Direct Spark Ignition (DSI) burners are set up specifically for one fuel type (liquid propane or natural gas) and to operate as cleanly and efficiently on that one fuel. If the flames are very low and blue it is possible that the burner is set up for liquid propane but natural gas is being supplied to it. Verify what gas the burner was designed to operate on and what gas is being supplied to the system.
If the fuel type of the burner and the fuel being supplied to the burner match, the unit may be receiving gas at a lower pressure than what is required for proper operation. A properly sized and adjusted gas supply is the responsibility of the licensed gas professional installing the gas supply for the burner. The ideal gas pressure for natural gas installations is 7 in. WC and for propane installations it is 11 in. WC. These pressures should be measured while the unit is in operation per Pg. 15 of the CF-DSI Manual by a licensed gas professional. Contact OGC for more information.