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So I recently upgraded my printer to heat the bed with 110v AC. I've been a bit paranoid about this and have added safety checks to the printer, however I am worried what effects the printer has on the house electrical system as a whole. I have two solid state relays driving a total of 1050W worth of power and I noticed toggles quite a bit once it reaches the target temp. The relays are cool to the touch, but I am worried if they pose any hazard to the outlets them selves.
Hello. This effect is referred to as pulsing not toggling. As in Pulse Width Modulation or PWM and it is what Solid State Relays were made for. Because the moving parts in a traditional relay would fatigue and wear out and also the repeating collapsing fields from the coil being energized and release so many times would wear down the controlling electronics. I say as long as you are using a good quality SSR then you should be fine. Once setup and running you will most definitely want to do the PID autotune thing. I am running a 1000w mains powered silicone bed heater on my TronXY build. I used a genuine Crydom SSR. And while some say it is not necessary I got a heatsink for my SSR just to make sure everything stays cool. The most important thing to remember in our setup is the protection device for the worst case scenarios. This comes in the form of a thermal fuse that should be wired in line with one of the power wires to the bed. I am using a 133c thermal fuse. It is taped to the bottom of the silicone bed heater with high temp tape. This way if for any reason the bed achieves greater than 133c it will break the power circuit before setting my home on fire. DO NOT overlook the safety. Best advice anybody could ever give anybody ever. Be Safe.
So my concern is more about the effect it has on the rest of the house. So to use plumbing as an analogy, rapidly opening and closing a faucet causes water hammer which stresses the plumbing in the house. Electrically, does the pulsing of an SSR have a similar effect? I've taken measures to ensure the printer itself doesn't burn down.
Well a water hammer arrestor will not help you here. This is a little different. A 110v sine wave a/c current is constantly swinging back and forth from -110v to +110v at a fundamental frequency of let's say 60hz. Now all devices that connect to this 110v signal will use integers of this fundamental frequency. You know like 120, 240, 480, etc so that all the pulses of power are at the right time and go with the slope of the sine wave instead of fighting it. And it is hard to understand how a SSR being pulsed by a 24vdc mainboard looking at a temp sensor and kp ki and kd settings only is going to sync itself with an a/c sinewave. And so if you are concerned you could use a lab scope to look at your sinewave from various sockets in your home while you run your printer to better understand what if any harmonics are being created. Typically we need the THD rating to be below 6% for sensitive electronics and if you are seeing a sinewave being distorted by your printer another way of dealing with that might be to buy a pure sine wave battery backup to run your bed heater. This uses wall power to charge the batteries and generates its own sinewave from the batteries for the load device. So it is never actually connected to wall power. This will remove your pulsing device that doesn't care about fundamental frequencies from your home's sinewave. But these heaters do not even work the SSR's to the point of needing a heatsink. I would run the printer first and see if the lights flicker when the bed is heating. If so then I might be inclined to look at the THD.
So if I have bulb on the same outlet it will flicker but only from that socket, but everything else seems unaffected. A few days ago I thought it had a greater reach but then realized the florescent tubes were slowing dying out and weren't related.