Our round trip is probably about 440-460' including thru the HX. At times when there are 4-5 minutes between the blower coming on, I typically see in the neighborhood of 1 deg drop round trip. And, unbelieveably, sometimes less. Last year, which was our first wood boiler season, I had an extremely hard time keeping our house warm and saw a 10 deg or worse temp loss in the round trip. Our problem was water saturated insulation in the pex lines. Could be lots of things but your situation sounds like dejas vu to me. Not hard to compute the BTU loss at 10 deg and your flow rate, but its a bunch. Haven't read all posts on this thread so someone may have already done the calc. Could be lots of things but when I read "wrapped insulation" all the warning bells go off.
