Has anyone ever heard of installing a transformer for a 200a to 400a upgrade?

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I went to my local utility to ask them what size conduit was feeding my customers service. I need to know this because I wanted to upgrade them from a 200a panel to a 400a panel, and wanted to make sure the service entrance conduit is large enough to receive new cables if needed. The utility company told me that it is irrelevant because we would have to instal a transformer on the customers property in order to upgrade the service. This is a underground fed service.

I upgraded another service from 200 to 400a a year before underground fed but it was with a different utility company. The conduit and cables were large enough to handle the upgrade.

Why would there be a need to install a customer transformer on the property just for more amperage? The voltage will remain the same it's the amperage that needs upgrading. Could it be that the utility's transformer can not handle the additional amperage? Has anyone ran into this situation before?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I have seen that situation. In the instances of which I am aware, POCO had run a service lateral to a splice box and then fed more than one residence. When load was added the main feed was inadequate and they were required to install a transformer where the splices were originally. As is often the case these days, the customer was asked to pay a portion of that cost.
 

BJ Conner

Senior Member
Location
97006
Yes

Yes

Yes-not unusual.
Factors to be considered are: size of the existing transformer, how many other customers are on it, why is the service being upsized?
 
The utility did not even check to see if the current utility transformer was enough. They told me to provide them with load calcs before they can provide me with an estimate, They also said to upgrade it may cost 5k to 100k depending on the situation. And of course at the customers expense. This will kill the upgrade for sure and may even kill the solar project if the main breaker can't be resized to accomadate the solar.
 

bob

Senior Member
Location
Alabama
The utility did not even check to see if the current utility transformer was enough. They told me to provide them with load calcs before they can provide me with an estimate, They also said to upgrade it may cost 5k to 100k depending on the situation. And of course at the customers expense. This will kill the upgrade for sure and may even kill the solar project if the main breaker can't be resized to accommodated the solar.

I really find it hard to believe that a utility would ask a customer to put up $5k to $100k to pay for an increase in service capacity. It seems to me that they are in business
to provide this to the customer. They should be happy that the customer is going to pay them more money. Now sometimes a small utility may need to ask for help with the construction cost. I once worked for a utility that was part of Southern Company, a small unknown utiltiy:p, and never once did they ask a residential customer to pay anything for their service. For commercial and industrial there was a 3 to 1 ratio for the job cost vs estimated revenue. If the cost to revenue did not meet this ratio, the customer might have to pony up some money but that was a rare event. I have read numerous posts here where the customer was asked for money.
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
When I did my 200A to 400A upgrade, I asked for a 50 KVA transformer. There was a 20 KVA on the pole existing serving only my house. I had to pay the difference between a 20KVA and a 50 KVA which was about $1000. I also wanted larger wires from the street which was supposed to cost $300 extra. They "forgot" the larger wire and gave me a 1/0 service drop (200A services get a #2 service drop). The flicker is acceptable, and it hasn't burned up yet.

I didn't have a buried service lateral to worry about. But around here, the utility always wants 3" pipe in the ground to the house. That should be fine for a 400A service, as I used 3" GRC for my mast.

The POCO wanted a load calc too, and the other big parameter they wanted was the locked rotor current of the heat pump.
 
When I did my 200A to 400A upgrade, I asked for a 50 KVA transformer. There was a 20 KVA on the pole existing serving only my house. I had to pay the difference between a 20KVA and a 50 KVA which was about $1000. I also wanted larger wires from the street which was supposed to cost $300 extra. They "forgot" the larger wire and gave me a 1/0 service drop (200A services get a #2 service drop). The flicker is acceptable, and it hasn't burned up yet.

I didn't have a buried service lateral to worry about. But around here, the utility always wants 3" pipe in the ground to the house. That should be fine for a 400A service, as I used 3" GRC for my mast.

The POCO wanted a load calc too, and the other big parameter they wanted was the locked rotor current of the heat pump.

Yeah welcome to sothern California, I just spoke to an electrical inspector and he confirmed what the utility said. Which means this is a job that will never happen. the utility is asking for a 5k down payment prior to starting any work.
 
Why would a transformer be needed again?

This is my best guess.........

[FONT=&quot]The utility has determined that the existing transformer(s) can not supply the additional load. It could be because the transformers are not large enough to supply the additional load or a governmental jurisdiction wants all power to go underground. Rather than upsize the existing overhead system they will install a pad mount transformer to supply the underground service lateral. Over the next years they then switch the loads over to the pad mount as customers decide to upgrade.[/FONT]
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
120325-17543 EDT

If solar was not a factor, then does this house need more than a 200 A service?

With solar added what is the maximum RMS current per 120 V phase that the solar can produce?

Theoretically if the solar maximum is under 200 A, excluding any main panel limitations, then why does the service from the power company have to be greater than 200 A? Approximately, there should never be more than 200 A to or from the power company transformer. If there are other customers on the same transformer, and they do not have solar, then the transformer load would be less than 200 A, or whatever loading the power company considers acceptable for the transformer, under most normal conditions.

Solar at 200 A and 240 V as a ballpark is 48 kW. This is quite large for a house, and might cost 300,000 to 350,000 dollars.

Can you provide better values than my ballpark estimates?

Also how is the solar connected to the utility?

.
 

BJ Conner

Senior Member
Location
97006
The customer wants to install solar, he has a large house and uses a lot of electricity. It may be needed to accept the solar load.
I didn't see that in the original post.
That bring up more issues. 1- Are there more than on house fed off the existing transformer? 2.) Is the whole area/neighborhood being reworked so it's all underground? Are the cost for the rework being paid by everyone in area? Usually when the utility does it they don't charge for it if it's on their schedule. Customers will pay for it but not as a one time , up front charge.
3. Where does the metering go? The utility should have a standard.
4. If there is no additional load in the house does he really need 400 amps? The solar installation will subtract from 200 amp load ( if the existing load is 200 amp or less)
5. If the new solar installation can run the current house load and put 400 amps back on the grid it's making pretty good money
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Maybe I missed something here. I have seen many homeowners change their service from a 200 amp to a 400 amp, and we will leave the same 4/0 wire in the conduit. As for the solar, how big is the system? I can tell you for sure that if a customer of ours wants to add a solar system to grid tie, we will not supply any items for free (XF, wire, extra metering) BTW, we do not accept net metering installations. I would think that the load would actually be reduced on the utility if all you are doing is adding a small solar generator.
 
120325-17543 EDT

If solar was not a factor, then does this house need more than a 200 A service?

With solar added what is the maximum RMS current per 120 V phase that the solar can produce?

Theoretically if the solar maximum is under 200 A, excluding any main panel limitations, then why does the service from the power company have to be greater than 200 A? Approximately, there should never be more than 200 A to or from the power company transformer. If there are other customers on the same transformer, and they do not have solar, then the transformer load would be less than 200 A, or whatever loading the power company considers acceptable for the transformer, under most normal conditions.

Solar at 200 A and 240 V as a ballpark is 48 kW. This is quite large for a house, and might cost 300,000 to 350,000 dollars.

Can you provide better values than my ballpark estimates?

Also how is the solar connected to the utility?

.

The solar system will be a 11kw system, the house is 5000 sqft with a fully loaded 200a service, pools, jacuzzi, 4 1 ton AC units etc. I have not calculated the electrical load I was only trying to find out how easily the service could be upgraded. Without wasting a bunch of time and Money own calcs and visits and or energy audits if this upgrade is going to cost 15k it won't be worth the time because the owner will not want to spend that much on just the upgrade. As far as the Utilities single line I just started researching this project and have not spoken to the service planner about their equipment sizes. But the service planner informed me that this project would need an added customer transformer from Jenson, and an upgrade of the utility transformer.<br><br>I have to verify via code and calcs. but I don't think a 200a service is rated to handle a 48kw solar system. I see you are multiplying 200a times 240v is how you come to the 48kw load, but the solar load can't exceed a certain percentage of the bus rating I think it's 120% of the bus rating but I can't be sure until I verify that in the code book.
 

97catintenn

Senior Member
Location
Columbia, TN
If the house is using 200amps now from the utility, wouldn't it be less after the solar install?

Reading this thread, it makes it sound like the house will now be pulling more than 200amps once the solar install is complete.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
120325-2325 EDT

www.llpconstruction.com:

You misunderstood my comment.

But now that you have added additional information I have these additional comments.

The solar part of your original question is not your real problem. So for the moment forget the solar. You have to determine whether the 200 A present service is adequate for the load on it. Primarily that will determine whether you have to upgrade.

Solar primarily reduces the load on the power company. Where you could run into a problem would be if the house presented no load when solar was generating, and the peak power from the solar system was sufficient to overload the power company supply in the reverse directions. I used ballpark figures to show about how large the solar system could be and not overload the transformer. That is where the ballpark 48 kW came from. Then I illustrated the likely cost of such a solar system to simply illustrate that it was highly unlikely that a house with only a 200 A service at present would have such a large solar system.

Now you have provided a much more likely size for the solar, and my guess is that this won't produce more than a maximum possible 70 A into the power company transformer. If the house has any moderate base load like 2400 W during the day, then the maximum possible would be reduced by about 10 A.

You might have more of a problem with overvoltage on the inverter with a moderately high impedance from the power transformer and lines to the house.

Rereading I see the solar was only 11 kW, thus its max is probably less than 46 A.

.
 
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BJ Conner

Senior Member
Location
97006
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"I went to my local utility to ask them what size conduit was feeding my customers service. "
My guess is that if you went to the power company with as much information as you presented here -they told you something just to get rid of you. It took three interations here to find out whats going on.
Utilities are cheap, they fired all the guys with crystal balls and are working the rest like rented mules. They don't have time to do you job.
 

Open Neutral

Senior Member
Location
Inside the Beltway
Occupation
Engineer
I really find it hard to believe that a utility would ask a customer to put up $5k to $100k to pay for an increase in service capacity. It seems to me that they are in business
to provide this to the customer.

I'll tell my client that..... he's forking out $53K for his new residence.

Welcome to California.
 
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