Pull Power from House or New Service?

[nsula_country]

Apparently transformers can be way overloaded. My pole mounted transformer is a 15Kva and serves two houses each with 200 amp service.

My new loads add an additional 200 amp to that transformer and the power company is going to swap that out with a 100Kva transformer.

Tell me that wasn't overloaded

POCO has 3 of my rentals (MH's, all electric) on about 400' of service drop, multiple connections on a 25 kVA. Everyone's lights blink when an AC kicks in. It did blow a couple of winters ago (all electric heat, 3 houses). Replaced it with a 25 kVA.

CT

 

[nsula_country]

So, if he's pulling 250 A for more than a minute, will the fusing trip at the transformer or at his main first?

Depends on what size fuse the POCO installed!

CT

 

[ard]

.

Never checked voltage drop though with everything churning.

I know how to size a xformer. I question the POCO all the time about their sizing. They fall under a different play book because it's all "open air" so I've been told. POCO rarely sizes their primary xformers as we are required to size our secondary xformers. At least in our area...

Pissed me off when they required me to use 500 MCM copper and they used a 4/0 Al drop...

CT

IMO, it is also becuase they know that people will not be logging voltages and holding their feet to the fire when voltage drop impacts the service during these transient peaks.

 

[DC73]

Apparently transformers can be way overloaded.

Correct. Transformer load (like loads on other electrical equipment) is a function of temperature. Transformers are rated for a certain output at a certain temperature. You can easily overload a transformer by double for very short periods of time (motor startup, etc.). Most transformers can be operated for extended periods at 20% overload (more in the winter).

The reason PoCos don't size their transformers based on the main size of their customers is wasted capacity if they did (more on this later). They size transformers using formulas and a concept called "load diversity". That basically means that it would be very unlikely for a group of customers served by a single transformer to all have their maximum load operating at the same time.

For example, I have 320 amps of service installed to my house and shop combined. I will NEVER use 320 amps of service all at once. That would mean ever single piece of equipment I own would be operating at the same time plus I would still need additional equipment plugged into many of the vacant outlets. If I have a neighbor with a system similar to mine on the same transformer, it's even more remote of a chance that both of us would be using power near maximum load at the same time.

But, codes don't allow for diversity and require building wiring, main sizes, etc to be sized for "total connected load" whether its likely those loads will operate at the same time or not. The power company has no such restriction which is why the meter that serves my house and shop is only a 200 Amp meter. There was simply no need for them to install a larger meter.

Back to the transformer wasted capacity mentioned earlier. Power systems have "losses". This means wires, transformers, etc consume electricity that never gets to the customer. As current flows through equipment, some energy is used to heat that equipment and that energy never makes it to the meter. So, a power company has to make more power than is sold at the meter and the difference is called "system losses". Larger transformers have greater system losses. That's why they don't want their equipment to be any larger than it has to be to serve the customers.

The total of all main sizes served by a power company could easily be 3 times their actual system peak load.

It's all about being cost effective.

Hope this helps.

DC

 

[sberry]

I negotiated with the poco engineer when I did an upgrade for the wire size, I have 400 on a 320 and only 15KVA can.

 

[barnee]

Correct. Transformer load (like loads on other electrical equipment) is a function of temperature. Transformers are rated for a certain output at a certain temperature. You can easily overload a transformer by double for very short periods of time (motor startup, etc.). Most transformers can be operated for extended periods at 20% overload (more in the winter).

The reason PoCos don't size their transformers based on the main size of their customers is wasted capacity if they did (more on this later). They size transformers using formulas and a concept called "load diversity". That basically means that it would be very unlikely for a group of customers served by a single transformer to all have their maximum load operating at the same time.

For example, I have 320 amps of service installed to my house and shop combined. I will NEVER use 320 amps of service all at once. That would mean ever single piece of equipment I own would be operating at the same time plus I would still need additional equipment plugged into many of the vacant outlets. If I have a neighbor with a system similar to mine on the same transformer, it's even more remote of a chance that both of us would be using power near maximum load at the same time.

But, codes don't allow for diversity and require building wiring, main sizes, etc to be sized for "total connected load" whether its likely those loads will operate at the same time or not. The power company has no such restriction which is why the meter that serves my house and shop is only a 200 Amp meter. There was simply no need for them to install a larger meter.

Back to the transformer wasted capacity mentioned earlier. Power systems have "losses". This means wires, transformers, etc consume electricity that never gets to the customer. As current flows through equipment, some energy is used to heat that equipment and that energy never makes it to the meter. So, a power company has to make more power than is sold at the meter and the difference is called "system losses". Larger transformers have greater system losses. That's why they don't want their equipment to be any larger than it has to be to serve the customers.

The total of all main sizes served by a power company could easily be 3 times their actual system peak load.

It's all about being cost effective.

Hope this helps.

DC

Makes sense, but in my case when I added another 200 amps to that 15Kva transformer which already had two 200 amp services on it, the poco said that the transformer needed to be upgraded (at my cost). Using your rational I would think that the poco would put in maybe a 25Kva transformer, but they insisted that it now needs to be 100Kva. If they were paying for it they would say that the 15Kva was fine. Rules change depending on who is paying the bill.

 

[NUTTSGT]

OP, is there a chance that the shop will ever become a business ? If so, you may want to add that to the consideration for a second service.

Once nice thing about having a second service is in case of a service line is taken down during a storm or something happens in the home (like a house fire, heaven forbid) or vice versa, you can still have some power available via extension cord as a temp fix.

 

[DC73]

Using your rational I would think that the poco would put in maybe a 25Kva transformer, but they insisted that it now needs to be 100Kva. If they were paying for it they would say that the 15Kva was fine. Rules change depending on who is paying the bill.

You got taken advantage of. I'd be livid with the PoCo. There is no justification for a 100 kVa transformer for three 200 amp services.

DC

 

[donpauli2]

Under the use you indicate. I would do ok with a 125 sub panel with heavy enough wire.


Sent from my iPhone using Tapatalk

 

[ard]

Makes sense, but in my case when I added another 200 amps to that 15Kva transformer which already had two 200 amp services on it, the poco said that the transformer needed to be upgraded (at my cost). Using your rational I would think that the poco would put in maybe a 25Kva transformer, but they insisted that it now needs to be 100Kva. If they were paying for it they would say that the 15Kva was fine. Rules change depending on who is paying the bill.

Not sure what your regs are, but it is not beyond the possibility that they charge you for something you should NOT have been charged for..... Did you look into this in detail??

 

[wyliesdiesels]

For grins, I just went out and looked at mine. When I started my first business here on the farm, I turned my 3 HP compressor on and watched the lights pulse with each stroke of the pump. Went in the house, and the TV was dancing across the floor. The TF was the original one put in when electricity was first invented out here. A phone call resulted in them coming out in a very timely manner and swapping it out for something a little more modern. That was 44 years ago. Now even though we shouldn't pay attention to labels I am pretty sure that where you see the shadow of one on there it said "10". Does that sound about right Wylie?
I didn't have a minivan for comparison handy, but I think that the wife's Trailblazer is close.

Thats a lot bigger than the 10Kva cans we have out here. That looks to be at least 25Kva if not 37.5...

So, if he's pulling 250 A for more than a minute, will the fusing trip at the transformer or at his main first?

That all depends on the cutout ratings. So we cant answer that.

Apparently transformers can be way overloaded. My pole mounted transformer is a 15Kva and serves two houses each with 200 amp service.

My new loads add an additional 200 amp to that transformer and the power company is going to swap that out with a 100Kva transformer.

Tell me that wasn't overloaded

My PoCo overloads their transformers quite a bit.

 

[rburke65]

Well for a "one man band" shop you have plenty of power to tap into your house. You will ever pull 100amp in that shop.

 

[Dragfluid]

"That looks to be at least 25Kva if not 37.5..."--Wylie

OK, like I said, many moons ago. So at least I don't have to worry about it being too small,,,,,,,,,,,,,,,,,,, ever.


Lost juice for a couple hours this afternoon. Some ****** managed to clip an overhead on the highway 3/4 mile away. And he just kept going. Wonder what his loaded height was?

 

[alexb2000]

Was that just a nice to have or did you actually do load calcs to justify that upgrade? You must have some very high demand loads in both the house and shop.

Couple of reasons:

1. Having a 200 amp panel in the garage allows me to do anything I want, no running out of spaces, or having to upgrade later, etc. Also separate from the house loads including 5 tons of AC that rarely shut off in the summer.

2. It was actually cheaper to do. My house panel is in a closet and running a sub off of it would not be easy. Adding a run from the meter base was easy as it is outside the house.

3. Most of us do not know what our load calls will be, because we don't know where this hobby will take us. I used to have a little Craftsman compressor, now I have a 7.5 HP IR compressor. I used to think I would never need to weld with 300 amps, now I do once a month (aluminum). Years ago I started doing machine work, so add a phase converter, etc. I am currently thinking about adding 2 tons of AC to the garage, nice that I have to power to do that. I have NEVER regretted having 400 amp service.

4. Seems like doing things twice is three times as expensive.

 

[James-W]

Parts and labor:

125amp pulled from house, trenched to shed, 125 amp, 40 circuit panel in garage, grounded per code. $2350

200amp meter pedestal, 200amp 40 circuit panel in garage, grounded. $925. Run service from pole to meter $311. $0.15 a day second meter fee forever(rate could go up in future). Same kw/hr rate as primary service to house.

W.E. Energies will run the first 100 feet for a new service for free. They ran the 200 amp service to my garage for free but I had to get a meter base, mast, mast head, electrical panel, ground the panel, and run the cables from the mast head down to the meter base and then into the panel. Once the city inspector checked it out, he contacted the power company and they came and hooked it up.

Yes, I have a monthly meter charge that will go on forever, but now I have a 200 amp service in the garage and I didn't have to screw around running power from the house (100 amp service in the house) out to the garage. I could have done that, but this way I have all the power available in the garage I will ever need and I don't have to worry about tripping the main breaker in the house.

 

[barnee]

Not sure what your regs are, but it is not beyond the possibility that they charge you for something you should NOT have been charged for..... Did you look into this in detail??

Sorry to veer off the original topic with my comment so Ill end it with this. I bitched like hell and talked to the supervisor and the final fee to replace the transformer to a 100 Kva, replace overhead conductor to support new 320 amp service, remove a tree, provide a new meter can was $1,800 which is OK. Not sure if I got any deal but they are sort of a monopoly.

 

[Dragfluid]

" Not sure if I got any deal but they are sort of a monopoly."-Barnee

Yea, I mean, are you going to say, "I'm taking my business elsewhere!"

They don't do it anymore, but years ago the PoCo used to advertise. Even as a little kid I didn't get that.

 

[ard]

Sorry to veer off the original topic with my comment so Ill end it with this. I bitched like hell and talked to the supervisor and the final fee to replace the transformer to a 100 Kva, replace overhead conductor to support new 320 amp service, remove a tree, provide a new meter can was $1,800 which is OK. Not sure if I got any deal but they are sort of a monopoly.

Since it might be helpful to others dealing with PoCos, it isn't entirely OT...

In exchange for being able to be a 'monopoly', most states have very tight regulation of utility's- with detailed rules, policies and procedures as well as oversight by a public utilities commission. Although there is a lot of variability from state to state. If you don't like the answer you get from a poco or a supervisor, find out their authority in their state documents- and if you think they are out of compliance, or are making up stuff, or it is ambiguous, you can go to the PUC.

But $1800 isn't so bad.

 

[bruincounselor]

I'm in the process of adding a garage. I have 200 amps in house and want another 200 in garage. Easiest is to do 400A at garage and sub to house. POCO is charging $444 to bury line from pole to garage (all of 16'). They will do overhead feed for free, but then I'm paying electrician to make a hole in a brand new roof for the mast - cost wise it's a wash.
Just another data point FYI.

 

[duwem]

Talked to the electrician and he said the 60' of wire house to shed was $500 so going smaller for less amps isn't gona save me much.

 

[duwem]

Other thoughts? Other then the issue that the circuit breaker box and all wires routing to it would be on opposite sides depending on the choice, I could run from the house for now I could use the money I saved from not having the meter fee could pay for separate service in the future, but not sure how would get power through the shed to the breaker box.

 

[duwem]

Anyone? Thanks.

 

[ard]

I'm lost as to what you want or what you are asking. Your participation was so sporadic, and short, that it is hard to understand your needs....