Looking for pointers re; control box build

[philistine]

Hey Dudes,

I've got a few questions for the electronically confident among us here...

Im getting to the part of my herms build that I actually know next-to-nothing about - making a controller. I can google and ebay the **** out of anything, but at this point Im getting a little confused and Im not sure if Im getting the right stuff.
I've pretty much settled on a design and I've probably acquired most of the components by now. (to sum up its pretty basic, just 2 x PIDs and 4 illuminated selector switches)
My idea is to build the box with all the components installed and then get a sparky to do all the wiring.

So far I have these things:
1x PID with SSR and heatsink for HLT (2800W)
1x PID with SSR and heatsink for HEX (3000W)
2x Auber Instruments RTD probes with braided cables & XLR connectors
1x illuminated selector switch for pump 1
1x " " for PID 1
1x " " for pump 2
1x " " for PID 2
1x Big Red emergency STOP button

i know the question might seem a little vague, but what else do I need?
A circuit breaker? What kind?

One thing that I know is missing are power outlets for everything and Im thinking of using C13 sockets (like these). The reason being that they're compact and will fit neatly along the bottom edge of the enclosure.
Is there any reason for not using them? It would involve cutting off the standard plugs from my pumps, but that's not really an issue....

Sorry if the questions seem dumb, like I said, I know very little and Im hoping to present an electrician with somethign that makes sense so they can just finish it off for me without too much trouble...

Thanks in advance

 

[micbrew]

take alook at the brauduino on youtube for some inspiration and these are actually available as a kit as well

hope that helps

 

[boybrewer]

Do a search on the forum lots of info . Type in electrical control box .

 

[klangers]

If you're not experienced with electronics, the one thing to make sure you nail is the circuit breaker/RCD (different things but can be one combined into 1 component these days) and earthing. Then at least you know you're not going to burn the house down. I'd get a CB/RCB combo for each main load - 2x heaters and 2x pumps. The current rating of the CBs needs to be a little higher than the rated running current of the pumps and heaters. If they then draw more than this current, the CB will trip. If some current "leaks", the RCD will trip.

I'd also recommend going to 24V for control circuitry. It does add complexity and cost but is best practice. Then you can use relays to add interlocks to your system. Without this, your e-stop is more of a main switch. E-stops are not designed to carry full current, typically.

I'm a little worried that you're attempting to build a mains voltage control box for lethal currents with no understanding of how to do so. EDIT: Sorry just saw the part where you said a sparky is finishing off for you.

I don't think you need to bother with the fancy plugs, but as long as they're rated for the current necessary and have a pin for earth then it should be fine.

 

[mr_wibble]

What do you want the control box to do _exactly_ ?

Balance wort temp based on HERMS-coil-exit temperature ?

Something else?

Do you want the switches to simply turn pumps on & off ?

Your household "fuse box" might already be holding a bunch of circuit breakers.
(If not, I would strongly recommend replacing all fuses with appropriate breakers)


EDIT: Your linked sockets (IEC Panel Mount) are only rated to 10A.
Your proposed elements (2800, 3000) will both draw more than 10A (at 230V[1]) individually.
Obviously if they're powered simultaneously it's 5800 watts (plus minor power requirements for instruments).
Amps = Watts / Volts.
Thus A = 5800 / 230 = 25.22A

So as an absolute minimum your input-power connectors need to be rated for this.
Maybe 32A would give you a good margin. Ask your sparky.


[1] The AU standard is now 230V, some houses (mine included) receive the old 240V. Obviously this reduces your current (amps) a bit.

 

[philistine]

Thanks guys, plenty for me to chew on there!

Klangers - are you suggesting a circuit breaker for each component? (Ie. 4 in total?)
You lost me on the 24v control circuitry bit , but like i said plenty to chew on. Im gunna google the **** out of it.
And yeah - electrician for sure!
Basically im just gonna cut holes in the enclosure for all the front panel mounted stuff and put it together without any wiring whatsoever, then hand it over!

Mr wibble - thanks for that, thats exactly the answer i needed. The whole amperage requirements/limitations thing was completely absent from my thoughts until just this morning when i realised id started building a thing that required some serious wizardry to operate.
I've canned the IEC c13 sockets idea and have opted for 20A powercon style locking sockets/plugs instead.
To answer your question tho, the controller's pretty simple.
One PID controlling a 2400w birko urn as an HLT - probe mounted to the urn.(i made a typo earlier when i said 2800)
One PID controlling an external herms HEX i built using a hermit coil and a 3kw element, probe mounted on outflow.(might downgrade to a 2.4kw element)
Then two switches controlling two separate pumps and two switches to isolate the heating elements .... thats about it.
23 amp total draw if everything is on at the same time.

I was talking thru this in another thread, but Ive since re-thunk my approach and have made enquiries to have a sparky install a fresh 32A circuit with two 15A outlets for my brewrig and workshop anyway, so if that goes ahead it should all be fine.

 

[Moad]

Hey mate,

I've just had my setup rewired after moving. I've got another board in the shed with a feef from the main board. The circuit breakers in the shed board are rated higher than the max draw and are RCD. My control panel is hard wired with 2 circuits from the board, one connected to a 40a breaker and one 25a. Make sure you have the right gauge cable for the circuit too. I had to run 16mm down to the shed and 6mm from the board to the control panel.

For the elements ive got neutrik connectors, you can get them for up to 40a I think.

For pumps I've got socket mount jug cord, not sure of the name of that connection.

Valves I use m12 connectors

I can send you pictures of the control panel if you like, if you haven't already purchased your pids and you have a bit of spare budget I strongly suggest looking at a bcs 462 controller. It may be overkill now but would future proof you for upgrades later.

Note I'm not an electrician, as anyone here will say make sure you consult one!

Cheers,

Nick

 

[klangers]

Thanks guys, plenty for me to chew on there!

Klangers - are you suggesting a circuit breaker for each component? (Ie. 4 in total?)
You lost me on the 24v control circuitry bit , but like i said plenty to chew on. Im gunna google the **** out of it.
And yeah - electrician for sure!
Basically im just gonna cut holes in the enclosure for all the front panel mounted stuff and put it together without any wiring whatsoever, then hand it over!

Mr wibble - thanks for that, thats exactly the answer i needed. The whole amperage requirements/limitations thing was completely absent from my thoughts until just this morning when i realised id started building a thing that required some serious wizardry to operate.
I've canned the IEC c13 sockets idea and have opted for 20A powercon style locking sockets/plugs instead.
To answer your question tho, the controller's pretty simple.
One PID controlling a 2400w birko urn as an HLT - probe mounted to the urn.(i made a typo earlier when i said 2800)
One PID controlling an external herms HEX i built using a hermit coil and a 3kw element, probe mounted on outflow.(might downgrade to a 2.4kw element)
Then two switches controlling two separate pumps and two switches to isolate the heating elements .... thats about it.
23 amp total draw if everything is on at the same time.

I was talking thru this in another thread, but Ive since re-thunk my approach and have made enquiries to have a sparky install a fresh 32A circuit with two 15A outlets for my brewrig and workshop anyway, so if that goes ahead it should all be fine.

Yeah a CB for each major draw, if you correctly size the breaker, can avoid "commissioning complications". Ie if your heater draws too much current, you'll trip a common CB in your residence. Have to reset clocks, might annoy people etc. But you'll not know what actually caused it. Wheras if you have a breaker for each, you'll protect other stuff on that circuit as well as have better troubleshooting ability. You can also isolate each sub-circuit in your brewery individually.


24V control circuity allows you to do a lot more interlocking and fancy stuff without taking up huge amounts of space or large wires. Moreso, it's significantly safer and allows you to intergrate with microprocessors and PLCs easier.

That's probably more than you need, I guess I come from an industrial point of view.

 

[malt junkie]

Best tip: reading the construction guide at the electric brewery. I'm not telling you that is what you should build, it will however help you get your head around the circuitry and control mechanisms.

The BCS as Moad states, is a good bit of kit, and has the ability to completely automate wort production, not just temp control, so if further automation down the track is in your thoughts the BCS would be something to consider.

Good luck with thew project.

 

[huez]

I just upgraded from the bcs460 to the 462. They are great bits of kit. If you're interested i might be willing to sell the 460.

I also use the neutrik connectors, the same as moad. They're great because they lock in, i think you will regret using the iec connectors.

 

[philistine]

Alright guys, thanks for all the help so far - Ive managed to learn a few things using the advice given here.
I've had to change the design of the controller a little bit to take my power limitations into account, which meant including a 3 position selector switch to control the elements (in other words, I'll only run one at a time)

I stumbled across a really simple design for a controller on instructables complete with this wiring diagram which has been quite enlightening!
My design is slightly different in that it only uses 2 PIDs, but looking at it has raised some more questions though.. and they may seem a bit dumb - but hey, like I said earlier, I know f**k all about electronics and Im trying to learn as best as I can! ;-)

Anyway, everything in that diagram makes sense to me and matches the components I already have, except for the 3 x relays.
Why use relays? What do they do in this particular application? are they necessary? if so, can someone help point me at an ebay link or similar to something that would be suitable for my project?

Thanks in advance dudes, I appreciate all the help so far and the also patience some of you must be maintaining when reading this !


EDIT: I also found this on youtube. no need to watch it, but the controller he's built is pretty much exactly the same as the design and layout im going for, minus the amp meter and the third (superfluous) PID.
He's based his design onsome of the Electric Brewery site's ideas - which Ive been reading through too by the way. They all use relays and Im just trying to understand why and how.

 

[lmullan]

When you say relay do you mean a contactor? In these cases the contactor relay is a safety measure used for a few reasons. 1 is typically used to isolate the entire control panel ie ON/OFF, you can't use a typical switch for this normally because they can't handle the amount of electricity passing through (these contactors are rated at 40A) the other two typically isolate the heating elements completely. They serve two functions, 1 is to ensure through use of a selector switch, that only a single element can be turned on at the same time (keeping from overloading your circuit) the other is less important but SSR's leak, a tiny bit of electrical flow occurs even in the off state, the contactor allows zero flow when open (off).

Hope that makes sense!

 

[philistine]

Thanks mate, that does make sense.
So just to clarify, if im using a relay in conjunction with the main/master on/off switch, does that particular switch still need to have an amp rating that matches/exceeds the total draw of the system while its operating?
Ie. the max possible draw at any one time of my current design (2 pumps plus one element) would be about 10.3 amps - if im using a relay, will a switch component rated at 10A be adequate?

My other question is basically "what relays should i get?" (Or "help me find them!")
The ones listed on the electric brewery site seem overkill (30A ratings etc)
But regardless, i dont know how to find them anyway.
We dont have amazon here, so im stuck with ebay or an actual electronics supplier....
If i type something like 240v 30A dpst (or dpdt) relay into a search on ebay, i get a bazillion different options with a massive difference in price ranges.
I get completely lost and the specs listed on the various component descriptions may as well be written in another language ......

Just to re-iterate, i WILL NOT be wiring this up myself, i am fully aware that my lack of understanding rules me out of that part of this process!!!!
But , i just want to make sure im sourcing the right components so i can at least assemble it before letting someone qualified do the wiring

 

[klangers]

Yes, everything that has to pass a certain current must be rated for it.

Look, relays aren't essential. If you're not confident in designing it, then I'd stay away. I think the KISS principle should be applied here if you're not confident with electronics. At some point you're gonna have to repair/troubleshoot the system.

 

[philistine]

Thanks Klangers.
Im liking that relays aren't *essential*, especially given that by the looks of things theyre gonna set me back a minimum of $50 each.....
Im just concerned coz i thought i had it all figured out (as in i thought id finished buying stuff!) but now that im starting to delve deeper, im seeing that just about all the designs im looking at use them.

Im down with a KISS approach, but would prefer to get it "right" the first time.... or if not "right", then at least good enough that it wont burn itself out with normal usage within a short timeframe

I'm guessing you guys are probably reading this all thinking "man this guy just needs to f***ing give up or do an electrical engineering course and figure **** out already!"

Thanks again for your time and patience!

 

[philistine]

Im also hesitant to walk into a place like jaycar and say "i need sumfing wot the internet told me" and then get told i need to buy a thing that costs 10 million dollerz when i could have bought the equivalent off ebay for 2cents

 

[philistine]

I feel like that conversation would something like :
Me: "Hi there , im building a brew controller, i need these things called relays..... thats all i know"
Them: "come right this way sir, we've got just what you need............ " (leads me to the back room and we pass thru a series of airlocks before decending via elevator into the hidden subterranean vaults below the store. A quick keypad and retina scan, followed by a dual key authentication process assisted by an armed guard with an earpiece and body armour then opens a 4meter thick nuclear blast proof concrete door into yet another room. We don gortex jackets and gloves rated for prolonged periods in the arctic circle and proceed to a plinth in the center of the room surrounded by lazer beams made visible by the traces of halon gas that linger in the room. Floating above the plinth is a liquid nitrogen cooled superconducting pod that contains my relay switch.
"......this relay here has just been imported from one of our manufacturing plants on mars by way of time travel future logistics. It's constructed from 100% pure unobtanium and i can assure you, it is of the highest quality.."

 

[philistine]

As i cradle my courtesy puppy in one arm and sip my complimentary 150yo single malt with the other i pause thoughtfully before saying "that sounds great, but ithink i need 3 of them"

 

[klangers]

Hahaha, all good

Relays are basically a little switch that controls a bigger switch. The SSRs are solid state versions; a traditional (mechanical) relay is actually tiny little electromagnets which physically throw a switch.

The relay can have double poles (DP) with double throw (DT) - DPDT - or a single pole etc etc. This means one relay can switch two independent poles simultaneously, which is what you want normally so you can isolate both active and neutral from your load.

What relays do you need?

• Current rating should be 10-20% higher than the highest load they're tasked with switching. No harm having a relay bigger than necessary. Smaller than necessary - will fail.
• DPDT is fairly standard
• Non-latching
• Normally open, except for e-stop. (ie applying control voltage closes the switch and current flows). Normally this is just how it's wired.
• Rated load voltage - at least 250V
• Control voltage - make sure this matches (24V is a good standard, but 12 and 5V are common too)
• Get ones that can be mounted on a DIN rail - this is a standard bit of cabinet hardware that allows one to slot on a whole heap of components without screws. You mount the DIN rail to the cabinet and slide on the components. Sometimes there's actually a "relay holder" that has screw terminals for the wires to be terminated into, and the relay's pins just slot in so it's all neat and tidy

Then, you'll also need a stepdown transformer for your "control voltage" (24V normally).

This is how I see your cabinet:

• Main Isolating switch - mains power
• Main safety switch - mains power, switched by relay upon input of 24V from e-stop. In series with main isolating switch. This will need to be a normally closed relay, as you want it to fail safe. So when you hit the e-stop, you actually take control voltage OFF the relay, which goes back to its resting state and turns everything off.
• Selector switch - control voltage, sends 24V to relevant element's relay. Relay switches mains power to element
• Pump switches - control voltage, sends 24V to pump's relay. Relay turns on pump.

Does that make more sense?

 

[philistine]

Yep, its starting to make a bit more sense.
Im scrapping the e-stop by the way- just gonna use a regular on/off switch.
So, re: using a step-down transformer (which adds another layer of sorcery i wasnt aware of by the way) - theres no mention of one in the wiring diagram im using as a reference.....
View attachment 97406
i would assume that the two relays being used by the PIDs would need to be 12v control, so would that mean a step down transformer should only be needed for the relay that services the main isolating/ on-off switch - is that right?

By the way, i am actually gonna get a friend to help me with this eventually- he's an electrical engineer who builds medical robots (no ****)
We just live about 150km away from each other, so im trying to refine my problems and questions down a little before hitting him up!

 

[klangers]

There's no point using the relays I mentioned if your PIDs are running on mains power. The whole point of a control voltage is to minimise the number of components that use mains voltage. So NOTHING should be 240V apart from:

• Main isolating switch
• Elements and their SSR
• Pumps
• And the load-side of the relays that power the above

Everything else should be done in low voltage. You need a transformer to make this low voltage. It's kind of all or nothing - as I said, it may be easier to just keep it simple and not worry about relays. There is absolutely no point in using mains power as a control voltage for relays (unless your load voltage is >20kV).

This is really really hard to describe with words. A diagram would be better.

Good that you have access to an electrical engineer, although switchboard design is a far cry from robotics. I'm a manufacturing engineer; I have some formal uni training in automation/robotics and electrical engineering so I get by, but it's not my forte.

 

[Zorco]

Only a tiny addition I think.

'Everything else should be done in Extra Low Voltage'.

PELV or SELV,

http://www.snowyhydro.com.au/CorpPortalOHS/AR/Docs/SP24-65%20Working%20with%20Extra%20Low%20Voltage%20(ELV).PDF

 

[philistine]

Ok, so that clears some of it up. I think.
But now im back at a previous point of confusion - that being The amp rating of the main on/off switch.

Its frustrating because i dont even really know how to ask the right questions..... im getting this overwhelming sense of having bitten off more than i can chew......

Im a horticulturist. I understand plants.

Anyway, im sort of using a few different sources as references for my own build.
The main one being "the electric brewery" site followed by a build documented as an "instructable" by a guy who wanted to do a dumbed down cheaper version of the electric brewery build.
Both of those builds use 10a rated switch components (for all of the switching requirements) and yet the amperage those builds are sucking down is huge. Way more than mine!

So, Going back to just the main on/off switch, the only difference i can see in my build vs. theirs is that they include relays.
Does the use of a relay somehow "buffer" or in a sense "bypass" the switch component itself from the excessive power being drawn by the system? From what i can tell, they're using 10a switch components but theyre running 15-30a loads.
So i guess in a way, im trying to figure out - when set up with a relay, is the main current load that passes through the system when in use basicaly going straight through the relay with the "on/off" switch being used solely to trigger the relay itself?
In other words, the switch itself is not actually handling the load..... is that right?

Im sorry if we're going round in circles! I just dont really know who else to ask these things to be honest!

I just really want to understand and would hate to "throw in the towell" because i cant wrap my head around some basic circuitry!

 

[klangers]

It helps knowing your background, as I can try and draw comparisons to something you find intuitive.

A fairly good analogy of electricity is water flowing through pipes. The water is the electricity, and the pipes (and valves etc) are the wires and components in the circuit. The analogy degrades fairly quickly, but works very well for basic stuff. I suggest you try and draw up a circuit diagram and post up. Don't even worry about active vs neutral, just do a single line diagram.

Voltage is then analogous to water pressure; current to flow rate. A switch is analogous to a valve.

If you have a valve (switch) that's not rated to the water (electrical) pressure (voltage), it'll burst spectacularly (arc, catch fire and burn your house down). If you have a valve that's not big enough for the flow rate, when it closes it'll hammer like crazy and physically damage itself. Switches that attempt to close an excessive current can arc and burn out, or even weld the contacts together.

Similarly, if you have lots of sprinklers branching off a main, then the main needs to be sized to the worst-case but still possible scenario. The largest load that's possible to occur, and it depends on how you operate the system:

• All sprinklers on at once - add all the loads together (big main pipeline; max running load = connected load)
• Only one sprinkler at once - the largest single sprinkler (littler main pipeline; max running load << connected load)

Electrically, the proportion of the "connected load" compared to the actual load is known as the "diversity factor". If we all designed every electrical switchboard to be rated to the connected load, we'd have no money and no copper left on earth. We design to the worst-case that's actually possible.

I can't speak for the electric brewery, but it's possible that they have determined that only a proportion of their connected load is on at any one time, and thus at any one time they cannot draw more than 10A.

If, however, they are using 10A switches with a 30A load then that's bad bad bad.

I think you've got the idea of the relays - the relay does the heavy switching, and the switch turns on the relay with a little control voltage.

 

[philistine]

Ok awesome- its all falling into place, thank you!

Well, in that case, it makes sense that i either need to install at least 1 relay (that being at the very start, the mains on/off) OR i need to replace the switch component itself to something rated for 15A.
I'll get round to attempting a diagram of sorts and see how it looks to experienced eyes.
Then try and work out which is the better and more cost effective way to get over this final hurdle.

Thanks HEAPS dude!

 

[Camo6]

I'd recommend you make use of relays or preferably contactors (generally higher current ratings) for a few reasons.

One reason is for safety - if you run an ELV (ie 24v) control circuit you reduce the hazard of having LV touch potential in a switch likely to be handled in a wet area. Even using contactors with 230V coils will eliminate the presence of high currents in the control circuit.

Another reason is to reduce cost - this is more of a cost saving exercise practised in industry. Relays/contactors allow a load to be switched by a much lighter load therefore allowing the use of lighter gauge copper and switch gear at the control location. Reduces cost, space and demand.

Then there is functionality and reliability to consider. Controlling a heavy load by switching the active conductor will create an arc which in turn results in a carbon build up on switching contacts. This can quickly lead to component failure. While a contactor isn't immune to these effects, it is specifically designed to switch loads. As the coil on a contactor is of negligible load, control components can comfortably handle repeated switching without suffering the effects of arcing.

Lastly, there is a certain satisfaction in hearing the 'thunk' of contactors kicking in when you throw the switch.

 

[klangers]

I'd recommend you make use of relays or preferably contactors (generally higher current ratings) for a few reasons.

Lastly, there is a certain satisfaction in hearing the 'thunk' of contactors kicking in when you throw the switch.

Yeah my terminology is a little "flexible"... probably should say contactors cause that's what I mean rather than a "relay" as such.

And indeed that thunk is very satisfying.

 

[mofox1]

And indeed that thunk is very satisfying.

Easily the best part of my brewery.

 

[philistine]

Thanks again guys, it's starting to make much more sense now.
So I guess my next questions are:

Are either of these two options suitable?
https://www.jaycar.com.au/240v-ac-panel-mount-relay/p/SY4044

Link from another thread - so I know its suitable

What's the difference between the two? Is one better suited than the other?
I found the first one by searching for "240v relay' on the jaycar website, the other I found refferred to as a contactor in a similar discussion.

 

[lmullan]

That jaycar one looks reasonable. The important parts are that the coil can be switched using 240VAC which is handy. If you read through that thread that you linked to, they discuss using 24VDC to operate the coil, while this makes it safer (lower voltage flowing through the buttons and switches that the user touches) it does mean you need a power supply with a 24VDC output which adds complexity!

In short as far as I can see reading the data sheet from jaycar, that one should be fine. Often the term relay and contactor are interchangeable, a contactor being a sub category of relay.