Where are all the TARM guys? I know we have a few on this board, some are burning anthracite.
The 502 appears to be the same as their currently produced Excel 2000 but without the coal option. It looks like one difference is a ceramic heat sink in the Excel's belly and the 502 has shaker grates. There is no ash drawer on either and I wonder how the ash is dealt with on these boilers.
They appear to be very well built. One thing about them is the oil fired option runs a very high efficiency for a combo @ 87%.