Critique my controller wiring

[sicktght311]

Pulled the trigger finally on building my 3v 120v brewing controller. I've been using a hacked up inkbird IPB for over 2 years and its finally time to build something where i'm not constantly moving cables and wires, and can handle a full 20amps.

Basically a stripped own version of the Kal/ElectricBrewery controller, all running 120v 20amp power to control a 2000watt element in the boil kettle, and HLT. I'm currently running 1650watt elements but i'm upgrading to triclamp 2000watt elements soon, so i'm building this with 20amp in mind. Input power will be a 12/3 cable through the controller with a cable clamp to secure it, and the low voltage will be 16awg since its just powering PIDs, and the two pumps i use barely draw 2 amps max together (tan DC solar pump, and 25watt mark II). The controller box will be an IP67 plastic enclosure so i went for a ground bus strip instead of grounding to the enclosure like on the Kal.

My only question is instead of running the 12awg input off the power relay into a bus bar and distributed from there, should i run the 12awg out of the contactor directly to the first SSR, and piggy from that SSR over to the 2nd, and tie a 16awg off the contactor output and run THAT to the bus to power the pids and pumps? Thereby keeping all of the high amp drawing power leads off of the bus? Or does it really not matter and so long as the bus bar is rated for the voltage and amperage, it shouldnt be an issue and keeps everything neat and tidy without having to crap two 12awg wires into one SSR terminal

 

[sicktght311]

And for another check, should i pass the incoming Neutral through the 2nd pole on the startup contactor? Or is it redundant and unnecessary.

While i dont see myself moving to 240v any time soon, i'm building this panel because it will suit my needs at 120v, and can be retrofitted eventually if i need to upgrade to 240v by switching out the contactors, the lights, and wiring, which is significantly less than rebuilding entirely.

 

[doug293cz]

Doesn't hurt to run the neutral thru the contactor, but it's not necessary.

No need to change contactors to upgrade to 240V. The 120V coils will work fine connected to 1 hot line and neutral. You only need new wiring if you want to use more than 20A @ 240V. Some 120V lamps will need to be upgraded to 240V.

You should have multiple hot bus bars. One segment for 20A connections, one segment for 10A/16AWG wiring (pumps), and maybe a third for all the low current loads (PID's and contactor coils) which can be wired with ~20AWG (which is much easier to work with.) You should have a 10A fuse/breaker on the feed side of the 10A bus segment, and a 1A fuse on the feed side of the low current segment.

Your control wiring to the SSR's is incorrect. The control inputs do not connect to system neutral, but rather the "-" output on the PID.

Brew on

 

[sicktght311]

Thanks Doug!

1) I thought the SSR goes back to the PID, but i realize i misread one of Kal's diagrams and forgot i was looking at the contactor, not the PID. Noted. Send and return for the signal for the SSR both come from and to the PID. Got it
2) So wouldn't it make more sense to just bypass the Bus bar for the hot 20A connections and go right to the SSRs? Then use a Hot bus for the 1A or less items? The Mark II pump only draws .2 amps, and the tan dc solar pump draws about the same. I figure nothing on the low current bus would then be pulling any amperage to cause concern. Can always put a 1a fuse on that bus bar, since I doubt i'll upgrade pumps to anything that would draw more power until i upgrade to 240v. Just seems silly to build a bus just for 2 elements, and then another for 2 pumps, and a third for all the rest of the low wattage stuff. Thoughts?

 

[sicktght311]

Revised based on what i mentioned above. Wired the 12awg directly to the SSRs, powered the hot bus through a 7awg fuse (i might even reduce down to 4 or 5amps) on 16awg supply line, and then 16awg out to the pumps, contactor coil wiring, lights, and PID power. Will use 20awg wiring for things like the wiring to the temp probes, and to the on/off for the SSRs from the PIDs

 

[doug293cz]

Bus bars are not required, they can just make the wiring job easier. So, running the 12AWG directly to the SSR's is fine.

Brew on

 

[sicktght311]

Bus bars are not required, they can just make the wiring job easier. So, running the 12AWG directly to the SSR's is fine.

Brew on

Yeah i'm a big fan of neat and tidy so i like having terminal blocks and bus bars where i can. Approval given by doug, good enough for me! I'll post the build when all of the parts are here

 

[sicktght311]

One last question. I broke out my multimeter last night to test the switches to ensure i'm clear on what connectors are what, but i want to make sure i'm clear on lighted switches

At the bottom on lighted latching NO rotary switches, i see two blocks. Tested with my multimeter, one block (3 and 4 number on the terminal posts) is for the powered circuit (120v) to determine signal open or closed. The other side, doesnt seem to have any continuity between the two 4 terminal posts no matter switch position when tested with a mulitmeter, and i'm assuming this is for the neutral line to power the light. Does the neutral wire go in terminal post x1 or x2?

 

[doug293cz]

Neutral can go to either X1 or X2. AC is not polarized. The other X terminal is usually connected to the switched side of the contact pair.

I wouldn't expect to see continuity thru the lamp. It's not a simple incandescent filament type lamp, nor is it a simple LED.

Brew on

 

[sicktght311]

Confused a little bit. What do you mean by “The other X terminal is usually connected to the switched side of the contact pair.”

do you mean 120v hot goes to 3, 4 goes out to the destination, neutral goes to x1, and x2 gets jumpered to 4?

 

[sicktght311]

Confused a little bit. What do you mean by “The other X terminal is usually connected to the switched side of the contact pair.”

do you mean 120v hot goes to 3, 4 goes out to the destination, neutral goes to x1, and x2 gets jumpered to 4?

Actually if this is what you mean, totally makes sense. I wasn’t thinking of the light Block as it’s own circuit. Pulls the switched power off the out of the hot side block from the switch, neutral to the other side to complete the circuit for the light

 

[doug293cz]

Confused a little bit. What do you mean by “The other X terminal is usually connected to the switched side of the contact pair.”

do you mean 120v hot goes to 3, 4 goes out to the destination, neutral goes to x1, and x2 gets jumpered to 4?

Correct. The terminal numbers don't really matter. What you show is one of the several ways to wire the switch that work.

Brew on

 

[doug293cz]

Actually if this is what you mean, totally makes sense. I wasn’t thinking of the light Block as it’s own circuit. Pulls the switched power off the out of the hot side block from the switch, neutral to the other side to complete the circuit for the light

I think you've got it. All the blocks are electrically independent, and the switch blocks are mechanically coupled.

Brew on

 

[sicktght311]

Never ends

So as i'm putting this together, i'm like 98% done, and now in the testing phase and i'm finding a few issues with the SSRs

1) I'm getting 16-18volts coming through the contactor to the output legs if the switch is turned to the on position for that particular element, when the element signal from the PID isnt firing. I noticed this immediately by the fact that my "element on" lights are turning on whenever i put the switch over to the particular element position, even though i expected the lights to be off. When the PID starts pulsing to fire the element, the light gets brighter when on, and dimmer when off, but never fully off. I read that SSRs leak voltage in the "off" position, so is it because have 120v lights since its a 120v system, and not 240v lights, i'm seeing it turn on because the voltage leaking through is 1/10 of the full rated power for the lights instead of 1/5 like with 240v lights? I have them powered from the hot leg of the output of the contactor, and the neutral is just back to the neutral bus bar
2) Also along the lines of bad SSRs, one of them pushes through 120v when a signal from the PID to turn the element on functions, but the other SSR isnt. Just a continuous 16-18v regardless of PID state and i can hear it humming, so i'm assuming that SSR is just completely bad.

Both SSRs are brand new Inkbirds from amazon. I've heard Inkbirds are generally reliable, but guess i got a dud? Does everyone's SSRs leak that constant 16-18volts in the off state? Just ordered a new set to replace the bad one and see if that fixes the 120v issue, but still, the lighting issue is not what i expected.

If its just the way its designed, and having an element light dimmer when off, and brighter when on, is the only way it works, i suppose thats fine. Just want to make sure i'm not missing anything, or if i should pop in 240v lamps instead of 120v, even though my system is 120v

 

[sicktght311]

Ok the more i read, without the actual element plugged in, the voltage leaking is going all to the lamp. With the element plugged in, it acts as a capacitor almost and the leaking voltage doesnt affect the light, but also shouldnt energize the element enough where it makes a difference. Just confirmed by bringing the controller to my brew area, and plugging in the element with the probes removed so nothing turns on. Light immediately went off when switched to the outlet. Looks like thats solved, but still theres definitely a bad SSR that needs to be replaced. New ones should be here sunday!

 

[doug293cz]

SSR's are not like mechanical switches. They switch between a high resistance state (~160,000 ohms) and a low resistance state (~0.055 ohms.) "Off" is the high resistance state, and "On" is the low resistance state. They leak current, not voltage. Below is a simplified model of how an SSR behaves.

The above drawing is for a 5500W @ 240V element. A 2000W @ 120V element has a resistance of 7.2 ohms.

In a 120V system, the voltage difference between nodes "A" and "C" is 120V, whether the SSR is on or off. What's more interesting is the voltage difference between nodes "A" and "B" (i.e. the voltage across the element.) The voltage across the element is given by the voltage divider equation:

​

Velement = V0 * Relement / (Relement + RSSR)​

​

When the SSR is off then RSSR is 160,000 ohms, and the voltage across the element is:

V = 120 V * 7.2 / (7.2 + 160000) = 0.0054 V​

​

The power delivered to the element is given by P = V^2 / R, where V is the voltage across the element, and R is the element resistance. So, the off state power to the element is:

P = 0.0054^2 / 7.2 = 0.00000405 W, [or effectively 0]​

​

When the SSR is on, then RSSR is 0.055 ohms, and the voltage across the element is:

V = 120 V * 7.2 / (10.5 + 0.055) = 119.1 V​

​

And power to the element is:

P = 119.1^2 / 7.2 = 1969.8 W​

​

So, even though the SSR is a leaky switch, it is very effective at turning the power in a heating element on and off.

When you have an element firing light in parallel with the element, and the element is not connected, then the voltage divider in the circuit diagram above consists of the SSR and the LED lamp. Since you get ~17V across the element firing light when the SSR is off, we can solve the voltage divider equation for the effective resistance of the LED lamp.

17 V = 120 V * R / (R + 160000)​

(R + 160000) * 17 = 120 * R​

17 * R + 2720000 = 120 * R​

2720000 = (120 - 17) * R​

103 * R = 2720000​

R = 26,400 ohms​

So, measuring voltage at the outputs when the element is disconnected and an element firing light is used, is normal behavior. Without the element firing light in place and element disconnected, you should read 120 V at the element output whether the SSR is off or on. Testing SSR's is kind of funky as you have discovered.

Sounds like your one SSR is DOA as you surmised.

Brew on

​

 

[sicktght311]

Thanks as always doug! Makes much more sense! Everything else is functioning properly except for the dead SSR, so i ordered a new one and should be here tuesday. Once its replaced i'm going to fire the system up and do an auto tune ahead of a brew day. Will report back!

 

[craigmw]

Thanks as always doug! Makes much more sense! Everything else is functioning properly except for the dead SSR, so i ordered a new one and should be here tuesday. Once its replaced i'm going to fire the system up and do an auto tune ahead of a brew day. Will report back!

Doug is pure gold and there to make sure we don't burn our stuff (or ourselves) up! I've learned so much from reading his posts.

 

[sicktght311]

Controller is finished and functioning as expected!

My only question is heat sink temps. I’m running a water test right now in anticipation for tomorrow’s brew day, and starting with 46 degree water, my element has been running over an hour heating the water up. Duty cycle is running 100% so things are obviously running on full, and my heat sink is warm to the touch. I used a bbq style meat thermometer wedged in the fins and I’m reading 120 degrees on the heat sink. It’s a 3x6x1.5” aluminum heatsink with the SSRs mounted directly with thermal paste

I can easily rig up a 120v fan on top of it to cool it down, but is 120degrees ok as is?

 

[day_trippr]

120°F is excellent - if the thermal coupling between SSR and heat sink is very low impedance (ie: very well coupled).
Conversely, you can imagine if the coupling is crap you could still see 120°F at the sink fins while the silicon inside the SSR is incandescent

Cheers!

 

[sicktght311]

I put a fan blowing over the heatsink and it was ice cold for the rest of the brewing day. I might forgo the fan next time to see how it does, and if i start getting much hotter temps than 120-130degrees at the heatsink, i'll just pop a 120v fan over the top of the heatsink and call it a day

 

[sicktght311]

120°F is excellent - if the thermal coupling between SSR and heat sink is very low impedance (ie: very well coupled).
Conversely, you can imagine if the coupling is crap you could still see 120°F at the sink fins while the silicon inside the SSR is incandescent

Cheers!

I opened up the enclosure a few times during the brew just to make sure the SSRs werent melting, and all looked well haha both had a dab of thermal paste on them when i installed, so i'm sure they're well seated.