Regulating a shower heater coil by phase cutting?

[cupoftea]

Hi,
We wish to regulate mains power to a 500W shower heater coil (a resistor)...so we will use symetrical phase cut dimming.
It is leading and trailing edge dimming together, so as to improve mains harmonics to pass EN61000-3-2.

Is this common, or are heaters exempt from mains harmonics regulations?

Its only a little shower.....as it just is used to wash armpits and hair.

What about mains half cycle skipping for this application? (eg miss one mains half cycle in eight, or nine, say?)

 

[FvM]

Why not full wave switching?

 

[Easy peasy]

full wave is by far the better method, 1,0,1 or 1,0,0,1,0,01 ... or 3,0,3,0,3, ... etc

No DC in the mains, super quiet as OFF & ON are at zero xing ....

 

[dick_freebird]

Probably depends on whether "we" are making a product for
sale under said regulations, or just rigging a finer control than
a bang-bang thermostat in the privacy of one's garage. In the
latter case, nobody's business if you don't make it their
business.

 

[cupoftea]

Thanks, but that will cause visible flicker...and sorry i forgot to say,......its an IR heater, and that "missing" method causes visible flicker.....the light flicker cant be (cheaply) blocked from the customer, and thye wont like it.

 

[FvM]

Phase angle control isn't permitted for non-lighting applications. I don't get the purpose of using a filament IR lamp for water heating, in so far your flicker problem is purely self-induced.

 

[cupoftea]

Phase angle control isn't permitted for non-lighting applications

Thanks, though what about symmetrical phase angle control...which has much better mains harmonics?

--- Updated May 25, 2023 ---

full wave is by far the better method, 1,0,1 or 1,0,0,1,0,01 ... or 3,0,3,0,3, ... etc

No DC in the mains, super quiet as OFF & ON are at zero xing ....

Thanks, though we wonder about the flicker regulations, pertaining to this?

 

[FvM]

Thanks, though what about symmetrical phase angle control...which has much better mains harmonics?

Doesn't keep Class A harmonic current limits at lower power percent as far as I see. Check yourself.

 

[Easy peasy]

at 500W, flicker is unlikely to be an issue

 

[dick_freebird]

Does the fact that it's an IR "lamp" make it a "lighting application"?