The boiler was the largest of a German steam engine at the time the XX HV was brought into service and had exceptionally long heating tubes of 5.8 m in length. The grate was of almost square shape and had to be arranged above the frame due to its size. The boiler was used in the Saxon XVIII H as well, with only minor adjustments to decrease its weight which resulted in a heating area that was smaller by 10 m2. The boiler was supplied with water through two feedwater pumps that were later replaced by one injector and a Knorr feed pump with preheater.
