Hi Yanche, I thought about that, so I lasered the water pipe coming in and out, and the difference between the outside boiler and the inside propane boiler, All the same as normal. I loose only 3*F in the 150' run from the coal boiler to the heat exchanger in the basement.
The water temp at the input of my baseboard is only 3-4* lower than the temp of the water as it leaves the coal boiler. Total distance 150' + ~60' = ~210'. I was crawling on the floor this morning with the laser thermometer. Dogs thought I wanted to play.
I think one of the problems with my family room is that while I do get input water temp of 147* at the baseboard, the output is only 95*. I had to replace the circulator a year or two ago, and used a standard TACO 007 pump. The pump that had been in this loop was a bigger unit. It had a two speed switch and drew about 1.4 amps. I thought it was overkill. But it may be needed to circulate the water faster in this circuit. The piping is fairly long and is mostly 3/4" with some 1" . So I thiink I'm flow restricted.. I will eventually replace it with a bigger pump or swap with the other very short circuit that still has the bigger two speed pump.
But the heat exchanger and piping seem to be supplying plenty of BTUs, the rest of the house is pretty toasty, but the family room with the west facing wall that is all masonry [inside and outside, the same chunk of brick and mortar] and lots of windows, Too much heat loss with the very cold west wind. Inspite of R-25-30 ceiling insulation.
I just make the dogs lie on my feet to keep them warm!!