I just got the word that Ideal is having problems with production of it's circuit testers/analyzers, which I had ordered. I can test voltage and polarity with other testers I have, but I really wanted the ability to load test. Any ideas on something (small) I can make to load test 120 and 240 volts circuits. If possible I'd like to see what amperage the breakers trip at. Something more professional than heaters and toasters would be nice.

Dave

Dave I do not know if it is possible to get all those functions in a compact box without electronic control circuits. The problem is heat dissipation. A small box would get too hot too fast. In college for my senior project I made something very similar to the Sure Test meter using momentary switches, resistors, and banana test plugs for meter in a utility box (wished I had patented it). I also used a load box to test higher voltages like 240, but at the time I was an intern at a utility company so I was able to use precision “Ohm Spun” resistors from junk equipment. It would be very expensive to buy them on the market.

In order to test CB trip values you need to get resistance down to 1-ohm @ 100 W to test a 20-amp breaker. Granted a 100-watt resistor is not enough wattage for continuos load, but should work for instantaneous trip region of a 20-amp breaker if using a momentary switch rated @ 100-amps.

Another thought would be a bank of light bulbs, but that is not small. Which brings me back to the point I have been rambling on about. I do not think you can cram 10-pounds of poop in a 1-pound box.

Dave, one more thought, but it is not small and is ugly. To test breakers you might already have the equipment on the truck. A roll of 12 AWG wire. Figure out how many feet of wire it would take to make one ohm. Walla, a 1-ohm, high wattage, wire wound resistor.

Thanks guys, I appreciate the help. Would it simplify the problem if I made something only for 15 and/or 20-amp circuits at 120-volts? Also, it's been way too long since electronics classes. Wouldn't a 1 ohm resistor allow 120-amps? ...and at what current should breakers be tested?

Dave

Dave,
One thing you have to be aware of, is the power dissipation at such a low resistance in the circuit.
With 120V flowing through your 1 ohm resistor, you are dissipating 14.4kW of heat.
(P=V2/R)
Question is, are breakers required to be tested to this degree?.

{Message edited to fix up formula}



[This message has been edited by Trumpy (edited 01-17-2005).]

The wound romex resistor idea reminds me of firing up a PVC heater off of a temp service. Did not want to cut a piece so I pulled one end and tied it to the temp. pulled the other and went to the heater. Left the coil on the ground. Long story short, I came back to a coil of smoking melted plastic.

I feel a bit dumb about this, but I'll continue. At 120-volts I want to load the breaker past it's rating to test that it trips. I set up 300-watt bulbs with 5 on the first switch.

1500W/120V=12.5A. Then switch on another 300-watt bulb for 1800W/120V=15A. Then I continue throwing switches until the breaker trips. Is this an effective way to load test? With inverse-time breakers what should the load be? ...and most of all...Is there something better than light bulbs???

Dave

Dave, when I was in the business of commissioning electrical distribution systems we tested at the instantaneous trip level of a breaker, 1-second or less. Generally speaking that level is at 6 times the OCPD rating. It varies, so it is not gospel. The one ohm I quoted is for a 20-amp breaker @ 120 volts. We used custom made load boxes with electronic timers, and switch selectable load resistors. It is not practical for residential and most commercial jobs. That is why I related to my college and poor man hybrids.

Trumpy is right, heat dissipation is a factor. However if you can control the duty cycle, you can use say something like a 1-ohm resistor @ 100 watts. For a poor mans version I thought of using #12 AWG wire. Do not know what the wattage rating is, but I think it is safe to say it is over 100 Watts, but less than 14KW. Duty cycle is the key.

You can certainly use light bulbs; they are cheap and can safely dissipate the heat safely without regard to duty cycle. How many depends on the breakers characteristics and what amount of time you would want the breaker to operate.

If it were me I would wait until the sure test meters are available again. Just too much work for something that doesn’t amount too much more than a toy, and an ugly one at that. However play with it on paper and do some of the math, you would certainly learn from the experience.

Be aware that you'll get a significant magnetic field when passing 120 amps thru that coil of wire. Things like this were used to demagnetize color TV sets back in the early days of vacuum tube color TVs. You could wipe your credit and ATM cards with it, but there would be more important safety issues that I'd want to be well away from the coil of wire anyway.

Dave I have to ask why would you want to test this?

Personally I feel it is a bad idea to try to test the breakers trip level at the far end of the branch circuit.

If you want to test the breaker do it at the breaker.

You also need to know the trip curves of the breaker, a 20 amp breaker may run for days with 25 amps of load applied.

Remember that dereckbc was talking about testing the instantaneous trip at about 100 amps for a 20 amp breaker. At that level it trips right away without heating the branch circuit wiring.

It seems you want to test the thermal trip which may stress the insulation of the branch circuit wiring.

I do not believe the ideal circuit analyzer tests the trip level of breakers.

Thanks guys. I'm wondering if the tester I was going to get does a load test for a voltage drop reading, or harmonics, or voltage under load, or something other than tripping the breaker.

Dave

PS What I'm after is performing some kind of testing of residential electrical systems other than the usual visual inspection. Any ideas?

Dave, (or anyone) out of curiosity, do you know what the production problems are with the Sure Test meters?

Roger

[This message has been edited by Roger (edited 01-17-2005).]

Dave
I, like Bob, would not want to see that test performed at any length too far from the CB. SureTest is not the only manufacturer producing this type of equipment. There are others and if you cannot wait for the SureTest, you may want to opt for one of those.

Pierre

The word from the supplier is that they aren't getting a part that they need for it and are considering discontinuing it. I was looking at the Ideal Sure Test 61-158, I don't know if the problem was only with that one tester.

Now that I read the catalog it does say "Test voltage drop under actual ISA load". Greenlee doesn't have this kind of tester, but Fluke may.

Thanks.

Dave

Dave have you tried looking for the meters from distributors?

The tester do test the circuit under load, and even applies load between L-G. Although it will not test the trip point of the breaker, it will give you the L, N, & G impedances and you can determine the calculated fault current with a little math.

I agree with the crowd here you do not want to test breakers at the far ends unless you can test in the instantanious region. And that region should really be done with engineered manufactured equipment that has UL approval. Sorry about taking you down the home brew road, just the ham radio in me.

Dave,

The Ideal SureTest will load test, check impedence of each lead, etc. Nice unit. I would expect Ideal to get production back on track soon.

As far as performance testing a 15A or 20A single pole breaker on a 120V circuit--there's a commercially available unit that does exactly that. It's called the "circuit breaker analyzer-1000" by KO Instruments.

See their website at
http://www.koinstruments.com/

I've used one of these units to check old breakers. I offer it as an alternative to replacing an old panel.

The breaker analyzer pre-tests the branch circuit by checking voltage drop at 20 amps. If o.k., you then run the test; if during the test, there's evidence of weak points (what KO engineers call "voltge droop"), the unit aborts the test. The instrument is UL listed.

I wouldn't even think of using a home-brew set up to performance test a breaker--the liability issue looms large if the breaker doesn't work. What if you burn the circuit open with your home made tester, or worse, start a fire somewhere?

The CBA-1000 isn't cheap. But I charge a premium for each breaker I test with it.

And no, I don't have any connection to the company.

Cliff

How do you get a lot of heat out of a little box? There are many ways, but if we exclude the more exotic ones, like placing it in a wind tunnel, I can see only three options:

1.) A box with metal "fins" that lets the air cool the surface. A fan will make it even better but it still won't be very small. Perhaps one of those portable heating fans (or whatever you call them) could do? (The sort you use on construction sites and other places)

2.) Evaporative cooling. Use a water cooled resistor and let the water boil off. When the water level goes too low, some switch cuts power. (Could happen if you find a faulty breaker or test a breaker with a higher rating.) Could be rather small, but it will be steaming.

3.) Water heater: heat water from a tap and let it back into the drain. This way you get a small unit and you get the heat out of the house. The downside is that you get two long hoses...

{Edited for spelling}

[This message has been edited by C-H (edited 01-18-2005).]

Dave,
Why not just get a tester like the one mentioned in this thread .
Sure it won't let you trip breakers, but it will give a decent figure of what the breakers should be tripping at, in Amperes.

Cliff are you aware that unit is only checking the instantaneous trip? (short circuit trip)

It looks like a great unit, I would like to have one but it does not test the breakers thermal trip. (overload trip)

I talked with the supplier again today and it seems Ideal is discontinuing that line of about 5 or 6 testers.

Dave

I have made myself a loadbank with 4 1875Watt small size hair dryers and a receptacle on the side. when i plug the load bank in and turn on all of the units it draws about 50Amps at 120 volts (give and take)at that current a 20 amp cb breaks in an instant. Then at the same time i can check for voltage load with the units off and measure for voltage with the units on then take the difference and calculate VD%. Furthermore, when i have the load bank pluged in a GFCI with only one tester/hair dryer on i short across the neutral and the grounding on the receptacle installed on my load bank and that trips the GFCI.

Which tells me that the GFCI trips under load.

You may want to try www.loadbanks.com

Edward

iwire--

Excellent point about the KO unit. It performance tests the magnetic trip components, and of course the contacts and the mechanical parts (pivots and linkages).

Do you think that the bi-metallic strip that comprises the overload trip mechanism would be less likely to have a problem than the magnetic part? I'm thinking so.

And BTW, thanks for serving as moderator. I find this forum to be an invaluable resource and sometimes a source of real entertainment (I'm thinking of the car salesman's flying rug story...)

Dave55--I'll be at ElectricWest in Anaheim in early Feb, I'll ask the Ideal people what the scoop is on the SureTest units, and report back.

Cheers,

Cliff

Yesterday, I talked to the tech person at Ideal for the Sure-Test product line.

She said that the Sure-Test is being revamped/improved based on comments from users. For instance, an improved display panel with backlighting is being added.

Evidently it'll be several weeks before the new units are in the distribution pipeline.

I like the current models, we'll see if they drop any features that I like. IF so, I may run to the supply house and pick up one of the old ones! Am I gettin' old, or what?

Cliff

Cliff... I feel the same way as you. I must be an old dog and unwilling to change. I really like the old Sure Test, and have used one for years.

I always wondered when it would go by the wayside. It was originally manufactured by the inventor, then Daniel Woodhead (the version I have) picked it up, and they sold it to Ideal. It's been a challenge keeping up with a supplier and asking questions.

I'm always skeptical about "improvements."

Revamping/Improving sounds so much better than...we're having problems getting parts for the units, or it's not a very profitable line. Anyway, I appreciate the information & in the meantime I had to "settle" for a Fluke Ammeter/Multimeter.

Dave