Jandy LXi, Installation And Operation Manual

Page 44

LXi

™

 Pool/Spa Heater Installation and Operation Manual

control provides a pre-purge of the combustion 

chamber. Once the pre-purge is complete the 

ignition control then applies electrical power to 

a “hot surface” igniter. When the igniter is hot 

enough, the ignition control opens the gas valve.  

It has sophisticated means to sense ignition and 

fl

 ame condition so that unburned gas will not es-

cape. Once the ignition control has sensed 

fl

 ame, 

it de-energizes the igniter. After the burner is shut 

off, the ignition control continues blower opera-

tion to provide a post-purge period.

5. 

Igniter -

 The hot surface igniter is a crystalline 

element which becomes very hot when electri-

cal power is applied to it. The hot surface igniter 

directly ignites the air/gas mixture in the combus-

tion chamber.

6. 

Limit Switches - 

Two limit switches prevent 

excessive water temperature - one at the heat 

exchanger outlet and one for water leaving the 

heater.  If either senses excessive temperature, 

burner operation is interrupted.

7. 

Water Pressure Switch

 - This control senses 

whether or not water is available to the heater by 

measuring back pressure inside of the heat ex-

changer. If the pool water pump fails or the water 

fi

 lter is blocked, the pressure switch prevents 

operation of the burner. 

8. 

Fusible Link - 

This is a single-use switch which 

detects abnormal temperature in the component 

compartment of the heater.  It is a fusible link 

which is held to the combustion chamber just 

above the burner tray by a sheet metal bracket.  

Excessive temperature in the component com-

partment, possibly due to a burner 

fl

 ash-back 

will cause the link to fail.  This opens the safety 

circuit which shuts off the gas valve and shuts the 

heater down.

9.   

Air Pressure Switch -

 This switch veri

fi

 es that 

air is 

fl

 owing through the combustion system 

by sensing pressure.  It shuts off the heater if air 

fl

 ow is inadequate.

10.   

Flame Sensor -

 The 

fl

 ame sensor is the electrode 

through which the ignition control detects "rec-

ti

fi

 cation" of current passed through the 

fl

 ame.  

Inadequate recti

fi

 cation indicates an unsatisfac-

tory 

fl

 ame condition.  The recti

fi

 cation signal 

can be measured by attaching the leads of a DC 

ammeter to the two pins on the connector of the 

ignition control labeled "FC".  A wire harness, 

available from Jandy, makes it easier to attach the 

voltmeter leads. The 

fl

 ame current should not be 

less than 1.5 micro-amps. If the 

fl

 ame signal is 

less than 1.5 micro-amps, verify correct gas sup-

ply and manifold pressures.

10.4  Special Service Issues - Premix 

Combustion System

10.4.1  System Operation

Premix combustion systems are less tolerant of 

fuel and air imbalance than other technologies. Fuel 

gas properties, incorrect supply or manifold pressure 

affect their operation and reliability. If fuel gas heat 

content is low, combustion is "lean" and tends to be 

unstable. Flames may lift off the burner, causing out-

age. If heat content is high, "rich" combustion results, 

with low, hot 

fl

 ames that can overheat the burners. 

Likewise, low gas supply or manifold pressure results 

in lean, unstable combustion and high manifold pres-

sure results in a rich process and hot burners.

The air pressure inside the burner throat also 

effects combustion. Incorrect air pressure will affect 

performance and reliability of the heater. The burner 

throat pressure should be adjusted to 1.0" W.C. (See 

Section 10.4.3

 for adjustment procedures.) If the air 

pressure is too high, combustion will tend to be “lean” 

and unstable. Flames may lift off the burners and be 

extinguished. If air pressure is to low, the combus-

tion will be “rich”. The 

fl

 ames will be low and hot. 

This could lead to burner overheating and failure. The 

burner throat and gas manifold pressure need to be bal-

anced for stable combustion to occur.

The sealing of the combustion chamber and 

fl

 ue 

assembly is also important to maintaining good com-

bustion. The combustion chamber of the LXi runs at a 

slightly positive pressure (0.08" W.C. to 0.18" W.C.). 

It is important that combustion products do not leak 

from the combustion chamber or 

fl

 ue collector inside 

the cabinet of the heater where they will be pulled into 

the combustion air fan. Most of the oxygen in combus-

tion products has been consumed. If these combustion 

products are pulled into the combustion air fan, it may 

cause a rich combustion condition and that will lead to 

a short yellow streaked 

fl

 ame that can decrease burner 

life. Combustion chamber and 

fl

 ue collector sealing 

must be maintained in “factory” condition. Service 

operation involving burner, heat exchanger or fuel col-

lector removal must be conducted with this in mind.

10.4.2  Field Service and Adjustment

As with all gas-

fi

 red appliances, the 

fi

 rst order of 

business is to verify correct gas type, supply pressure, 

manifold pressure, and burner throat pressure as speci-

fi

 ed on the heater rating plate and in other sections of 

this manual.

If the problems with lifting or short yellow/or-

ange 

fl

 ames cannot be corrected with the slight change 

in manifold pressure and burner throat pressure, it is 

likely that the fuel supply dffers greatly from average. 

In this event, it may be necessary to replace the gas 

ori

fi

 ces. Contact the Jandy Technical Service Group at 

1.707.776.8200, extension 260 for assistance.