300 volt heater cable used where

[Bill D]

I bought some self regulating heat trace cable used for deicing. Normal 120 volt ac stuff.
It also included roll of what looked like zip cord. One end was crimped into U turn like the other cable. the other end was bare. The wire looks like stranded copper wire. added a plug and Plugged it into 120 volts. I could not feel any heat after 30 minutes. So I read the tiny black on black print on the jacket. It is like 5 watt/foot at 300 volts. Why 300 volts?
Where is 300 volts used maybe on a ship? 240, maybe but 300 volts?
Bill D

I will give it to my wife to tie up flowers and bushes.

 

[johnoder]

277v comes to mind - its one leg of three phase 460 to neutral (?)

 

[Bill D]

I thought of that so I wondered if some other country, maybe China?, used 300 volts.
Bill D

 

[4GSR]

China uses mostly 480v or like John said 277v to neutral, probably to ground over there.

 

[Bill D]

not like there is any problem translating volts to a different language or metric volts vs English volts. Just seems odd to be a nice even 300 volts.
Bill D

 

[EmGo]

China uses mostly 480v or like John said 277v to neutral, probably to ground over there.

380v 50hz for three-phase, 220v single for house wiring. I believe same as Yurop ?

 

[EmGo]

Mixed. Japan and/or Australia may have been the preferred model?

Not Japan for sure. They have all this weird stuff. Australia I don't know. What did the Soviet Union use ? Good chance it came via there, maybe originally from Germany ? Which would not have been in great condition in 1949 either, but still ....

 

[4GSR]

380v 50hz for three-phase, 220v single for house wiring. I believe same as Yurop ?

The industrial area I was in, it was 480v 60hz. Agreed older parts of the old city was still on 380v 50 hz. Ran into the same down in Brasil many years ago, too.

 

[Bill D]

Ermmm.. Not odd. Not at all..

Resistance heaters "work" at any Voltage up to the point they become a "fuse" and break their conductive path.

300 Volts - with a not-known-to-us safety margin atop - is that "safe operating" maximum set by the maker.

Maximum. There IS NO lower bound. No need.

That simple.

It will produce SOME heat at 12 Volts.

I will try again at 120 volts. I suppose I knew it should be making some heat at lower voltages. Thanks for that wisdom. I guess it was designed to be used at 277 volts with some safety margin.
I will give it longer and see if it can heat enough to be felt. I only need to raise it from about 45 to 50 F to prevent condensation on my machine in the winter garage.
Bill D

 

[johansen]

just run it on 240.

 

[Doozer]

Surprised no electricians post here.
It is a pretty good guess that 300volts
is the class of insulation rating, and
not the required voltage of the heat tape.
Insulation classes are 300 and 600 volt ratings.
Just look at any Service Cord in your machine shop.
SO is 600V and used for 480v
SJO is 300V and used for 240v

--Doozer

 

[johansen]

If its self regulating polymer stuff, it isn't going to get warm, that's the whole point. 5 watts per foot at 50F might be 1 watt per foot at 60F for all I know, without knowing what you bought, hard to find a datasheet.

at 40F it should be a lot more than 5 watts per foot. try measuring the current with the coil in a bucket of ice water.

 

[EmGo]

The industrial area I was in, it was 480v 60hz. Agreed older parts of the old city was still on 380v 50 hz. Ran into the same down in Brasil many years ago, too.

Unusual, and definitely not "old city still ran" .... where was this ? Have never been anywhere in China that was not 380v 50 hz (or 220 or so for single phase.) Been places a long time ago where the voltage would change by 60 v during the day, but base was always 380 and definitely 50 hz. 1990, had to change the speed of a hard drive by changing pulleys

 

[1yesca]

"UK is still in the early stone-age when it comes to sorting out how this new fad of "electricity" should be dealt with"

they [the uk ] could have ruled it. if they could have just make it leak oil

 

[motion guru]

Surprised no electricians post here.
It is a pretty good guess that 300volts
is the class of insulation rating, and
not the required voltage of the heat tape.
Insulation classes are 300 and 600 volt ratings.
Just look at any Service Cord in your machine shop.
SO is 600V and used for 480v
SJO is 300V and used for 240v

--Doozer

Bingo . . . Standard cable voltage rating tables here - https://code-authorities.ul.com/wp-content/uploads/2014/04/WC_MG.pdf

 

[EmGo]

Flat belt, ISS-80 pre-Winchester Labs "flying" heads technology, so had fixed heads for 14" stacks in removable cartridge. Had one in my residence. Frame survives holding a surface plate and 40-taper TG-100 racks.

One had no need to change speed. It weren't a teletype machine.

Storage devices have been self-clocked from the outset.

Untrue.

Even a computer with a mere 600 KHz CPU clock (GA SPC family) had no concern about spindle RPM of a storage device.

General Automation came along much later. K&T used PDP-8's in the C controls and their own computer in the D. I never had an A or a B. As I remember there was some sort of trigger marking on the outer edge of the disk and it had to be in synch with the i/o card. There was a process for setting it up but I've totally forgotten now.

Shugart 8" disk, used in C and D control Kearney Treckers. Separate motor, for 50hz had a kit to get the speed back up to where it belonged. It was even cheap, $30 or something. One pulley and a belt. You just changed the one on the motor, even had a K&T part number. They sold overseas to 50 hz countries.

Sorry about the "unboxing" aspect but you can see how they work somewhat here

https://youtu.be/c8aipwPTLr4

In the K&T's the side that's covered in this video has a molded plastic semi-transparent cover, you can watch the disk spinning and the arm moving.

Later on they developed a kit to retro these with a SCSI disk. Was about $4,000. Too much for me, the Shugart worked okay.

...genius.

Indeed.

 

[EmGo]

*sigh* You didn't even know what you were looking at.

No foul. It wasn't your cuppa. Then OR now.

Appliance users don't need to understand how the bones work.

They just f**k things up if they assume they DO.

QED

As usual, this is what you come back with when you are totally wrong - a giant porcelain bowl of pigshit.

FACT : Shugart 8" hard drives had an external motor that spin the disk via belt.

FACT : They had different pulley setups for 50 and 60 hz to get the correct disk speed.

FACT: They were used in K&T controls

In other words, you are, as usual, blowing hot stinky air out your ass.

 

[EmGo]

..your lazy, careless bluster got your ignorant ass into yet another hole you can't bullshit your way out of?

Uhh, no. The video of the Shugart 8" hard drive with the external motor and belt would have answered this question for anyone with two eyes and a functioning brain cell. I'd go hunt up the K&T part number for the 50hz kit if I thought it would do any good.

I'm mostly kinda surprised that there's no one else around here who ran Kearney Treckers ... wow.

But thanks for the sixteen column inches of idiocy trying to bullshit your way out of a black hole.

 

[EmGo]

^ What was that line ? "A tale told by an idiot, full of sound and fury, signifying nothing ?"

 

[EmGo]

Let's see how long you can keep struggling ... Lassie ! quick, run get Timmie, there's a pompous blowhard fell into the quicksand ! Bring a rope ... no, better make it a chain ! And the tractor, the big one !