How to minimize voltage drop caused by heavy machine?

[trader_4]

Since you were seeing a 5V drop at the service itself, that makes sense.

[Doug Miller]

yyy378 wrote in news:maaqr3$mdb$ [e-mail]:

Aaaaaaand there's your problem, right there.

10KW @ 220V = 45A.

Your service is way undersized.

[Ed Pawlowski]

That is a pretty good drop with just one piece of equipment Given your location, it is quite possible the service is just plain inadequate right back to the power station and nothing you do will fix it.

[Jerry.Tan]

It's become very obvious your service entrance is under rated. A 10KW meter, probably the SE cables themselves. That second breaker panel was probably added later on, and just hooked to the same meter and serv ent cables.

You seemed a little shocked when I said 2000W is not much. Compared to many machines in factories and other businesses, it's 'small'. A common electric water heater or kitchen range in a home, are around the same wattage, + or - a little. Farms have grain dryers that use that much or significantly more power.

I'm wondering what the main breaker is in BOTH of your breaker boxes? That i'm sure you can tell us, but then what is the gauge size of the Service Entrance wires? And the overhead (or underground) cables that go between the Pole Transformer and the SE Head?

If you dont want to upgrade and replace all that wiring, (since you lease the place), maybe you can just have an electrician add a seperate NEW Serv Entrance, right from the transformer to a dedicated breaker box just for the saw. Or (I think you said there are 3 buildings), a new SE to one building (the one with the saw preferably).

You really dont need an electrician to advise you (or bullshit you). Of you can determine what gauge ALL the wires are, which feed your MAINS. ALL of them between the transformer and your MAIN breaker, we can tell you what kind of load you can handle. Then if you want to invest in one of those clamp around AMP METERS, and measure the draw of your whole business, (with and without the saw), we can tell you how much you're under rated.

• Clamp around AMP meters are simply clamped around wires at the MAINS. They measure power draw by inductance. You dont really have to touch any live wires. (of course you still need to do this safely, since you're very near the bare connections). These meters are around US. At least they used to be, when I bought one around 20 years ago. Maybe they're less now????

[yyy378]

I am told 10000W is the limit for a single phase meter. With 3 phase, it can go higher. Since there are only two wires coming to the building, it must be single phase. There is no point to install a 3 phase meter. Do meters really limit the current? I think the real limiting factor is the wires. The two incoming wires don't look terrible big. I'll measure them tomorrow.

[yyy378]

I'll measure the wire gauge tomorrow.

The transformer is located in this building, the one we lease. Thus, it would be easy to add another meter or replace the existing one and run cables directly to the transformer, bypassing the cables that go to the landlord's office. I did inquire about this option and was told it would cost $600 to add a 3 phase meter. The 2.5 cm cables to the transformer are the biggest cost. But then, I'm also told there can only be one set of cables coming out of the transformer, meaning cannot add additional cables to the transformer. (There are, of course, already existing cables going to the landlord's office.) True or not, I don't know.

[Doug Miller]

yyy378 wrote in news:mabml5$jco$ [e-mail]:

In a sense they do -- if you try to push more current through *anything* than it's physically capable of transmitting, it will act as a fuse. :-)

Well, yes, of course -- the point is that since your meter isn't rated for more than 10KW, the wires supplying the meter probably aren't capable of carrying more than that.

That may not be your only problem, though: I bet the transformer isn't rated over 10KW either.

[Fred McKenzie]

Just measuring the steady voltage while the saw is operating does not tell the whole story. The saw probably has a high peak start-up current that might be 3 or 4 times the running current. Even without the scanner problem, you seem to have excessive voltage drop.

Your scanner may be sensitive to power fluctuations, but a good UPS should take care of that. Try unplugging the UPS, and see if it keeps putting out voltage. Plug a lamp into it to provide a load. It may just have weak batteries.

If you replace the scanner, consider one that is powered from the computer's USB port such as a Canon LIDE. A computer's power supply should provide buffering from power fluctuations.

Fred

[Ralph Mowery]

The meters don't really limit the curent. Usually the transformer that cuts the high voltage down to the building voltage is what limits the current. They usually have a fuse inside them that will limit the current, then the wiring going to the building is sized for that ammount of load. The meter is probably sized for a range of power as to where they are the most accurate. A small building like yours may only need about 10 kw to operate as a large company may need 1000 KW. A meter rated for the 1000 KW would be on the low end for your building and may not be as accurate.

Probably what is really causing the voltage drop is the starting of the saw. When a motor is first started it will draw lots more current (often several to 10 times) than its running current. Fuses often have a small time delay before they open depending on the ammount of overload. Say overload it by

5% and it may take 30 seconds, overload it by 25 % and you have 2 seconds, and by 10 times the ammount, a tenth of a second as an example.

It looks like the size of the wiring possiably going to the building and inside the building is not large enough to handle the high current loads. I remember in my younger days the TV set would often do funny things every time the refrigerator would start up.

[Stormin Mormon]

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[Jerry.Tan]

I cant tell you about your codes and number of wires to the transformer since you're not in the US. You'll just have to speak with the inspectors and a RELIABLE electrician. $600 does not sound like a bad deal at all. If you have computers fail, or the motor on the saw fails because of improper voltage, it may cost a lot more than $600.

If the meter is changed to 3phase, you can feed off each phase so there may be no need to have more than one set of cables on the transformer (per phase). Having 3 phase power is not something everyone has access to. You should have adaquate power and much more.....

Plus, using 3 phase properly and balanced, could cut your electric bill at least a little bit.

Otherwise, you can run some real heavy cables from the xformer to a MAIN DISCONNECT box. Something like a 400 Amp main, they have sub feeds of

100A or higher, going to different buildings/ locations.

[Ashton Crusher]

My simple solution would be to put the scanner on it's own dedicated UPS and unplug that UPS just before starting to use the scanner. If the existing UPS is large enough to handle the scanner and computer system for a while, you could leave the computer plugged in to it too.

[yyy378]

It is actually a printer/scanner.

Yesterday, the saw started while the printer was printing. The printer aborted the first page half way into printing it but the printer then printed starting from the first page again and printed the entire document even though the saw had started at least twice during that time. This time, the printer/scanner was plugged directly to an outlet, not to a UPS.

[yyy378]

OK. I opened the panel and checked the size of the incoming wire. I can't believe what I saw. The wire, including the sheath, is only 0.7 mm. I touched the wire. It's lukewarm. The saw has been working on and off for about an hour. I'll see how much it would cost to replace the wire with a bigger one.

[yyy378]

OK. I checked the wires coming from the landlord's office. They are 0.7 mm thick, including the sheath. And they were lukewarm when I touched them. I don't know if the warmth is due to the start-up current or the constant 8.8 A (2000 W) draw.

[bob haller]

my work around was to set the exposure lamp as brite as possible, then the key operator could use a high wattage dimmer to darken the copies as needed......

it worked well for a couple years till the building was demolished for a highway project

I will add the state demolished the building but never used the land, today its a parking lot. which is kinda sad

[trader_4]

.7mm, including the sheath? That would smoke. Maybe you mean 7mm? Did you ever post the main breaker size on the panel?

[Jerry.Tan]

Yea, that has to be 7mm. According to a little conversion program I have, that would be .276 Inches (rounded). Or just slightly over 1/4". Since he measured it WITH the insulation, that is not much of a wire in gauge size. If I had a piece of #6 gauge wire around here, I'd guess that would be close. #6 is nrmally used to wire a kitchen range, on a

50A breaker. Even a #4 is under 100A. Then too, is this cable copper or aluminum. Alum S.E. cable needs to be quite a bit thicker.

I do not recall the OP ever posting the breaker size.

If the wires are warm, that alone indicates a problem with the system. I am almost fully convinved that Service Entrance is way undersized. That whole system is likely only capable of 60A from the main.

[trader_4]

Well, he did say the meter was rated at 10KW. #6 is fine for that ampacity.

Even a #4 is under 100A. Then too, is this cable copper

I don't either. I asked that today.

Probably only 40A, since that's what it appears the meter is rated for. But even if it is rated for 40A, the question is what is he actually pulling? Conductors shouldn't be getting warm and the voltage shouldn't be dropping 5V from an increase in load of 8A. The latter is clear indication that something is undersized.

[Jerry.Tan]

A 40A main is nothing in today's standards. Here in the US, 60A was the minimum allowed for a home, 50 years ago. Today, It's a 100A minimum, or has the NEC increased that lately????

And the OP is running a business as well as a home on that 40A. It's no wonder the wires are warm. That saw alone is using a large portion of the avialable power. Then he has lights, a bunch of computers, and we can only guess if there is an elec water heater, range, and who knows what else....

I've asked the size of the main breaker several times.

Either way, it's apparent that this system is under rated and needs to be replaced, or an additional Service entrance installed.

Appparently the codes are not as strict outside the US.

I'm on a farm, and I have a 400A main disconnect on the power pole, which is feeding 100A main in my house, 100A main in my garage/shop,

100A main in my barn, and an outdated 60A fuse panel main in a very small shed (which is mostly just used for a couple lights). I really dont need that much power, but I'm glad it's over rated. I never see voltage drops.