Control Boxes

[reg]

OK you are obviously more experienced at electrical stuff than me.

Insert:Sound of one pulling ones head in

 

[gibbocore]

Answering gibbocore's question again, yes you can just use switches to control pumps and heater elements. If you're using switches rated to the load (I like the 15A illuminated rockers) you get zero benefit from adding relays as well.

wicked, these are the switches i was gonna be rocking (bad pun).

I will however now be running two PID's as opposed to one set point controller, so a couple of SSR's will be in order. I'll still be keeping the curcuits switchable though.

Cheers for the advice!

 

[reVoxAHB]

Dead right, Barramundi, but that doesn't mean that all controllers need output relays to protect them. The same would be true of any controller, switch, microcontroller computer or relay which was controlling a load with greater power requirements (voltage and/or current) than it was rated to supply. In your case, the controller provides the right voltage, but its current rating is only 8A for a load of 10A. Of course you need an output relay.

Reg, I'm afraid the idiosyncrasies you're referring to are just that - idiosyncratic. Engineers and sparkies don't (or at least shouldn't) design anything to be more complex than it needs to be to adequately meet the requirements. Most of them need some work in not overspecifying the requirements, but anyway... If you've got a 10A switch controlling 400-600W worth of heat lamps and it's arcing excessively, then you need a new switch. A relay would probably also solve the problem, but so what? A 1000A contactor would solve the problem too, but neither the contactor nor the relay is necessary when a new switch will work just as well. The relay's contact behave in exactly the same way as the switch's contacts, are rated to the same load, which is at least 4x the load required. It just means you've got a faulty switch, and you could just as easily have got a faulty relay, though you wouldn't have heard it arcing up in the roof.

Your comment about having to run less wires to the switch has some merit if you're talking about a 20m run, but is cancelled by the added complexity, cost and failure modes if you're talking about a foot to a door. You can get four wires there as easily as two.

As an aside, a contactor is a different beast entirely. It's a special kind of relay designed to suppress the arcs which occur when breaking very high voltage or current, particularly with inductive loads (like transformers or motors). We're talking about much much bigger loads than 2400W elements though. For this application you can pretty much completely deal with arcing by using a switch or relay which is well overrated for the load (15-20A switches are ideal) and even if you have to replace it every few years, you're still spending much less than a contactor.
My own solution will be a microcontroller driving some fat SSRs, but then I've specced my requirements rather higher than most (I did say it's a weakness). Answering gibbocore's question again, yes you can just use switches to control pumps and heater elements. If you're using switches rated to the load (I like the 15A illuminated rockers) you get zero benefit from adding relays as well.

 

[JSB]

shit its the flux capacitor !!!

Sorry just had to do it !!

Cheers
JSB

 

[LethalCorpse]

heh, check zizzle's brewbot if you want flux capacitor action. My own (if I ever get round to building it rather than talking about it) will be of similar complexity.

BTW guys (this is directed at pok mostly) I got a quote the other day from the stainless shop in Sydney for a 316 camlock pair at $28.

 

[zedford]

Hi, Just to let you know I also have a large inventory of new relays and terminal bases, as well as several small plc systems if anyone is interested. I dont have all the small stuff catalogued but bigger items are now at www.blackboxproductions.com.au there are still some of the boxes discussed above available as well as others. As well as various bits of stainless plant.

Regards tim

PS Im keen to see some photos of peoples finished systems.

 

[hockadays]

Rather then start a new thread I'll post my completed control box here. It has 2 circuits a 10A one that powers the pump and heat exchanger and the other is 15A that runs the HLT which has a 3.6kw custom element from stokes. I used illuminated switches from Jacar to isolate the different elements and two PIDs from Auberins. The Pid that controls the Heat Xchanger is programable and runs four differents mash schedules. 55-64-70-76, 66-76, 67-76, 55-67-76. All I need to do now is get some lettering for the front of the box and give it a test run once I finish the rest of the brewery.

 

[browndog]

Nice work there Hockadays, I reckone even the feared Lethal Corpse would be impressed with that work.

cheers

Browndog

 

[beerbrewer76543]

*whiney voice* Can you make me one?

Awesome work there!

I forsee a huge surge in Micro breweries in a few years when our brewing obsession finally trows a noose around our necks, drags us down to the bank and forces us to take out a mortgage to fund the new venture...

 

[hockadays]

Thanks Guys, the fun is definately in the building.