Household Appliances and SSR's

[onthekeg]

I recently started using my SSR and PWM and I got myself wondering if I am damaging my refrigerator, freezer, or dishwasher that may be running at the same time due to the voltage buck and boost caused by the SSR action?

Maybe I am worried for no reason, but I wanted an electrical guru's opinion on this. Anyone have any ideas?

 

[pickles]

I'm not sure I'm following you, but the SSR is simply turningthe circuit on and off rapidly. Im not sure what you mean by "bucking and boosting"?

 

[onthekeg]

I'm concerned that the current in the house would be bouncing around some due to the rapid turning off and on millions of time of the SSR as it is throwing around 5500watts of current.
I don't think my killawatt will even measure the rapid voltage swings, but I am curious if the voltage for my 120v outlets would be moving from 110v-130v as the SSR turns off and on.

 

[jkarp]

I'm not aware of any issues on the inbound side of SSRs. The switched side can be a concern with inductive loads depending on where the SSR cuts in on the AC waveform but most SSRs have zero-crossing circuitry to compensate for that, plus our load is resistive anyway.

I would keep the PWM cycle time somewhat sane though. Cycling SSRs more than once per second generally isn't recommended.

 

[onthekeg]

I'm not aware of any issues on the inbound side of SSRs. The switched side can be a concern with inductive loads depending on where the SSR cuts in on the AC waveform but most SSRs have zero-crossing circuitry to compensate for that, plus our load is resistive anyway.

I would keep the PWM cycle time somewhat sane though. Cycling SSRs more than once per second generally isn't recommended.

So you don't think that the voltage is swinging around too much? I was just concerned that I may wreck my refrigerator or freezer if its running when the SSR is doing its thing. (Household voltage)

 

[jkarp]

So you don't think that the voltage is swinging around too much? I was just concerned that I may wreck my refrigerator or freezer if its running when the SSR is doing its thing. (Household voltage)

I really don't. I've never experienced any issues while running my system over the years.

 

[Maxkling]

If this was the case wouldnt you think that all the other houses on your transmission line would effect your home? Or homes that share more than one transformer would effect one another? Your totally fine. What you/we do with electric brewing may seem signifigant, but in reality the power consumption and load isnt high in most new construction/up to date applications standards.

 

[onthekeg]

I can understand that point Maxkling, when I turn on the grain dryer fan its a 20hp motor, and it will dim the lights for a few seconds, but when its on, it is on for days, so it only affects everything once. The SSR is blinking away like crazy and I wasn't sure if that was spiking the power around the house.

 

[Maxkling]

Yea, usually with a large load like a motor, you get a in rush current on start up. After that it will drop to its running amperage(depending on its load). Also depending on what circuit the load is on will effect that circuit, if light are on the circuit for your garbage disposal you most likely see them dim as you turn it on. A large load might effect your whole house, like the AC (nowadays it really shouldn't).

Also take your meter and and probe your outlets in your house, you should see a voltage fluctuation. The service going into your home transformer fluctuates, usually not much. There are cases, especially in the summer where you'll get rolling brown outs, where so many people are running their AC units for so long that the draw on the service will bring it down.

 

[audger]

i can tell you that if you had some sensative electronics, like a computer power supply, plugged into the same breaker circuit as your SSR is on, yes it will absoloutely affect the voltage to the other equipment and put more stress on it.

you can even blow a power supply by doing that. the voltage converter inside is trying to keep an extremely steady output power, and varying the input power by sitting it next to a 20 or 30 amp load which switches on and off even once per second will put great stress on the p.s.'s capacitors and regulators.

you will also hear the effects of the SSR as signal noise if you have any decent audio equipment plugged into the same circuit. this is the whole point of line conditioning and "auto voltage regulation" on battery backup units. it will also happen with any large pulsating motor like in a washing machine, that swtiches back and forth over and over.

If this was the case wouldnt you think that all the other houses on your transmission line would effect your home?

the scale is not the same. if you have a 500w power supply next to a 5500w SSR, there will be an effect. if you have a 100amp load in your house, you would only notice the same thing if you neighbor started switching his 5000amp panel on and off. there is also much greater distance and the sheer size of the mains on the street poles pickup the bucks/boosts.

 

[Inodoro_Pereyra]

If you want to be rigorous, there's no easy answer to your question.

For starters, SSR's will create a lot less voltage "jumps" (sorry, I don't know the right English word) than mechanical relays or contactors, as they have a smoother ON/OFF transition.
That said, the real cause of those voltage jumps is much more complex that just the type of relay you're using. Contrarily to what most people think, wires are not just resistors. A wire is a resistor with a coil in series, and several capacitors between it and other wires, ground, etc. What that means is that a wire has inductive and capacitive components, that are related to its length, diameter, distance to other wires, ground, walls, etc. All of that will make the wire act like a filter, showing a differential attenuation for different frequency disturbances. Add to that that the transformer that feeds your house also has inductive (of course) and capacitive components, and you can see how complicated it can get.

Bottom line, if you're an electronics engineer, with LOTS of time on your hands, and you happen to LOOOOOOVE math, maybe you can calculate it. Other than that, the only accurate way to know the amount of variation produced by your SSR's switching would be to hook up a digital oscilloscope to the line, and run your machine. So, if you have, or know someone who has a digital oscilloscope, you can try it. Otherwise, I wouldn't worry too much. Most appliances are pretty resilient, and the sensitive ones will start functioning erratically way before they crap out on you.

One test you could do would be to hook up a desktop PC right on the same outlet (or as close as possible) your brewing setup is plugged into. If you see the PC acting weird when you're brewing, you should look for a solution. If the PC works fine, you're OK. Just make sure it's a DESKTOP, as laptops are protected by their battery.

Finally, if you see some of your appliances starting to act crazy when you're brewing, a couple of fairly cheap solutions to your problem would be to minimize the length of common wire between your appliances and your brewing setup (meaning, putting your setup on a dedicated circuit, right off the house main breaker), and, if that doesn't solve it, getting an isolation transformer for it.

 

[audger]

One test you could do would be to hook up a desktop PC right on the same outlet (or as close as possible) your brewing setup is plugged into. If you see the PC acting weird when you're brewing, you should look for a solution.

this is similar to trying to find a gas leak with a match.

you may or may not notice your computer "acting weird" but the voltage swings could still be damaging/stressing the power supply components (usually the big electrolytic storage caps are the first to go).

if you do not have the proper equipment to test for these electrical problems (good multimeter or scope) dont intentionally plug household electronics that you care about into the circuit just to see if they "act weird". digital electronics that are very susceptable to noise, like TVs, audio equipment, computers, power supplies, should all be plugged into another circuit just in case.

analog electronics like your toaster, incandessant lights, heaters, fans, etc. should be mostly unaffected.

For starters, SSR's will create a lot less voltage "jumps"

i think you are refering to settling time and jitter that you get from the physical contacts snapping closed and 'bouncing' before coming to rest, which isnt exactly the problem we are talking about. but you are correct, SSRs are "cleaner" signal-wise. what the OP was asking about was voltage surges and sags produced when a very large load is repeatedly turned on and off again.

 

[o4_srt]

If you want to be rigorous, there's no easy answer to your question.

For starters, SSR's will create a lot less voltage "jumps" (sorry, I don't know the right English word) than mechanical relays or contactors, as they have a smoother ON/OFF transition.
That said, the real cause of those voltage jumps is much more complex that just the type of relay you're using. Contrarily to what most people think, wires are not just resistors. A wire is a resistor with a coil in series, and several capacitors between it and other wires, ground, etc. What that means is that a wire has inductive and capacitive components, that are related to its length, diameter, distance to other wires, ground, walls, etc. All of that will make the wire act like a filter, showing a differential attenuation for different frequency disturbances. Add to that that the transformer that feeds your house also has inductive (of course) and capacitive components, and you can see how complicated it can get.

Bottom line, if you're an electronics engineer, with LOTS of time on your hands, and you happen to LOOOOOOVE math, maybe you can calculate it. Other than that, the only accurate way to know the amount of variation produced by your SSR's switching would be to hook up a digital oscilloscope to the line, and run your machine. So, if you have, or know someone who has a digital oscilloscope, you can try it. Otherwise, I wouldn't worry too much. Most appliances are pretty resilient, and the sensitive ones will start functioning erratically way before they crap out on you.

One test you could do would be to hook up a desktop PC right on the same outlet (or as close as possible) your brewing setup is plugged into. If you see the PC acting weird when you're brewing, you should look for a solution. If the PC works fine, you're OK. Just make sure it's a DESKTOP, as laptops are protected by their battery.

Finally, if you see some of your appliances starting to act crazy when you're brewing, a couple of fairly cheap solutions to your problem would be to minimize the length of common wire between your appliances and your brewing setup (meaning, putting your setup on a dedicated circuit, right off the house main breaker), and, if that doesn't solve it, getting an isolation transformer for it.

Transmission line theory....nice

 

[Inodoro_Pereyra]

this is similar to trying to find a gas leak with a match.

you may or may not notice your computer "acting weird" but the voltage swings could still be damaging/stressing the power supply components (usually the big electrolytic storage caps are the first to go).

if you do not have the proper equipment to test for these electrical problems (good multimeter or scope) dont intentionally plug household electronics that you care about into the circuit just to see if they "act weird". digital electronics that are very susceptable to noise, like TVs, audio equipment, computers, power supplies, should all be plugged into another circuit just in case.

analog electronics like your toaster, incandessant lights, heaters, fans, etc. should be mostly unaffected.

Not really. Checking gas leaks with a match is dangerous. Using a PC to check for voltage variations, and especially line noise, is only dangerous to the computer power supply if you leave it working under those conditions for a very long time. And, even if that's the case, a PC power supply is $30, a lot less than a digital oscilloscope.

A multimeter (good or bad) is not the appropriate testing equipment for that kind of problem, as it has a big delay, has no way to data log, and tends to integrate the signal. The reason I suggested using a PC, and not a TV or other kind of electronic device, is because a PC will literally go crazy way before suffering any real damage.

Does anybody still use incandescent lights at home???

i think you are refering to settling time and jitter that you get from the physical contacts snapping closed and 'bouncing' before coming to rest, which isnt exactly the problem we are talking about. but you are correct, SSRs are "cleaner" signal-wise. what the OP was asking about was voltage surges and sags produced when a very large load is repeatedly turned on and off again.

SURGES!!! That's the word I was looking for!!! Thank you!:rockin:
I understand the OP may have asked about that, but he didn't specify, and, if your stuff gets screwed up by a power surge, it's just as screwed as if it dies because of a level variation. Other than that, for a properly designed/wired electrical installation, switching 30A on or off shouldn't produce more than a couple of volts up or down, hardly enough to do any damage, even in the most sensitive household appliances.

Transmission line theory....nice

Didn't know you called it that...
Either way, I'm glad you liked it...

 

[onthekeg]

Thanks for the answers people. I wasn't sure if it was going to cause my other appliances with motors undue harm with the rapid cycling of the SSR. I would have thought others would have mentioned something if indeed it was messing with the household electricity. For a lack of a better term, making the electricity supply "dirty"

 

[Sawdustguy]

Thanks for the answers people. I wasn't sure if it was going to cause my other appliances with motors undue harm with the rapid cycling of the SSR. I would have thought others would have mentioned something if indeed it was messing with the household electricity. For a lack of a better term, making the electricity supply "dirty"

It's a good thing you are not an audiophile. There would be tons of snake oil salesmen out there trying to sell you all kinds of useless power conditioning equipment.

 

[o4_srt]

Anything used to transfer electricity is considered a transmission line, having capacitance, reactance, inductance, resistance, etc. The values depend on line length, width, materiel, etc.

Or so I am told by the engineers I work with. Haven't had a class on it yet, still workin on gen-eds.

 

[Inodoro_Pereyra]

making the electricity supply "dirty"

Just so we're clear: don't use starsan to clean it up!!!
Seriously though, you should be OK. But if you have doubts about your house's wiring, do the PC test.

It's a good thing you are not an audiophile. There would be tons of snake oil salesmen out there trying to sell you all kinds of useless power conditioning equipment.

Hummmmmmm...

Anything used to transfer electricity is considered a transmission line, having capacitance, reactance, inductance, resistance, etc. The values depend on line length, width, materiel, etc.

Or so I am told by the engineers I work with. Haven't had a class on it yet, still workin on gen-eds.

I see your point. Just didn't know the name..

Gen-eds?

 

[Sawdustguy]

Anything used to transfer electricity is considered a transmission line, having capacitance, reactance, inductance, resistance, etc. The values depend on line length, width, materiel, etc.

Or so I am told by the engineers I work with. Haven't had a class on it yet, still workin on gen-eds.

That is correct. Any transmission line can be represented as a complex combination of R, L or C and can be calculated using a Vector Diagram and expressed as an number with magnitude and phase in a complex number.

 

[o4_srt]

General education credits in college, the courses required for a degree that have nothing to with the degree being earned. For instance, one of my gen Ed coursed is an arts class, although my major is electrical engineering.

 

[Inodoro_Pereyra]

Wow...I thought that BS only happened in my country...

 

[o4_srt]

Wow...I thought that BS only happened in my country...

Nope, I wish there was some way around it, but in order to get a bachelors degree, you need a bunch of pointless classes. Personally, I'd like to take more classes within my field of study, resulting in a better understanding of my field, but it's not up to me.

 

[Inodoro_Pereyra]

Hmmm...that sucks.
But look at the bright side. At least you'll be able to do all kinds of cute drawings in your wiring diagrams...

 

[o4_srt]

Hmmm...that sucks.
But look at the bright side. At least you'll be able to do all kinds of cute drawings in your wiring diagrams...

Lol luckily I was able to snag a rock and roll history class that counted as my arts credit. Much more interesting than van gogh, Georgia o'keefe or michangelo.

 

[Inodoro_Pereyra]

You should see if they have a homebrewing class...

 

[onthekeg]

It's a good thing you are not an audiophile. There would be tons of snake oil salesmen out there trying to sell you all kinds of useless power conditioning equipment.

I don't buy snake oil anymore, I am single with 4 boys. 2 are teens and 1 just graduated college. None of them have jobs. Snake oil would cost way to much and I have learned that I can't have anything nice until they are all out of the house.