Hey Kal,
I was reading your guide, and I got a little confused. My system is going to be much different than yours, so I'm trying to figure out what is actually necessary.
I understand that you use a contactor after the main power switch because this way you can use a 120V key switch to complete the 240V circuit (the same reason an electric car uses one- the auxiliary systems can energize the main battery pack). However, in my system I'm going to be running a 120V, 1500W ULWD element, so I will be running my pump, electronics, and element of a dedicated 120V 15A receptacle (that's roughly 92% capacity, but I am lacking 20A breaker's in my main control box so I don't have much choice).
Here are my questions:
1. is a contactor required after the key switch if everything will be running at 120V? If so, why?
2. I see that you use contactors in conjunction with your SSRs. Is that necessary in the case of a RIMS system with just one element? I believe your reasoning is that even if I have my element switch off, the SSR still poses the threat of shocking me (I think that's what I read?). The addition of the contactor would of course prevents this entirely (right? haha).
3. I keep hearing that we are using SSR's because they have the ability to switch almost instantaneously. But in your design, you have a SSR and a contactor in series. Wouldn't that not only limit the speed of the response to the speed that the contactor switches (rate limiting step), but also force the contactor to switch faster than it's intended (whenever the PID says so instead of a couple times during the brew session).
Thanks,
Jay