Troubleshooting - Weil-McLain BMC Install And Operation Instructions

Weil-mclain boiler user manual

Hide thumbs

Table Of Contents

Table of Contents

BMC and BMC-6X Installation and Operation Manual

SENSOR INPUTS

Display shows Sensor OPEN or SHORT

When OPEN, Check the sensor is connected and the wires are continuous to the BMC. Finally

follow the procedure for Incorrect Temperature or Pressure Display. When SHORT Remove the

wires from the sensor terminals. The display should change to read OPEN. If it does not, the

BMC may be damaged.

Display shows an Incorrect Temperature

Remove the wires from the sensor terminals. The display should change to read OPEN. If it

does not, the BMC may be damaged. Take an ohm reading across the detached sensor wires.

The ohm reading should correspond to the Temperature sensor Table. If it does not, the sensor

may be damaged.

CONTROL OPERATION

No Heat

Season - Make sure that the Season is set to Winter. Check Message Display Line on page 24.

•

Prove - Even though, the system relay may be energized, the BMC will not energize and stage

relays unless the Prove is shorted. Check Message Display Line on page 24.

Shutdown - The BMC will activate stage outputs when the Shutdown terminals are short.

•

Check Message Display Line on page 24.

•

Tstat - The BMC will activate stage outputs when the Tstat terminals are open. Check Message

Display Line on page 24.

Sensor Fault - When the Sensor Fault is set to All Off in the startup menu (see page 16), the

•

System sensor fault (in all Sensor Type modes) or the Outdoor sensor fault (in Reset mode) will

de-energize all stage relays. Check the display for sensor values.

•

System or Outdoor Sensor - If the System or Outdoor sensor reading was higher that the

actual temperature, the BMC might not bring any stage on. Check "Display shows an Incorrect

Temperature" section.

Too Much Heat

Check if the control has any of the following:

Domestic Hot Water call - The BMC will raise the temperature of the system to either 200˚F or

•

Maximum Water Temperature on a DHW call, connected to terminals 29 and 30. Check to see

if there is a call for DHW and the length of time it lasts.

Reset Ratio and Offset - If excessive heat occurs only in certain weather conditions, adjust the

•

Reset Ratio and Offset (See Understanding Operating Concept on page 5). If excessive heat

occurs year round, reduce the Offset.

•

Boiler Mode Settings - The BMC will only modulate boilers their mode is set to Auto or

Standby. Check to if any boiler stage is set to Manual or On. See Mode on page 25.

Control Settings - The Last Stage Hold will allow only the Lead boiler to stay on for an

•

additional number of degrees. If the setting is too high, and only the Lead boiler is on, the

system can over heat. Reduce the Last Stage Hold setting. See page 21.

Too Little Heat

Check if the control has any of the following:

•

Reset Ratio and Offset - If reduced heat occurs only in certain weather conditions, adjust the

Reset Ratio and Offset (See Understanding Operating Concept on page 5). If reduced heat

occurs year round, increase the Offset.

•

Setback and Day/Night Schedule - If reduced heat occurs only during speciﬁc hours, check

the Day/Night Schedule and the Setback values. Either reduce the Setback setting (See page

20).