200A Service on a 10KVA transformer

[DirtBound]

Hi all!

I have a pole building that is zoned industrial and it has a 200A single phase service that they bill as residential for some reason. I looked at the pole and noticed that it is only on a 10 KVA transformer.

We run a metal fabrication shop in the building. 4 welders, 5 HP air compressor, 85A Plasma table, 25 HP rotary phase converter, 5 HP air filtration system, air conditioning, lighting, computers. 4,000 sqft of power sucking equipment.

Everything has been fine, but we just purchased a 15 HP 3 phase belt sander for cleaning our metal parts. Just starting this will max out our phase converter, but when I mentioned this to my electrician friend he thinks were gonna pop that transformer out on the pole.

What all do you think, is the 10KVA undersized for our service? Should I try to get the POCO to upgrade it or just let it rip and if it pops it pops?


I should note that a normal day will see multiple pieces of equipment on at the same time. The sander will be used while the plasma, air filter and compressor are running along with whatever my fabricators are using.

 

[mm08822]

Yes it appears to be very undersized for this new load alone assuming it pulls 15hp load. Even at 1/2 load you're on the hairy edge. Then you have all the other equipment running randomly.

Most POCO's want to know when you are connecting a load greater than 5 hp on a single phase distribution.

Don't start the belt sander - call the POCO. You're looking at a larger service lateral (with larger xformer) at a minimum.

 

[wyliesdiesels]

Sounds very undersized.

It may have something to do with it being a residential account.

Do load calcs then call the PoCo. They will want to know what your load calcs are.

 

[Kevin Essiambre]

It's not unheard of for the POCO in my area to load transformers up to 300%... but I would do a load calc and call the POCO and to double check. If it has to be changed it'll be (or at least should be) on their dime.

Sent from my SM-G920W8 using Tapatalk

 

[dw1]

Yes it appears to be very undersized for this new load alone assuming it pulls 15hp load. Even at 1/2 load you're on the hairy edge. Then you have all the other equipment running randomly.

Most POCO's want to know when you are connecting a load greater than 5 hp on a single phase distribution.

Don't start the belt sander - call the POCO. You're looking at a larger service lateral (with larger xformer) at a minimum.

I agree, if you have power problems inside the building that causes problems with the power company ( without them knowing) you could find yourself disconnected

 

[Bert_]

You should always let them know if you're adding a large load. The transformer is often sized to the load not the service size.

 

[walta]

How much will you be using the 15 HP machine?

If it is only for a few hours once or twice a week a diesel generator may cost less to set up and run than upgrading the electric service and upgraded phase converter.

If it will run 40 hours a week a real 3 phase service would likely use 15% fewer kWh than the phase converter.

The smart move may be to avoid any changes to the electric service if they change you to business account it may you cost 60% more each month.

Let the sleeping dog lay if you can.



Walta

 

[DirtBound]

If all goes to plan this will be used about 3-4 hours a day, we also run our phase converter and air filtration system almost 8 hours a day. Going to 3 phase service would be ideal but I would personally like to wait until our next building happens at winch point we will need 3 phase service.

I guess I will give them a call and just see what they say about that running the sander, last time I asked about 3 phase they just said a rotary would be best. Despite it being available 2 poles down, about 200 ft. But maybe with these larger loads they will change their minds now.

How much will you be using the 15 HP machine?

If it is only for a few hours once or twice a week a diesel generator may cost less to set up and run than upgrading the electric service and upgraded phase converter.

If it will run 40 hours a week a real 3 phase service would likely use 15% fewer kWh than the phase converter.

The smart move may be to avoid any changes to the electric service if they change you to business account it may you cost 60% more each month.

Let the sleeping dog lay if you can.



Walta

 

[sberry]

Mine is 15 on a 400 service but the load is low.

 

[DirtBound]

Well Xcel Energy came out (that was quick) and he starts to laugh at how small that transformer is and noted that it is probably already in bypass mode as we are currently drawing much more than the recommended load.

So now we are in contact with the designer to see if they can get us a larger transformer or if we are going to just bite the bullet and get 3 phase ran in from 2 poles down. Fun! So now I have a $18K machine that I cant touch...

 

[sberry]

3 phase line power is the best if its practical. Its worth some juice to get it.

 

[DirtBound]

3 phase line power is the best if its practical. Its worth some juice to get it.

Yea I think they are going to try and get us a larger transformer temporarily and then plan a 3 phase install. They are about 2-3 months out for new installs so well keep our fingers crossed they can get us something soon.

 

[wyliesdiesels]

Well Xcel Energy came out (that was quick) and he starts to laugh at how small that transformer is and noted that it is probably already in bypass mode as we are currently drawing much more than the recommended load.

So now we are in contact with the designer to see if they can get us a larger transformer or if we are going to just bite the bullet and get 3 phase ran in from 2 poles down. Fun! So now I have a $18K machine that I cant touch...

Bypass mode? What does that mean?

I have not heard of that term before.

 

[walta]

This is business get the job done and make some money. Rent a generator until you work out a long term solution as long as the numbers will show a profit.

Walta

 

[Dragfluid]

Hey Dirt, where are you at in MN?

 

[mm08822]

Bypass mode? What does that mean?

I have not heard of that term before.

That's a bs line for sure.

 

[wyliesdiesels]

That's a bs line for sure.

yeah pole transformers have no such thing. They do not have controls or any kind of brain.

its simply 2 coils of wire wrapped around iron sitting in a bath of oil.

 

[u3b3rg33k]

what are your actual loads not nameplate?

for example I've got a 40hp rated motor/blower that only pulls 15kva while under load.

 

[DirtBound]

Hey Dirt, where are you at in MN?

Center City, Between Taylors Falls and Forest Lake

yeah pole transformers have no such thing. They do not have controls or any kind of brain.

its simply 2 coils of wire wrapped around iron sitting in a bath of oil.

Thats what I thought...

what are your actual loads not nameplate?

for example I've got a 40hp rated motor/blower that only pulls 15kva while under load.

With our plasma running and only one fabricator working were pulling 100-135 amps on one hot leg. With just lights on, air filtration/rotary converter (runs all day) and no other equipment besides computers etc... were pulling about 35-45 amps.

When I turn on the rotary converter (25hp) we get a spike of about 300 amps, and the 5hp air filtration system a quick jump of about 175 amps. I will state that if our CNC plasma is running turning on either of these will cause the table to crash due to the power draw.

 

[u3b3rg33k]

Center City, Between Taylors Falls and Forest Lake


Thats what I thought...


With our plasma running and only one fabricator working were pulling 100-135 amps on one hot leg. With just lights on, air filtration/rotary converter (runs all day) and no other equipment besides computers etc... were pulling about 35-45 amps.

When I turn on the rotary converter (25hp) we get a spike of about 300 amps, and the 5hp air filtration system a quick jump of about 175 amps. I will state that if our CNC plasma is running turning on either of these will cause the table to crash due to the power draw.

Not sure how you're measuring that (inrush meter?), but it doesn't mean much. a 5hp single phase motor will show 130 amps on startup, give or take.

but it sounds like you need to do some load management or get a bigger service. VFDs are great. they make them for single phase source, and you can spread that spike out over 3 seconds or so instead of starting stuff DOL without much impact.

 

[DirtBound]

Not sure how you're measuring that (inrush meter?), but it doesn't mean much. a 5hp single phase motor will show 130 amps on startup, give or take.

but it sounds like you need to do some load management or get a bigger service. VFDs are great. they make them for single phase source, and you can spread that spike out over 3 seconds or so instead of starting stuff DOL without much impact.

Measured using a Clamp-on ammeter at the main panel between the meter.

A bigger service is in our books, its just a waiting game now for Xcel as they are dragging their feet. "Hello, I want to get a bigger service so we can **** up more power so we can pay you more"... Radio Silence... haha

The cost for a VFD large enough to run a 15 hp 3 phase machine just to slow the spike would be counter productive, as that money would be better spent just bringing in utility 3 phase.

 

[wyliesdiesels]

Measured using a Clamp-on ammeter at the main panel between the meter.

A bigger service is in our books, its just a waiting game now for Xcel as they are dragging their feet. "Hello, I want to get a bigger service so we can **** up more power so we can pay you more"... Radio Silence... haha

The cost for a VFD large enough to run a 15 hp 3 phase machine just to slow the spike would be counter productive, as that money would be better spent just bringing in utility 3 phase.

Does you clamp meter have in-rush current capability?

 

[DirtBound]

Does you clamp meter have in-rush current capability?

No does not look like mine does...

 

[wyliesdiesels]

No does not look like mine does...

what is the make and model of your clamp meter?

without the in-rush current measurement capability, the measurement will be inaccurate.

Clamp meters such as the Fluke 381, have this feature.

 

[DirtBound]

what is the make and model of your clamp meter?

without the in-rush current measurement capability, the measurement will be inaccurate.

Clamp meters such as the Fluke 381, have this feature.

I have a ideal 61-744

 

[alfredeneuman]

I have a ideal 61-744

I had one of those and although an accurate meter it doesn't have a peak hold option.

 

[MrSurly]

I think "By Pass Mode" could be the colloquial term for "a length of #6 bare" in place of the fuse link.

 

[wyliesdiesels]

I had one of those and although an accurate meter it doesn't have a peak hold option.

Peak hold is not the same as in-rush current measurement capability.

The meter needs to be able to respond to and measure current in millisecs as inrush current occurs within a couple hundred millisec of the motor start sequence.

 

[DirtBound]

I think "By Pass Mode" could be the colloquial term for "a length of #6 bare" in place of the fuse link.

haha the thought of that makes sense, its not the case. We did blow the fuse once, and they replaced it with a new fuse.

 

[DirtBound]

Peak hold is not the same as in-rush current measurement capability.

The meter needs to be able to respond to and measure current in millisecs as inrush current occurs within a couple hundred millisec of the motor start sequence.

I am not really worried about the in-rush, more to the fact that we are loading the transformer 100-150% during business hours and that they don't want us to run the new machine. So a larger service is required no matter what way we look at it.

I would love to just get 400A 480v ran in so we are set for any future equipment purchases as from this point out its all larger 3 phase equipment.

 

[wyliesdiesels]

I am not really worried about the in-rush, more to the fact that we are loading the transformer 100-150% during business hours and that they don't want us to run the new machine. So a larger service is required no matter what way we look at it.

I would love to just get 400A 480v ran in so we are set for any future equipment purchases as from this point out its all larger 3 phase equipment.

You will have to get a 480/240-120 transformer and panel to run all your single phase stuff.

 

[DirtBound]

You will have to get a 480/240-120 transformer and panel to run all your single phase stuff.

yup That's what my electrician is thinking, install a new 3 phase panel then step down transformer to feed our current single phase panels.

 

[DirtBound]

Well looks like we have some options to think about, both upgrades require a new service wire. If we stay with single phase we still may need a larger phase converter but we wont know until we try our loads, we also have the max combined HP the POCO wants us to run on single phase, so it seems silly to upgrade that.

If we jump to 3 phase we can sell the phase converter to recoup a few grand.

I am waiting for my electrician to stop by so we can come up with a game plan and figure the remaining cost, but I still think 3 phase 480 would be the best bet.

Option #1: 3-phase

The cost to upgrade 2 spans of wire to 3-ph, install 3-ph overhead transformer, upgrade 1 existing transformer to serve existing customers fed of a 1-ph transformer that needs to be removed, install 1 span overhead secondary, traffic control, replace 2 poles to handle the new 3-phase, and other related items is $8,616.76. This does include justification for your additional load.



Option #2: 1-phase

The cost to upgrade the existing 1-ph transformer to a large transformer justifies. This does not upgrade your existing underground service wire or meter box on the building.

 

[wyliesdiesels]

If you can get 480Y/277v GO FOR IT!!

It opens up the ability to run all kinds of equipment. Lots of used equipment goes for cheap because 3-phase is hard to come by for some people.

Also, dont forget you will need a step down transformer to run your single phase panels and equipment.

That will add to your cost.

 

[mm08822]

Option #1 for sure!

And don't cheap out on the 480 - 120v xformer size. It's less expensive to buy it once than twice!

 

[alfredeneuman]

Peak hold is not the same as in-rush current measurement capability.

The meter needs to be able to respond to and measure current in millisecs as inrush current occurs within a couple hundred millisec of the motor start sequence.

I had an old Fluke 36, that would measure in-rush current when set to the peak hold function.

 

[DirtBound]

Option #1 for sure!

And don't cheap out on the 480 - 120v xformer size. It's less expensive to buy it once than twice!

I found a 30kVa 480 > 240 3 phase transformer for $500 should be plenty, but i'm still waiting for my electrician to stop by.

Some of my larger equipment will run on 480 3 phase so that will get re-wired for that.

 

[W-Cummins]

I found a 30kVa 480 > 240 3 phase transformer for $500 should be plenty, but i'm still waiting for my electrician to stop by.

Some of my larger equipment will run on 480 3 phase so that will get re-wired for that.

I would use a 480v to 208v 3 phase transformer. Also 30kva 3 phase transformer is about 83 amps MAX, you need 75kva to get to around 200 amps. The Power co can use a small transformer to provide a 200 amp service but the NEC will not let you.



If you want to run a single phase transformer then 480-240 would allow you to run your current panel.



You should rewire ANY machines that will run on 480v to do so. It's normally easy to do this as 480V is 1/2 the amps of 240V, and all the stuff (wiring, motor starters etc.) are 2x oversized, unlike when going the other way. The only downside to a 208v transformer is that you might need a buck/boost setup for any 240V stuff you can't run on 480V. In my case only a few 2 speed motor driven devices (stock feeders) that can't be rewired.



As for the used transformer make sure you can use it in a new installation as some places you need to run a high efficiency model. Even if it is allowed, you might want to get a new high e model as it will pay for its self rather quickly.


William....

 

[mike93lx]

Hit up the utility for rebates on the transformer and any motor upgrades. At least in MA, they hand out money for that stuff like crazy.

We are doing a $465k lighting project and will get $300k in rebates.