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This limit provides boiler shutdown in the event the boiler water temperature exceeds the set point of the limit control. Certain Local Codes require an additional water temperature limit. In addition, certain types of systems may operate at temperatures below the minimum set point of the limit contained in the boiler. If this occurs, install an additional water temperature limit (Honeywell L4006 Aquastat) located in the system piping as shown in the Water Piping and Trim Section of this manual. Wire as indicated in the Electrical Section of this manual. nOTiCE all wire, wire nuts, controls etc. are installer supplied unless otherwise noted. 9 • Black – Line voltage “hot” • White – “Neutral” for boiler and circulators • Red – “Heating” circulator “hot” • Blue – “Indirect Water Heater “ circulator “hot” • Green – Ground connection 2. Maximum circulator continuous current draw is 2A. With primary/secondary piping, it may be desirable to use the boiler to directly control the primary circulator in addition to the secondary circulator. If this is done, control both heating circulators using a relay with a 120VAC coil, such as a Honeywell R4222, as shown in Figures 37A and 37B. Select a relay with a contact rating in excess of the combined draw of the two circulators. 3. Low Voltage Connections (Figure 35) – These connections are screw terminals located on the terminal strip next to the junction box on the left: • Terminals 1 and 8 – “Heating” thermostat connections • Terminals 5 and 6 – “External Limit Control” connections • Terminals 3 and 4 – “Outdoor Reset Sensor” connections • Terminals 2 and 4 – “Domestic Indirect Water Heater” thermostat connections • Terminal 7 – “Flame Signal Reading” • Heat anticipator setting for the thermostat connection is 0.1 A when thermostat is connected directly to terminals 1 and 8. WaRning When making low voltage connections, make sure that no external power source is present in the thermostat or limit circuits. if such a power source is present, it could destroy the boiler’s Microprocessor Control (MCBa). One example of an external power source that could be inadvertently connected to the low voltage connections is a transformer in old thermostat wiring. 4. If the outdoor sensor is connected to terminals 3 and 4, the boiler will adjust the target space heating set point supply water temperature downwards as the outdoor air temperature increases. If used, this sensor should be located on the outside of the structure in an area where it will sense the average air temperature around the house. Avoid placing this sensor in areas where it may be covered with ice or snow. In general, locations where the sensor will pick up direct radiation from the sun should also be avoided. Avoid placing the sensor near potential sources of electrical noise such as transformers, power lines, and fluorescent lighting. Wire the sensor to the boiler using 22 gauge or larger wire. As with the sensor, the sensor wiring should be routed away from sources of electrical noise. Where it is impossible to avoid such noise sources, wire the sensor using a 2 conductor, UL Type CM, AWM Style 2092, 300Volt 60°C shielded cable. Connect one end of the shielding on this cable to ground. Figure 5: Wiring Connections Diagram Figure 6: Ladder Diagram Figure 37A: Modified Wiring For DHW Priority When Using Low Flow Circulator Piped Off System Header Heating (with Central Heating Circulators) Plus alternately Piped indirect Water Heater 5 Figure 37B: Modified Wiring For DHW Priority When Using Low Flow Circulator Piped Off System Header Heating (with Central Heating zone Valves) Plus alternately Piped indirect Water Heater 5 Figure 8: Wiring for MCBa Modulating Boiler Control Time Delay Relay Box 5. If the boiler installation site may be subject to low supply voltage conditions or “brownouts”, that would affect MCBA Modulating Boiler Control operation, a separate optional Time Delay Relay Box (P/N 101693-01) installation is strongly recommended. See Figure 38 “Wiring for MCBA Modulating Boiler Control Time Delay Relay Box” and follow the following installation steps: a. Turn off power to boiler. b. Remove 120 volt power wiring, L1, L2 and ground. c. Remove cover to MCBA Time Delay Relay Box. d. Mount MCBA Time Delay Relay Box on secure surface near boiler. e. Connect wiring to MCBA Time Delay Relay Box as per wiring diagram (Figure 38). f. Connect additional field wiring (not included in the kit) from MCBA Time Delay Relay Box to 120 volt power wiring as per wiring diagram (Figure 38). g. Install cover on MCBA Time Delay Relay Box and restore power to boiler. h. Measure time from when power is restored until the boiler actually powers up (LED numbers will reappear on MCBA display panel). This MCBA Time Delay Relay Box has a delay on make timer that delays powering of the boiler for 3 minutes whenever power is lost to the boiler. Timing should be approximately 3 minutes, but no longer than 4 minutes. i. Cycle boiler per...

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