Randall EBM 2.1 Boiler Efficiency Control

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The EBM 2.1 Boiler Efficiency Control is designed, with one simple user adjustment, to maximize the efficiency of gas fired wet domestic central heating systems. This is for systems which incorporate time and temperature controls (TRV or room thermostat and cylinder thermostat) and motorized valves. Suitable for both new and existing installations incorporating conventional or condensing boilers in either gravity or fully pumped systems.

The following pages show various systems and their wiring diagrams, however, before turning to these it is important to note the following:

1. The EBM 2.1 should be mounted where it is clearly accessible.
2. The OTS outside sensor should be mounted on an outside wall on the coldest side of the house (usually north facing) about 18 inches below eaves height and away from chimneys, flues or windows, etc. Connection must be made with cable suitable for 240V as follows:
– Terminal 1 on the OTS to terminal 11 on the EBM wallplate.
– Terminal 2 on the OTS to terminal 10 on the EBM wallplate.
3. The BRS boiler return sensor should be mounted on the common return to the boiler between the boiler and by-pass. In gravity hot water systems it should be mounted on the heating return. Connect to EBM as follows:
– Brown lead to terminal 12 on the EBM wallplate.
– Blue lead to terminal 10 on the EBM wallplate.
4. The cylinder thermostat and any motorized valves shown are not included in the kit.
5. The pump should be connected to terminal 5 of the EBM in all cases, even if the boiler has its own pump connection or pump overrun facility.
6. In gravity hot water systems, it is necessary to cut an internal link in the EBM by prizing offthe back cover and cutting the grey link wire located inside the housing on the left.
7. The boiler thermostat should be set to maximum.

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