larger than the largest
ungrounded service-entrance phase conductor. In addition,
for service-entrance phase conductors larger than 1100 kcmil
copper or 1750 kcmil aluminum, the grounded conductor
shall not be smaller than 12½ percent of the area of the
largest service-entrance phase conductor. The grounded service
entrance conductor of a 3-phase, 3-wire delta service
shall have an ampacity not less than the ungrounded conductors.

-Which brings me back to the #4 copper conductor specified in 250.66



I have looked at the existing dwelling and farm building calculations etc etc because my service is unique. When I am gone my machinery (toys) will be sold off and the entire house will be back in a state where the 100A service would be quite adequate. I anticipate there will be many more electrically powered devices in the future but those items will be far more efficient than today's units.

Just look at the lighting loads specified in the code. With lighting going over to CFLs and other fluorescents and eventually to LEDs and then to who knows what else the lighting loads drop considerably. It seems refrigerators and AC units using mechanical refrigeration may be in for some big changes soon. Kitchen appliances are getting more efficient. Insulation is getting better. My new windows made a huge difference in my heating and AC bills. I am still waiting for the Fifth Element to drop out of my autowash shower though.

 

[hidollartoys]

Are you asking...."Do I wire this to code or not to code?" Your arguments (discussions) concerning the code are warranted, and objective but do not have any bearing on the fact that your AHD requires your dwelling wiring to be accomplished to the code requirements, at a minimum.

For the sake of simplicity and based on the length of your run, it would just be simplier to install (3) entrance conductors of the same gauge. You are required to install "2 entrance service conduit and the required cu conductors will fit w/o any issues.

 

[Torque1st]

My following of the code references brought me to the #4 copper neutral. Which according to my own calculations is oversized as is. I just want to know where in the code it says anything different. Service entrance cable already uses an undersized neutral. I will be using individual wires though and they have to be "color coded" per the NEC. Bare copper is sold for this purpose and meets the color coding requirement.

I am required to use a 2" mast but I will probably use a 2-1/2" mast. I have some prime examples of what happens when 2" mast is used with a long cable run and no guy wires right across the street. I have a large tree and limbs to consider with my shorter drop. The PVC conduit from the meter box to the panel will probably be 2".

It is just the engineer in me that says the glass is twice as large as it needs to be.