Controller Plans, looking for feedback

[DNelson]

Switching to electric with 5500W Camco elements in both the HLT and kettle.
Please take a look at my plans for the controller and let me know if I've got the wrong idea on any of this.

There will be one PID with a double pole, double throw switch after the SSR. This should allow me to cut all power to the elements while avoiding the need for extra relays.

Aside from a couple of switches and the lights, these are all components that I already have.

Thanks and cheers.

 

[BeardedBrews]

Everything looks sound, only a couple of thoughts:

1. Please let us know how much you end up spending for that 30A-240V-3Position-DPDT switch. I haven't been able to find a budget version of that anywhere.

2. Consider using some form of panel mount and disconnects for your temperature probe on the PID. It would be nice to be able to swap the probes between the HLT and Boil during the brew day.

3. You could eliminate the 3-position switch and use a second 2-position switch if you were willing to un-plug the HLT element and plug in the BK element during the brew day (cost savings, wiring space, etc)

4. Once or twice I've wished that I put a small toggle switch on my PID so I could reboot it without having to kill power on the whole system. Your preference may vary, but it's not a big cost to do.

[EDIT]
5. If you take the Element Lights off the Black Leg in your diagram, then they will only be on when the SSR is on. They will not give a continuous indication which outlet is "Switched On". If that was your intention, you're golden.

 

[gibbsdoc]

Just started looking at this thread again. One thing I tend to always recommend is the use of a onboard fuse for the whole thing. It is possible to get a short or a failure in a component and a fuse may save the entire project for almost no money.

 

[DNelson]

5. If you take the Element Lights off the Black Leg in your diagram, then they will only be on when the SSR is on. They will not give a continuous indication which outlet is "Switched On". If that was your intention, you're golden.

(Edit: I changed the plans above so that the element lights are now running off the red wire.)

I don't yet have the switch, so maybe my assumptions of how it works are wrong. Here's the one I'm looking at:

http://www.amazon.com/Leviton-1288-I-30-Amp-277-Volt-Double-Pole/dp/B003AUIRNY


If wired as pictured below, when the switch is in the down position, I believe Element 2 and Element 2's light would be on, and Element 1 and its light would both be off.

Is that right?

 

[kal]

I don't see any temperature probes. PIDs need temp probes to work (at least in auto mode. You can 'fake' it with with a fixed resistor if you're only using manual mode, but if that's the case you may as well not use a PID).

Generally speaking you can't have one PID powering two different systems as they may behave differently, causing inaccuracies. It usually has to be a single PID/temp probe/heat source per system. The reaction time/dampening factor of each is different and if you want it to be accurate you usually have to train the system to learn how the system reacts.

Most temp probes have different errors that you set in the PID as an offset. If you have two temp probes, you can't do this without it being very annoying (changing it a minimum two times during the brew day).

Good luck!

Kal

 

[DNelson]

I don't see any temperature probes. PIDs need temp probes to work (at least in auto mode. You can 'fake' it with with a fixed resistor if you're only using manual mode, but if that's the case you may as well not use a PID).

Generally speaking you can't have one PID powering two different systems as they may behave differently, causing inaccuracies. It usually has to be a single PID/temp probe/heat source per system. The reaction time/dampening factor of each is different and if you want it to be accurate you usually have to train the system to learn how the system reacts.

Most temp probes have different errors that you set in the PID as an offset. If you have two temp probes, you can't do this without it being very annoying (changing it a minimum two times during the brew day).

Good luck!

Kal

I see your point. I'll be using a Watlow controller with the ability to setup and run multiple programs. I'll have to check and see if it can save PID settings for each. If so, then I can have a Mash program and a Boil program (followed by a switch to manual power output control, as I believe you recommend).
PID controllers I've used just have a thermocouple wire running off of them. For now I was thinking I would just find some food safe TC (but haven't gotten that far yet).

 

[DNelson]

Just started looking at this thread again. One thing I tend to always recommend is the use of a onboard fuse for the whole thing. It is possible to get a short or a failure in a component and a fuse may save the entire project for almost no money.

I installed a GFCI breaker so my assumption was that any short would trip the breaker. If that's not the case, where would you recommend a fuse be put in?

 

[doug293cz]

...
[EDIT]
5. If you take the Element Lights off the Black Leg in your diagram, then they will only be on when the SSR is on. They will not give a continuous indication which outlet is "Switched On". If that was your intention, you're golden.

It doesn't actually work that way. With the light between the red wire (switched by the SSR) and neutral, when the SSR is off the light is still connected thru the element to the black (unswitched) wire. A 5500W, 240V element has a resistance of about 10.5 ohms, so the light is in series with a 10.5 ohm resistor across 120V and neutral. The lights typically are less than 5W, so at 120V they will draw less than 0.04A. At 0.04A, the 10.5 ohm element will only drop 0.44V, so the light still has almost the full 120V across it, and it will be lit up constantly whenever the selector switch connects that element.

If you want an element powered (vs. element enabled) indicator, you need to put a 240V light across the two hot legs. You can't use an indicator connected to neutral.

Brew on

 

[Dougal]

It doesn't actually work that way. With the light between the red wire (switched by the SSR) and neutral, when the SSR is off the light is still connected thru the element to the black (unswitched) wire. A 5500W, 240V element has a resistance of about 10.5 ohms, so the light is in series with a 10.5 ohm resistor across 120V and neutral. The lights typically are less than 5W, so at 120V they will draw less than 0.04A. At 0.04A, the 10.5 ohm element will only drop 0.44V, so the light still has almost the full 120V across it, and it will be lit up constantly whenever the selector switch connects that element.

If you want an element powered (vs. element enabled) indicator, you need to put a 240V light across the two hot legs. You can't use an indicator connected to neutral.

Brew on

I believe BeardedBrews was correct. At the time the drawing showed the lights being powered by the black wire which is being controlled by the SSR. So with the black and the neutral the light would have indicated when the SSR was sending power to the element.

After he pointed that out though, I changed the plans so that the lights are now powered by the red wire and should be on when the switch is on. I prefer it that way since the PID controller has a light that shows when it's cycling on.

Edit: Oops. switched to my laptop and I guess it logged me in under an old username. -DNelson

 

[doug293cz]

I believe BeardedBrews was correct. At the time the drawing showed the lights being powered by the black wire which is being controlled by the SSR. So with the black and the neutral the light would have indicated when the SSR was sending power to the element.

After he pointed that out though, I changed the plans so that the lights are now powered by the red wire and should be on when the switch is on. I prefer it that way since the PID controller has a light that shows when it's cycling on.

I did mix up which color wire was switched by the SSR in my earlier post, but that really makes no difference. With the light connected between either hot wire (switched by SSR or not) and neutral, the light will be on whenever the mechanical switch selects the corresponding element. The light functions as an "element enabled" indicator, not an "element powered" indicator. In order to have an element powered indicator, the light has to be connected between the two hot wires.

Brew on

 

[BeardedBrews]

(Edit: I changed the plans above so that the element lights are now running off the red wire.)

I don't yet have the switch, so maybe my assumptions of how it works are wrong. Here's the one I'm looking at:

http://www.amazon.com/Leviton-1288-I-30-Amp-277-Volt-Double-Pole/dp/B003AUIRNY


If wired as pictured below, when the switch is in the down position, I believe Element 2 and Element 2's light would be on, and Element 1 and its light would both be off.

Is that right?

Doug is absolutely right, my brain had temporarily shut off. It won't matter if you used the red or black wire.


That switch will do what you're thinking, but you need to confirm the pin assignments on the back of the switch, your lines aren't connecting to the correct screws unless your switch is different. Just read the back of the box once you get it:

My only other comment here is that your switch at $80 costs quite a bit more than using a low amperage switch and contactors:

3-Position Switch for $1 + 2x Contactors for $10 each gives you the same functionality for $21

2-Position Switch for $1 + 1x DPDT Contactor for $10 gives you A or B (no off) for $11


Also, if you're feeling adventurous, this rotary switch might be worth a look. It's probably just a collection of stacked switches, but it might get you On-Off-On in one part for $10.00

It doesn't actually work that way.
Brew on

You're completely right Doug, I'm a doofus today.

 

[Dougal]

the light is still connected thru the element...

I get it. Thanks for that, it makes sense now.


Edit: Oops. Switched to my laptop and I guess it signed me in under an old username. -DNelson

 

[BeardedBrews]

I see your point. I'll be using a Watlow controller with the ability to setup and run multiple programs.

Most people have their PID "Tuned" to their typical mash conditions and then they will switch the PID to manual mode and just set a constant power level for the boil.

Regardless, you will need some temperature probes. Most people go with the PT-100 RTD type, and in retrospect I wish I had bought removable connections for mine to make cleanup easier.

I installed a GFCI breaker so my assumption was that any short would trip the breaker. If that's not the case, where would you recommend a fuse be put in?

I didn't use any fuses in mine, which is probably dumb.

You at least want a small amperage fuse between the main line and the PID so you can't fry the expensive component. Many people also put a fuse between the main line and the pumps so that you don't accidentally burn those out.

Something like the attached image could work. Normal twist-lock in line automotive type fuses can work just fine.


The other thing would be to confirm that the amperage at your breaker box matches the wire gauge between breaker and controller, and between controller and element. If you're just using a 50A GFCI breaker inside your main box, then the 10 gauge wires aren't the right pick.

 

[DNelson]

That point about the light still getting power through the element made me wonder. When the element is on, do both hots now have 240v flowing through them? If so, do my element lights need to be able to handle 240v?

I'm new to 240v and hadn't thought of what happens after both hots connect at the element.

 

[DNelson]

your switch at $80 costs quite a bit more than using a low amperage switch and contactors:

I don't have a lot of experience with electrical components, just some basics, so I guess I was looking at the switch because it's simple.

I'll look up how that contactor would be wired up before ordering the switch. Thanks.

You at least want a small amperage fuse between the main line and the PID so you can't fry the expensive component. Many people also put a fuse between the main line and the pumps so that you don't accidentally burn those out. Something like the attached image could work.

Thanks for the image! I'll throw some fuse connectors into the shopping cart.

The other thing would be to confirm that the amperage at your breaker box matches the wire gauge

It's a 30A breaker with 10 gauge wire to the receptacle.

 

[doug293cz]

That point about the light still getting power through the element made me wonder. When the element is on, do both hots now have 240v flowing through them? If so, do my element lights need to be able to handle 240v?

I'm new to 240v and hadn't thought of what happens after both hots connect at the element.

No. Connecting between either hot and neutral will only put 120V on the light. With the element receiving power, you should measure about 240V between the two element terminals. It will be a little less than the actual line-line voltage due to a small voltage drop in the SSR. Either element terminal to neutral will measure about 120V if the element is selected, whether the SSR is on or off. Once the previous sentence makes sense to you, you are starting to understand how 240V works.

Brew on

 

[DNelson]

No. Connecting between either hot and neutral will only put 120V on the light. With the element receiving power, you should measure about 240V between the two element terminals. It will be a little less than the actual line-line voltage due to a small voltage drop in the SSR. Either element terminal to neutral will measure about 120V if the element is selected, whether the SSR is on or off. Once the previous sentence makes sense to you, you are starting to understand how 240V works.

Brew on

I think my original intuitions were correct then. Thanks, I appreciate the help.

 

[DNelson]

My PID controller has "a non-operator-replaceable fuse Type T (time-lag)
rated at 2.0 or 5.0A @ 250V."

if "2.0 or 5.0A" means that the soldered on fuse could be as low as 2A, does that mean I ought to put in something like a 1.5A fuse?

The PID will be getting 120v, based on my current wiring plans.

 

[doug293cz]

My PID controller has "a non-operator-replaceable fuse Type T (time-lag)
rated at 2.0 or 5.0A @ 250V."

if "2.0 or 5.0A" means that the soldered on fuse could be as low as 2A, does that mean I ought to put in something like a 1.5A fuse?

The PID will be getting 120v, based on my current wiring plans.

Any PID should draw less than 1A current. 1A @ 120V is 120W. A PID drawing anywhere near 1A would get very hot, and need to be cooled. FYI the SSR driving a 5500W element at 240V is only dissipating 30 - 35W, and it needs a heat sink.

Brew on

 

[BeardedBrews]

I called it a 5A fuse because I was too lazy to look it up.

If you get a fuse holder you could pop in a 100Milliamp fuse and if it blows, go up from there

I'd bet your PID has a current draw listed in its power requirement specifications.

On the switch, I have no experience personally with the rotary selector, but I know that style is used all the time to switch power supplies and shore power in large boats (50Amp service). The marine ones are as expensive as your light switch, but the generic ones from China probably work as well.

 

[DNelson]

If you get a fuse holder you could pop in a 100Milliamp fuse and if it blows, go up from there

Normal twist-lock in line automotive type fuses can work just fine.

The fuse situation is confusing me a bit. Wouldn't the automotive fuses be 12v? I'd think I would need 120v fuses, which I also am having trouble finding inline fuse holders for the sizes I'm finding the 120v one in.

 

[BeardedBrews]

Cheapest option is something like this:

http://www.lowes.com/pd_536979-73694-BP/HMK-RP_1z0yntw__?productId=50193537&pl=1

Don't get caught up in what the name of the fuse holder is, the electricity doesn't care. Make sure the wire gauge matches what you want for power rating, and then you can grab the little glass fuses in whatever strength you want.

[EDIT to remove misinformation]

 

[DNelson]

A 30 Amp fuse rated for 32 Volts is basically a 7.5 Amp fuse at 125 Volts

That works the other way too then? Meaning that the standard glass fuses at Lowes labeled 5A and rated for up to 250v, are going to be 10A at 125v?

Thanks a million for the help. Some of the details take a minute to wrap one's head around.

 

[doug293cz]

That works the other way too then? Meaning that the standard glass fuses at Lowes labeled 5A and rated for up to 250v, are going to be 10A at 125v?

Thanks a million for the help. Some of the details take a minute to wrap one's head around.

No, fuses don't work that way. The filament/wire inside the fuse acts as a resistor. The power dissipated in the fuse is equal to the square of the current flowing thru the fuse times the resistance of the fuse (W = I^2 * R, W is power in watts.) At a well controlled power level, the filament/wire inside the fuse gets hot enough to melt, and the fuse "blows." Since the resistance of the fuse is fixed by design, the only thing that affects when it blows is the amount of current flowing thru it. Blowing is unaffected by the value of the voltage which is pushing the current. The voltage rating on a fuse has to do with the voltage withstanding ability of the non-conductive fuse materials, just like voltage ratings for insulated wire. Using a fuse rated for low voltage in a high voltage application could lead to insulation breakdown (arcing, burning, etc.) Conductors don't have voltage ratings, only current ratings.

Brew on

 

[doug293cz]

...

Just keep in mind Watts = Volts * Amps

A 30 Amp fuse rated for 32 Volts is basically a 7.5 Amp fuse at 125 Volts

In the equation Watts = Volts * Amps, Volts is the voltage drop across the load. In the case of fuse operation, the load of interest is the fuse itself. The voltage drop across the fuse is given by Ohm's law: Volts = Amps * Resistance, where resistance is the resistance of the filament/wire inside the fuse. Substituting Ohm's law into the power equation gives: Watts = Amps^2 * Resistance. So the power dissipation (heating) inside the fuse in given by Amps^2 * Resistance. The voltage driving the current doesn't determine when the fuse blows. The current flowing thru the resistor is determined by the total resistance of the circuit which is very much larger than the fuse resistance. If something reduces the total resistance of the circuit (a short, smaller load resistance, additional loads on parallel, etc.) then the current flowing in the circuit (and fuse) increases, and the power dissipation in the fuse increases. When the internal power dissipation of the fuse reaches a set level, the fuse blows.

Brew on

 

[DNelson]

The voltage rating on a fuse has to do with the voltage withstanding ability of the non-conductive fuse materials... Conductors don't have voltage ratings, only current ratings.

Ok great. So the 10A fuse rated up to 250v will blow at 10A and the non-conductive materials are good up to 250v. Sounds like I can go with those. Thanks for the explanation.



I like the idea of switching to 12 gauge or 14 gauge wire after the fuse, so I'd like to go with an inline fuse holder that uses 10 gauge wire. The only one I've found so far doesn't list any kind of voltage rating, and seems to be made for boats. Is it safe to assume that if the wire is 10 gauge that the rest of the housing would be able to handle 120v as well?

http://www.amazon.com/420555-1-Watertight-Inline-Holder-Gauge/dp/B001FDWP4A?ie=UTF8&keywords=sea%20dog%20fuse%20holder&qid=1458866495&ref_=sr_1_1&sr=8-1

 

[doug293cz]

Ok great. So the 10A fuse rated up to 250v will blow at 10A and the non-conductive materials are good up to 250v. Sounds like I can go with those. Thanks for the explanation.



I like the idea of switching to 12 gauge or 14 gauge wire after the fuse, so I'd like to go with an inline fuse holder that uses 10 gauge wire. The only one I've found so far doesn't list any kind of voltage rating, and seems to be made for boats. Is it safe to assume that if the wire is 10 gauge that the rest of the housing would be able to handle 120v as well?

http://www.amazon.com/420555-1-Watertight-Inline-Holder-Gauge/dp/B001FDWP4A?ie=UTF8&keywords=sea%20dog%20fuse%20holder&qid=1458866495&ref_=sr_1_1&sr=8-1

That fuse holder looks fine for 120V use. Just make sure you can get the fuses with the current ratings you need that fit that holder. There are several different "standard" sizes for cartridge fuses.

Brew on

 

[DNelson]

That fuse holder looks fine for 120V use. Just make sure you can get the fuses with the current ratings you need that fit that holder. There are several different "standard" sizes for cartridge fuses.

Awesome. Thank you very much for all the help. I'll update the plans to show the fuses and repost. Thanks again, doug293cz & BeardedBrews for walking me through this. Much appreciated.

 

[DNelson]

I ended up going with these from Frys:
http://www.frys.com/product/6578423?site=sr:SEARCH:MAIN_RSLT_PG


Realized I was overthinking the wire gauge on the fuse holders when I said I wanted 10 gauge. With a max fuse of 10A, there's no risk of the wire burning up whether it's before the fuse or after it.

Thanks again for all of the help.