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Old 08-27-2020, 06:13 AM
Antti Torstensson Antti Torstensson is offline
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I did some re-reading and re-thinking. The Kanthal handbook says this:

"As there is no current flow for part of the supply
cycle, phase-angle controlled loads will give rise
to an apparently poor power factor, even with a
purely resistive load, and this can lead to problems
on large installations, especially if the firing angle
is small. Generally, the starting voltage with new
elements should not be less than 60% of the supply
voltage, to minimize this effect."

I now think this must mean that the elements should be sized in a way that you initially get full required power with 60% or more of the supply voltage. Although thatís not what it says, itís the only way I can make sense of it.

Still seems that the power factor would be really low especially while the furnace is idle. Why exactly is a poor power factor an issue? Does it make the electricity company unhappy?
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