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Help me design my service pedestal

7K views 39 replies 10 participants last post by  zappa 
#1 · (Edited)
The only building on the property is a barn and I’m in the process of trenching primary to a pad mount transformer.
A house, and eventually maybe, a workshop and a larger barn will be added in the future.
The green rectangles are showing flat building sites that I'm limited to.
The diagrams of the pedestals are not to scale or detailed but just to get a general idea. There will be more space left over for future stuff.
Some of the future buildings may be subbed from other buildings but I know that the house, existing barn, and workshop will come off of the pedestal.
I want to design the pedestal so I don’t have to tear out any existing work, but to add on for the future.

Conduit, raceway, which would be the better choice?

Any suggestions, even for the small details would be greatly appreciated.

I just learned that service can be extended to buildings with 2 unfused hots and a neutral. Am I going about this the wrong way by having the fused disconnects? Can 3 conductor service still be extended on the other side of the generator transfer switch? I would rather stick with 4 conductor if it's safer.

Thanks!!





 
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#2 ·
I wouldn't suggest disconnects or to have a transfer switch up there.
When you need to do or later change something? Rent a Ditch Witch.

Each building will get it's own sub panel when it gets built.
Don't put too much concrete down or too deep until then.

Interconnections between the buildings will/should be limited to
a few yard lights with 3 and 4 way switching.

KISS.
 
#7 ·
I wouldn't suggest disconnects or to have a transfer switch up there.
When you need to do or later change something? Rent a Ditch Witch.

Each building will get it's own sub panel when it gets built.
Don't put too much concrete down or too deep until then.

Interconnections between the buildings will/should be limited to
a few yard lights with 3 and 4 way switching.

KISS.
I'm sorry, I don't understand any of your suggestions. If I don't use a pedestal I will get a transformer close to the existing barn with a meter mounted on the barn. Most of the other buildings would be too far to run off of the transformer.

Yes, there will be panels in the buildings.

Lights and switches?
 
#6 ·
I would add a basic cut off switch right after the meter. That way you can cut your service completely off if any maintenance needs to be done on anything else including the generator transfer switch. Also a great way to test the transfer switch by simulating a power outage.

I would also look at maybe adding all the extra stuff in a mini building of some sort, but keep the meter outside so it can be read.
 
#8 · (Edited)
I would add a basic cut off switch right after the meter. That way you can cut your service completely off if any maintenance needs to be done on anything else including the generator transfer switch. Also a great way to test the transfer switch by simulating a power outage.

I would also look at maybe adding all the extra stuff in a mini building of some sort, but keep the meter outside so it can be read.
The transfer switch would need to be service rated and should have a main breaker if it's an ATS.
 
#20 · (Edited)
You have a very good point Julius. I'm fascinated with older stuff mainly because it is built so well and I will be using a 1961 military generator. It's not quite large enough at 15KW but military equipment is very underrated and I'll bet it will do 18KW 24/7 without breaking a sweat. I want to have power available to the whole property but I will have to be careful with how many things are running at one time by selecting breakers in my house panel. Emergency back-up are the key words here. This property is so far back in the woods there will never be an address for it and as long as I have enough power for the essentials I will feel blessed and I get the enjoyment of using my old crap. :laughing:



 
#21 · (Edited)
I like the first diagram.

I'm not sure about the generator but likely it has neutral and ground bonded. If so IMO you need to have a 2 pole double throw transfer switch meeting the specifications that brric mentioned.

I would advise you to work closely with the utility and building authority on the generator installation.

I'm not sure how long your going to be before building the dwelling but you will need some form of temporary power during its construction. You probably already have that figured out.

There isn't much reason to add equipment to the distribution point to feed anything other than the existing barn.

You mentioned being allowed 3 wire unfused service from the distribution point (common pedestal) to each outbuilding and dwelling and only one meter ?? I'm not real familiar with that and I'm not real sure how you get around not having a service disconnect(s) grouped at the common pedestal. Maybe you have a service disconnect with ocpd at the pedestal and they allow 3 wire tap feeders to the buildings and dwelling with the ocpd in the building subpanels .

At any rate if you have service equipment at the pedestal and ocpd disconnects for each building and dwelling with 4 wire feeders to the buildings and dwelling sub-panels that would be compliant. My point being service disconnects must be grouped at the pedestal.
 
#22 ·
I like the first diagram.

Thanks for your valued input. I have never worked with a trough so I don't have any experience to go on.

I'm not sure about the generator but likely it has neutral and ground bonded. If so you need to have a 3 pole double throw transfer switch meeting the specifications that brric mentioned. This allows you to switch the neutral from the utility to that of the generator without having those dreaded parallel paths due to the bonding of neutral and ground at the generator and service equipment (transfer switch). Essentially it will make the generator a separately derived system and you will need a ground rod at the generator.

The generator has seperate neutral and ground.

I would advise you to work closely with the utility and building authority on the generator installation. Will do.

I'm not sure how long your going to be before building the dwelling but you will need some form of temporary power during its construction. You probably already have that figured out.

It's going to be quite a while, money is tight and I want to do a lot of the work myself. I want to build or buy a small shed for the generator which will be close to the pedestal and I would like a small circuit for lights and receptacles. My well will most likely be in the same area also which has me thinking about using a meter main (meter and small panel in one enclosure) with feed through lugs at the bottom of the bus bars. I'm thinking that would be an easy way to provide some small circuits in that area plus an outdoor receptacle for power.

There isn't much reason to add equipment to the distribution point to feed anything other than the existing barn.

I was trying to show future equipment so yes, there will initially be one disconnect.

You mentioned being allowed 3 wire unfused service from the distribution point (common pedestal) to each outbuilding and dwelling and only one meter ?? I'm not real familiar with that and I'm not real sure how you get around not having a service disconnect(s) grouped at the common pedestal. Maybe you have a service disconnect with ocpd at the pedestal and they allow 3 wire tap feeders to the buildings and dwelling with the ocpd in the building subpanels.

I need to look into this as well. I was going off of comments by J.V. and yourself and I don't know what is allowed. A friend in SD has a similar setup (service extensions) but it is overhead. His POCO has multiple unfused feeders bugged and taped at the top of the pole. It's kinda scary having long lengths of large unfused conductors but that's what they do. I guess in my situation they would be spliced together in a j-box or trough. I think having a generator transfer switch or some sort of disconnect right after the meter will prohibit me from doing this.

At any rate if you have service equipment at the pedestal and ocpd disconnects for each building and dwelling with 4 wire feeders to the buildings and dwelling sub-panels that would be compliant. My point being service disconnects must be grouped at the pedestal.
Thanks for your time Stubbie. :)
 
#23 · (Edited)
Just wanted to add that I really get nervous when it comes to these generator installations as there is a lot to understand about the correct bonding and whether or not the transfer switch is the service equipment or not the service equipment.

In your first diagram the transfer switch is the service equipment and this makes a difference about switching the neutral. I believe I was in error on my original advice based on the location of your transfer switch. IMO you would not switch the neutral and would use a DPDT transfer switch rated as service equipment to at least match your service size in amps. This allows bonding of the neutral and ground at the service equipment.

I have edited my 1st post to correct this error. My apologies I've been retired for a few years and I'm a little rusty on this generator stuff..

I'm going to attach a utility link that will show you the differences. Just consider some on site professional help during the installation or if possible get a guide like I have attached from your power company.

In your case your interested in figure 2 or 3 depending on what your power company approves.

http://www.alliantenergy.com/wcm/groups/wcm_internet/@int/documents/document/012676.pdf
 
#25 ·
Before I can discuss more on the generator unit can you run me the model number and the voltage on the name plate due most miltiary generators typically useally have triphase supply and to run on single phase it can get little tricky if not carefull with it.

The other thing when you decided to pick a service size I know many place will provide 200 amp service without issue however when you get into 320 amp ( 400 amp ) service this will become a game changer due some POCO will use straight 320 amp meter socket and other will use the CT's ( current transfomer ).

I know in state of Wisconsin which I have dealt from time to time for non farm useage it can get away with 320 class socket but for farm no it have to be CT'ed for other POCO's that will varies a bit so you will have to talk to them and see what is their specs on that.

Ditto with meter socket type some will provide you one and most case no ., the customer will own meter socket but the meter itself is POCO item but anything else is customer owned even with lateral run ( this you will have to check on that carefull some will cover both primary and secondary but most will say secondary side )

15 KW generator is ok for basic load as long you use the MTS ( Manual transfer switch ) but ATS ( Automatique Transfer switch ) it may not meet the code so that is a catch 22 there.

Merci,
Marc
 
#26 ·
Hi Marc, thanks for looking in. The generator is a couple of hours away at my property and I don’t have the model but I can explain some things. The generator has 4 different shorting bars to configure the output. The one in the picture (with 14 nuts in 2 rows) is for Y 120/208 3 phase and I have since installed the bar for 120/240 single phase. I can’t remember the other 2 bars but I think one is for a delta connection.

An interesting note about this model. Its purpose was intended as a back up generator for another generator system. It spent most of its life standing ready in case the primary generator failed so even though it’s 50 years old it only has 43 hours of runtime and is almost like new, operational wise.

My POCO doesn’t use CT’s until a 600 amp service so the 320 (400) would be a normal meter socket which I have to purchase. They said if I want 400 to just call them before they come out so they can bring larger secondary wire from the xfmr to the meter socket. I know it’s a load calculation thing but I would think they should install a 50KVA xfmr if I requested a 400 amp service. They are installing a 25KVA xfmr, the smallest they stock, for both 200 and 400 amp service. Nothing changes except the wire size and of course my service equipment which would be downsized to 200 amps as soon as possible because I won’t be using a 400 amp feed for any of the structures. So I'm not really sure if I should request a 400 amp service. It would be free at this point but it would cost me if I had the 200 amp upgraded in the future.

An ATS would be nice but I would like to keep it simple. Plus, I don’t like to start engines up and place them under load until they are warmed up nicely and besides, this generator is a very manual unit. I should be ok with my loads without too much intervention. I may want to turn the breaker off for the water heater while running the heat or A/C but we will see once things are installed. The barns would have battery maintainers but they draw next to nothing. My shop will have a large air compressor but I always turn them off unless I’m in the shop working.

I don’t know how reliable the grid will be but the overhead is very old and nasty looking and a generator will be nice if there are extended power outages. I’m laying 1800’ of conduit through 3 creeks and hilly terrain from the last pole up to the pad mount transformer.

I spent some time last night reading the NEC trying to figure out where service equipment ends and feeders take over. It would be nice if I could just have a meter socket, generator transfer switch, and a large enclosure or wire trough to splice all of my feeders in, present and future. I don’t mind the extra cost and labor of having all of the disconnects but the less equipment that is outdoors the better as far as reliability IMO. I do want to cover the pedestal with a lean-too structure that is only open in the front. It might be wise to place the generator shed first and install the service equipment on the side of the building with lean-too overhead unless there is a code problem with doing that. More reading, I hate trying to decipher the NEC. I called the AHJ a while back who will be doing the electrical inspection and they mentioned the Residential Building Code so that is something else I should be looking into.

Cheers

Cable management Electrical wiring Electronics Electrical supply Electrical network


This is before I bought the generator. It's all nice and clean inside now. You can see the other shorting bars clamped to the top of the vented panel towards the bottom.

Machine Vehicle
 
#28 ·
Cool that will be a good item to use for your meter box but before you jump on this make sure you snag the model number of that or print that pic and show that to the POCO so they can see if they can allow that type of meter socket in your area.

I think you should not have major issue with that if your POCO say ok with it.

Merci,
Marc
 
#29 ·
Cool that will be a good item to use for your meter box but before you jump on this make sure you snag the model number of that or print that pic and show that to the POCO so they can see if they can allow that type of meter socket in your area.

I think you should not have major issue with that if your POCO say ok with it.

Merci,
Marc
Their eyes glaze over pretty easily with new fangled gizmos. :jester:
 
#30 ·
Plus it has two breakers that use the safety interlock idea, one for the main service and one for the generator. I don't see a way to bottom feed it though. :(

This is a Durham but if they make them maybe there is hope that other big manufactures make something similar with a bottom feed.
 
#34 ·
A little off subject from the thread but part of the overall project.

A little off subject from the thread but part of the overall project.

Last weekend I started the 900’ run of 3” in which 600’ of it is down a very steep hill. The 2 sweeps that you see here will come up into a junction box (pull point) for the POCO. After I finish the run I will level the ground up and place a 6” thick base of gravel. The POCO will bring a 4’ x 4’ x 6” thick precast concrete slab and set it over the sweeps. On top of the slab they place the plastic junction box. The pad has the same dimensions as a transformer so in the future if I want to tap secondary from this point all they have to do is remove the junction box and place a transformer at this location.

Pipe Soil




I’m trying something new on this run that I think will save me a lot of time, work, and aggravation. The 500’ run and 400’ run which I have been working on was dug with a 12” bucket and I placed the 2” phone conduit about 1 foot on top of the 3” power conduit. I was basically doing twice the amount of work because I had to bed the conduits at different levels and the amount of rocks in the soil is overwhelming. So, make a nice rock free flat bottom for the 3”, then backfill one foot by hand to keep the major sharp rocks away from the conduit. Compact tightly for minimum settling of the second conduit and make a flat rock free bottom for this conduit to lay on. Then backfill by hand to keep the sharp rocks away from the 2” phone conduit and finally fill the trench to the top.

So I’m thinking I will switch to a 24” bucket and bed both conduits on the bottom instead of 2 different levels. I’m finding another big plus to this idea because trying to work in a 12” wide 3’ deep trench is just plain brutal. You have to walk sideways, roots are constantly grabbing at your hips, your pockets fill to the top with dirt, and there isn’t enough room for the conduit and your feet. Another big problem was trying to glue the 20’ sticks together by myself. I wanted to glue them in the bottom of the trench but that’s impossible while you are standing on top of the conduit and you can’t bend down far enough to work because your shoulders wedge in the trench. They will slide together nicely when flat and aligned but the only flat place is the bottom of the trench. So anyway, working in this short section of 24” wide trench that I dug was like getting out of a claustrophobic hole in the ground to nice wide open spaces with no limits in my movements.

It’s hard to tell in the pic but I slowly ramped the smaller phone conduit down to the same level as the power conduit. There is also no extra digging time between a 12” and 24” trench. You are making the same number of scoops but removing twice the material.

Soil Geological phenomenon Construction Foundation Tree




Some of the larger rocks I’m running into.

Soil Grass Rock Geology Geological phenomenon




My ******* wire and pull string feeding contraption. 2” conduit may seem like overkill for a ¼” diameter phone wire but it was cost effective at 50 cents per foot because the supplier orders tons of it. Smaller conduit was actually more expensive and it only came in 10’ lengths.

Soil Tree Vehicle






 
#36 ·
At least that gives you the option to add other cables like cable TV and cat5 if needed. Very nice. What size service are you installing?
I'm lucky to get regular twisted pair phone service. 1800' is too far for cable and I can't see the use for cat5. Maybe fiber in the far far distant future if it comes to the area.

Probably 200 amp maybe 400.....haven't made that decision yet.
 
#39 ·
I highly doubt a cat 5 data connection will work at 900' much less 1800', much less expecting to power a camera at the end of that run. Fiber would be the best option, if not for your service provider for your self to have a data connection at the other end. Fiber media converters for a standard 10/100 network are fairly cheap, even a lot of the gigabit media converters have come down in price.
 
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