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Old 08-18-2012, 09:24 AM   #11
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Originally Posted by geoffey View Post

Suffice it to say I plan on using lighting relays to control my 240v heating elements, relays which I am very certain can handle the switching cycle of my brewing system for at least 5 years.
Geoffey,

What specifications / brand / model number could I search so I could price a relay like that?

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Originally Posted by lschiavo View Post
I use a relay to switch the elements in my HLT via PID. It has worked fine for a few years now. An auto tune and a little tweaking of the delay time and I don't get any overshoot. The only real difference is the noise from the contactor.
Ischiavo,

I am also very interested to know what relays you're using. It sounds like you have something that works, and might work for my situation...

I kinda made a mistake. I've been gathering parts for a three keggle, single tier HERMS system, and want to use a 3500W 240V element to control the temp in my HLT. Wanting to keep things as simple as possible, I bought a couple of Johnson A419ABC-1C controllers and planned to use one to control the heating element in the HLT, and keep one for future projects. I read on Johnson's website that the controller has a built in relay capable of switching a 16 amp load.

Today, I was looking back at the instructions for the controller and realized that it's capable of a 16 amp load at 120V but only 8 amps at 240V. A 3500W element at 240V will draw almost 15 amps. So I am considering one of two options: 1) Attempt to return the Johnson controllers and buy a PID controller and use a SSR. I don't really want to do this - I got a good price for the A419s ($119.07, delivered, but I had to buy two of them). Plus, I want to use one for temperature control of a fermentation chamber at some point. Option # 2) Use the Johnson controller to control a contactor or lighting relay, as is being discussed in this thread.

I'm planning on constantly recirculating the wort through a HEX coil in the HLT using one pump, and constantly recirculating water from the bottom of the HLT back to the top of the HLT, to keep it stirred up and maintain a uniform temperature in my HLT. Would a lighting relay work for me and give me a relatively stable mash temperature? Do I need to look for a specific type / duty cycle / IEC Utilization Category?

Or am I way off base with the Johnson controller and just need to back up and punt (go with the PID idea)?
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Old 08-18-2012, 01:31 PM   #12
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The other thing to consider is that moving from solid state relays to mechanical relays you dont have the heat generation problem due to the losses within the SSR. I think its a good idea, and dont think you will lose much accuracy at all.

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Old 08-19-2012, 09:36 PM   #13
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Originally Posted by AggieBrewer01 View Post
Geoffey,

What specifications / brand / model number could I search so I could price a relay like that?



Ischiavo,

I am also very interested to know what relays you're using. It sounds like you have something that works, and might work for my situation...

I kinda made a mistake. I've been gathering parts for a three keggle, single tier HERMS system, and want to use a 3500W 240V element to control the temp in my HLT. Wanting to keep things as simple as possible, I bought a couple of Johnson A419ABC-1C controllers and planned to use one to control the heating element in the HLT, and keep one for future projects. I read on Johnson's website that the controller has a built in relay capable of switching a 16 amp load.

Today, I was looking back at the instructions for the controller and realized that it's capable of a 16 amp load at 120V but only 8 amps at 240V. A 3500W element at 240V will draw almost 15 amps. So I am considering one of two options: 1) Attempt to return the Johnson controllers and buy a PID controller and use a SSR. I don't really want to do this - I got a good price for the A419s ($119.07, delivered, but I had to buy two of them). Plus, I want to use one for temperature control of a fermentation chamber at some point. Option # 2) Use the Johnson controller to control a contactor or lighting relay, as is being discussed in this thread.

I'm planning on constantly recirculating the wort through a HEX coil in the HLT using one pump, and constantly recirculating water from the bottom of the HLT back to the top of the HLT, to keep it stirred up and maintain a uniform temperature in my HLT. Would a lighting relay work for me and give me a relatively stable mash temperature? Do I need to look for a specific type / duty cycle / IEC Utilization Category?

Or am I way off base with the Johnson controller and just need to back up and punt (go with the PID idea)?

I am using relays from Wattstopper, part number BZ-150. You could probably still use your Johnson controller to run these, you'd need to use two of them (one for each 120v circuit of your 240v heating element). The BZ-150's are controlled via low voltage input. You would take the 24vdc lead from the BZ-150 and run that through your Johnson Controller contact, and run a return wire back to the BZ-150 and connect it to the "control input" wire. To wire two BZ-150's you'd just wire them in parallel on the low voltage side. (I am sure I could come up with a wiring diagram for you, it's really quite simple.)

I chose this model because it has a "hold off" input which can be used in our application as a safety measure. I created a virtual button on my touchscreen which has to be pressed before the system will allow the elements to fire.

My build is almost complete and I will be posting pictures of my progress here in the next couple weeks.
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Old 08-20-2012, 06:28 PM   #14
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I am using relays from Wattstopper, part number BZ-150. You could probably still use your Johnson controller to run these, you'd need to use two of them (one for each 120v circuit of your 240v heating element).
Be careful here - These Wattstopper relays are not necessarily a bad idea, but there's a couple big asterisks to keep in mind...
They are rated for 20 amp loads on 14ga wire. Note 14ga wiring in the home is rated for 15 amps. Granted this is stranded, and as long as your lead length is short it should be OK. BUT, if you have 10' of 14ga cable running 240v to the element, it'll probably get hot. IF you use larger wire to the element, the 14ga at the relay effectively becomes a "fuse" as the weakest link in the circuit. The 14ga wire can heat up. As heat increases, so does resistance, causing more heat. It's a vicious circle.
Also, there are NOT (2) 120v circuits in a 240v element. There's ONE 240v circuit. You can switch only one leg of the 240v circuit, and the element will be 100% off. People switch both legs for safety (Touching the unswitched leg to ground will obviously be a very bad idea, even though the element is not drawing current and creating heat)
I mention this to emphasize one point: If you use 20 amp rated relays, and utilize 2 of them thinking you're going to have a 40 amp switching capacity, you're going to risk a fire if you drive 5500 watt elements. I'm sure there's some fudge factor with the 20 amp rating, and a 5500 watt element will pull 23 amps. But that's still 3 amps OVER the rated load of the relay (Or SSR).
Now, if your household electrical system is only delivering 215 volts under load, you're going to be pulling 25.5 amps through your 20 amp rated device. This is where it gets risky.

On the topic of relays vs SSR's, the only thing I like to mention is MTBF on the relays. Givin the low switching rate, everything should be fine. But, if you run into the higher switching rates you can get close to the rated lifetime cycle count on the relays in a hurry (A year or 2 maybe?)
If a relay is rated for 1 million cycles, and you have a 10Hz cycle rate, that's 27.7 hours of use before you actually hit the MTBF. Just something to keep in mind - The math adds up quick!
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What does the primary pressure gauge on the tank tell us? That's right, the temperature. Put it on a scale if you want to know how much is in it...
Put some duct tape over the gauge - Or better yet - Replace the high pressure gauge with a plug - High pressure gauges are useless!
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Old 08-21-2012, 12:18 AM   #15
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Sweetsounds- appreciate the input here. I'm not 100% following you though. You say it's not 2 120v circuits, and that's where you lose me. I am feeding the elements with a double pole breaker, each pole is a 120v circuit. Each relay is controlling only ONE of the two poles. Are you saying that only one of the two relays is a power handling device in this setup? I am of the understanding that each relay is handling about 13amps each. (I'm also using 10 gauge wire).

I've already done some testing of this system, albeit not of a very thorough nature, (more testing to come) but if what you are saying is true then I'd have easily fried one of those relays already, and I haven't.

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Old 08-21-2012, 12:45 AM   #16
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Sweetsounds- appreciate the input here. I'm not 100% following you though. You say it's not 2 120v circuits, and that's where you lose me. I am feeding the elements with a double pole breaker, each pole is a 120v circuit. Each relay is controlling only ONE of the two poles. Are you saying that only one of the two relays is a power handling device in this setup? I am of the understanding that each relay is handling about 13amps each. (I'm also using 10 gauge wire).

I've already done some testing of this system, albeit not of a very thorough nature, (more testing to come) but if what you are saying is true then I'd have easily fried one of those relays already, and I haven't.


No! (Sorry, but this is important)
240 volts is NOT 2 120v lines. You have 4 wires in your electrical panel. A ground, 2 Hot's and a Neutral. What we are talking about here is electrical potential measured between any 2 lines.
Hot to Neutral = 120 volts
Hot to Hot = 240 volts
Hot to Ground = Sparks, fire, death

Ground is NEVER part of an electrical circuit - It's there to give the current somewhere to go besides through your body, and cause the breaker to trip
Neutral IS part of an electrical circuit. But ONLY 120 volt circuits, because the electrical potential (Voltage) between hot and neutral is 120 volts.

Your 240 volt element connects to both hots and is 240 volts. 240 volts alone, and not 120 volts (Because the neutral is not involved). It's not (2) 120 volt lines, just as your vacuum cleaner, when plugged into your 120 volt receptacle is NOT 2 60 volt lines. Follow?

A 120v element would use one hot and the neutral - Because the electrical potential between hot and neutral is 120 volts! (This is how every standard outlet in your house is wired)

This is voltage, and it's critical you understand how that works.

Now, for load: (Even more critical, because voltage doesn't start fires, Current starts fires)
Current creates heat - This is, after-all, exactly what we're all using it for.

Back to the vacuum cleaner analogy:
If your vacuum cleaner draws 5 amps at 120 volts, it's not drawing2.5 amps per wire. It's drawing 5 amps in one wire, and out the other (Over-simplification, but accurate)
Same for the element in your rig - it's drawing 23 amps in one wire and out the other. Kinda like a battery, except instead of electricity flowing from positive to negative (Direct current), it flows back and forth, switching directions 60 times per second (Alternating Current) (This is where 60 Hertz comes from)

So - At the end of the day, you are going to pull 23 amps through your 20 amp relays. (Assuming 1 5500 watt element) It doesn't matter if you use one or two or ten relays, It's still 23 amps at 240 volts.

One saving grace about AC is duty cycle. Since the current switches directions 60 times per second, it's actually 0 volts 60 times per second, too. Passing through 0 essentially gives the circuit a "break" and it can cool off. This is why a switch may be rated for 10 amps AC, but only 4 amps DC - direct current never goes to 0 volts, and things heat up faster because the contacts never get time to "rest".
It will heat up. When it gets hot, resistance increases. This creates more heat, causing higher resistance. Once you reach a critical mass, you get Chernobyl.

Again, I'm not saying they are bad relays. I'm just saying you need to be aware of the limitations of your device, and how close you may be running to those limits.

Edit: Sorry - You're using mechanical relays, not SSR's. Edited for accuracy
Edit-Edit: I'm going to change my "Relays! Nifty!" view of your build - Just buy the SSR's man - They're cheaper than melting your rig and starting over.
Edit-Edit-Edit: I'm back to "Nifty! 30 amp Relays!" Carry on

You haven't mentioned your elements yet - How many watts are you asking the relays to switch?
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Originally Posted by Ecnerwal View Post
What does the primary pressure gauge on the tank tell us? That's right, the temperature. Put it on a scale if you want to know how much is in it...
Put some duct tape over the gauge - Or better yet - Replace the high pressure gauge with a plug - High pressure gauges are useless!
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Old 08-21-2012, 05:50 AM   #17
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I get what you are saying. I'm not an electrician or an electrical engineer by any means. But i DO have a basic understanding of electricity - understand AC vs DC and understand 120v is a hot and a neutral and that 240v isn't (unless you're in Europe). But you will have to explain how I am passing 240v through any of my relays when none of them are connected to 2 hots. And how this would be any different using SSRs.

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Old 08-21-2012, 08:12 AM   #18
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I am not an electrician, and this might be an over-simplification, but this is how I understand it. Here is a highly professional-looking (insert sarcasm here) drawing that might help. In the pictures, the yellow boxes represent relays and the blue loops represent heating elements. The entire circuit through the heating element is considered a 240V circuit. I assume you agree that you are passing 240V through the heating element. It is one part of the circuit. It is also important to realize that all other parts of that circuit "see" the 240 volts and whatever amp load the element is drawing as well.

Look at the bottom drawing - I purposefully drew the relay on the 'end' of the circuit, where the heating element was drawn in the others. (This would be wired exactly the same way as the top left picture.) Maybe if you visualize the relay on the 'end,' you will be able to understand how it is all part of the same circuit, therefore subject to the same voltage and amp load. Does this make sense? SweetSounds, please correct me if this is not the information you are intending to convey.

relays-water-heater-element.jpg  
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Old 08-21-2012, 01:12 PM   #19
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I get what you are saying. I'm not an electrician or an electrical engineer by any means. But i DO have a basic understanding of electricity - understand AC vs DC and understand 120v is a hot and a neutral and that 240v isn't (unless you're in Europe). But you will have to explain how I am passing 240v through any of my relays when none of them are connected to 2 hots. And how this would be any different using SSRs.
I'm sorry, but you don't understand.


You are missing the key point:
Each relay IS connecting to two "Hot's"!
The one going into it and the one coming out of it.

Because, 240 volts is the voltage of the CIRCUIT and the voltage of every single wire in it.
Your element is 240 volts. It doesn't matter if you're measuring at terminal 1, terminal 2, or if you could measure somewhere in between. It's still 240 volts. I'm having trouble coming up with another way of explaining it...

Let me try it this way.
Lets pretend you have a 9 volt battery, and you connect it to your heating element.
Do you have 4.5 volts per wire? No, you have 9 Volts! 9 Volts of DC electricity passing from the positive terminal on the battery, to the negative terminal on the battery. The heating element just happens to be in the electricity's way. But believe me, it's still 9 volts. On every wire in the circuit.

That's all there is to it. Forget for a minute about hot and neutral and heating elements. The voltage running through any single wire in any circuit is what it's fed by.

Or maybe this is an easier way to understand:
If you look at Aggie's drawing - The top left one. You know that if you put a volt meter across the terminals of the heating element, you'll get 240 volts right?
Now, if you put your volt meter across the terminals of the relay, What will you measure?
240 volts. Have we suddenly created a new hot? No, it's just a wire. It's got 240 volts on it. Just like every other wire in that circuit.

All 3 wires in that simple circuit are carrying 240 volts. And if it's a 5500 watt element, all 3 wires in that circuit (And the relay itself, the 14 gauge wires connecting it, and the 20 amp rated contacts inside it) are carrying 23 amps!

SSR's are designed for quickly switching loads. They don't have a "Break current" limitation. This is my biggest concern with using little mechanical relays over their rated load. You can literally weld the terminals together when they touch.
I say use SSR's because they are "normal" It's what they do. They can handle the load. They can handle the switching rate. You only need 1 or 2 of them, and they are not that expensive.
Again, your relays might be fine! And kids playing with matches in the basement don't always start the house on fire. You need to fully understand what you've built and what it means to each component you pass 115% of its rated current through.

This is why most people here use 40 amp SSR's for their elements. The elements draw 23. It's a safety factor, and the SSR runs cooler because it's at 1/2 of its rated load.
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Originally Posted by Ecnerwal View Post
What does the primary pressure gauge on the tank tell us? That's right, the temperature. Put it on a scale if you want to know how much is in it...
Put some duct tape over the gauge - Or better yet - Replace the high pressure gauge with a plug - High pressure gauges are useless!
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Old 08-22-2012, 12:10 AM   #20
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Guys, thanks for helping clarify this issue for me. I think I understand much better and for safety sake I will make a change. Who knows, maybe you helped me avoid burning my house down! One easy change would be to swap the relays out for a different model which is rated for 30amps at 347v for resistive loads. OR I could just go ahead and buy SSRs but I'd need to put some further thought into how I'd install those in my system.

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