SSR heatsink- inside or outside of enclosure?

[Thedutchtouch]

those of you with experience in enclosure builds, do you mount your heatsinks inside or outside of the enclosures? looking around online i've seen builds either way, would prefer to mount them internally (with a fan if necessary) unless three's strong evidence to that would be a bad idea. raspberry pi build with 4 SSR driving 2 elements 2 pumps, max 1 element and 2 pumps (so 3 SSR) on at any one time. pro/con?

 

[flugelizor]

I mounted mine (4) on the outside for two reasons:
1) passive cooling means fewer moving parts.
2) quieter.

 

[doug293cz]

Why 4 SSR's for 2 elements? You only need one SSR per element. Using two per element will double the amount of heat generated by SSR's.

If you mount heatsinks internally, you need to have fan(s) and air inlets and outlets for the cooling air. The fan needs to be mounted to pull air into the inlet, or blow it out of the outlet, and the bulk of the airflow should pass parallel to the fins of the heatsink. If you are not sure what the preceding means, you shouldn't be designing an enclosure with internally mounted heatsinks.

Brew on

 

[flugelizor]

Why 4 SSR's for 2 elements? You only need one SSR per element. Using two per element will double the amount of heat generated by SSR's.

I set it up with one SSR for each of two elements, and one SSR for each of the 2 pumps.
Each of the 4 circuits is controlled by a 3 way switch On - Off - Auto.
I never use auto on the pumps, so if I was going to do it again I would just have two SSRs, and manual pumps

 

[Thedutchtouch]

2 elements, 2 pumps = 4 ssr (so the pumps can be controlled by the Pi gpio, i realize i could use a smaller relay for this but wanted to ahve some built in redundancy in case an element SSR failed- i could swap one out and brew with one pump in a pinch but it'd be harder with only one element). and yeah, no problem understanding any of that, airflow perpendicular to the fins wouldn't make sense, then there wouldn't be any air circulation to the majority of the surface area (or at minimum, half). I was interested in some real world feedback from people who have build both versions, like has anyone had SSR or another part fail due to possible high heat, or the like?

 

[doug293cz]

There are some reports on HBT from folks who have had SSR latch up, presumably due to over heating. When an SSR latches up, it stops turning off, but when you check the system later it seems to work ok (after the SSR cools off.)

If you use 25A or 40A SSR's for the pumps, they won't need heatsinking, as the pump current is only about 1.4A.

Brew on

 

[processhead]

Not sure what the justification is for using an SSR for pump control vs a relay or just a switch?

An SSR is the preferred device for precise control requiring a high switching rate.
Pumps don't really need this and a relay or even a switch would be the normal switching method.

My panel uses two SSRs , one to control a 5500 watt element for the HLT and BK and a second one to control a 1300 watt RIMS tube.

For a heat sink, they are both mounted on the 12" x 16" steel sub-panel inside the enclosure with no provision for fans. This has been working fine for the last 7 years with no sign of overheating.

I know there are a lot of panels being built using heat sinks and cooling fans. I suspect there is a lot of over-building going on for what is required to run a typical electric brewery.

Many of the SSR failures may be attributable to inferior SSRs rather than inadequate cooling

 

[Dustin_J]

FWIW, I have 2 heatsinks, 1 each for SSRs controlling 4500w and 5500w elements, respectively. They're mounted externally via a 1/8" aluminum plate (SSR --> Plate --> Heat sink). The heat sinks warm up quite a bit when the SSRs are firing, to the point that I'd not want them anywhere near wires. Nor would I want to count on a steel box to dissipate the heat. Of course, I'm no electrical engineer or physicist, but external mount via something that conducts well seem pretty prudent.

 

[Thedutchtouch]

Not sure what the justification is for using an SSR for pump control vs a relay or just a switch?

An SSR is the preferred device for precise control requiring a high switching rate.
Pumps don't really need this and a relay or even a switch would be the normal switching method.

My panel uses two SSRs , one to control a 5500 watt element for the HLT and BK and a second one to control a 1300 watt RIMS tube.

For a heat sink, they are both mounted on the 12" x 16" steel sub-panel inside the enclosure with no provision for fans. This has been working fine for the last 7 years with no sign of overheating.

I know there are a lot of panels being built using heat sinks and cooling fans. I suspect there is a lot of over-building going on for what is required to run a typical electric brewery.

Many of the SSR failures may be attributable to inferior SSRs rather than inadequate cooling

thanks for the feedback. as i said in the post 2 above yours, the SSR driving the pump is overbuilt on purpose in the event that one of the SSR's for an element fails, i can swap the pump SSR over to keep going while i wait for a replacement to come in the mail. likely not necessary, but since the raspberry pi needs some sort of relay that takes 3v input anyway, made sense to me to build in some redundancy. the pumps will be controlled by a 3 way switch, connected to the SSR and to a contactor that bypasses the SSR... this will allow me to run them in auto (SSR controlled by Pi) mode or in manual mode (switching the contactor on and off manually) so that if i need to scavenge a SSR i'll still have the ability to run the pump... heck i only have one pump now anyway and i'm designing the panel for 2, so ill have a backup regardless. thanks for the feedback on the internal mounting, i think i'm going to go with internal mounts, but design the layout so that there's a side of the enclosure available that they could be moved to if necessary. i've built my spa panel etc, next to order the enclosure and start putting all these components inside.

 

[flugelizor]

I never use auto on the pumps, so if I was going to do it again I would just have two SSRs, and manual pumps

I was just looking at my panel, and pump2 was on "auto" and I said to my self: "oh yeah, I use 120v pump circuit on auto all the time for fermentation heaters" Duh!
So, yes, if I was doing it again, I would still have 4 SSRs.
By the way, I am using BCS, so I have lots of controllers.

An SSR is the preferred device for precise control requiring a high switching rate.
Pumps don't really need this and a relay or even a switch would be the normal switching method.

processhead, what is the benefit of a relay over ssr?
Use Electo-Magnetic Relay for...

• Applications requiring a wide output range from the relay. (fermwrap heater - NO)
  
• Applications using motors & transformers requiring high starting amps.(fermwrap heater - NO)
• Applications where the initial installation budget is very limited. (My ssrs were quite inexpensive)
• Applications prone to current surges and voltage spikes. (fermwrap heater - NO)

 

[processhead]

After re-reading the earlier posts, I would agree that an SSR is a better choice for a control device in the applications you sited.

It was late when I first read this post and I did not read it as carefully as I should have.

An SSR input is a much better fit with a low-level controller output, no question.

 

[Thedutchtouch]

this is the potential layout (yuco 16x16 enclosure, the thinner line is the size of the backing plate) theory being i can either 1. shift the SSR/heatsinks to the top where there's already a removable panel (hopefully it fits all 4) or add a fan on the top right, and an exhaust on the side wall bottom if needed (the load terminal blocks will actually liekly be shifted more to the left, but shouldn't interfere with a fan regardless as it's a 6 inch deep enclosure. i have everything except for the enclosure, which should be arriving some time next week or the week after. i dodn't draw in all the wiring, but main feed input will come in the left side, all plugs/output/temp probes will be other right (so i can set the whole thing on a table either on its bottom or back), switches and lights on the bottom half of the enclosure door, and 7 inch touchscreen for the pi on the top half of the door (havent decided if i'm cutting a large home and siliconing it in to "waterproof", or building a small secondary enclosure on the face for the screen).

 

[flugelizor]

Nice! Another option, (and what I did):
I went through the side with the SSRs.
(right side in your case)
That way, the natural convection pulls the hot air up, parallel to the fins.
As we already established that provides better heat transfer.
If you mount them on the top, air has to come in from the sides, change direction, then up.

Not a big deal, but it's an option.

 

[Thedutchtouch]

Nice! Another option, (and what I did):
I went through the side with the SSRs.
(right side in your case)
That way, the natural convection pulls the hot air up, parallel to the fins.
As we already established that provides better heat transfer.
If you mount them on the top, air has to come in from the sides, change direction, then up.

Not a big deal, but it's an option.

hmm, interesting point about the SSR heatsink orientation. i'm not sure if that would work as i'd ideally like to have all my outlets on that side, but i may shift the main inlet down as far as possible, to try and leave room to move the SSR's to the left side if needed. easy step now and even if i don't end up doing this, having the input receptacle towards the bottom would be somewhat visually appealing too. i should have ordered my enclosure earlier but wanted to get all the components in first to verify sizing needs... now we wait. i should probably start a build thread, or change the title of this one.

 

[stevehaun]

For one more data point, I have built and used two different control panels. One was 50 amp for a 30 gallon system (see pic) and the second one was 30 amp for a 10 gallon system. I put my heatsinks inside the control panel and did not install a fan. I use crydom SSRs and the appropriate crydom heat sink. My SSRs were 40 amp. I have never had any problems with overheating. I think the size of the enclosure and the size of the heat sink are important variables. My 50 amp enclosure was 20" x 16" x 8" and my 30 amp enclosure is 16" x 12" x 8".

 

[Thedutchtouch]

thanks, i'm going with a 16x16x6 enclosure, should be here tuesday, though as i have an infant and a toddler at home, build progress will be slow ( i justified the electric build by "if i can brew inside, instead of on my propane BIAB system, maybe i'll be able to get back to brewing more often as i'll be able to be around the kids and still keep a brew going in the kitchen/laundry room. we'll see about that as well lol ). I currently have mager SSR's with amazon heatsinks, not the best but... hopefully they work. if they don't or i have issues i'll debate a better SSR/heatsink vs external mounting vs a fan. all part of the fun i guess

 

[golfindia]

I use these to cool 2 40a SSRs. Drill and tap holes for screws.

https://m.ebay.com/itm/Cooling-Modu...um-Heat-Sink-Heatsink-Cooler-Fi-/322416441961