You need to be sure that you are selecting the correct SSR for the job and providing it with a proper heat sink. I have yet to kill an Opto-22 SSR. Check out:
http://www.opto22.com/documents/0859_Solid_State_Relays_data_sheet.pdf, look at page 14 it gives model # recommendations for various sizes of electrical motors. Also triple check what your motor is really drawing, 1 amp at 120V is around 1/10 HP (maybe) are you sure your pump isn't bigger than that?
Would it be that easy to recover if you blow your Optp?
yep, they plug right in/out, no worries and are MUCH more reliable than mechanical relays. You can use the smaller (rack mount) Opto-22 SSRs to drive large contactors/relays etc. This is useful as it provides both the optical isolation of the SSR and the current capability of the relay.
Wirng is so short that no shielding is necessary.....if things won't work it is a devil of a job finding where the fault is if you are trying to check voltages and everything through several "stages"....Try and plan everything to use just one voltage at "ground" level - which avoids any likelyhood of feeding something nasty back to the computer.
OK, 'grounding'...'(earth)ground IS NOT equal to DC common. They do not mean the same thing, unfortunately we all throw around the term 'ground' very loosely. 'Ground' is this context refers to 'Earth Ground' which is a safety device. The incoming mains voltage is referenced to ground (through the 'ground' rod(s)) and so is your equipment. This provides a path of least resistance to shunt the voltage away from important things like people in case something goes wrong. 'Ground' SHOULD NEVER carry any current, it IS NOT a common return path for all circuits. That is the job of DC common, and your system may have more than one DC common which is not a big deal.
The problem is that folks think 'ground' is this universal reference for EVERYTHING in a system and try to measure voltage to it from any given point, which is wrong. Think of it this way, if I were to nail three pieces of wood together at odd angles and ask you to measure their length how would you do it? Would you pick the bottom of the closet piece of wood and measure from there to every other piece? Or, from the floor (ground) to each piece? Nope, because that would not tell you a thing. You would run your measuring tape from end to end on each piece of wood (so your reference is the beginning of each piece of wood and you are measuring from that reference to the end of the wood to find its length.) Measuring voltages is the same idea, you are measuring from a reference point (common) to some other point in the same circuit (same piece of wood).
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