The Firebird Blue Supreme Slimline external Heatpac Boilers are similar in specification to their equivalent internal models, with the addition of a built-in frost thermostat. There is no requirement to house the boiler in a building, so this option provides an ideal solution if internal space is at a premium. The boilers have removable sides for ease of access to any part of the unit. Piping can be carried out from the back or from underneath