Just a little litterature for whoever. We use CRYDOM solid state relays and they require a diode. As the link shows a diode also allows collapsing fields/transient voltages (motors, relays, etc...) to drain to ground when de-energized so not to damage components. Anyways, something that some people don't know!!!! The diagram and info is on page 2.
http://www.crydom.com/userResources/...crydom_1dc.pdf