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Hey! So I bought this Black and Decker 14" corded string trimmer, GH3000. I'd like to run a 100' or really 200' cord with it, so I can go far back on my lawn.

But the owner's manual has a chart. The chart says two things:

- my cord shouldn't be more than 10Amp

- a 101'+ cord needs to be 12 gauge.

When I look online, all the 100 foot 12-gauge cords are 15 amp. (And I can't even find 200' cords.)

So how do I get a long cord with the correct amp rating? what happens if the amp rating on the cord is too high? Too much power?

Thanks!
Bill

bakersman said:

Hey! So I bought this Black and Decker 14" corded string trimmer, GH3000. I'd like to run a 100' or really 200' cord with it, so I can go far back on my lawn.

But the owner's manual has a chart. The chart says two things:

- my cord shouldn't be more than 10Amp

- a 101'+ cord needs to be 12 gauge.

When I look online, all the 100 foot 12-gauge cords are 15 amp. (And I can't even find 200' cords.)

So how do I get a long cord with the correct amp rating? what happens if the amp rating on the cord is too high? Too much power?

Thanks!
Bill

Click to expand...

Make one. Home depot has all the supplies and is not diffucult.

I moved your thread to the Electric & Battery Operated Forum. :smile:

Due to the amperage draw at 200' you are going to fry you trimmer by using that much cord.

You want a cord that can handle at least 10 amps. A 15 amp cord would be ok. Most residential outlets are 15 amp and some dedicated are 20 amp.

Hey, thanks for all the quick responses. So far the options are:

- Make one. Like, by connecting some 25' 12-gauge 10A cords? (Despite warnings not to connect the cords.) Or by finding outdoor Romex wire that is somehow both 150', 12gauge, but also will only allow a max of 10A? Is that even possible? Could i put something on the end of the cord to enforce a maximum draw of 10A? I am totally new to this.

- Go with a 15amp - the higher amp rating won't hurt the engine.

- OR: the higher amp rating will fry the trimmer.

This is where I guess I need to understand basic electricity terminology. I'll go dig up some tutorials.

Does anyone else use a corded trimmer with more than a 50' cord?

For instance, here's an 80' cord reel with 14-gauge. If I plug in a 50' 16 gauge, now I have 130' altogether, which the booklet says should all be 12-gauge. Am I worrying too much? What is the worst that can happen if the total length of the cords = too thin a wire for a length? The booklet says "loss of power and overheating" -- anyone ever fried a trimmer or electric mower like this?

Bill

I think you misunderstand the instructions.

The cord size cannot be too big, but it can be too small.

The higher the current load from the motor (amps) or the longer the length of the cord (feet), the bigger the cord must be.

Wire size is measured in AWG, where a smaller number means a bigger size (diameter) wire.

For a 10 amp motor and a 200 foot cord you need about a 10 AWG cord to get a 5V drop from the electrical outlet, so if the outlet provides 120 Vac, then the motor will see about 115 Vac.

For 150 feet, you can use a 12 AWG cord.

For 100 feet, you can use a 14 AWG cord.

For 50 feet, you can use a 16 AWG cord.

You can make a longer cord by joining two shorter cords together. For example, you can make a 150 foot cord by joining a 100 foot and 50 foot cords together. Loop them together into a knot so that they don't pull apart. I've seen this done a lot on construction jobsites.

Thanks, MowerMike. I hadn't thought much about the voltage drop.

MowerMike said:

The cord size cannot be too big, but it can be too small.

Click to expand...

Well, this is where I'm unclear, because the instructions say "not more than 10Amps". I should clarify that I made a mistake earlier: the motor is actually 7.5 Amps, not 10 Amps. So for a 7.5 amp rating, the instructions say the ampere rating for the cord must be between 6 and 10 amps.

An earlier post seemed to suggest that if the amp rating on the card were too high (if the cord were too large, right?) then the motor could
pull too many amps and fry. Or maybe that post meant the opposite, that a 200' 16AWG cord would be too small and overheat.

You can make a longer cord by joining two shorter cords together. For example, you can make a 150 foot cord by joining a 100 foot and 50 foot cords together. Loop them together into a knot so that they don't pull apart. I've seen this done a lot on construction jobsites.

Click to expand...

But if I join two 14 AWG cords, don't I now have a 150' 14 AWG that is too small, since it isn't the required 12 AWG?

Thanks again to everyone for help with these basic cord concepts. If someone posts a link to a good tutorial on this stuff I will gladly read it. Everything I find is either too conceptual (what is a volt?) or too specific (what gauge do you need to rewire your bathroom?).

Although, this article looks helpful: What痴 the Right Extension Cord Length for My Tools? | DO IT: Projects, Plans and How-tos
Obviously, it is dangerous to have too small a wire over too great a distance. Small wire = motor working too hard = fire/destruction. What I can't figure out is whether the wire can be too *big* (as the warning in the book seems to indicate, saying not to use a wire with a rating over 10 amperes).

bakersman said:

Thanks, MowerMike. I hadn't thought much about the voltage drop.



Well, this is where I'm unclear, because the instructions say "not more than 10Amps". I should clarify that I made a mistake earlier: the motor is actually 7.5 Amps, not 10 Amps. So for a 7.5 amp rating, the instructions say the ampere rating for the cord must be between 6 and 10 amps.

An earlier post seemed to suggest that if the amp rating on the card were too high (if the cord were too large, right?) then the motor could
pull too many amps and fry. Or maybe that post meant the opposite, that a 200' 16AWG cord would be too small and overheat.



But if I join two 14 AWG cords, don't I now have a 150' 14 AWG that is too small, since it isn't the required 12 AWG?

Thanks again to everyone for help with these basic cord concepts. If someone posts a link to a good tutorial on this stuff I will gladly read it. Everything I find is either too conceptual (what is a volt?) or too specific (what gauge do you need to rewire your bathroom?).

Although, this article looks helpful: What痴 the Right Extension Cord Length for My Tools? | DO IT: Projects, Plans and How-tos
Obviously, it is dangerous to have too small a wire over too great a distance. Small wire = motor working too hard = fire/destruction. What I can't figure out is whether the wire can be too *big* (as the warning in the book seems to indicate, saying not to use a wire with a rating over 10 amperes).

Click to expand...

Having too large of a gauge wire is not a problem. Pretty much never a problem as long as the physical size doesn't make it too heavy or too large. An extension cord is not designed to limit current. The motor will pull as much current as it needs. If there is a short or a problem than the circuit breaker will trip. Outside of that, you want the largest gauge wire needed to deliver the current without causing a voltage drop.

Chris

bakersman said:

Well, this is where I'm unclear, because the instructions say "not more than 10Amps". I should clarify that I made a mistake earlier: the motor is actually 7.5 Amps, not 10 Amps. So for a 7.5 amp rating, the instructions say the ampere rating for the cord must be between 6 and 10 amps.

An earlier post seemed to suggest that if the amp rating on the card were too high (if the cord were too large, right?) then the motor could
pull too many amps and fry. Or maybe that post meant the opposite, that a 200' 16AWG cord would be too small and overheat.

But if I join two 14 AWG cords, don't I now have a 150' 14 AWG that is too small, since it isn't the required 12 AWG?

Thanks again to everyone for help with these basic cord concepts. If someone posts a link to a good tutorial on this stuff I will gladly read it. Everything I find is either too conceptual (what is a volt?) or too specific (what gauge do you need to rewire your bathroom?).

Although, this article looks helpful: Whatç—´ the Right Extension Cord Length for My Tools? | DO IT: Projects, Plans and How-tos
Obviously, it is dangerous to have too small a wire over too great a distance. Small wire = motor working too hard = fire/destruction. What I can't figure out is whether the wire can be too *big* (as the warning in the book seems to indicate, saying not to use a wire with a rating over 10 amperes).

Click to expand...

One more time:

1) The required wire size is a minimum, not a maximum. A motor will pull the same current (amps), regardless of wire size. If the wire size is too small, it will overheat and the voltage drop will be too high so the motor will not get sufficient voltage to operate properly.

2) If you join cords to make a longer cord, then the cords each need to be the proper size. If you make a 12 AWG 15 foot cord from a 50 foot and a 100 foot cord, then each cord must also be 12 AWG.

3) If your motor only draws 7.5 Amps, then the minimum size cords you need are:

Up to 100 feet - 16 AWG

Up to 150 feet - 14 AWG

Up to 200 feet - 12 AWG

How much are those extension cords going to cost?

Did you consider a nice lithium battery powered trimmer? No cords to hassle with or limit your freedom of movement. Might not be much more money overall.

Get a "Yellow Jacket" brand cord. I have four of them, each 100' long. They are construction grade, are 12 awg and are rated at 15 amps. I have a feeling the instruction manual was probably written in the same language as the country the mower was built in, and therefore a translation error is causing the manual to state a maximum of 10 amp rating for the cord.

Think of a cord as a water hose, and think of the electric mower as a spray nozzle. Assume a particular spray nozzle has a 4 gpm flow rating @ 50psi. Please don't check my math, I'm just pulling numbers out of the air for discussion purposes. Let's assume a 1/2" diameter, 50' long hose will flow precisely 4 gpm @ 50 psi. With that hose, the nozzle will produce 4 gpm. Put a 5/8" diameter hose on that nozzle that will flow 7 gpm. Guess what, that nozzle will still only produce 4 gpm. Using too large of a cord with your mower is just like using a larger diameter water hose. However, switch that hose to a 3/8" diameter one that only flows 2.5 gpm, and you'll only get 2.5 gpm from the nozzle. Doing this to an electric motor will burn it up, overheat the cord, start a fire, or possible all three.

Think of electric flow in terms of water flow. The wire gauge is the hose diameter. Amperage is the same as water flow in gallons per minute. Voltage is similar to pressure in the sense that you have to increase it as the wire gets longer to account for voltage drop.

Here is a simple calculator I found on the net.
Voltage Drop Calculator JavaScript

bakersman said:

Hey, thanks for all the quick responses.

For instance, here's an 80' cord reel with 14-gauge. If I plug in a 50' 16 gauge, now I have 130' altogether, which the booklet says should all be 12-gauge. Am I worrying too much? What is the worst that can happen if the total length of the cords = too thin a wire for a length? The booklet says "loss of power and overheating" -- anyone ever fried a trimmer or electric mower like this?

Bill

Click to expand...

Just a note about coiled power cords if everything else wasn't enough. Allways fully unwind the reel before you use it. Don't ask me how I know that these 2 things are happening in a coiled extension lead.

The first I'll explain is inductance between the coils If you have 2 coils of cable next to each other and pass a current through either of them then that has an effect on the other - inductance which like you suggest causes a reactance in the cable. This has the same effect as a resistance in the cable and current flowing through it heats the cable. Obviously the more coils you have the greater effect this has (1 coil has 1 effect, 2 coils, 2x effect etc in simple terms)

The second thing that happens is that the coils wrapped round each other prevent the build up of heat in the cable from escaping - so it builds and builds and eventually the cable can overheat. Some reels come with overheat protection.


1 last thing, the rating for a cable in amps is for the cable to be fully unwound - if it is coiled then the current rating drops

Thanks for all the replies and help! It's great to finally have a grasp of these basics.

I'm realizing I'm lucky I didn't burn out a miter saw with a 16AWG cord.

I did think about a battery trimmer, but honestly the batteries on my cordless drill drive me crazy. Going corded is about reliability.

I have a feeling the instruction manual was probably written in the same language as the country the mower was built in, and therefore a translation error is causing the manual to state a maximum of 10 amp rating for the cord.

Click to expand...

Yes, exactly! I finally saw in another manual a longer version of the same chart. This chart included additional rows, so under "more than 6 | not more than 10" was "more than 10 | not more than 12". So, they must have just copied the "more than 6 | not more than 10" line into the first manual. I guess it just meant that, for an appliance using between 6A and 10A, these were the *minimum* gauges. It would have been better just to remove the amp range to avoid confusion.

Again, thanks for all the tips. I will definitely be sure to uncoil the cord! I had seen references to that, but I didn't realize the inductance doubled so quickly and dramatically.

Joining in late here, but I've been away from LMF for a long time.

bakersman said:

I did think about a battery trimmer, but honestly the batteries on my cordless drill drive me crazy. Going corded is about reliability.

Click to expand...

Does your cordless drill use NiCad or Lithium batteries? I've been a lot happier with lithium battery tools, including my Worx string trimmer.

Not sure if it's the battery so much as they just seem to build better charging circuitry when it's for a lithium-powered tool, to protect the battery from overcharging or over-discharging.

I will point out 1 gotha ... with connecting multiple cords... keep the connectors (plugs and receptacle ends) clean and free from dirt or crud, that causes higher resistance in the connections, which cause heat and voltage drop.

put some serious thought into a new battery powered trimmer

a 200' #10 extension cord will be quite expensive and heavy. I can almost guaranty you'll hate dragging it around