My Tarm solo 60 came with a L4008B aquastat.  I believe that is for the overheat protection.  I was told I need a Honeywell L4008A for my storage tanks to tell my forced air furnace if there is enough hot water or if the propane furnace needs to kick on.  There is different models of the L4008A,s and I dont know which one to get?

Have to look and see one maybe a normally open and the other maybe a normally closed. I will look them up and repost.

The Johnson Controls a419 is a lot more versatile than the Honeywells when it comes to monitoring and controlling things beyond the boiler itself. 

You get a digital readout to be able to see the temperature, and it’s easy to program desired on and off points, etc. 

And if you Google around you can find them at pretty moderate pricing. 

Or look at some of the temperature controllers at http://www.auberins.com/

Tarm also reccommended a Ranco 30 degree delta T unit , but they also make many different models.  This is a very confusing part of my install for me to grasp?

any of the electronic types will have adjustable differentials.  All the big name control companies have universal electronic temperature controls.  Very easy to program, like a digital wall thermostat.

Johnstone Supply has the new White Rogers 16E09 on sale this month A great price on a very nice control.  About 20 bucks more than a mechanical control but nice features, just the read out display alone is worth the extra bucks.

hr