The Great Bottle Opener Giveaway

Home Brew Forums > Home Brewing Beer > DIY Projects > SSRs are for Chumps

Reply
 
LinkBack Thread Tools
Old 08-25-2010, 12:23 AM   #1
craley1
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jul 2010
Location: St. Louis, Missouri
Posts: 13
Default SSRs are for Chumps

So I'm not real thrilled with the prospect of installing a bunch of SSRs with huge heat sinks in an already small electrical box. The alternative I have found is a Miniature Power Relay. Here is a link.

The main disadvantage I can see is that because it is not a solid state unit, the number of operations are limited to 100,000 at their rated current. I figure if these were used once a week, they could potentially need to be replaced after a year and a half.

Has anyone used these instead of SSRs? Are there any other options to SSRs that are cost effective (contactors don't appear to be very cheap).

__________________
craley1 is offline
 
Reply With Quote Quick reply to this message
Old 08-25-2010, 12:31 AM   #2
Bobby_M
Vendor and Brewer
HBT_SPONSOR.png
Vendor Ads 
Feedback Score: 2 reviews
 
Bobby_M's Avatar
Recipes 
 
Join Date: Aug 2006
Location: Whitehouse Station, NJ
Posts: 21,822
Liked 899 Times on 600 Posts
Likes Given: 26

Default

If you're using it as a temp controller, you're fine. If you want to use a PID in manual mode for effective 50% power output for instance, you're looking at burning it up in 50,000 seconds of use.

__________________
BrewHardware.com
Sightglass, Refractometer, Ball Valve, Weldless bulkhead, Thermometer, Decals, Stainless Steel Fittings, Compression Fittings, Camlock Quick Disconnects, Scale, RIMS tube, Plate Chiller, Chugger Pump, Super Clear Silicone Tubing, and more!

New Stuff?
Bobby_M is offline
 
Reply With Quote Quick reply to this message
Old 08-25-2010, 01:09 AM   #3
SweetSounds
Feedback Score: 1 reviews
Recipes 
 
Join Date: Jan 2010
Location: Des Moines, Iowa
Posts: 1,429
Liked 17 Times on 16 Posts
Likes Given: 4

Default

Yep...

Mechanical relays aren't designed to be switched on and off every 2 seconds.

Not that it won't work, but it's outside the spec.

OTOH, they are cheaper than SSRs...

100,000 cycles/2 per second = 50,000 seconds = 833 minutes = 13.8 hours of element control. That's about 10 batches of beer - Less if you are using it for sparge water and boiling.
100,000 is MTBF too, it could be less or more...

__________________
Quote:
Originally Posted by Ecnerwal View Post
What does the primary pressure gauge on the tank tell us? That's right, the temperature. Put it on a scale if you want to know how much is in it...
Put some duct tape over the gauge - Or better yet - Replace the high pressure gauge with a plug - High pressure gauges are useless!
SweetSounds is offline
 
Reply With Quote Quick reply to this message
Old 08-25-2010, 01:18 PM   #4
craley1
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jul 2010
Location: St. Louis, Missouri
Posts: 13
Default

Thanks for the feedback. That's what I was afraid of. Are there any other solutions available, something I haven't mentioned? Or is there an SSR that has a smaller footprint?

Also, back to the power relays: what about for the pumps? Once they start pumping, they stay on until their process is complete, correct? That would at least reduce the space requirements for two of the SSRs (assuming 2 SPST SSRs for each 240v heater element and 4 heaters and two more SPST SSRs/power relays for the pumps).

__________________
craley1 is offline
 
Reply With Quote Quick reply to this message
Old 08-25-2010, 01:25 PM   #5
SweetSounds
Feedback Score: 1 reviews
Recipes 
 
Join Date: Jan 2010
Location: Des Moines, Iowa
Posts: 1,429
Liked 17 Times on 16 Posts
Likes Given: 4

Default

Quote:
Originally Posted by craley1 View Post
Thanks for the feedback. That's what I was afraid of. Are there any other solutions available, something I haven't mentioned? Or is there an SSR that has a smaller footprint?

Also, back to the power relays: what about for the pumps? Once they start pumping, they stay on until their process is complete, correct? That would at least reduce the space requirements for two of the SSRs (assuming 2 SPST SSRs for each 240v heater element and 4 heaters and two more SPST SSRs/power relays for the pumps).
They will work fine for the pumps - Provided they are rated for the pump's current draw (Buy you knew that already)

SSRs are around because a solid state switch MTBF is far higher than a mechanical equivalent.

I'm installing 2 enclosures in my rig for this very reason. One will house all of the high voltage stuff - Contactors, relays, and distribution stuff. The "Low voltage" panel will have things like the SSR/relay trigger signals feeding back to the "High voltage" panel.

May not be an option for you, but it's there.

Mine looks like this:
Schematic

High Voltage panel:


Low voltage panel:
__________________
Quote:
Originally Posted by Ecnerwal View Post
What does the primary pressure gauge on the tank tell us? That's right, the temperature. Put it on a scale if you want to know how much is in it...
Put some duct tape over the gauge - Or better yet - Replace the high pressure gauge with a plug - High pressure gauges are useless!
SweetSounds is offline
 
Reply With Quote Quick reply to this message
Old 08-25-2010, 01:56 PM   #6
craley1
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jul 2010
Location: St. Louis, Missouri
Posts: 13
Default

Quote:
Originally Posted by SweetSounds View Post
Mine looks like this:
Schematic
Wow. That's an impressive set up. I like your idea and had considered two separate compartments/panels for all the electrical.

I'm going to go a little off my topic: why do you have contactors and SSRs in series on your heaters? Wouldn't two SPST (or one DPST) SSRs alone work?
__________________
craley1 is offline
 
Reply With Quote Quick reply to this message
Old 08-25-2010, 02:08 PM   #7
SweetSounds
Feedback Score: 1 reviews
Recipes 
 
Join Date: Jan 2010
Location: Des Moines, Iowa
Posts: 1,429
Liked 17 Times on 16 Posts
Likes Given: 4

Default

Quote:
Originally Posted by craley1 View Post
Wow. That's an impressive set up. I like your idea and had considered two separate compartments/panels for all the electrical.

I'm going to go a little off my topic: why do you have contactors and SSRs in series on your heaters? Wouldn't two SPST (or one DPST) SSRs alone work?
Theoretically yes,
But SSRs have a bad habit of "Failing closed", and the contactors give me a failsafe to know that there is no way power is getting to the elements.
I could just use really big switches, but it's designed so that when I want to go to full automation I just have to trigger low voltage signals to the elements and pumps. IOW replace the switches in the low voltage panel with a BCS or similar, install solenoid valves in place of the ball valves, and off we go.
It also allows me to install interlocks like a float switch or temperature interlock inline with the contactor trigger. It's easier to get a float switch that can handle 24 volts than 240 volts @ 25 amps
__________________
Quote:
Originally Posted by Ecnerwal View Post
What does the primary pressure gauge on the tank tell us? That's right, the temperature. Put it on a scale if you want to know how much is in it...
Put some duct tape over the gauge - Or better yet - Replace the high pressure gauge with a plug - High pressure gauges are useless!
SweetSounds is offline
 
Reply With Quote Quick reply to this message
Old 08-26-2010, 12:15 PM   #8
Bobby_M
Vendor and Brewer
HBT_SPONSOR.png
Vendor Ads 
Feedback Score: 2 reviews
 
Bobby_M's Avatar
Recipes 
 
Join Date: Aug 2006
Location: Whitehouse Station, NJ
Posts: 21,822
Liked 899 Times on 600 Posts
Likes Given: 26

Default

Is there any issue with switching an RTD line? Less sensitive to noise than a thermocouple?

__________________
BrewHardware.com
Sightglass, Refractometer, Ball Valve, Weldless bulkhead, Thermometer, Decals, Stainless Steel Fittings, Compression Fittings, Camlock Quick Disconnects, Scale, RIMS tube, Plate Chiller, Chugger Pump, Super Clear Silicone Tubing, and more!

New Stuff?
Bobby_M is offline
 
Reply With Quote Quick reply to this message
Old 08-26-2010, 02:13 PM   #9
SweetSounds
Feedback Score: 1 reviews
Recipes 
 
Join Date: Jan 2010
Location: Des Moines, Iowa
Posts: 1,429
Liked 17 Times on 16 Posts
Likes Given: 4

Default

Quote:
Originally Posted by Bobby_M View Post
Is there any issue with switching an RTD line? Less sensitive to noise than a thermocouple?
I haven't built it yet

It was an afterthought really - That's why it's not in the schematic.

I was designing the panel with temp sensors everywhere, and thought "How cool would it be to switch the RTD input for the mash PID?"
__________________
Quote:
Originally Posted by Ecnerwal View Post
What does the primary pressure gauge on the tank tell us? That's right, the temperature. Put it on a scale if you want to know how much is in it...
Put some duct tape over the gauge - Or better yet - Replace the high pressure gauge with a plug - High pressure gauges are useless!
SweetSounds is offline
 
Reply With Quote Quick reply to this message
Old 08-27-2010, 07:19 PM   #10
Walker
I use secondaries. :p
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
Walker's Avatar
Recipes 
 
Join Date: Sep 2005
Location: Cary, NC
Posts: 11,235
Liked 72 Times on 64 Posts
Likes Given: 11

Default

Quote:
Originally Posted by Bobby_M View Post
Is there any issue with switching an RTD line? Less sensitive to noise than a thermocouple?
RTDs, provided that they are the 3-wire type, can be run long distances and through lots of interconnects without losing accuracy. That third wire is the reason.

My understanding of them is that the signal goes out from your meter on one wire. It then goes two places. One is through the probe material and then back to the meter on one wire. The other place the outgoing signal goes is directly back to the meter.

The meter can then use the information on the output signal vs the simply-reflected return signal to see how the leads and interconnects along the path affected the original signal.

If you negate the effects of the wires, switches, plugs and then compare the value of the returning signal (the one that actually went through the probe material) then you can get an accurate reading.
__________________
Ground Fault Brewing Co.
Walker 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
240V Heating Element - 1 or 2 SSRs Douglefish DIY Projects 27 02-19-2013 08:52 PM
New SSRs! Trying to find a good heat sink, Can I mount both to one heat sink? Squeeky DIY Projects 1 05-27-2008 09:07 PM