Distance from Remote Meter to Service Panel?

Status
Not open for further replies.
D

derbatt

Member
For a single family residence I am designing we have a remote electrical meter (200 amp service) that is mounted on a post next to the electrical company's transformer. Are there any guidelines as to how far away from the meter the service panel for the residence can be before voltage drops occur? My local electrical company says 200' is the maximum distance. My client moved the location of the house and the distance would now be 293'. Should I advise my client that she needs to move the remote meter closer or would it be OK? :confused:
 
Re: Distance from Remote Meter to Service Panel?

You'll certaily have voltage drop at that distance. How do architects usually deal with this? Do you know how to calculate voltage drop?

Edit: And there's voltage drop on both sides of the meter. Unless the utility will move the meter for free (I don't think they will) then there's not much point in moving it.

[ July 12, 2005, 05:24 PM: Message edited by: physis ]
 
Re: Distance from Remote Meter to Service Panel?

A meter that far away from the house is a new one for me.... and no, I don't know how to calculate voltage drop, I can barely balance my checkbook... I could ask an electrical contractor I know but I hate to bug him.

Would the electrical company have to move the transformer also to avoid a voltage drop?

[ July 12, 2005, 05:34 PM: Message edited by: derbatt ]
 
Re: Distance from Remote Meter to Service Panel?

Well I'm gonna be honest. I don't mind helping you but I feel a little funny about doing your job for you.

Do you have a load calculation for the building?
 
Re: Distance from Remote Meter to Service Panel?

Not yet, the residence is pretty small, about 1,700 square feet. It is still in design development, if you know a formula for calculating voltage drop I could give it a try. Just trying to figure out whether my client needs to move the meter & transformer closer or whether it is OK where it is. :confused:
 
Re: Distance from Remote Meter to Service Panel?

If the power company said the maximum distance is 200', I'd be inclined to verify with the appropriate official in that PoCo that, in fact, they will hookup and energize a service at a greater distance.

Getting an agreement in the record with that customer, PoCo, and yourself would allow you to instruct the installing electrician to "size the service conductors appropriately to control voltage drop". In my opinion, it will be necessary to specify a design load and the percentage of allowable voltage drop and where the voltage measurement(s) will be taken.
 
Re: Distance from Remote Meter to Service Panel?

Thank you for your advice, will follow up with the power company and see what they say.
 
Re: Distance from Remote Meter to Service Panel?

Do have a copy the NEC?

I don't really know what the utility will or wont do for you but I'd expect you'll end up running service conductors from the existing meter or transformer location to the building.

this is the formula I use:

Vd = 2RLI

Vd = Voltage Drop
R = Resistance (per foot)
L = Length (in feet, one direction)
I = Current

You can find the resistance per 1000' of conductors in table 8 of chapter 9 in the NEC. You'll need to divide that number by 1000 to find the Resistance per foot.

You're gonna have to base the calculation on some value of current. You can probably use an arbitrary value of 150 amps for your 200 amp service, but it is arbitrary.

Edit: that's for single phase by the way. For three phase replace the 2 with 1.732.

[ July 12, 2005, 05:57 PM: Message edited by: physis ]
 
Re: Distance from Remote Meter to Service Panel?

At this distance I would say 300 AL or 3/0 CU would run this 200 amp service fine at 300'.

I figured 150 amps of load with only 3% VD.

derbatt Along with Al's great advice I will say that in general voltage drop can be overcome with larger conductors.

300' is not that much of a problem, if you said 800', 1000' the conductors required would get to be a cost problem.
 
Re: Distance from Remote Meter to Service Panel?

I get 2.87% for 3/0 copper. :)

Edit: At 300' and 150 amps.

[ July 12, 2005, 06:04 PM: Message edited by: physis ]
 
Re: Distance from Remote Meter to Service Panel?

Derbatt, what you should be aware of is how conservative your electric utility is on a normal basis. For canned service calculations, they will likely use the cable that is their stock cable for the service size and calculate the voltage drop at 80% of the switch size. This will permit the generation of a table so that an office person can pick out the size of wire for the circumstances without having a technical background. The service will not likely be loaded that much and you can control the wire size as indicated by Sam and Bob (physis & iwire).

In my opinion, your local electrician or electrical engineer should be calculating the voltage drop after doing the load calculations. Then the wire may be sized that will be adequate. You may wish to upsize the wire a little to allow for future load growth. :D
 
Re: Distance from Remote Meter to Service Panel?

By the way, moving the meter will not accomplish anything, the voltage drop will start at the transformer. Unless the transformer is moved, the voltage will be the same as long as the electric utility uses the same size of wire or cable that you do. :D
 
Re: Distance from Remote Meter to Service Panel?

This is one of the things that I don't agree on is figuring your load for the service. iwire said us 3/0 which is good for 150 amps. Well if I'm putting in a 200 amp service then I think it is good the figure that the load might make it there at some point of time. So myself at 290' I would be using 300kcmil. This would give you a 5% VD at 200 amps. This is how I think we should be doing it but again your ways are correct by the book. What I'm trying to say if you put a 200 meter and panel box in a house and you only figure the load at 100 amps you're not going to run #2 or #4 copper wire to the panel are you! Just thinking but maybe I should be quiet.
Bye now,
Jim
 
Re: Distance from Remote Meter to Service Panel?

I get

With 3/0 Cu, 3.83% for 200 amps at 300 ft.
With 2/0 Cu, 4.84% for 200 amps at 300 ft.
 
Re: Distance from Remote Meter to Service Panel?

The bottom line is - do not move the house nor the transformer. Use bigger wire. 200 amps service for 1700 sqf house is IMO overkill. For all practical purposes 100 amp service 240/120 is more than sufficient. Voltage drop at 75% load should not exceed 5% at the main panel. NEC has nothing to do with that.
 
Re: Distance from Remote Meter to Service Panel?

derbatt
you said
the residence is pretty small, about 1,700 square feet
Click to expand...
I don't think you can put enough load in this size house to pull 200 amps. I doubt you would see 125 amps.
Charlie bring up a good question. Who is installing the conductor, your electrician or the utility?
 
Re: Distance from Remote Meter to Service Panel?

Even though this house might not ever see the 200 amp service fully loaded, any large motor as in a AC unit will produce a large startup load that will dim lights if the service is even half loaded. so if the service has a 100 amp load on it and the AC unit kicks in the short time load could be as high as 200 amps and if there is a VD at 200 amps lights will dim. I think thats what most home owners hate to see is the lights dimming when the AC kicks in. :eek:
 
Re: Distance from Remote Meter to Service Panel?

Originally posted by hurk27:
Even though this house might not ever see the 200 amp service fully loaded, any large motor as in a AC unit will produce a large startup load that will dim lights if the service is even half loaded. :
Click to expand...
Originally posted by james wuebker:
This is one of the things that I don't agree on is figuring your load for the service. iwire said us 3/0 which is good for 150 amps. Well if I'm putting in a 200 amp service then I think it is good the figure that the load might make it there at some point of time.
Click to expand...
These are the types of reasons IMO the code leaves it as a design decision.

There certainly can be times where I agree with James that the VD should be calculated on the full rating but I would not say it needs to be done that way every time.

First think of how we arrived at a 200 amp service, someone did the NEC calculations and came up with a figure that IMO will already be on the high side of reality. The power companies wire sizing tends to support my thoughts here.

This figure may have shown a 160 amp service was sufficient but the next standard size service is typically 200 so now we have a service that is even larger than required.

IMO a 200 amp service to a typical 1,700 sq ft house is never going to approach 200 amps of load and while we could size the conductors on that IMO the person paying the bill should get some input here if they want to pay for substantially larger conductors for a load that may never happen.

On the other hand if I was told that the people run a machine shop out of the garage I would be thinking the 200 amps may well be used.

My point here is each situation is different and I do not think we would be doing the customers any favors by always figuring worst case. :)

Get all the facts you can and make an educated design decision. :)

JMO, Bob
 
Re: Distance from Remote Meter to Service Panel?

Now you did it Wayne, I hope you're happy, you woke Bob up. :D
 
Status
Not open for further replies.
Top