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Old 11-10-2010, 03:41 PM   #1
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Default Critique my plans...

So, here's a schematic I recently made with the plans to build a 2 vessel RIMS system. The idea behind this is a compact system that still allows for full functionality and fly-sparging.

The system will use 2 Sanke kegs, 2 3800w HWD elements mounted in a copper RIMS tube, one pump, and a CFC.

The MLT and BK will both be tied to the inlet of the pump, then two valves on the outlet will direct the flow either to the RIMS tube and back into the MLT or through the CFC and into the BK.

Mashing will be standard RIMS pumped through the 2 3800w element tube that is switched to 120v, so only putting out 1900w. The sparging will be on-demand fly-sparge using city water pressure through the RIMS tube running on 240 and putting out 7600w. The runnings are pumped into the BK.

At this time, the BK can be heating the runnings on low (4500w element at 120v = 1125w) to conserve energy because the setup would need to be fed with a 60A GFCI panel, plus the contactor would need to be 60A as well, plus much heavier wiring, etc, equals a lot more money. Once sparging is done, the power is killed to the elements and pump, and the power is switched over on the BK element to high. I may incorporate some sort of safety devise or switch to make sure only one setup is running on high at any given time. Or, just get rid of the switching capability of the BK all together and only sparge, or only heat the BK. That would be one less thing to worry about (or go wrong).

The BK element will be run off of a 555 chip PWM board with a potentiometer. This way I can just turn it up or down as more or less heat is needed.

Please critique these plans and the drawing for issues, as I really don't know what I'm doing.

Here's the schematic. I can't get my PDF to attach, it's too big, so here's a lower quality JPG.

rims-v1.0.jpg  
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Old 11-10-2010, 05:29 PM   #2
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You would need to latch in your main power circuit with a set of contacts on the main power contactor around the "ON" switch.
What is the 12VAC transformer supplying to the PWM module? Or is it a 12VDC power supply?
Are those solid state relays supplying power to the elements? That is going to be a lot of switching for an electro-mechanical relay.
With the switches in the positions shown, the "top" of the elements are not connected in a circuit. Keep the top of the elements always connected, and just switch the "bottom" from the opposite 240V line and neutral.

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Old 11-10-2010, 06:36 PM   #3
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Quote:
Originally Posted by evanmars View Post
You would need to latch in your main power circuit with a set of contacts on the main power contactor around the "ON" switch.
What is the 12VAC transformer supplying to the PWM module? Or is it a 12VDC power supply?
Are those solid state relays supplying power to the elements? That is going to be a lot of switching for an electro-mechanical relay.
With the switches in the positions shown, the "top" of the elements are not connected in a circuit. Keep the top of the elements always connected, and just switch the "bottom" from the opposite 240V line and neutral.
Not sure what you are talking about latch in the main power circuit. The power swith is a maintained switch, with that on, won't it energize the contactor as is? I guess I don't understand. I really only have experience with DC current.

Yes, the transformer is for 12v DC current to power the 555 board.

I did forget to label the relays for the elements. Yes, they are 40A SSRs.

The top switch isn't really needed in either element circuit, yes, but with that, I can kill the control voltage to that SSR as a safety feature. I can and may eliminate that for simplicity, but should opperate as drawn, no?
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Old 11-10-2010, 08:41 PM   #4
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If you have a maintained "ON' switch, you can kill power with the "E-STOP", but when the E-STOP is reset, if you forget to open the "ON" switch, power will automatically come back on. You should put a set of normally open contacts from the power contactor around the non-maintained "ON" switch. That way, when you hit the E-STOP, power will drop out and you have to intentionally push the "ON" switch to turn power back on.

I was looking at the two switches coming off of the controllers as one 2-pole switch. My mistake, it makes more sense as an SPST and an SPDT switch. Just remember that you'll have to turn the bottom switch to 120V position when you kill SSR power for safety, or you'll still have the power connected on that side.

As far as the bottom SSR goes, there is really no need for that. You don't need (or really want) to switch your neutral. You really could get away with not having the middle SSR either. A single electro-mechanical relay to switch between 240/120 for that would work. You really only need to control one leg with an SSR.

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Old 11-10-2010, 11:00 PM   #5
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Ah, I do see now. Thanks for the clarification.

I will look for a 40a relay that will allow the NC contacts to be hooked to neutral and the powered closed contacts to be hooked to 120, that way, the element remains hooked to neutral for safety. That would simplify my switches too. I could use two SPST switches instead of a SPST and a SPDT.

Thanks!

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Old 11-10-2010, 11:04 PM   #6
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No problem. Glad I could help.

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Old 11-11-2010, 04:35 AM   #7
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Quote:
Originally Posted by RedLight_Brewing View Post
I will look for a 40a relay that will allow the NC contacts to be hooked to neutral and the powered closed contacts to be hooked to 120, that way, the element remains hooked to neutral for safety. That would simplify my switches too. I could use two SPST switches instead of a SPST and a SPDT.Thanks!
I am not sure if you mean two SPST switches per element, or two SPST switches total. I believe you just need the latter.

Like evanmars suggested, you really should be using an SSR to switch the power on/of from the PID/PWM. The relays will quickly wear out. Not to mention driving you nuts with their constant clicking.

My suggestion: Replace the relay of the upper element connection with an SSR, switching L1 on/off to the element. Put a 40A SPDT relay switching L2 or Neutral to the lower connection, which I am sure you already are planning to do. Now the only SPST switch you need for this element is to switch the coil of the SPDT relay on for high power and off for low power.

Edit: Now I think you are planning on using the second switch to turn off power to the upper relay/SSR. That is actually a good idea. I think you have it figured out.
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Old 11-11-2010, 01:40 PM   #8
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Ya, those relays are supposed to be SSRs, but, I had to settle for a relay picture. I forgot to mark them.

I looked around last night and I am having trouble finding a SPDT 40a relay. I have found a 30a at a reasonable price, so maybe I need to reduce one of my elements down to 2500w so I draw less than 30a safely.

Ya, when I re-draw this, it will have one switch to kill power to L1s SSR and another to control L2/Neutral switching for each heating circuit, so 4 element switches total.

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Old 11-11-2010, 02:18 PM   #9
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I think it's important to distinguish a contactor relay from an SSR (solid state relay)....it's kind of confusing in this thread for those of us lurkers. Something to think about too....SSRs will fail closed....so if you forget to switch off the contactor you could have a situation where the element is still on even if the PID isn't sending the "on" signal to the SSR.

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Old 11-11-2010, 02:21 PM   #10
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Quote:
Originally Posted by RedLight_Brewing View Post
I looked around last night and I am having trouble finding a SPDT 40a relay. I have found a 30a at a reasonable price, so maybe I need to reduce one of my elements down to 2500w so I draw less than 30a safely.
If it's that much cheaper/easier to use a 2 pole contactor, you can just use one of the poles.....just don't put both elements on the same contactor!!!!!
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