Jandy Legacy LRZM, Installation And Operation Manual

Page 37

Legacy

™

 Model LRZM Pool/Spa Heater Installation and Operation Manual

ture, which should be thoroughly investigated before 

replacement of limit switches. Excessive water temper-

ature may be caused by low water 

fl

 ow. Water 

fl

 ow 

de

fi

 ciency may be due to obvious problems such as a 

defective pump or blocked water 

fi

 lter. Alternatively, 

excessive water temperature may be due to over-

fi

 ring, 

or to a problem with the water piping or the heater's 

internal bypass control. Over-

fi

 ring might be a result 

of an incorrect gas ori

fi

 ce or supply of propane gas to a 

heater intended for natural gas. 

If there are no such fundamental problems, 

identify which of the switches is open. Limit switch 

access is through the limit switch plugs on the inlet/

outlet header. Remove the limit switch plugs from 

the bottom of the header and gently remove the limit 

switches from the wells. Move the black lead of the 

meter to the terminal on the 150°F limit switch (test 

point 7) that is connected to the 

fi

 reman switch termi-

nal block. Less than 220mV at this point means that 

the wire between the terminal block and the limit 

switch has a poor or broken connection or a partial 

short. Replace the wire assembly. If at least 220mV is 

detected at test point 7, then move the black lead of the 

meter to the other terminal of the 150°F limit switch 

(test point 8). Low or no voltage here means that the 

limit is open and must be replaced. 

If 220mV or more is detected at test point 8, 

move the black lead of the meter to the terminal on the 

130°F limit switch (test point 9) that is connected to 

the 150°F limit switch. Less than 220mV at this point 

means that the wire between the two limit switches has 

a poor or broken connection or a partial short. Replace 

the wire assembly. If at least 220mV is detected at test 

point 9, then move the black lead of the meter to the 

other terminal of the 130°F limit switch (test point 

10). Low or no voltage here means that the limit is 

open and must be replaced. If voltage is detected at 

test point 10, move the black lead of the meter to the 

terminal of the water pressure switch where the white 

wire from the high limits is connected (test point 11). 

Less than 220mV at this point indicates that the wire 

connecting the high limits to the water pressure switch 

is faulty or poorly connected. Correct the problem or 

replace the wire.

NOTE 

The limit switches have different trip points, 
and it is important that replacements are 
correct. The 150°F switch has a red dot on the 
top of the switch, and must be installed in the 
rear port of the header. The 130°F switch has 
no dot and must be installed in the front port of  
the header.

10.4.6  Water Pressure Switch

If the meter shows at least a 220mV signal at test 

point 11, move the black lead of the meter to the other 

terminal on the water pressure switch (test point 12).

If there is no voltage, the pressure switch contacts 

are open. This is almost always due to a water 

fl

 ow 

de

fi

 ciency, the most common one being a blocked water 

fi

 lter or defective pump. However, sometimes it is due 

to blockage of the copper tube or mis-adjustment of 

the switch. Investigate thoroughly, referring to Section 

7.5 on “Water Pressure Switch Adjustment”. If there 

is no problem with the pool system or pressure switch 

adjustment, replace the pressure switch.

10.4.7  Temperature Control Circuit

The temperature control circuit consists of four 

(4) major components which must all be working 

correctly for the signal to be transmitted to the gas 

valve. The four components are the ON/OFF toggle 

switch, the variable temperature control (potenti-

ometer), the temperature sensor (thermistor) and the 

temperature control board. Use the following proce-

dure to check each component for functionality. 

Check the temperature control as a complete 

circuit before checking each component individually. 

With the red lead of the meter still at test point 1, place 

the black lead of the meter on the TH terminal of the 

temperature control circuit board (test point 16). If the 

meter shows more than 220mV at the pressure switch 

(test point 12) but not at test point 16, then one of the 

components of the temperature control circuit is faulty. 

Proceed with the following sections to test the compo-

nents.

10.4.7.1 ON/OFF Toggle Switch

Remove the temperature control panel from the 

bezel on the front of the heater to gain access to the 

switch. Be sure that the toggle switch is in the "ON" 

position. Place the black lead of the meter on the 

toggle switch terminal (test point 13) that is connected 

to the pressure switch. Less than 220mV at this point 

indicates that there is a problem with the black wire 

that connects the pressure switch to the toggle switch. 

If at least 220mV is detected at test point 13, move the 

black meter lead to the other terminal on the toggle 

switch (test point 14). A reading of less than 220mV 

here indicates a faulty switch. If the reading is more 

than 500mV, turn the switch "OFF" and then "ON" 

again to be sure that the internal contacts are working 

correctly. The volt meter reading should drop to zero 

when the switch is "OFF" and return to at least 220mV 

when the switch is placed back in the "ON" position.

10.4.7.2 Variable Temperature Control 

The variable temperature control is a 0-10,000 

ohm variable resistor. Set your ohmmeter to the 0-20K 

range.  Remove the temperature control wires from 

the control circuit board. Place one lead of the meter 

on each of the wires (test points 18 & 19). With the 

control set to MIN the meter should read near 10,000 

ohms. Now turn the control to the MAX position. The 

meter should read close to zero. If the meter shows an