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Looking for 200-ampere main breaker

Posted by donk4kyv (My Page) on
Fri, Aug 24, 07 at 19:19

Three solid weeks of triple-digit temperatures and running the air conditioner full blast has taken its toll on my main circuit breaker. I noticed yesterday that the entire box was warm to the touch. I took off the front cover, and discovered that the problem is the main 200 amp breaker. It hasn't tripped, but one of the wires coming in from the meter was hot to the tough. In fact I could (carefully) touch the wire terminal with a wet finger, and it would sizzle just like on a clothes iron. I measured the voltage drop at the terminals, and they all checked out OK, but across the breaker itself, there is anywhere from 150 to over 500 millivolts of drop. This is on just one side of the line. The opposite side shows only about 5 to 15 millivolts drop across the breaker. The main entrance wire got so hot it actually burnt off about 2" of the insulation near the breaker from conducted heat.

As expected, when I called several local electrical parts suppliers, no-one had a replacement breaker. The original was installed in about 1970, so at 37 years old, the part is "obsolete", even though the company is still in business. One more case of a replacement part becoming unavailable about when the original gets old enough to need replacement.

I flipped it on and off a few times, and evidently it is making better contact now and although it is still running hot, is no longer hot enough to fry spit, but I need to replace it ASAP.

Just in case someone might happen to have a new-old-stock one lying around, it is a Square D type Q2MT, rated to trip at 200 amps, with 10,000 amp SYD (surge).

Nothing found on the Square D website. Anyone know where I might order one online?


Follow-Up Postings:

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RE: Looking for 200-ampere main breaker

I do not have time at the moment to do so myself but I suggest Google. Type in the description Square D type Q2MT. Also obsolete breakers. Southland deals in such, if memory serves me correctly. Search eBay.


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RE: Looking for 200-ampere main breaker

try here

Here is a link that might be useful: breaker


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RE: Looking for 200-ampere main breaker

If the wire burnt - Perhaps that wire connection is loose and/or the bolted? bus end too.


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RE: Looking for 200-ampere main breaker

If the wire is damaged maybe its time to consider replacing the wiring and the panel?


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RE: Looking for 200-ampere main breaker

is this what you are looking for?
http://circuitbreakersuperstore.com/content/p/8/pid/1176/catid/434/Q2M2100MT


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RE: Looking for 200-ampere main breaker

In the future, I'd strongly suggest using alternate methods for testing electrical equipment that touching the terminal of a 200A main breaker with a wet finger! (carefully...sounds like an oxymoron) I'm not trying to be rude, just looking out for your safety, but that breaker can pass enough current to kill and still not trip. Keep in mind even with the main breaker off or removed there are parts of the panel that are still live! If you don't have experience working around this stuff, maybe hire a pro. I'm also with jason1083 on this one; While SqD makes fine quality products, couldn't hurt to consider replacing the whole panel... especially if replacement breakers are hard to find and expensive. If the main is dying who says the others aren't too far behind?

Above all else...Stay Safe!!!


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RE: Looking for 200-ampere main breaker

Geese, why didn't you just stand in a puddle and touch the terminal post? Oh, wait a minute, don't do that until you put me in your will as the sole beneficiary :)

You have very succinctly solved the problem, you just don't know it yet. This is basic Ohm's Law electricity.

A breaker does not provide a Voltage drop. It's purpose is to monitor the amperage level of the line and if the Amperage is High Enough for a long enough period of time, the breaker will trip.

Let's think, what makes heat in an electrical circuit? Certainly, it is caused by electricity moving through the wire (Amperage) across a load (Resistance). The higher the flow the hotter the components and the line.

I would chase this problem by using an AM-Meter (clamp on). This type meter allows you to clamp the lead inside a meter loop that measures the current flow (Amperage) of the line.

The very hot weather and the continuous running of the AC and hot wires tell me that the circuits are near overloading and tripping the breaker. The easiest thing to do is go through the house and turn any load that has no reason to be on, OFF. Reduce the load, reduce the current flow. Reduce your electric bill.

Also, you must check the Amperage at the breaker because if your breaker is labeled at 200 Amps (usually stamped onto the to the toggle arm) and the meter is showing you a sustained 220 Amps then the breaker needs to be replaced before you let the house burn around you because the breaker failed to trip when it should have.

Also, please consider this, the local utility may have re-mapped its power distribution and your house is now getting 250 Amps instead of 200 Amps by mistake. 250 Amps is almost the standard for residences now-a-days. Call them and tell them to correct the error immediately!

Good luck
yours will have a tolerence level built in just to keep the breaker from tripping on spike on the line.

Check the rating on your breaker to see what amperage level will trip the breaker. I would suspect that


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RE: Looking for 200-ampere main breaker

In order to work on the main breaker with any degree of safety is to pull the meter. The outside temps and running your A/C has nothing to do with the condition of your main breaker. The way these connections work is three 00 cables come down from the service entrance to the top side of the meter base. From the bottom side of the meter base the same type of three 00 cables come into the main panel and are attached to lugs in the panel box. I don't think replacing the main breaker will solve your problem. My guess is that one of the lug connections is loose. My suggestion is to hire a master electrician to access the situation before you burn the house down. If you are stupid enough to touch a wet finger to one of those cables I hope you have a good life insurance policy. You are lucky to be alive!


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RE: Looking for 200-ampere main breaker

A breaker does not provide a Voltage drop.

Sure it does. Darn little, but how else is it going to monitor for long-term overloads? It's thermal.

the local utility may have re-mapped its power distribution and your house is now getting 250 Amps instead of 200 Amps by mistake.

I'm sorry, this makes no sense at all.


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RE: Looking for 200-ampere main breaker

Quoted from a previous post: "Also, please consider this, the local utility may have re-mapped its power distribution and your house is now getting 250 Amps instead of 200 Amps by mistake. 250 Amps is almost the standard for residences now-a-days. Call them and tell them to correct the error immediately!" BALONEY!
Agreeing with Texasredhead that a loose connection is highly likely to be the real cause of the problem. It could be a bad lug on the breaker, perhaps stripped setscrew or lug that has split. I personally would replace the breaker, found some available at $71.00 each. If the conductors are copper, a light cleaning is all that is necessary. Overheated aluminum must be cut back to an undamaged portion or replaced.


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RE: Looking for 200-ampere main breaker

Yep, previous post, love it when people get on this forum and distribute information that is completely wrong. Don't we already have the home store employees do that. (:


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RE: Looking for 200-ampere main breaker

Okay, I dispute the statement that outside temps have nothing to do with any thing.

If you are looking at trippile digit heat without a heat index causing the problem as in Fort Worth, TX. then you need to consider the demand load on the utility company and what that is doing to the VAC and AMP. These are factors that can and do cause homeowners problems. As checking the amperage with a clamp on Amp Meter, if I'm concerned about the breaker failing to trip properly wouldn't it be prudent to establish what the output amperage of the breaker is?
I also resent that the information I've given out is "completely wrong" If any of you blessed with the exact science of electricity and code as you are would have responded before I did I might not have answered the question.

Finally, I stand by the info I put into this item. Nothing I said would get anyone killed and by golly, it would still lead the homeowner to a failing component!


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RE: Looking for 200-ampere main breaker

Don, I'm sorry, don't take this personally - but your statement, "the local utility may have re-mapped its power distribution and your house is now getting 250 Amps instead of 200 Amps by mistake" is both incorrect and irrelevant to the situation.

If you learned that in school, go back and complain. Seriously.


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RE: Looking for 200-ampere main breaker

I live in the Ft. Worth area and have for 39 years. Last year we had 49 straight days over 100 degrees. Guess what, my main breaker did not fail and never has!!!


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RE: Looking for 200-ampere main breaker

Has Ohm's law been repealed in some parts of the country? It is still in effect here as far as I know...


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RE: Looking for 200-ampere main breaker

wow utility does something to force everyones' house to pull 250 amps 24/7? Hate to pay those electric bills and bet those feeders are hot!


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RE: Looking for 200-ampere main breaker

A circuit breaker does have a voltage drop, although a small one usually in the milivolt range. The magnetic-trip only breakers have the least drop. The major loss is resistive and contact drop. A thermal-magnetic trip breaker has more voltage drop due to the thermal trip portion. However, the watt loss of the thermal trip is very low, not enough to smoke the insulation of the connecting wires. Most household breakers are thermal-magnetic. If your wires were running very hot near the breaker terminals, then there must have been a poor connection. Aluminum wire is the leading cause of connector heating. If aluminum wire is used, then the connectors must be rated for aluminum - some connectors are not - and some connectors may overheat anyway from other factors even though rated CU-AL.

If you wish to stay alive, call a qualified electrican to replace main breakers. The incomming wires are always HOT until disconnected from the power comapny.

You should be able to get replacement breakers for a Square-D box. However, the sale of main disconnects may be limited to professionals.

Bear in mind that the Square-D Comapny ceased to exist a number or years ago. They were purchased by Telemecanique and are part of that orginization. The Square-D tradename and products are still made today but are under the design control of the new parent.


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RE: Looking for 200-ampere main breaker

When you purchase a new box it comes with the main breaker installed. There is an outfit in Arlington, Texas, called Breaker Broker Company. 1-800-553-2431.


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RE: Looking for 200-ampere main breaker

Texadsredhead

How Do? I lived in Watauga from 1988 through 1991. I worked out in Southlake at an IBM R&D lab. Small world.

We've just finished with some nasty hot weather here. When I said the the power company may have remapped a grid, I know that is very far fetched and fact I agree with you that it is very unlikely. But it does get him where he needs to be for help on source power problems.

I have no idea what tools and test equipment are available to the ouestioner, but I don't want him running up and down a breaker box sticking meter probes into it. A clamp on AM meter is far safer than probes or fingers.

The HD nearest me uses retired electricians and plumbers so their advice is usually pretty decent. Personally, I use Graybar's counter for my electrical supplies, pricey yed but worth it to me for the quality.

I hope this makes sense to ytou, I left my glasses home abd my typing skills are nil.


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RE: Looking for 200-ampere main breaker

don-ump, it would not matter if the POCO supplies you with a 250 amp feed and you only have a 100 amp panel. your main breaker still will trip at overload. the amount of power available to the meter from the POCO makes no difference.

now, if they were giving you 300 volts instead of 240, THAT would be a problem. but the amps are only there on demand. if you don't try to pull tha tmuch, they will not force it on you.

to the OP, if 2" of the insulation is missing, are you gonna have enough wire to make to back to the connection? if the feeder has to be replaced, you may as well go on and replace the whole panel, it won't be that much more compared to replacing the feeder, or at least in my area it ain't.


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RE: Looking for 200-ampere main breaker

David, thanks for the message, however I'm not the one who needs it.

If the box and the breakers are hot to the touch, then something is pulling a load out of the main block.

My first concern would be to determine how much of a load is being drawn and why. Yes I would visually check the wires looking for burn marks but first I want to know what line is the bad one. I clamp on my trusty am meter and lo and behold, one side is pulling 190 amps. Futher down the stack I find that the clothes dryer is the villain because of the amp. on that line. Now I go and see what's going on a the dryer. Well, look at that, the dryer panel is "Christmas Treed" and the power supply is cooking away.

I don't think I would then go fix the panel box for this, I'd probably fix the dryer.

Don


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RE: Looking for 200-ampere main breaker

I Googled "Christmas Treed" and got a test taking procedure
and a way of stacking steel. What's your definition?

Thanks
Chris


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RE: Looking for 200-ampere main breaker

Texasredhead, Spenser electrician, bus boy.

In the year 2000, out in Garrad County, KY alongside US27 South, The local co-op was pre-wiring during site development. No one took notice because it was just standard work. When the site started coming on-line, houses in the adjacent development started having electrical problems that looked like a low voltage problem. When they tracked it backward and started pointing fingers it was determined that someone (of course unknown) had taken drops off the adjacent neighborhood either intentionally or because of a severe case of stupidity.

I know on the North Side of 27 we were fine and were laughing about the problems, but then we were not on a cooperative, we had "Blue Grass Power".

Human stupidity isn't something that novices only are guilty of. Apparently, professionals are sometimes prone to episodes of brain dead activity also.


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RE: Looking for 200-ampere main breaker

Good to know. But as Saltcedar asked, what does "Christmas Treed" mean? Inquring minds, etc.

FYI, the other guy's "handle" is Bus Driver, not Bus Boy.


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RE: Looking for 200-ampere main breaker

David, thanks for the message, however I'm not the one who needs it.
obviously you do, electricity don't work like that. i have 100 amp power supplies on my workbench, yet i can fix a pager that draws less than 250 MILLI-amps and not french fry it. if the supply amperage were forced on the end devices, then every one would require custom supplies to exactly match their house hold, and when they are not drying clothes or running electric heat then their lights would burn up from pulling an additional 100 amps. my house has 400 amp service to it since it had 2 20kw electric heaters plus everything else was electric when we bought it. since i now only need a MAX of 200 amps if i turn on everything in the house, including both heat and ac at the same time, does that mean i need to call the POCO and have my service down graded, because that is EXACTLY what you stated.

If the box and the breakers are hot to the touch, then something is pulling a load out of the main block.

this does not necessarily mean it is an EXCESS load though. it could be within the specs of the box and all subsequent breakers, but a bad connection WILL cause heat.

My first concern would be to determine how much of a load is being drawn and why. Yes I would visually check the wires looking for burn marks but first I want to know what line is the bad one. I clamp on my trusty am meter and lo and behold, one side is pulling 190 amps. Futher down the stack I find that the clothes dryer is the villain because of the amp. on that line. Now I go and see what's going on a the dryer. Well, look at that, the dryer panel is "Christmas Treed" and the power supply is cooking away.

I don't think I would then go fix the panel box for this, I'd probably fix the dryer.

yes, you first check the load and if it exceeds capacity of the ciruit you find out 2 things, why it exceeds it and why the protection did not trip. you fix them in reverse order, the protection FIRST with the excess load disconnected, then the excess load is repaired before it is powered back up.

i know this was hypothetical, but for others sake if you have a dryer pulling 190amps, you have a fire. the wire won't handle that load and neither will the dryer itself. keep in mind tha tto some who read this board electricity is in teh realm of magic and anything and everything they read they believe. if you are going to give an example, at least make it realistic.


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RE: Looking for 200-ampere main breaker

"Christmas Treed" = all lights on the control panel are lit. Much like a fully decorated "Christmas Tree".

Davidandkrasie,

You missed a change, not me. I stated that if you plug a 110/120 VAC (Voltage, not amperage) device into a line that has mistakenly been changed to 220 because of shoddy work, that device is going to cook and probably take the device's power supply and most of the circuit boards also.

For example, back when I was a repair tech with IBM, I received a call for a local Va. Bch. attorney. The complaint was that the Typewriter was running to fast and smelled.

What the real problem was: an electrician had just completed wiring the office for a 220VAC line for an air conditioner. Somehow he managed to get the 220VAC to drop across the outlet for the secretary's desk outlet.

Apart from the drive motor on the typewriter, I had to replace the PS and PSMC (Power Supply Motor Control) board.

Also the attorney had to replace the lamp and pencil sharpener.


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RE: Looking for 200-ampere main breaker

i swear i must be blind, because i still don't see the change you say.


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RE: Looking for 200-ampere main breaker

I hate discussions that degenerate like this one has - but.....

Resi service equipment (panels, disconnects, etc) usually have a current interruption rating prominently displayed. This number is usually something like 10,000 AMPs or 22,000 AMPS. This is the amperage the main breaker (or fuse) can reasonably be expected to interrupt in the event of a direct short. While the service wiring and overload protection aren't designed to carry this much current for long periods of time it is usually available at most service drops. This is also why you wear personal protective gear when installing a meter.

The capacity of the electrical service is determined by the ratings of the service entrance conductors (wire size) and the overload protection (the main breaker and adequately sized busses in the panel). If you walk out in the back yard of almost any neighborhood with overhead electrical services you will see a number of poles carrying wire from the secondary of a transformer (and in many places several hooked up together) that supply every house. The same supply feeds the houses with 60 AMP, 100 AMP, 125 AMP, 150 AMP, 200 AMP, 225 AMP, and sometimes larger services. If anybody can explain how the wire itself sorts this out and provides an individual source rated at 250 AMPs rather than 200 AMPs I'm all ears.

At any rate, a loose connection at a breaker or buss in a panel is far more often a cause of cooked wire than what's on the other end.

Residential circuit breakers are built to function in two ways. They detect short circuits and thermal overloads. A short circuit will cause an almost instant trip but it is well within reason to expect that a main breaker rated at 200 AMPS would carry a 220 AMP load for a while before tripping. This is a usual and expected situation. This is DEFINITELY not the way "electronics" overloads operate as most overloads open the protection immediately.


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RE: Looking for 200-ampere main breaker

David,

The change to VAC is in a different thread. I apologize but to tell you the truth, I feel a little like Custer did when and his Pals camped by a river one night and when Custer looked out the tent flap and saw the Indians circling and asked, "Who invited the neighbors!"

Itsunclebill:

How is what you are saying different from what I said? Granted you fleshed it out more than I did, but that's okay.

I said earlier that breakers are made to trip if the amperage goes to high to long. It's still basic Ohms Law.

Something within the block is now sucking up current causing an inrush of amperage. If the Amperage climbs to high for sustained amount of time, the breaker trips.

A short circuit gives the same result. A 220VAC line across a 50k Ohm load yields an amperage of 0.0044A. A short occurs and the resistance drops to 5 Ohms. The amperage is now is equal to 44 Amps. Put that across a 20 Amp breaker and who is going to last longer, the short or the breaker?


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RE: Looking for 200-ampere main breaker

Trying one more time- HEAT from poor connection(s) at or near the breaker can cause tripping at AMPERAGE loads far below the rating of a breaker.


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RE: Looking for 200-ampere main breaker

Well Bus, hopefully the OP took away the fact he probably had loose terminals and will likely need to acquire a bit more free wire to cut back on the service side, or replace some wire. I can't count the number of houses I've been to where the main breaker is tripping due to a loose lug on the supply side - I almost suspect some guys leave them like that for callbacks.

FWIW, the heat from a bad connection at the supply end will work back toward the load. There's not much point in checking what's on the load end if only a couple of inches of wire on the supply end have been hot enough to melt the insulation. If it's ALL melted then there's likely a lot more wrong than just a load issue (see FPE issues)


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RE: Looking for 200-ampere main breaker

Most of the lugs now have torque specifications for tightening. I bought a high-dollar torque wrench that clicks at the preset (adjustable) value. Checked behind myself a few times. Some were too tight, some were not tight enough. Now I use it for all lugs. Given the tendency to sue in event of problems, protecting oneself in another way is just necessary.


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RE: Looking for 200-ampere main breaker

Now I know why I would never again buy any repair services from IBM. (Don-ump's former employer.)


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RE: Looking for 200-ampere main breaker

Alright no more cheap shots!
I do think, however, that someone needs to go back and study the difference between amperage and voltage before giving any more advice...


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RE: Looking for 200-ampere main breaker

"Also, please consider this, the local utility may have re-mapped its power distribution and your house is now getting 250 Amps instead of 200 Amps by mistake."

Unbelievable.
The ultimate example of ignorance in action.


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RE: Looking for 200-ampere main breaker

don-ump,

Based on several of your posts in different threads in this forum, I think it would be great if you would stop giving advice in the area of household wiring. You really don't know 1/10 as much as you think you do.


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RE: Looking for 200-ampere main breaker

I still want to know what an "AM meter" is. Does it come with FM too?


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RE: Looking for 200-ampere main breaker

I'm sure surprised that you did not realize that it is a typo. It's an "AMP Meter" It let's you measure the amount of current flowing through a wire. For example if a breaker is rated for 15 amps and you see it's output is 25 amps, then why hasn't the breaker tripped?

Is it possible that you wouldn't care why you would just replace the component without a valid reason?

As to SBS9's comment, I'60, I started learning electricity when I was 10. I was a parts runner from the shed to the line for an electrical company in the Bronx, NY. I still don't have a toe tag on me because I did something dumb, so I guess I know enough to not get dead.


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RE: Looking for 200-ampere main breaker

For example if a breaker is rated for 15 amps and you see it's output is 25 amps, then why hasn't the breaker tripped?

Well, it could be a defective breaker.

Or, it could be because it hasn't been carrying 25 amps for long enough. That kind of overload isn't dangerous for a few minutes, and most breakers are designed to allow some overload for some time. The amount of time before they trip is typically inversely proportional to the size of the overload.

This is under the control of a thermal device, so overheating of a terminal can fool the breaker into tripping early.

If you know the breaker's specifications, then you can better judge whether it should have tripped under the circumstances.


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RE: Looking for 200-ampere main breaker

An ammeter is a measuring instrument used to measure the flow of electric current in a circuit. Electric currents are measured in amperes, hence the name. The word "ammeter" is commonly misspelled or mispronounced as "ampmeter" by some.

granted, it is from wiki but...


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RE: Looking for 200-ampere main breaker

Don, my car battery has the capacity to deliver 650A. Does that mean it delivers it at all times? Of course not. Even a dragging starter will start burning up cables at 400A. And that little 18 ga. wire to your radio would be gone in a heartbeat. Power is consumed by the load required, not what is provided.

I've talked to you about this before. I would seriously consider the post by SBS9. I've made some educated guesses here, but I always try to preface those remarks by stating just that...and to go to one of the pros here for a definitive answer.


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