Welcome to the site Wink. And I would personally like to welcome you to the world of Shaver OWB.
I will not go into details about my escapeds as you can read them here on the forum.
You are quite correct in that their owner's manual is somewhat vague. I had a professional heating/cooling shop wire up my t-stats, as I wanted it done correctly. Just so happens one of the repair guys owns an OWB.
I have connected to my house furnace a "strap-on" Honeywell aqua-stat t-stat that has its own relay that somehow along the line gets connected to the house t-stat. This works very well. We went this way because I did not want another ugly t-stat next to the programmable one up stairs in the great room...ok, actually my wife did NOT want an ugly round t-stat on the wall next to the square programmable t-stat.
Just looking at it, I'm not certain how it's wired. One of the other experts will chime in here and get you going. Everyone on here who owns a Shaver swears that by the time you get the kinks worked out, they're great units. Mine was ugly too, but I told them to take it back...and they did, but along the way I also upgraded to the 250.
Hang in here Bill....and welcome to the site. I actually spend more time on here reading and learning than I do on my hot rod site. by the way, where do you reside?
Lugnut
aka: Jerry