Troubleshooting - heat-timer Mini-Extension Installation And Operations

Sequencing modulating control for hydronic heating systems

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Manual (4 pages)

Table of Contents

Heat-Timer Corp.

TEMPERATURE INPUTS

Display shows Sensor OPEN

Check the sensor is connected and the wires are continuous to the Mini-MOD. Finally follow

the procedure for Incorrect Temperature Display.

Display shows Sensor SHORT

The Mini-MOD sees a short across the input terminals. Remove the wires from either the

SYSTEM TEMP or OUT TEMP terminals (whichever is reading SHORT). The display should

change to read OPEN. If it doesn't, the Mini-MOD may be damaged.

Display shows an Incorrect Temperature Display

Remove the wires from either the SYSTEM TEMP or OUT TEMP terminals (whichever is

reading incorrectly). The display should change to read OPEN. If it doesn't, the Mini-MOD

may be damaged. Take an ohm reading across the detached sensor wires. The ohm reading

should correspond to the side chart. If it doesn't, the sensor may be damaged.

CONTROL OPERATION

No Heat

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(Check Diagram on next page)

Too Much Heat

Check if the control has any of the following:

Domestic Hot Water call - The Mini-MOD will raise the temperature of the system to either

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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, adjust the Reset

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Ratio and Offset (See Understanding Operating Concept). If excessive heat occurs year round,

reduce the Offset.

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Boiler Mode Settings - The Mini-MOD will only modulate boilers their mode is set to Auto

or Standby. Check to if any boiler stage is set to Manual or On.

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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.

Too Little Heat

Check if the control has any of the following:

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

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Ratio and Offset (See Understanding Operating Concept). If reduced heat occurs year round,

increase the Offset.

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

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the Day/Night Schedule and the Setback values. Either reduce the Setback setting or change

the Day and Night Schedules.

Boiler Mode Settings - The Mini-MOD will only modulate boilers their mode is set to Auto or Standby. Check if any boiler

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stage is set to Manual, Off, or Standby.

Boilers are Short-Cycling

Lag Delay - Increase the Lag Delay only if all boilers tend to short-cycle.

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Last Stage Hold - Increase the Last Stage Hold only if the lead boiler tends to short-cycle.

System is Overshooting or Undershooting

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Gain - If the system is overshooting reduce the Gain.

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Gain - If the system is undershooting increase the Gain.