Leak in indirect coil?

Del

Hi-

This is on a 15 YO Burnham hot water boiler zoned with circulators and a Amtrol indirect tank.Had to go back on a call yesterday where one of our techs replaced the fill valve and relief valve to remedy a problem of the relief valve dripping. Well, it was still dumping water. I got there and checked the pressure with my gauge and found it to be right at 30psi with the water around 170* F. Relief valve dripping slightly. Lowered pressure to 15psi and Checked P 60 tank, no evidence of water logging. Anyway, I taped a digital thermometer lead to the supply and upon firing up the boiler, I noticed the temp going up to 212+ with the aquastat set at 170 with 10 differential. I thought it must be a bad aquastat, so I checked the temp in well with thermometer and I got 210, so no problem with the well. Proceeded to change the aquastat, ran the boiler through a few cycles, noted no pressure increase or overheating. Seeing that there was a Lwco installed, i shut the ball valve to the feed and left the job. Got a call back this morning that relief valve dumping again. Got there, and pressure once again at 30 PSI with water around 170. Seeing as there could be no other way for the pressure to increase that much except for excessive temperature, I diagnosed that there must be a leak in the indirect coil allowing fresh water into boiler. Talked to the original tech, and he said the original call was for loud percolating noises and that the owner didn't know the relief valve was leaking. This leads me to suspect a makeup water problem. Any ideas?? Thanks!!

Paul Pollets

Amtrol indirects

These tanks had a poorly designed coil with a 5-10 year life expectancy. Expect a leaker.