In order to maximize the water temperature entering the boiler, the 5AT will be fitted with twin feedwater heaters mounted above the boiler. Heat to these will be provided from a small proportion (approx 16%) of the exhaust steam from the cylinders.
Wardale has designed the water heaters to raise the temperature of the feedwater to 105oC [refer FDC 1.3 line 94 and FDC 9].
In addition the front section of the boiler will be partitioned off to form an "economizer" or water preheating section (as described elsewhere on the website).