# How to minimize voltage drop caused by heavy machine?

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• posted on January 28, 2015, 10:09 pm

On 28/01/2015 22:15, Doug Miller wrote:

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.
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<%-name%>
• posted on January 28, 2015, 10:41 pm

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.
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<%-name%>
• posted on January 28, 2015, 11:05 pm

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.
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<%-name%>
• posted on January 28, 2015, 1:36 pm
yyy378:
My biggest takeaway from all the suggestions here is to get either the saw or the scanner off the same circuit as the other. If there are spare circuits in your breaker, have the saw moved to its own.
Simplistic I know, but that's how I think.
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<%-name%>
• posted on January 28, 2015, 2:12 pm
On Wednesday, January 28, 2015 at 8:36:15 AM UTC-5, snipped-for-privacy@gmail.com wrote:

Did you see the recent post where he reported that the saw, when running, pulls 8A and that results in a steady 5V drop measured at the *service*?
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<%-name%>
• posted on January 28, 2015, 2:54 pm

What's the service, a hamster wheel? Or a breaker box fed by 100 feet of cheap extension cord?
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<%-name%>
• posted on January 28, 2015, 2:56 pm
On Wednesday, January 28, 2015 at 9:52:47 AM UTC-5, rbowman wrote:

Did you see the next recent post, where he reported that the meter is rated 10KW? Not exactly a hamster wheel, but it sounds like 40A. Given that he says the 8A motor load drops it by 5V, the 100ft of cheap extension cord, or cheap something, sounds possible.
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<%-name%>
• posted on January 28, 2015, 2:13 pm
On 28/01/2015 20:06, snipped-for-privacy@gmail.com wrote:

The entrance cable feeds two breaker panels which are wired in parallel. I have moved the saw from one panel to the other with no noticeable difference.
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<%-name%>
• posted on January 28, 2015, 2:57 pm
On Wednesday, January 28, 2015 at 9:13:19 AM UTC-5, yyy378 wrote:

Since you were seeing a 5V drop at the service itself, that makes sense.
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<%-name%>
• posted on January 28, 2015, 9:44 pm
On Wed, 28 Jan 2015 06:57:14 -0800 (PST), trader_4

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 \$50 US. At least they used to be, when I bought one around 20 years ago. Maybe they're less now????
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<%-name%>
• posted on January 28, 2015, 10:25 pm
On 29/01/2015 04:14, snipped-for-privacy@spamblocked.com wrote:

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.
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<%-name%>
• posted on January 28, 2015, 11:25 pm
wrote:

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.
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<%-name%>
• posted on January 29, 2015, 3:38 am
On 29/01/2015 05:55, snipped-for-privacy@spamblocked.com wrote:

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.
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<%-name%>
• posted on January 29, 2015, 11:56 am
On Wednesday, January 28, 2015 at 10:38:29 PM UTC-5, yyy378 wrote:

.7mm, including the sheath? That would smoke. Maybe you mean 7mm? Did you ever post the main breaker size on the panel?
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<%-name%>
• posted on January 29, 2015, 8:35 pm
On Thu, 29 Jan 2015 03:56:20 -0800 (PST), trader_4

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.
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<%-name%>
• posted on January 29, 2015, 10:32 pm
On Thursday, January 29, 2015 at 3:39:06 PM UTC-5, snipped-for-privacy@spamblocked.com wrote:

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.
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<%-name%>
• posted on January 30, 2015, 1:10 am
On Thu, 29 Jan 2015 14:32:32 -0800 (PST), trader_4

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.
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<%-name%>
• posted on January 30, 2015, 2:02 pm
On Thursday, January 29, 2015 at 8:13:58 PM UTC-5, snipped-for-privacy@spamblocked.com wrote:

It still doesn't affect the physics. If the total load is within that limit, the conductors are properly sized, then turning on or off an 8A load shouldn't cause a 5V voltage drop.

I know he talked about how it was wired up, but it wasn't clear to me that the house was also served by the one meter, that it wasn't a separate meter for the business, but you may be right. In which case, I agree, it makes it worse. But curiously, if the service is really that small and serves a house and business, there is no mention of other problems, eg main breaker tripping. Maybe there are no large loads, eg water heater, electric cooking, AC, etc. If all you have are lights and some small appliances in a small house/business, 40A will go a lot farther.

And I guess we never got an answer.

Agree, that's typical.
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<%-name%>
• posted on January 30, 2015, 4:38 am
On 30/01/2015 03:05, snipped-for-privacy@spamblocked.com wrote:

to the main breaker which is rated 32A (if my guess is correct). From the breaker, the wires go to a switch. The switch is to switch between power from grid and from generator. From the switch, wires go to two breaker panels.
The wires between the main breaker and the switch are two 4mm wires. Instead of using one bigger wire, the person who set it up use two smaller wires. (There is a total of 4 wires, two for hot, two for neutral.) This 4mm is not diameter but cross section. So, actually, it should be 4 mm2. These wires are warm and the switch is hot, estimated 60 oC.
I have a spare switch with larger capacity and 10 mm2 wires. I'll replace the switch and wires first and see if the situation is improved.
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<%-name%>
• posted on January 30, 2015, 9:35 am
wrote:

32 A is s weird rating, but I'm only familair with U.S. equipment. Either way, that is a really small Service. Heck, I have a 30A breaker just on my elec water heater, and another on my clothes dryer.

No wonder you have so much voltage drop. You are way underrated, dn if that stuff is getting warm and hot, you better do something soon, before you end up with a fire. Even if it costs some money, I thik you should replace the entire service entrance from the transformer to at least those two sub panels, and maybe more. Your meter is too small, the wires are too small, and the main breaker is too small. At least get a 100A main in there and upgrade all the wiring to match. And if possible, get rid of those two sub panels and put it all in one box. A breaker panel with a 100A main, and slots for at least 12 small breakers are under \$100 (U.S.). You'll probably have to replace the meter socket. The power company supplies the meter. The rest of the cost is the wire itself.
If you intend to add any other larger power tools, I'd suggest a 150A or 200A main. (Assuming those are rated the same. You might have 108A or something???? Actually, I always thought breakers and fuses were rated the same, worldwide. I guess not!
Regardless, you really need to upgrade even if it costs some money. A fire will cost much more, and that saw motor wont last long running at 20 or 30 volts below its rating. The computers may lose power supplies too, and who knows what else.
Unless you rewire everything, I think I'd run a dedicated separate cable to that saw from your new main. It sounds like those wires are also too small, because you have a considerable voltage drop at the saw, IN ADDITION to the main dropping already.

Yea, that switch must be way too small to be getting that hot. You know that you're paying money on your electric bill, just to make those wires hot. That's a waste of \$\$\$\$.