Tags: Danfoss

Hot water service

Set the programmer to hot water constant, central heating off, and cylinder thermostat to maximum. Set boiler to the design flow temperature of 82°C.

Lamps 1 and 2 will illuminate and boiler and pump will start, except in gravity hot water systems, in which the pump will not start. The hot water valve will open.

Central heating service

Set programmer to hot water off, central heating constant and boiler as above. Where a heating motorized valve is fitted, it will open. Illumination of lamp 3 signifies that the boiler has stopped and after a time lamp 1 will go off, indicating pump stopped.

After testing, set the programmer and cylinder thermostat to the required settings.

Fault finding

When the ‘on’ lamp on the front of the BEM 4000 does not illuminate, check the power supply.There should be 240V across terminals 12 and 13. If this is OK, check the built-in fuse on the rear of the BEM 4000, and if blown, there is a spare attached to the rear of the unit. If this fuse is OK the fault is probably within the electronics, and the BEM 4000 plug-in front plate should be replaced.

Where a zone valve will not open, check that 240V exists at the valve leads. If OK change valve, if not check programmer and other wiring.

In the event of difficulties, the BEM 4000 can be overridden by inserting a link between terminals 14 and 15, ensuring that the power is turned off first.

The Boiler Energy Manager (BEM) is an electronic controller which can be added to almost any central heating system to eliminate unnecessary boiler cycling and improve boiler seasonal efficiency.

The BEM 4000 consists of an electronic controller, an outdoor temperature sensor and a strapon flow temperature sensor. It can be used in conjunction with a room thermostat (utilized as a frost stat) and TRVs. Boiler performance is improved when the flow temperature is varied according to the outside temperature. The outside temperature sensor should be mounted on the coldest elevation of the building away from opening windows and the boiler flue.The flow sensor should be fitted within 6 inches of the boiler outlet on the flow pipe, or on low-water content boilers it can additionally be fitted between the boiler and the bypass. A cylinder thermostat should be fitted as normal. All diagrams show Danfoss programmer and thermostats, but others can be used. In all cases, if a room thermostat is to be utilized as a frost or lowlimit thermostat, connect to terminals 3 and 11.

In Figures 11.2 and 11.3 two boilers are shown – one with pump overrun and one without. Select diagram as appropriate, remembering to insert Link 2–4 when using boiler without pump overrun.

Figure 11.1 Gravity hot water, pumped central heating

Figure 11.2 Fully pumped system with two motorized zone valves

Figure 11.3 Fully pumped system with mid-position valve