Condensate Loops

jimmsc

Good Morning,
I recently quoted a replacement boiler job for a residence with 559sqft of steam radiation and 2 zones of 3/4" hot water baseboard totaling 64ft. The home is currently serviced with a 250k btu input boiler with a condensate loop. The homeowner complained to my customer that her baseboard never seemed to work well.
There is plenty of capacity in the existing chimney, and I quoted a two boiler system with a small hot water boiler to service the baseboard. The homeowner received another quote for a single boiler system servicing the baseboard through a tankless coil.
I was not comfortable running that much baseboard off the steam boiler, but I see in your book "How Come" that as long as the baseboard load does not exceed the 33% pick up factor of the boiler's D.O.E Heating Capacity the system should work. So let's say from a cold start both the baseboard zones and the steam side call for heat. I feel like the boiler will be using it's pick up load to overcome the loss through the cold steam mains, and at the same time the baseboard is robbing significant btus from the boiler to meet its demand. I am concerned that there won't be enough capacity to heat all of the radiation resulting in call backs for radiators that don't get fully hot. What am I missing?

jimmsc

Thanks for your input. I understand the math, but how do you know that a pickup factor of 21% is adequate? What is the lowest pickup factor percentage that you are willing to accept for a steam system which you feel has a reasonable layout of steam piping?

jimmsc

Thank you very much for the info. We can reduce the boiler capacity by the full amount of the pickup factor, but by doing so we sacrifice some speed at which the radiators fully heat.

ChrisJ

I'm running a single pipe system with only a 10% pickup factor.