Our house here in Alaska was built in 2004 with the G115-21/lt160 combination with the Riello BF3 burner. By 2011, the previous owner had to pay our local mechanical contractor (@+$150 per hour) to pull the lt160 from under the G115 and replace it (another +$1800). This past summer, the boiler began leaking from the pressure relief valve. The coil on the second lt160 had failed. After getting a $3500 quote to replace from the same mechanical contractor, I did enough research and calling around to realize that many, many Buderus indirect water heaters have this problem. One Seattle contractor said they have a 50% failure rate on the water heaters! That is very bad! There were so many failures that he cut one of the failed tanks apart and found that the coils were formed with "wrinkles" in them, which causes erosion of the tubing interiors and early failure (higher erosion rates with hot water and constant flow). The key, of course, is better maintenance, but the cost can be high. Replacing the anode that prevents coil corrosion can be $300-$600 per time, and has to be done at least once every two years and better if done every year. You have to turn off the domestic water, depressurize the house, and drain the tank each time. By the time you do that two times, you might as well have bought a stainless indirect water heater. As for the Riello burner, it was pretty good, but just the basic "emergency" kit costs $253 for getting it up and running, and that doesn't include our local company's upcharge. In sum, I would avoid the "over-and-under" Buderus at all costs. If you use the GW115 series, use the Beckett burners for serviceability. Use a stainless steel indirect water heater (Triangle Tube and Super Stor were recommended to me, I found a trade-out SST-45 for $400 in Juneau), and be prepared for correspondence with a company that can't admit it has a problem and won't come clean with its customers or its "front-line" service companies.