Ok .. I need help. I have an OWB. The current aquastat is a strap on model working off contact to the water jacket. The manufacturer has since switched to an imersion type and I am told that they are much more efficient and safer so I am looking to retrofit mine. I have only used two of the 1 1/2 inch ports in my boiler so I am thinking i can install it in there. The boiler manufacturer is using a Honneywell L4006A aquastat. I found some on Ebay and thought I was in luck but found out not all l4006A are the same!! Seems there are 4 digits after that and no one can tell me what they stand for .. even wrote honneywell but got no ansewer. Is anyone in the know about these? I need and imersion type operating range to 240 degrees I would guess .. adjustable differential that will kick the blower on at a certain temp.. shout it off at high limit and when it goes back below the low limit start all over again. Like I said I have gound some of these L4006A with a manual high reset, no diffential and some I talk about it being a contact or break set up .. I am so confused!! help!!