I have searched this form and found lots of useful information. I have not landed on a decision. Here my question: What can I use to automate my old pool relays to switch the relay off and on? Details: I have a bunch of really old but super awesome relays for my current pool setup. Everything is great manually. I was wanting to take each of the relays where the 110v Is energized to turn the device on have some type of zwave of zibee device to handle it. That way I can have SmartThings set up automation or manual on and off. I am aware of running a pi or Arduino with a relay module. I just want to make sure that what every can survive 110 degree plus heat waves and 25-30 degree Winters. I’m a quick learner but would need to be pointed in the right direction. Here is a pic of my current panel.
One product that comes to mind is the Aeotec Heavy Duty Smart Switch. This product is compatible with SmartThings and can be found here.
Not sure about the 25-30 degree part, but it is outdoor rated.
Another smaller option would be the Linear FS20Z-1. I think this one would need to be inside, however.
Hope these get you started with some potential options!
Below freezing is outside of specs it seems.
Operational temperature: 5°C to 40°C;
Just thought I would share my thoughts.
I use a sonoff smart switch. I only need 10Amps and I use it for my pool perfectly. I mostly set it on a timer but when I need to I even ask Google to turn off and on the devices
maybe put an old school 60+ watt light bulb at the bottom of the box to turn on when the temp goes below 40 deg? this is what we do for the water valves in the wall box behind the washer.
Shoot! Sorry about that. I’ve worked with those devices before and definitely seen people utilize them for pool applications.
Here is a device I had not yet seen before (seems new). I’m not finding it in our Supported Device List catalog, but operating temperature is -22 to 104 degrees F and it’s GE/Jasco, so the experience shouldn’t be too questionable.
I was wondering if being in an enclosure with anything generating a bit of heat would keep it in the specified temps…
I live in similar climate to the OP but don’t have a pool to deal with.
The GE 14285 was itself certified in 2018, and was a zwave plus update of an even older device.
https://products.z-wavealliance.org/products/2939?selectedFrequencyId=2
There have been some people in the community who have used it or the prior model as sometimes it’s the only device that works well for an outdoor installation of 40A equipment like a water heater or a pool pump.
The main reason it isn’t more popular is because it’s so expensive, nearly $200 unless you can find it on sale.
Since these relays are already in a cabinet, I think you can consider some less expensive individual options. Plus it doesn’t look like you have the same high amperage requirements for your individual switches.
Another possibility would be the fortrezz mimolite, which has an operating range of down to 14°F and up to 150°F but you would probably need to add a transformer and it might get a little complicated. And it’s not cheap either, although it’s about a third the cost of the GE device. These are particularly popular for HVAC equipment like vents were the environment is pretty brutal but the actual operating load is not that high.
https://www.fortrezz.com/shop/mimo-lite
Does it actually freeze inside the cabinet? That would be fairly unusual outside of Minnesota or Alaska. 
I agree the Linear FS20z-1 is a good zwave candidate if it doesn’t actually freeze inside the cabinet. The operating specs are
Operating Temperature Limits 32° to 122° F
But again remember that most mains powered smart devices are always running a little current through them to keep the radio going, and that actually helps warm the device slightly. This means the ambient temperature around the installation is a bit warmer than ground temperature, and of course the cabinet also helps.
So again unless we’re talking Alaska or Minnesota or Canada, I think this is probably a good candidate on the low side. But the cabinet can actually make the high side worse, and overheat inside. So that’s where the fortrezz has an advantage. 
If you would be OK with a Wi-Fi solution, and the load is light enough, I would go with @Dechlan_jacobs ‘ suggestion of Sonoff, but go one step further and get the four channel Wi-Fi device and mount it on a DIN rail.
Looking at your picture, you ought to be able to get two or three of them at least into the cabinet in the center pretty easily and that would run all your relays at under $75.
https://www.amazon.com/Sonoff-Automation-Self-Locking-Appliances-Compatible/dp/B075H8Y8H9
There are multiple options for integration, from just using an Alexa routine to IFTTT to maybe flashing the firmware (I’m not sure if that works with that specific model, though). Anyway, since they are just on off switches, any of the integration options should be fine.
And the temperature specs are great
operating temperature -40 Degrees centigrade to 125°C
And it looks like you have room for a DIN rail right in the center there, Which would keep everything much neater than most of the alternatives since you need multiples.
It’s true that the integration with smartthings isn’t as tight as a Zwave device, but it doesn’t sound like you would need it for this. I mean even if you have a few seconds of delay due to lag, you should be OK. So that would be my personal choice for a first candidate. 
Of course if you need to handle higher loads, you’re going to have to go to more expensive devices, and we’re back to the other candidates.
How many individual relays were you planning on automating?
Quick question. can you give me the link for the sonoff switch?