Raypak 750 User Manual download pdf (Page 52)

• Freeze Protection Feature

The CPW board is programmed to turn-off the blower in case there is a lock-out condition. If there is a call for heat

signal, and the pilot valve signal is removed and not reactivated within a pre-set time for any reason, the CPW board

will turn off the blower to prevent blowing cold air continuously and freezing the heat exchanger. The blower drives

will open and the system will lock in the off state. To restart the system, primary power or the thermostat signal must be

turned off and back on. The pre-set freeze protection feature time is approximately 5 minutes.

U-2 Diagnostics Board

The U-2 Diagnostics board is a solid-state electronic fault indicator that has been engineered to enhance safety, simplify

troubleshooting and minimize equipment down time. The U-2 safety board is the central point for wiring, operations

monitoring, and fault indication for the boiler safeties. By having each safety report directly to the U-2 board, each

safety function can be individually monitored. The U-2 adds complete diagnostics features that aid in the rapid diagno-

sis of irregularities in boiler operation.

A single U-2 Diagnostics Board can monitor a maximum of eight safeties at one time. If, due to code requirements,

more than eight safety devices must be monitored, two or more boards will be used to provided extended diagnostics

capabilities. Advanced Design Boilers equipped with the standard safety suite will utilize the configuration shown in

Table L-2.

Table L-2. U-2 Diagnostic Board LEDs

Light Color Indication

System Enabled Yellow U-2 Diagnostics safety board is functional.

Manual High Limit Red Water temperature is over the manual high limit setting.

Auto High Limit Red Water temperature is over the auto high limit setting.

Flow Switch Red Water flow rate is too low.

Low Water Cut-off (option) Red Insufficient water volume for boiler operation.

High/Low Gas Pressure Red Gas supply pressure is below or above the allowed minimum gas supply

pressure to ensure safe operation.

Burner High Limit Red Mixer or PVC vent pipe, if installed, is over heated.

Blower/Ignition Lockout Red Blower failure, not enough combustion air or the equipment has an ignition

lock-out condition.

Blocked Vent Red The vent pressure switch has detected a blocked vent.

The U-2 safety board has a series of red LED lights to indicate a fault occurring at a monitored safety. An additional

light indicates that the diagnostics board is energized and is currently monitoring for safety faults. (In order to prevent

spurious alarm conditions, the U-2 board monitors safeties only during the actual firing cycle.) Once a fault has been

detected, the U-2 board will illuminate the corresponding LED lamp, will shut-down the boiler, and will light the

flashing red LED “Service” lamp on the CPW board. If more than one fault is detected, the U-2 board will display the

priority fault based on the safety hierarchy as labeled on the U-2 board. Once the first fault is cleared, the second fault

lamp will illuminate until cleared.

WARNING Only qualified persons shall attempt to repair the boiler. Improper adjustment, service or mainte-

nance may damage the equipment, create a hazard resulting in asphyxiation, explosion, fire, electric shock, personal

injury or property damage, and will void the warranty.

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Raypak 750 User Manual Page 52