softening the startup load on my table saw?

On Mon, 3 Feb 2014 02:19:01 -0800 (PST), robobass


WHAT? You're running an entire flat and shop on a single breaker?

Well, 100A circuit breaker boxes with 20 spaces, including 5 breakers, go for $52 here in the USA. Double it for Germany, I guess. 200A 30-space boxes with 5 breakers go for $99.97 at HomeDepot. If you run the wiring and install the box, then let the electrician verify it's up to code and connect it, it'll save you $500 or so.

Inconveniences like that can end up causing fires, so it's good that you're going to do something to prevent it. The current sensing relay is probably your cheapest, safest, best bet.
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Well, it's not the cost of the box and breakers. It's how much juice is com ing to it which is at issue. If I can get away with running an extra line o r two from the courtyard box, I'm in good shape. If I need to run more wire from the main building, then I'm looking at bonfires of money.
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On Mon, 3 Feb 2014 09:54:38 -0800 (PST), snipped-for-privacy@yahoo.com wrote:

Hopefully, you have the capacity at the courtyard. G'luck.
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robobass wrote:

Closer to 400 volts between phases.
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On Wed, 05 Feb 2014 17:01:53 -0500, "Michael A. Terrell"

Yup - just under - 398.7 +/-
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snipped-for-privacy@snyder.on.ca wrote:

I know. I rounded it before posting. Anyway, what's 1.3V (.326%) among friends? ;-)
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That makes sense. I've never learned the maths on this, but sort of underst and.
Many stoves and instantaneous water heaters here run on 1 ph. 400v. So it w ould appear that as long as you have 3 ph. going into the building, then it 's easy enough to run two wires to the local box and get your 400v. As I sa id, most older buildings don't have this option, so either there's only one phase running into the building, or the construction electricians didn't f oresee the usefulness (or they did, but saw $$$ in the future by not doing it then!). In 1965 there were no blow dryers or microwave ovens, and in our flat there's not even central hot water to the kitchen! There was a stupid useless little 5 liter pressureless boiler under the sink when we moved in . I fixed that by running copper pipe from the bathroom, but I'm not sure t hat was even legal... Well, Germans lived pretty low to the ground in those days compared to the suburban house I grew up in in Ohio, but at least our houses and buildings don't burn down easily!
My shop troubles aside, I live in a 1965 five story apartment building wher e juice is also tight. I've got 4 16a/230v breakers to run my 1000 sq.ft. f lat. When I gut renovated the kitchen (where the power comes into the unit) , I had to be somewhat creative about how to partition things so that no br eaker was overloaded. The box and meter are across the common hallway, so r unning additional wires/circuits is cost prohibitive. We don't typically ha ve metal conduit in this kind of housing. The wiring is just tacked up to t he base layer, and plastered over. It's pretty primitive, but we mostly get away with it. Since it's 230v, no wire has to carry the amps that North Am erican wires do.
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On Tue, 28 Jan 2014 10:07:52 -0800 (PST), robobass
Possibles:
1- Replace regular fuse with same-amp slo-blow fuse type. 2- Replace regular fuse with same-amp circuit breaker. 3- Install a slightly larger fuse in the circuit. 4- Call Sheppach and ask them for advice.
#3 is not code-approved, but it's not really dangerous. I've seen people replace 15A fuses with 20-ampers and never get into trouble, but a possibility is there (for -sustained- higher-than-normal load) And the bathroom fixtures supplier shouldn't have any problem at all with #1 or 2.
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On Tue, 28 Jan 2014 10:07:52 -0800 (PST), robobass
A 50 foot extention cord would likely do it - particularly if it is a bit light - - - -
What is the circuit fused at?? Would a time delay fuse (aka fusetron) solve the startup current problem??
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I have a Sheppach table saw which constantly blows the fuse on startup. On the motor it says 14.5 amps at 230 volts, which I interpret to be about 4 1/2 horsepower. I share my power with a bathroom fixtures supplier, and they have the keys to the fuse box. Daytimes it's no problem. They are friendly enough about switching my power back on. But, if they aren't there and the power goes off, then I'm stuck for the day. People have suggested UPS's, but I don't see any fit for my application. Any way to simply limit the current spike for this motor on startup?
================http://www.ametherm.com/inrush-current/selecting-an-inrush-current-limiter.html jsw
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    You've gotten suggestions to get a motor rated breaker, which would be the proper choice.
    However -- at 4-1/2 HP, you are in the size range where a three-phase motor is a good fit. If that motor *is* three phase, then consider getting a VFD to go between it and the wall. A VFD can be configured to take however long you like to spin up to full speed, and in the process to reduce the starting current significantly. (Even if you have no benefit from the variable speed part of it all. :-)
    Enjoy,         DoN.
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Thanks everyone for all the advice. To clarify, it's a 16 amp breaker, 230v . I haven't looked at it, but it's almost certainly not a special "motor ra ted breaker". I'll try that first, as that would be quick and cheap. I didn 't realize until last night how big that motor was. In principal I have 3.8 kw on the circuit, which I have been abusing, running about 3kw for heating and not always shutting that down before starting up the saw. The box is c lose by, and it would be easy enough to run another circuit or two to the s hop, but the toilet guys are typical cautious Germans and won't let me do i t myself. Paying an electrician to do it would naturally be expensive, but I suppose I'll have to bite the bullet at some point. For now I just have t o be diligent about managing my current draw.
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On Wed, 29 Jan 2014 02:44:10 -0800 (PST), robobass

Ask if you could do the work yourself and then let the electrician connect it all up for you. That'll save you a lot of money. Find an electrician who'll do it for you, then check with the store owners.
You shouldn't have a saw and heater on the same line, anyway. It's no wonder you're blowing breakers.
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Yes, that's the plan. It will still be expensive though. These guys here are insane, and people put up with it.

Agreed. No choice at the moment. Only one line.
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On Wednesday, January 29, 2014 9:13:12 AM UTC-5, robobass wrote:

When the motor is running, it is putting heat into the building, so you do not need the heater when using the saw. _So you could add a relay activated by turning on the saw. The relay would cut off the heater.
Dan
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On Wed, 29 Jan 2014 08:21:33 -0800 (PST), " snipped-for-privacy@krl.org"

Greetings Dan, It it was me I'd use your suggestion. Easy enough to wire. In fact, contactors can be had with switches that turn off another contactor to prevent plugging. When I put a new control on one of my mills I did exactly this. And all the power coming from the motor does eventually end up in the shop. Eric
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On Wednesday, January 29, 2014 12:02:20 PM UTC-5, snipped-for-privacy@whidbey.com wrote:

motor does eventually

Many years ago, I suggested something similar. The Navy had a building wit h large electric heaters and a large air compressor. When both heaters and the air compressor were on, it exceeded the ratings of the transformers th at supplied the building. The Navy just swapped out the power transformers for larger transformers.
Dan
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robobass wrote:

Try putting an extension cord in series with the machine. There will be enough current limiting with a light duty cord.
John
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robobass wrote:

OK, this explains the problem! Note that most induction motors draw a current close to the full rating even when idling. This current is at a very lagging power factor, so the true wattage is small, but the current is large. As the load is increased, the phase angle changes, so greater wattage is drawn although the current reading only increases slightly. The breaker only senses current, and not power.
So, your 14.5 Amp motor most likely draws about 12 A with the saw idling, and could be 60+ Amps during the start. Obviously, you can't run more than a small light bulb on the same circuit at the same time without risking tripping that 16 A breaker. Especially if it is a standard breaker, and not a motor-load breaker.
You may be able to do most of the work (drilling holes, installing conduit, etc.) and then just have the licensed electrician make the final connection. You might save some money that way.
Jon
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On Wed, 29 Jan 2014 02:44:10 -0800 (PST), robobass

I take it this is a european setup?? Or british? Never see "16 amp" breakers in North America. If so, it is line to neutral, not line to line like here in the Americas. Get a SPDT switch or contactor and wire it so the saw and the heater can NEVER be on at the same time..
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