The BEM 5000 is an electronic control, which, when added to almost any central heating system, reduces unnecessary boiler cycling and improves boiler seasonal efficiency. It is compatible with most popular control systems including radiator thermostats, programmers, motorized valves and even room thermostats, although in systems having radiator thermostats it is recommended that the room thermostat be turned up to maximum or rewired as frost thermostats. Radiator thermostats are recommended, but are not mandatory. If they are fitted, then a by-pass valve should be fitted. If it is impractical to fit a by-pass valve, then one radiator should be left uncontrolled.
The BEM 5000 measures outdoor temperature and varies the temperature of water flowing to the radiators accordingly. This significantly improves boiler performance. A water temperature sensor is used to monitor temperature of water returning to the boiler. Any change in load on the system is measured and the boiler is controlled accordingly. To minimize energy loss from the boiler case and flue, the pump runs on after the boiler has stopped, circulating all useful heat to the system. When no more heat can be extracted, the pump is stopped. The BEM 5000 integrates the operation of heating and hot water. During periods of hot water demand, water temperature flowing to both water and heating circuits is boosted to boiler thermostat settings to ensure rapid recovery. Figures 11.4 and 11.5 show the BEM 5000 wired into a fully pumped system, one with two 2-port motorized valves and one with a 3-port, mid-position valve. It can also be utilized on a combination boiler.