240V Heating Element - 1 or 2 SSRs

When using a 240 V Heating Element, should you use 1 or 2 SSRs?

If you only use 1, will the element still be hot?

aarondrich said:

When using a 240 V Heating Element, should you use 1 or 2 SSRs?

If you only use 1, will the element still be hot?

Click to expand...

It will be HOT, but not hot...

It wont give off heat, but there is still a live wire there.

So what is the advantage of using 2 SSRs?

aarondrich said:

So what is the advantage of using 2 SSRs?

Click to expand...

If you use (2) then when the element is commanded off, NONE of the legs are hot. If you use (1) then one leg is always hot... you may not want the element leads hot when it is "off"

You can use a standard relay as well for the second leg if you want. Because you will not be cycling the second leg on/off very often. One of the reasons to use and SSR is lifespan of the relay. SSR has no moving parts. So a PID or another device can constantly turn the power on and off without much worry. With a mechanical relay, if you cycled it that often it would probably fail on you.

If you go with a mechanical relay make sure the relay is rated for the amperage you are using.

Also with a mechanical relay or SSR make sure the switch you are using is passing on the correct voltage for the relay. Mechanical relays have coils that are rated for the voltage you have at your switch. So make sure you get the right one.

You can do it with one, but it is best to use two.

Say you turn the element off, and pour in some more water for what ever reason. Some water runs down the back of the pot and hits the 1 live wire. The water conducts to the pot which conducts to the liquid inside of it, travels up the pouring liquid and into the metal pot your holding.

You wonder how much you trust that GFCI and ask yourself one question: do I feel lucky? Well, do ya, punk?

Kidding about the punk, couldn't help myself. But you can see how in one instant you'll wish you had splurged for the second SSR.

I went with (2) SSRs per element on my new system for that reason. I dont want (4) heating elements with live wires running to them when the system is "off". I want it off... off.

(10) SSRs total... 8 for elements and 2 for pumps

At $16 for an SSR+Heatsink... it was cheap to justify

This is why I have a DPST switch for each of my elements. I don't use my PID to turn my elements on and off. I simply use the PID to control temp. Hence, I only have one SSR per element. If I used the PID to turn my elements on and off, I would have two SSRs per element.

stevehaun said:

This is why I have a DPST switch for each of my elements. I don't use my PID to turn my elements on and off. I simply use the PID to control temp. Hence, I only have one SSR per element. If I used the PID to turn my elements on and off, I would have two SSRs per element.

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With an HOA switch and 2 SSRs you have the best of both worlds.

It's already been said but I would think you want a DPDT mechanical kill switch for the "real" off off.

Bobby_M said:

It's already been said but I would think you want a DPDT mechanical kill switch for the "real" off off.

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I agree. I like some indicator of true off. Call me old school but I used a definate purpose contactor for my HLT. It "clunks" on and "clunks" off and hums a bit when its on.

I haven't used them. Do they not make a 2-pole SSR?

lschiavo said:

I haven't used them. Do they not make a 2-pole SSR?

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Yep but much more expensive than two SSRs.

lschiavo said:

I agree. I like some indicator of true off. Call me old school but I used a definate purpose contactor for my HLT. It "clunks" on and "clunks" off and hums a bit when its on.

Click to expand...

I am also using a definite purpose contactor as well as a SSR. Turn switch on to activate the DP contactor, which feeds one leg to the SSR and one to the receptacle. The leg that goes to the SSR gets switched by the PID. That way, I know that if the switch is off, the element is NOT energized at ALL. Also have a lighted switch to know when it's switched on (as if the clunk isn't enough), as well as a separate indicator to show when the element is cycling on and off by the PID. Sounds like a lot, but it's actually pretty simple. Contactors are cheap ($14 at Auber for 40A), and are widely used in industrial controls.

Cheers!
MrH

lschiavo said:

Do they not make a 2-pole SSR?

Click to expand...

= Dual SSR or DSSR.

Bobby_M said:

It's already been said but I would think you want a DPDT mechanical kill switch for the "real" off off.

Click to expand...

This was available at my HD. Mixed in with all the 120V stuff. Even the guy working the aisle didn't know it was there. If you are looking for it, print this pic and take it with you. (Click on the pic below for a much bigger hi-rez version!)

when wiring up 2 ssr's for a 240 element do you run 2 wires from the controller (brewtroller in my case) terminals to the ssr or run them in series? (the 2 wire method seems logical, but i've been wrong before...)

buffalobrewer said:

when wiring up 2 ssr's for a 240 element do you run 2 wires from the controller (brewtroller in my case) terminals to the ssr or run them in series? (the 2 wire method seems logical, but i've been wrong before...)

Click to expand...

Run them in parallel. a set of wires from the BCS to the first SSR and then another set of wires from the first to the second SSR.

thanks for the confirmation. (probably should have said 2 sets of wires in my post to make it clearer).

passedpawn said:

This was available at my HD. Mixed in with all the 120V stuff. Even the guy working the aisle didn't know it was there. If you are looking for it, print this pic and take it with you. (Click on the pic below for a much bigger hi-rez version!)

Click to expand...

That's the one I used in my setup. The switch is a little bigger/thicker than your standard 15A wall switch, but it still fits under the cheesy all-weather switch covers that I'm using. Happy so far.

So someone on this thread mentioned that they were using 25A SSRs for a 5500W heating element? This is also a question I had? I have enough 25A SSRs, and 5500W is actually less than 25A but not in the 70% range? If I am using a heat sync, what is the down side to doing this? Does it just impact the life of these SSRs, or is there a danger concern?

I am temporarily using a 25A SSR that I had laying around with my 5500W element until the 40A SSR arrives from China. From what I hear, SSR's tend to fail closed, meaning "full throttle." I kept a very close eye on the temperatures of my heat sink and the intensity of the boil during my brew day a week ago. Everything went well with no excessive heat from the SSR and consistent operation, but I'm looking forward to swapping out the 25A unit in the near future. I did a 75 minute boil with ~15 minutes time-to-boil after the sparge, so around 90 minutes of continuous operation.

Faster cycle times and running near the rated amperage limit will create more heat which makes failure more likely.

Go ahead and use the 25A SSRs for the 5500W element. They will run hotter than say a 40A ssr on the same load. Either way, it's rated for 25A. Load<25A? then good. If not then get a bigger one.

Will it burn up over a long period of time and usage? Possible.

If I sound irritated it is because I am but not directly at you aarondrich or any one else for that matter. It's this notion that everything must be de-rated to the 'actual' working rating. Manufacturers rate their components for their intended uses with a reasonable life expectancy and limited liability for the manufacturer. So unless you are building a UL508 certified panel or any other form of certification that imposes a de-rating factor, use the manufacturers rating. If you are going to hit or you are reasonably afraid you are going to exceed the rating (read with in an amp), then buy the next size.

If you by a 25A SSR and it burns up after supporting a 22, 23A load then one of two things have happened. You didn't provide satisfactory cooling, OR it's from a crap manufacturer.

Okay, I feel better now.

I use a Crydom D2425D. This is a dual 25A solid state relay (DSSR). Without proper heatsinking, it will get very hot. With a nice heatsink it will drive 25A my 5500W element no problem. The heatsink only gets warm by the end of the boil. I switch both legs of the 240V with it.

This is the heatsink I use (it has space for 2 SSRs, which is what I wanted). It also specified the heat conduction in degC/W, which allows me to really know what the heck to expect.

[edit] oh yea, I should mention I put thermal paste (Arctic Silver 5) between the heat sink and the SSRs. They were pretty flat, but not wet lapped flat, so the paste is a good idea. OK, prolly overkill, but I had it sitting around.
http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=CC1702-ND&x=18&y=16

CodeRage said:

buffalobrewer said:

when wiring up 2 ssr's for a 240 element do you run 2 wires from the controller (brewtroller in my case) terminals to the ssr or run them in series? (the 2 wire method seems logical, but i've been wrong before...)

Click to expand...

Run them in parallel. a set of wires from the BCS to the first SSR and then another set of wires from the first to the second SSR.

Click to expand...

Unless I'm picturing that wrong in my head, isn't that wired in series as you described?

Ok, so I was wondering. If I use two 2 SSR's on the 5500W element, do the SSR's need to be 25A each or 40A each. Since I am only putting one leg per SSR is the 40A necessary on each or would the 25A be sufficient. Of course I would have heatsinks on each SSR.

liljimmynorton said:

Ok, so I was wondering. If I use two 2 SSR's on the 5500W element, do the SSR's need to be 25A each or 40A each. Since I am only putting one leg per SSR is the 40A necessary on each or would the 25A be sufficient. Of course I would have heatsinks on each SSR.

Click to expand...

25A each. But 40 will run cooler and is a better option if they only cost a few bucks more.

I've been running my 25A SSRs for a long time... with no problems, tho.

Adding more SSRs will work for safety, but adds more complexity and stuff in your brew box. I just finished my RIMS build and have a 5500W 240V element running at 120V (quarter power) on a 25A SSR. I just drilled a hole for my heating element power cord through a 1" plastic cap from home depot, gobbed on layers of liquid electrical tape on the exposed element wires, and pushed the cap over it.

I think this is appropriate... ha!
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