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Old 10-09-2012, 03:47 PM   #11
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Yeah, I edited my original post a bit, this DPST switch would be on the wall right by the dryer outlet - a main power on/off.
I also have a contactor in my panel that supplies the juice to the element - switched by a pretty lighted Auber push button switch

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Old 10-09-2012, 03:55 PM   #12
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Home Depot carries 30A DPST 240V switch on the shelf. Maybe $10. I have one of these on my box for all power to the elements, and also one on the wall under a wet location cover to cut all power to my box. Don't get me wrong, I like the idea of the contactors, but if you want to build a box as simply as possible, this does work. BTW, I have 2 elements controlled by one PID with a selector switch. Maybe you can find an idea there. See this.

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Old 10-09-2012, 03:59 PM   #13
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Quote:
Originally Posted by Dgonza9 View Post
So when you use the PID in manual mode and dial it down, doesn't it simply cycle the element on and off? Is this "fast switching"?

Part of me thinks that adding a contactor to the RIMS side of things may be a better way to go. This way I have a physical switch to make sure the element in the tube isn't firing if the SSR fails open. So now, same question. If I put a contactor after the SSR and switched the load wire to the coils of each contactor, would I wear out the RIMS contactor? I assume the BK contactor won't be firing on and off as often, but would I potentially wear that out as well?

Or does using a PID in manual mode operate in such a way that it won't be firing the contactor on and off if I dial down the boil?

Cheers.
You always wire the PID to control the SSR, the contactor is there as a separate safety measure - either on when using the element, or switched off when not using the element. But the rapid fire on & off is always done by the SSR, with the contactor simply being turned on and off at the beginning and end of usage. Maybe I'm not understanding the question properly?...
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Old 10-09-2012, 04:00 PM   #14
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I'll see if I can dig up the diagram. It looks to me like the SSR's control the coil on the contactors, which would lead me to believe that the contactors would be rapid firing when used.

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Old 10-09-2012, 04:02 PM   #15
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PassedPawn, I totally stole the idea for my main power switch from you and that pic

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Old 10-09-2012, 04:06 PM   #16
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Quote:
Originally Posted by Dgonza9 View Post
So when you use the PID in manual mode and dial it down, doesn't it simply cycle the element on and off? Is this "fast switching"?

Part of me thinks that adding a contactor to the RIMS side of things may be a better way to go. This way I have a physical switch to make sure the element in the tube isn't firing if the SSR fails open. So now, same question. If I put a contactor after the SSR and switched the load wire to the coils of each contactor, would I wear out the RIMS contactor? I assume the BK contactor won't be firing on and off as often, but would I potentially wear that out as well?

Or does using a PID in manual mode operate in such a way that it won't be firing the contactor on and off if I dial down the boil?

Cheers.
This is a bit complicated, but the switching rate of the PID is going to be quite high. You can not connect a PID to a contactor - It's just too fast. The contactor should be hooked up to a switch to simply turn it on and off.

Anything the PID controls with PWM needs to be through an SSR.

Remember how a PWM circuit works:
If your PID PWM frequency is 1 second, for instance, every second your contactor will change state twice, regardless of power setting.
If you set 50% power, it's on for .5 seconds and off for .5 seconds.
If you set 75% power, it's on for .75 seconds and off for .25 seconds, repeating over and over.

This is why you have to use SSR's for throttled loads - The SSR can handle that switching rate.

Since you want to be able to throttle both the RIMs and the BK elements, both need SSR's. The RIMs will be PID operated with a thermocouple and PWM controlled by the PID. The BK will be manually operated with PWM from the PID.

So these are really 2 different functions:
Contactors are the safety - Enabling you to have positive control of the voltage at the element - On and off. This is manual, and is a safety in case you need to feel safe while cleaning, or in case your SSR fails. Because SSR's usually fail "Closed" or "On". Bad.
The SSR's are what actually control the "heat" applied by the element by switching it on and off really fast.

These are 2 separate functions, and each function has an appropriate device.
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Old 10-10-2012, 12:21 AM   #17
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Quote:
Originally Posted by SweetSounds View Post
This is a bit complicated, but the switching rate of the PID is going to be quite high. You can not connect a PID to a contactor - It's just too fast. The contactor should be hooked up to a switch to simply turn it on and off.

Anything the PID controls with PWM needs to be through an SSR.

Remember how a PWM circuit works:
If your PID PWM frequency is 1 second, for instance, every second your contactor will change state twice, regardless of power setting.
If you set 50% power, it's on for .5 seconds and off for .5 seconds.
If you set 75% power, it's on for .75 seconds and off for .25 seconds, repeating over and over.

This is why you have to use SSR's for throttled loads - The SSR can handle that switching rate.

Since you want to be able to throttle both the RIMs and the BK elements, both need SSR's. The RIMs will be PID operated with a thermocouple and PWM controlled by the PID. The BK will be manually operated with PWM from the PID.

So these are really 2 different functions:
Contactors are the safety - Enabling you to have positive control of the voltage at the element - On and off. This is manual, and is a safety in case you need to feel safe while cleaning, or in case your SSR fails. Because SSR's usually fail "Closed" or "On". Bad.
The SSR's are what actually control the "heat" applied by the element by switching it on and off really fast.

These are 2 separate functions, and each function has an appropriate device.
Thanks for taking the time to write that explanation. I understand now. I mistakenly thought the SSR was switching the coils on the contactor, not the load wire.

Looks like what I need is another contactor. I can then use the 3 position switch to switch the line wire and let the SSR switch the load.

Here's the diagram I'm going to use. Many thanks to whomever created it, I think PJ.

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Old 10-10-2012, 01:53 AM   #18
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I just saw the post prior to this one. I think you've got it!

Quote:
Originally Posted by Dgonza9 View Post
So when you use the PID in manual mode and dial it down, doesn't it simply cycle the element on and off? Is this "fast switching"?
Yes, the PID cycles the element, but it does so using the SSR to switch the current. The contactor is turned 'on' at the beginning of using it and 'off' when you're done using it. The PID does the fast cycling of the SSR.


Quote:
Originally Posted by Dgonza9 View Post
Part of me thinks that adding a contactor to the RIMS side of things may be a better way to go. This way I have a physical switch to make sure the element in the tube isn't firing if the SSR fails open.
Correct.

Quote:
Originally Posted by Dgonza9 View Post
So now, same question. If I put a contactor after the SSR and switched the load wire to the coils of each contactor, would I wear out the RIMS contactor?
Nope. You'll be fine.

Quote:
Originally Posted by Dgonza9 View Post
I assume the BK contactor won't be firing on and off as often, but would I potentially wear that out as well?

Or does using a PID in manual mode operate in such a way that it won't be firing the contactor on and off if I dial down the boil?
The contactors will only be turned on at the beginning of their use and then off after you are done with them.

It goes like this.

PID -> SSR -> Contactor -> Element (Outlet)

When you are ready to use your RIMS, close the switch for the RIMS Contactor. The contactor closes. - Make sure the pump is running and wort or water is flowing.

Adjust the PID to the desired temperature. The PID will switch use the SSR to switch the current through the contactor to the element outlet. For the mash, the contactor would be closed for the mashing period, then opened.
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