SSR controlled heater - how to protect main line

using arduino and SSR to control 2000W heater element.
heat control working like a charm.
what seems as potential issue to me is that rest of electronics that reside on same phase. for instance, “regular” light bulb in same room is blinking quite observably especially when SSR working on slower rates.

is there any common approach how to protect other devices? cheaper would be better of course :slight_smile:

thanks a lot,

of course tried googling and searching forums. did not find any good solutions; maybe just did not know right keywords?

I'm assuming you're on North American power for the following analysis...

P (WATTS) = E (Voltage) * A (Amperage)


2000/120 = 16.67 Amps

Old American standard, 15 amp fuse on basic outlets, New NEC standard, 20 amp circuit breaker on basic outlets.

If you know your house circuitry, there are outlets for things like washing machines that will serve one socket from one 20 amp circuit breaker. Your 2000 Watt heater needs to be on one of these. Instead you're running it on a circuit that serves two or more sockets and the lights in the room (and in an older house possibly even more than that). And if you're unlucky, your circuit panel is a Zinsco/Sylvania which has been known to have the contacts either stick, or since the design is defective, 20 Amp breakers need 30+ amps to actually trip them.

Standard U/L approved supplemental heating equipment is rated at 1500 watts or less for a reason. It allows you to use the room heater without overloading the circuit as long as the other incidental loads are reasonable (not on the same circuit as your home entertainment system :) ).

Cheaper will not be better, your device needs a separate exclusive circuit and is pushing the limits of a single circuit (is the socket you are pulling the power from rated for 20 amps? most cheaply built McMansions have 15 amp sockets despite the bloated price paid for the house, is the wiring serving the socket in that exclusive circuit 10 gauge instead of 12).

And to reiterate Richard Crowley's warning, if the smoke gets out on this one, it soon combines with wood smoke and plastic smoke as overheated mains wiring will set stuff on fire. (True life instance during my youth that ended well, element on stove developed red spot (immediately turn off element, let it cool and trash it) and my mother used it that one last time. The arc jet burned through the muffin pan sitting on the burner and left a dark spot on the ceiling. It could have been worse.) Overheated wiring can set fires, and if the insulation burns off and you get an arc, the arc can easily hit 10,000 degrees F.

I’m @europe = 220V <10A
sorry for not stating it on first place (just remembered, came back to edit my post and … you were already here:)).

new house, new copper wires. it’s bathroom originally, should be supposed to deal with 2kW hair dryer.

16A ABB circuit bracker; 16A sockets; wire is “bigger” then regular though don’t konw exact size from top of my head.

It will be pulling 9 amps, what's the circuit breaker amp rating on that circuit?

thanks for your feedback and time so far.

16a breaker, yes.
checked hair dryer before posting - one was 1.5kW, other 2kW. cloth dryer is even 2.35kW.

just in case if it got missed - it does not blink when just switched ON on full power (but still slightly change can be noticed). when arduino/SSR turns down it to less power - lamp starts to flicker. and intensity increases with smaller analogwrite values.

You are suffering from what is known as "conducted emissions" from your controller. You are inducing voltage spikes into the wiring and they are briefly canceling out the mains voltage and hence you see the lights flicker. It happens at low settings because there is a larger delay from the start of the mains cycle and hence the SCR is being switched on when the voltage is higher. In fact you should get the maximum interference at 50%.

The standard way of dealing with this is to use mains filtering consisting of chokes and capacitors. They have to be rated for the current you are using, in this case it is quite high for a mains choke. This one is only 6A and is quite pricey:-

good news is that I am sure you will find a cheaper one.

I knew it is about finding right keywords :) sounds like sometging like this;item=69-629-42; for ~10eur will do.

Thank you all so much!

cheers, Austris

Yes that looks fine. If it doesn't cure it it will sure help a lot.

by "regular" meant "incandescent", yes. got the filter (w/out socket/just solder - less than 5eur) rated for 10A. plus changed wiring and got rid of cheapo extension cord (rated for 16A, but did not look good).

no flicker anymore neither at 10% nor 50%.

Thank you Gurmpy_Mike for filter idea and Richard for safety :)