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-   -   Adding selector switch to dial down boil and still use RIMS (http://www.homebrewtalk.com/f170/adding-selector-switch-dial-down-boil-still-use-rims-359785/)

Dgonza9 10-09-2012 01:01 AM

Adding selector switch to dial down boil and still use RIMS
 
I have an electric rig with a RIMS setup. My BK element has no PID or PWM and runs at 4500W. I sometimes find this is slightly too much juice for a 13-14 gallon boil. I'd like to use my existing PID to dial it down in manual mode. Plus, it'd be nice to have a physical switch on the RIMS element in case the SSR fails.

The difficulty is that the Bk element has a contactor and the RIMS an SSR controlled by the PID. Do I need to get another contactor to use with the RIMS in order to use one selector switch to control both?

Thanks for the help.

SweetSounds 10-09-2012 01:12 PM

The easiest way to do it would be to add another SSR on the boil element, and wire a switch on the PID output to each SSR. This way you can chose which SSR gets the PID signal, and which element fires.

Dgonza9 10-09-2012 01:27 PM

How well does an ssr work with a contactor. Will it wear it by cycling it?

passedpawn 10-09-2012 01:35 PM

Quote:

Originally Posted by Dgonza9 (Post 4482620)
How well does an ssr work with a contactor. Will it wear it by cycling it?

I think he means to replace the contactor with the SSR.

Use the selector switch on the low-voltage signal to the SSR.

SweetSounds 10-09-2012 01:41 PM

I'd leave the contactor just as an interlock of sorts. I'm a big fan of contactors inline with elements because SSR's always leak voltage, and are never truly "Off".

Just add a new SSR to the boil element hot lead (Or 2 SSR's and switch both leads, My preference) and wire the trigger side to a switch so you can chose which SSR gets the signal from the PID.

Contactors can't handle fast switching, but they are fantastic safety devices when you want to know for sure, that the power is off. Use SSR's for the fast PWM switching.

passedpawn 10-09-2012 02:38 PM

I've never understood the use of contactors in place of a simple mechanical switch to turn off all power to the elements. Maybe someone can illuminate me there.

SweetSounds 10-09-2012 03:09 PM

It's the current capacity - Contactors are rated for 10, 20, 50 amps. Good luck finding a 30 amp + rated switch.

Also, the ampacity rating on most switches is current carrying limit. NOT the current breaking limit. They are different.

Contactors are designed to make, and break high current loads.

DustBow 10-09-2012 03:38 PM

what about this DPST switch: http://www.homedepot.com/h_d1/N-5yc1...&storeId=10051

I was going to use it with one of the weatherproof switch covers so you would never actually be touching the switch carrying the current.
http://www.homedepot.com/catalog/pro...18fa35_300.jpg

I was going to run the 10awg wire thru this switch and into the 4 prong outlet, so there would be a "main power off" switch to shut down power to everything (and also have switched contactor in panel running power to the element)

Dgonza9 10-09-2012 03:40 PM

Quote:

Originally Posted by SweetSounds (Post 4482653)
Contactors can't handle fast switching, but they are fantastic safety devices when you want to know for sure, that the power is off. Use SSR's for the fast PWM switching.

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.

Dgonza9 10-09-2012 03:44 PM

Quote:

Originally Posted by DustBow (Post 4483016)
what about this DPST switch: http://www.homedepot.com/h_d1/N-5yc1...&storeId=10051

I was going to use it with one of the weatherproof switch covers so you would never actually be touching the switch carrying the current.
http://www.homedepot.com/catalog/pro...18fa35_300.jpg

I was going to run the 10awg wire thru this switch and into the 4 prong outlet, so there would be a "main power off" switch to shut down power to everything

You've touched on both objections to these kind of switches. First, you are potentially touching a high voltage connection in a wet environment. Secondly, a lot of people have spent time creating a control panel that looks good. I know I did and I like my illuminated switches.

So safety is the first reason (though the waterproof cover is a reasonable precaution) and vanity is the second.


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