As with all Grant boilers, Outdoor Modules are fitted with overheat thermostats making them suitable for use on sealed heating systems. Three pre-assembled sealed system kits are available to convert modules to sealed system operation one kit to suit both the 50/70 and 70/90 modules, one for the 90/120 and one for the 110/140 module. The sealed system kit includes an expansion vessel, automatic air vent, a pressure relief valve and circulating pump, all of which are neatly housed within the enclosure of the module. A filling loop and pressure gauge is also supplied as part of the kit, for fitting in a convenient location within the building, between the cold main and central heating system.