Spike Brewing 12.5 Conical Fermenter Giveaway!

Home Brew Forums > Home Brewing Beer > Electric Brewing > Contactor Question

Reply
 
LinkBack Thread Tools
Old 11-30-2012, 07:45 PM   #1
goybar
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2010
Location: Southern Maine
Posts: 250
Liked 5 Times on 5 Posts
Likes Given: 2

Default Contactor Question

Hi All,

I'm trying to figure out what the contactor in many(/all) of PJs diagrams is for.

If the SSR is turning on/off in conjunction with the PID, what is the purpose of the contactor?

I'm sure it is obvious, but I can't seem to wrap my mind around it.

-chris

__________________
goybar is offline
 
Reply With Quote Quick reply to this message
Old 11-30-2012, 07:59 PM   #2
jeffmeh
HBT_SUPPORTER.png
Feedback Score: 0 reviews
 
jeffmeh's Avatar
Recipes 
 
Join Date: Feb 2009
Posts: 1,816
Liked 131 Times on 112 Posts
Likes Given: 17

Default

An SSR can leak current, can fail closed (on), and is only controlling one leg of your 240V circuit. The contactor between the SSR and the element is there so that when you set the switch controlling the contactor off, both legs to the element are truly off.

__________________
jeffmeh is offline
 
Reply With Quote Quick reply to this message
Old 11-30-2012, 08:11 PM   #3
stlbeer
Senior Member
HBT_SUPPORTER.png
Feedback Score: 0 reviews
 
stlbeer's Avatar
Recipes 
 
Join Date: Jan 2008
Location: Fenton, MO
Posts: 878
Liked 33 Times on 32 Posts
Likes Given: 82

Default

Also, the SSR can switch the power off/on at a much higher rate than a contactor can. The two work in conjunction with each other.

__________________
My RIMS eBrewery build
stlbeer is offline
 
Reply With Quote Quick reply to this message
Old 11-30-2012, 11:27 PM   #4
goybar
Feedback Score: 0 reviews
Recipes 
 
Join Date: Apr 2010
Location: Southern Maine
Posts: 250
Liked 5 Times on 5 Posts
Likes Given: 2

Default

OK, so it really is more of a fail safe or safety item. Not really required but foolish not to use one.

__________________
goybar is offline
 
Reply With Quote Quick reply to this message
Old 11-30-2012, 11:33 PM   #5
Rarian
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2012
Location: Hamilton, Ontario
Posts: 25
Default

Quote:
Originally Posted by goybar View Post
OK, so it really is more of a fail safe or safety item. Not really required but foolish not to use one.
Without a contactor in a 240v system your PID would only be able to output between 50%-100% power; one leg would continually be Hot.
__________________
Rarian is offline
 
Reply With Quote Quick reply to this message
Old 11-30-2012, 11:38 PM   #6
milesvdustin
Feedback Score: 0 reviews
Recipes 
 
Join Date: Feb 2010
Location: Pensacola, Florida
Posts: 631
Liked 11 Times on 11 Posts
Likes Given: 23

Default

I don't use one. I always make sure the element is under water before I switch it on just in case.

__________________
Quote:
Originally Posted by djsethall View Post
It's like a big hot douche for my brewery.
milesvdustin is offline
 
Reply With Quote Quick reply to this message
Old 12-01-2012, 01:45 AM   #7
whoaru99
Feedback Score: 0 reviews
Recipes 
 
Join Date: Oct 2012
Posts: 1,589
Liked 124 Times on 101 Posts
Likes Given: 16

Default

Quote:
Originally Posted by Rarian View Post
Without a contactor in a 240v system your PID would only be able to output between 50%-100% power; one leg would continually be Hot.
Not sure that matters from a heating standpoint. Even if only one wire is switched the element only has two states...on or off. 0% or 100%.

From a hazard standpoint it matters through. If only one leg is broken you still have 120V to ground or neutral on the element, potentially a shock hazard.
__________________

Primary: Pre-prohibition Lager
Secondary: Russian Imperial Stout
Drinking: Chinook IPA
Drinking: Waldo Lake Amber
Drinking: Edwort's Apfelwein

whoaru99 is offline
 
Reply With Quote Quick reply to this message
Old 12-01-2012, 05:58 PM   #8
jgadbois
HBT_SUPPORTER.png
Feedback Score: 0 reviews
Recipes 
 
Join Date: May 2011
Location: Hillsboro, New Hampshire
Posts: 15
Likes Given: 1

Default

Quote:
Originally Posted by Rarian View Post
Without a contactor in a 240v system your PID would only be able to output between 50%-100% power; one leg would continually be Hot.
I think you are misunderstanding 240v.

Current flows from one leg thru the element and thru the other leg. If the SSR is off there is no current flow and therefore no power. With the SSR off there is a 120v potential to ground at any point in the circuit which may be what you were thinking.
__________________
jgadbois is offline
 
Reply With Quote Quick reply to this message
Old 12-02-2012, 12:21 PM   #9
stlbeer
Senior Member
HBT_SUPPORTER.png
Feedback Score: 0 reviews
 
stlbeer's Avatar
Recipes 
 
Join Date: Jan 2008
Location: Fenton, MO
Posts: 878
Liked 33 Times on 32 Posts
Likes Given: 82

Default

Quote:
Originally Posted by goybar View Post
OK, so it really is more of a fail safe or safety item. Not really required but foolish not to use one.
I'd add that when SSR's fail, they usually fail closed - allowing full current to flow through them - regardless of what the control circuit is doing. Since we only need to control 1 leg of a 240v system a contactor is a requirement to ensure the circuit is off.

Your life is more important than $10 your going to save by not putting in a contactor or the $50 you'll save by not buying the next larger sized panel.
__________________
My RIMS eBrewery build
stlbeer is offline
 
Reply With Quote Quick reply to this message
Old 12-02-2012, 03:25 PM   #10
gbrewing
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2008
Location: Washington State
Posts: 85
Liked 4 Times on 3 Posts
Likes Given: 2

Default

You can also use the contactor as an emergency off for the entire system. The big red mushroom looking button on control panels is usually wired to the power in contactor.

If things go wrong, you depress the mushroom button and it kills all power instantly.

__________________
http://www.gbrewing.com
gbrewing is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
SSR, Contactor? both? help me K.I.S.S mavrick1903 Electric Brewing 19 02-13-2013 05:57 AM
What value does a contactor add? Cromwell Electric Brewing 8 09-27-2012 07:43 PM
Question on energized contactor BigHefty Electric Brewing 15 03-04-2012 04:05 PM
Contactor question GRHunter Electric Brewing 3 05-25-2011 11:32 AM
Switch/Relay/Contactor Question egurney DIY Projects 2 03-08-2010 07:41 PM