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-   -   Electric Brewing - Control Panel Branch Circuits (http://www.homebrewtalk.com/f11/electric-brewing-control-panel-branch-circuits-197245/)

Bobby_M 09-23-2010 06:29 PM

Electric Brewing - Control Panel Branch Circuits
 
Side note: anyone think a dedicated "electrical" subforum makes sense in this equipment forum? Just thinkin.

So, I know this is going to opening a can of worms but that's fine. Let's go there.

Premise: The basic tenants of electrical safety say that the circuit breaker that feeds a circuit should trip before the wiring between that breaker and the load has a chance to overheat. Example, 26amp (planned) load on some 10/3 copper romex, should be fed off a 30amp breaker. If the actually load increases for some reason and it exceeds 30amps, the breaker trips so the romex doesn't burn up in the wall causing a fire. No argument there. It's even common sense. Branch circuits in a home wiring situation are typically dozens of feet long, if not even 100 feet and buried in the walls.

In practice: It seems like many electrical builds that involve a big control panel include a high amperage, large cable, main power connection. A lot of them are fed off a 4-wire, 50amp spa breaker panel. Of course none of the devices fed from the control panel represent a full 50 amp load so it involves branching. 30amp to each of potentially two 4500watt elements at a time and a little extra, couple amps, for pumps or whatever.

I see that a lot of builds include a rail and associated rail mount breakers for these branch circuits but it also adds over $100 to the build. Is everyone really that paranoid about overloading a 3 foot run of exposed cable that is used intermittently while its being supervised? Electrical codes are based on worst case scenario so let's talk about what that would be if two runs of 10/3 SJ are hard tapped off the 50amp main and run 3' to your vessel elements. I THINK in order for something bad to happen, the load on one of the branches would have to increase somehow to like 50 amps and hold there while the other branch was off. Even so, how long would that condition have to exist before the SJ cord self destructed? What exactly would cause a resistive load of typically 26 amps climb to only 40 or 50 amps and NOT a dead short? Of course, a short condition would trip the 50amp spa breaker before any of the branch wire was fried.

Am I talking out of my bung or are you following me? These aren't production breweries right, just a couple hours on the weekends.

Of course, this isn't advice so don't take it as advice. I'm just talking here.

Boerderij_Kabouter 09-23-2010 06:54 PM

I do not think internal breakers are necessary. I do think fuses are a good idea for protecting internal components and wires. So long as the system is designed properly, overload should never occur. If something goes wrong, you have the fuses, and if something really odd happens, the breaker should trip. I see no problem with standard branching.

Am I missing something?

Also, I think there should be an E-forum.

lschiavo 09-23-2010 09:03 PM

In building a control panel and supplying it with a single 240V feeder, we are "tapping" off that feeder to supply separate components. Providing fusing/circuit breakers on the tapped conductors will not provide additional protection for your feeder but will serve to protect the wiring and components after the tap is made.

Say you are using a 50A spa panel to protect your control panel feeder. In your control panel you tap the feeder with a #14 to supply power to your PID. Now should there be a fault in you PID nothing will stop the #14 wire from carrying the full 50A your feeder breaker is capable of.

As far as I understand the code, the above tap is legal without overcurrent protection as long as some conditions are met. The code section to search is 240.21 if you are interested.

Having said all that, I have no secondary fusing in my panel. I have it in a good enclosure with kill buttons if anything should go wrong and I feel safe using it.

airbalancer 09-23-2010 10:43 PM

I believe the breakers I used from automation direct were around 16 bucks each. The difference between those and fuses are probably negligible. Plus they give you a good wire connection point. If you’re going to spend the money to build a system it seems like the wrong place to save a penny.

Mike

P-J 09-24-2010 01:47 AM

Quote:

Originally Posted by Bobby_M (Post 2295157)
Side note: anyone think a dedicated "electrical" subforum makes sense in this equipment forum? Just thinkin. ...

I think it is an excellent idea.

Re: The balance of your topic, I'm with you 100%. The sensitive devices (PIDS et.al.) should be fuse protected anyway. As a side note, have you ever seen the guts of an electric range? No breakers, no fuses - fed from a 50 amp mains circuit. Elements fed (240V) using #14 or #12 wire depending. Lighting fed with #16 wire. (the outlets do have fuses or breakers though)

Interesting topic. I expect to see lots of info on this one.

Thanks.
P-J

TheBroonery 09-24-2010 02:00 AM

Just make sure that the fuse (circuit breaker) is the weakest link, and you'll be ok.

IrregularPulse 09-24-2010 02:21 AM

I think people get too hung on "code". I had an electrician over this spring to talk about splicing into my stove line to add a plug in the garage for my brewery. I asked about code, he said, it's your house. You're allowed to do whatever you want as long as you run the appropriate wire size for the load.

TheBroonery 09-24-2010 02:25 AM

Quote:

Originally Posted by IrregularPulse (Post 2296182)
I think people get too hung on "code". I had an electrician over this spring to talk about splicing into my stove line to add a plug in the garage for my brewery. I asked about code, he said, it's your house. You're allowed to do whatever you want as long as you run the appropriate wire size for the load.

What works and what is good practice are 2 very different methods.

IrregularPulse 09-24-2010 02:31 AM

I agree. Just putting that out there for the code nazis. We're not wiring warehouses full of CNC machines and boring machines. I am building an electric brewery myself. Like Bobby mentioned. These are monitored systems that get brought out for a few hours on the occasional weekend. I agree we need to be safe with stuff, but code enforcement is way over drilled in the forum.


I agree about a subforum. Electric systems are very popular these days.

klyph 09-24-2010 02:35 AM

The only breaker I use is the one in the house's panel. I do use a fuse to protect my PID.

http://i99.photobucket.com/albums/l2...g/DSC05058.jpg


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