Heat Tracing Questions

[Charz]

1. Why the heat tracing cables draw more current during starting at start up temperature?
2. How self regulated tracing cables are inherently safe and can be used in hazardous area?
3. How the Maximum circuit length is determined according to the breaker type? What is the equation used here?

 

[Dsg319]

1. Why the heat tracing cables draw more current during starting at start up temperature?
2. How self regulated tracing cables are inherently safe and can be used in hazardous area?
3. How the Maximum circuit length is determined according to the breaker type? What is the equation used here?
View attachment 2555391

I can only answer #3.....sorry lol. But any how here’s formula I’ve always used.

say you have HT that is 5w per foot you take that multiply by your footage, than divide by voltage. 5w x250ft=1250/240volt=5.2amperes.

Or if you knew you only had a 20 amp breaker to work with and needed to limit your footage you can simply take and reverse the equation.

20amp OCPDx 240volt=4800va/5w per ft= 960ft.

Of course you wouldn’t wanna load a breaker 100% like that but just for maths sake I done it.

 

[retirede]

1) Because resistance is lower at the lower starting temperature.

2) It depends on the classification of the hazardous area. Generally speaking, as long as an electrical device is not spark-making during normal operation, it is suitable for class 1, division 2. Induction motors are a good example. There are some exceptions to this - operating temperature can also be a limiting factor depending on the group.