Steve!! You may have struck an excellent idea! I'm not sure of the range of the detector, but that idea may solve the problem! If we have a 40'+ door, it may take a test to figure out the range & make the reflector operate a relay as you suggest to "enable" the lift pump. Windows, doors, and lights are a possive solution. Reflector activated relay will be a positive solution. Thus far, we've only had to rely on a beam going about 10' or so. Could be they'll work 50'...don't know.

Thanks again for idea Steve. We already use the reflectors on both the scale over the pit & the "fill point" on NH3 tank. Maybe there will be one more use for a hard-wired unit.