flue gas condensation

Larry (from OSHA)

I'd like to figure out how to proceed. I do not think that I can take full advantage of my outdoor reset control without considerable piping changes to my fairly simple system. I've got a weil mclain induced draft boiler (HE Series 2). 3 zones with zone valves. 1 taco 007 on the return side. No bypass. A basic on demand system. The reset control is the honeywell aq475a controller which appears to have a tekmar chip on it. Here is the issue: the controller won't go into reset mode unless boiler min. temp is set to off. The boiler needs 140 min supply temp per weil mclain. If I set it to a min boiler temp of 140 or so and a max of 180 or so I now have an aquatrol with a 40 degree differential as it goes to the high limit and coasts back to the min temp. If I set it to boiler low limit off, it works as an outdoor reset would be expected to, with lower max temps and coasting down to about 100 or less. My concern is that flue gas condensation will cause problems for the system. Does the induced draft help me in any way or am I still in a precarious situation? Stack temps are about 300+. I am assuming that since the cast sections are below 130 for some period of time, I'll get condensation and corrosion. This is nat gas by the way. My heating contractor will be installing an indirect fired dhw tank in a couple of weeks so he will be adding a zone for it and if there was ever a time to make changes, this is it. Also, the controller has a "feature" of running the circ for about 10 seconds after the call for heat is over to purge the boiler of some heat. Is dead heading the pump for 10 seconds ok or a problem? Your input is greatly appreciated.

Thanks for your help,

Larry in fairly frigid Minnesota