t3chiman Senior Member Joined: 26 Dec 2011 Posts: 15 Location: Chicago Expertise: I love coffee
Espresso: Cuadra Grinder: hand Drip: Brazen
Posted Sun Jun 23, 2013, 12:32pm Subject: Adding SSR to Cuadra, notes and experiences Sec 2/7
Replace the relay If your machine in in warranty, your simplest course of action is to contact 1st-line, and get a new relay board. The labor involved is a matter of 6 screws and 4 wires. See the red arrows on pic 2. Twenty minutes after receiving the new board in the mail, you will have a like-new machine. Out of warranty, you have three choices: 1. order up a new board from 1st-line, 2. replace the relay alone with another electromechanical part, or 3. use a solid state relay as a functionally equivalent replacement. Coffeegeek wisdom is to go SSR, mainly because it avoids the burnt-contacts syndrome (No contacts! Duh, as the young folks say). But EM relays have been around for over 100 years, and for good reasons: they are robust little buggers, immune to lots of crap that destroys new-fangled electronic gizmos. Voltage spikes, current surges, cosmic rays--no problem. Heat them up, they do fine. And when they finally fail, they do so safely, their normally open contacts remaining open. And they are cheap, a couple of bucks in quantity. SSRs are a different kettle of fish, to mix metaphors. Their main vulnerability: heat. They generate it, and they don't tolerate it. And when they fail, they fail closed. Their classic failure mode is 1. thermal runwaway, and 2. overdriving the load.
Doctor, it hurts when I do this Taking an SSR rated for 10A, and locating it in the same spot as the original EM relay, would result in failure after a few minutes of operation. You just can't put a heat-sensitive part two inches from a noninsulated boiler tank, and expect it to survive. So, don't do that. And, applying a part rated for 10A at a load of 10A cuts your operational margin to zero, always a Bad Idea. So, don't do that either. Your mission: get a more highly rated part, locate a relatively cool spot in the unit, mount it in a way that addresses the special mechanical and thermal issues of SSRs, and wire it in appropriately.
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