1. condensing boilers cannot deliver 200F water - Condensing boilers are designed for 140F water typically, not 180 or 200. Some cannot provide wtr above 140. OK some claim they can do 180, but never heard of condensing boilers delivering 200 wtr
2. Language of circulators are used for cast iron boilers to keep return water to the boiler above 140F - not for condensing boilers for which the lower the wtr temp, the better.
3. primary pumps should be sized each for one boiler total flow, secondary pumps are corectly sized for 100% of total flow, they need VFD's though and even PRV at discharge.
4. DO NOT Oversize Boiler too much, especially Fulton boilers, they have a maximum No of cycles at 12,000 per year, if too much oversized, they will cycle too much and you will wack your 10-year warranty in one winter. another reason not to operate BOTH boilers together with Fulton. Nothing against Fulton, just make sure your design matches their warranty.
5. Smoosh - Parallel pumps should not be designed for half the flow because the system curve is at a different point. Google parallel pumping. 2 pumps at 100% in parallel do not deliver more than one pump plus about 10% to 15% (that's right, check it out).
6. What is this business of the "circulators are sized by the boiler manufacturer"? Totally unacceptable in my book. Pumps must be sized by the Engineer, not the boiler MFTR. DO NOT let the MFTR design or size for you. It is a recipe for disaster, MFTR Reps are salesmen, Not Engineers (even those that hold engineering degrees).