My oil fired boiler and burner is 47 years old and it's time to replace them with another oil fired system (I don't have gas line). Before replacing, I'm updating the insulation and air sealing the house as per recommendations from an energy audit. I've done some investigation myself, have asked my friends and talked to couple of oil companies. I've the following questions that still remain unanswered -

1) Outside combustion air to oil burner: I need to install one, since my boiler room will be rather small, after I finish my basement. As I understand, this brings the outside air to the burner directly.

My first question - is it a sealed system, i.e. the cold air goes directly from outside to the burner via a pipe? Or the cold air will come to the boiler room, in which case the boiler room will be really cold in the winter and some of that cold air can leak upstairs too.

Second question - Does this system work with any burner, more specifically, Reillo and Carlin?

2) I want an outdoor reset, does it work with any boiler, more specifically Weil McClain or Buderus?

3) I'll have three zones, one for each floor. Which of the following two is a better option -

(a) Three separate circulator pumps
(b) One circulator pump with three separate zone valves.

In case (a), I'll have hot water at least in two zones, in case a circulator pump is down. However, how frequently do they go down. I've been living in this house for last 12 years and nothing happened to them.

4) I've the following two boilers in mind: Weil McClain WGO-4 (i.e. the one that works with an indirect water heater) and Buderus. Which one is better?

5) I've the following two burner in mind: Reillo or Carlin? Which one is a better option?

Thanks in advance for any information on the above questions.