Jandy LXi : installation and operation manual - Piscines et Spas ...

Page 44LXi Pool/Spa Heater Installation and Operation Manualcontrol provides a pre-purge of the combustionchamber. Once the pre-purge is complete theignition control then applies electrical power toa “hot surface” igniter. When the igniter is hotenough, the ignition control opens the gas valve.It has sophisticated means to sense ignition andflame condition so that unburned gas will not escape.Once the ignition control has sensed flame,it de-energizes the igniter. After the burner is shutoff, the ignition control continues blower operationto provide a post-purge period.5. Igniter - The hot surface igniter is a crystallineelement which becomes very hot when electricalpower is applied to it. The hot surface igniterdirectly ignites the air/gas mixture in the combustionchamber.6. Limit Switches - Two limit switches preventexcessive water temperature - one at the heatexchanger outlet and one for water leaving theheater. If either senses excessive temperature,burner operation is interrupted.7. Water Pressure Switch - This control senseswhether or not water is available to the heater bymeasuring back pressure inside of the heat exchanger.If the pool water pump fails or the waterfilter is blocked, the pressure switch preventsoperation of the burner.8. Fusible Link - This is a single-use switch whichdetects abnormal temperature in the componentcompartment of the heater. It is a fusible linkwhich is held to the combustion chamber justabove the burner tray by a sheet metal bracket.Excessive temperature in the component compartment,possibly due to a burner flash-backwill cause the link to fail. This opens the safetycircuit which shuts off the gas valve and shuts theheater down.9. Air Pressure Switch - This switch verifies thatair is flowing through the combustion systemby sensing pressure. It shuts off the heater if airflow is inadequate.10. Flame Sensor - The flame sensor is the electrodethrough which the ignition control detects "rectification"of current passed through the flame.Inadequate rectification indicates an unsatisfactoryflame condition. The rectification signalcan be measured by attaching the leads of a DCammeter to the two pins on the connector of theignition control labeled "FC". A wire harness,available from Jandy, makes it easier to attach thevoltmeter leads. The flame current should not beless than 1.5 micro-amps. If the flame signal isless than 1.5 micro-amps, verify correct gas supplyand manifold pressures.10.4 Special Service Issues - PremixCombustion System10.4.1 System OperationPremix combustion systems are less tolerant offuel and air imbalance than other technologies. Fuelgas properties, incorrect supply or manifold pressureaffect their operation and reliability. If fuel gas heatcontent is low, combustion is "lean" and tends to beunstable. Flames may lift off the burner, causing outage.If heat content is high, "rich" combustion results,with low, hot flames that can overheat the burners.Likewise, low gas supply or manifold pressure resultsin lean, unstable combustion and high manifold pressureresults in a rich process and hot burners.The air pressure inside the burner throat alsoeffects combustion. Incorrect air pressure will affectperformance and reliability of the heater. The burnerthroat pressure should be adjusted to 1.0" W.C. (SeeSection 10.4.3 for adjustment procedures.) If the airpressure is too high, combustion will tend to be “lean”and unstable. Flames may lift off the burners and beextinguished. If air pressure is to low, the combustionwill be “rich”. The flames will be low and hot.This could lead to burner overheating and failure. Theburner throat and gas manifold pressure need to be balancedfor stable combustion to occur.The sealing of the combustion chamber and flueassembly is also important to maintaining good combustion.The combustion chamber of the LXi runs at aslightly positive pressure (0.08" W.C. to 0.18" W.C.).It is important that combustion products do not leakfrom the combustion chamber or flue collector insidethe cabinet of the heater where they will be pulled intothe combustion air fan. Most of the oxygen in combustionproducts has been consumed. If these combustionproducts are pulled into the combustion air fan, it maycause a rich combustion condition and that will lead toa short yellow streaked flame that can decrease burnerlife. Combustion chamber and flue collector sealingmust be maintained in “factory” condition. Serviceoperation involving burner, heat exchanger or fuel collectorremoval must be conducted with this in mind.10.4.2 Field Service and AdjustmentAs with all gas-fired appliances, the first order ofbusiness is to verify correct gas type, supply pressure,manifold pressure, and burner throat pressure as specifiedon the heater rating plate and in other sections ofthis manual.If the problems with lifting or short yellow/orangeflames cannot be corrected with the slight changein manifold pressure and burner throat pressure, it islikely that the fuel supply dffers greatly from average.In this event, it may be necessary to replace the gasorifices. Contact the Jandy Technical Service Group at1.707.776.8200, extension 260 for assistance.