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Home Brew Forums > Home Brewing Beer > Electric Brewing > Why so many switches, led, and relays??
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Old 01-04-2013, 02:33 AM   #31
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Do you want to sell the 2nd ones cheap?
Nah, but thanks for the offer.

Never know what I might end up using it for in the future. I like horsing around with my equipment nearly as much as brewing... plus it makes a pretty snazzy thermometer!
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Old 01-04-2013, 02:39 PM   #32
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I use a Control Panel On/Off switch, an Element On/Off Switch, and a PID.

CP Switch turns the panel on (aka, PID turns on)
Element Switch allows current to the Element (aka, PID fires element)

It's about as bare bones as I think you can safely get... And I love it!


I also have an extension cord with a switch for the pump.

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Old 01-04-2013, 05:14 PM   #33
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I use a Control Panel On/Off switch, an Element On/Off Switch, and a PID.

CP Switch turns the panel on (aka, PID turns on)
Element Switch allows current to the Element (aka, PID fires element)

It's about as bare bones as I think you can safely get... And I love it!


I also have an extension cord with a switch for the pump.
Picture?
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Old 01-04-2013, 05:33 PM   #34
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This is the best I have for now. It's from my phone, so be nice... I'll be posting my build thread soon. Just gotta take real pictures first.

The CP is on the left. System is a 20gal Single Vessel BIAB with recirc and counterflow chilling. Top switch is System On/Off, bottom switch is Element On/Off.

setup.jpg   electrical2.jpg  
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Old 01-04-2013, 06:11 PM   #35
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There was some discussion earlier in this thread about the need for additional over-current protection (fuses or circuit breakers) on the individual circuits controlled by a panel. The comparison was made to an electric range and there was discussion of whether they have over-current protection for individual circuits.

Generally, an electric range doesn't have any additional protection on the individual circuits. Yes, a failure could overload a wire in the range but it is inside the range, an enclosure designed to limit the spread of the fire. A brewing control panel is similar up until the point where a cord is used to connect an external device to it.

Imagine a panel with a properly protected 50A feed and no additional over-current protection on the individual circuits. Now imagine a pump circuit coming out of that panel. Finally, imagine that pump motor seizes and the over-temperature protection in the motor fails to turn it off (not unheard of). Now you have a small guage cord and motor overloaded with only a 50A breaker for protection. That breaker won't trip and the cord/motor will continue to heat. Eventually something starts to burn and it isn't inside a fire resistant enclosure.

That is why it is important to have properly sized over-current protection on all of the circuits coming out of the panel.

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Old 01-05-2013, 12:26 PM   #36
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That breaker won't trip and the cord/motor will continue to heat. Eventually something starts to burn and it isn't inside a fire resistant enclosure.

That is why it is important to have properly sized over-current protection on all of the circuits coming out of the panel.
That sounds like what an insurance company will tell you when they refuse to pay for damages. If they can't sue the manufacturer (YOU) then they're not going to pay. When the bank comes looking for their money for the house that burned down, the insurance company will be wagging the finger at the homeowner. It pays to protect yourself.
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Old 01-05-2013, 12:58 PM   #37
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Matt,

I see a bunch of people using switches to power on their PID's, this seems overkill. Why does it matter if they are on, especially if you have a switch that will control power to the element. I am all for safety, but let's face it, there is enough electricity running through a household light switch to make it a bad day and I don't have redundancies there. I accept I am new to this and may be missing something...
Let me put the switch in perspective with an example from actual industrial controls. When controlling temperature with steam it's common practice to put a 2 position valve (open or closed) in line with the control valve. The 2 position valve must be open in order for the control loop (PID) to control temperature. It's done this way for 2 reasons - control valves can be prone to slight leakage and it prevents the media from being heated in the event the control loop is inadvertently left in auto or manual and not 0% open. Both conditions can lead to safety issues. I've seen installs where the customer did it on the cheap and next thing you know something was damaged because a 350 degree hotspot was created since the control valve was left 100% open but the product side of the heat exchanger was not flowing.

In the case of the switch, it's there to prevent dry firing the heating element Think of it as the same as the discrete valve. If you forget to set the PID control loop to 0% and manual but turn the switch off, you won't dry fire the heating element, which can both ruin the element and be dangerous in terms of burning something.

Sure, you can eliminate it but I would keep it there. It's a lot easier to remember to flip the switch than to put the control loop into manual and 0% open.
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Old 01-05-2013, 06:23 PM   #38
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Let me put the switch in perspective with an example from actual industrial controls. When controlling temperature with steam it's common practice to put a 2 position valve (open or closed) in line with the control valve. The 2 position valve must be open in order for the control loop (PID) to control temperature. It's done this way for 2 reasons - control valves can be prone to slight leakage and it prevents the media from being heated in the event the control loop is inadvertently left in auto or manual and not 0% open. Both conditions can lead to safety issues. I've seen installs where the customer did it on the cheap and next thing you know something was damaged because a 350 degree hotspot was created since the control valve was left 100% open but the product side of the heat exchanger was not flowing.

In the case of the switch, it's there to prevent dry firing the heating element Think of it as the same as the discrete valve. If you forget to set the PID control loop to 0% and manual but turn the switch off, you won't dry fire the heating element, which can both ruin the element and be dangerous in terms of burning something.

Sure, you can eliminate it but I would keep it there. It's a lot easier to remember to flip the switch than to put the control loop into manual and 0% open.
For the brewing application, this is better accomplished by running the hot output of the SSR and the other hot output (assuming 240V) through a double pole switch or contactor. Assuming one does this and also has a switch or contactor to cut main power, I do not see any utility to having a switch to turn off the PID. If you want everything off including the PID, cut main power. If you want to make sure the element is off, cut element power. You can then run your other circuits (pumps, etc.) with the PID on but no power to the element.
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