Jandy Legacy LRZM, Installation And Operation Manual

Page 27

Legacy

™

 Model LRZM Pool/Spa Heater Installation and Operation Manual

8. 

Return the pool temperature control to the 

desired temperature.

It may be necessary to repeat these steps to get 

a proper setting. The switch must be set so that the 

heater will not 

fi

 re unless the pump is running. If a 

proper setting cannot be reached, contact the factory 

service department.

7.6 Temperature 

Rise

NOTE  A temperature rise measurement kit is needed 

to perform this test, order part number 
R0336000.

The Legacy pool and spa heaters have an inter-

nal bypass which accommodates a wide range of 

water 

fl

 ow. The bypass is easily adjustable to change 

the temperature rise for optimum performance and 

length of heater life. The bypass assures constant heat 

exchanger 

fl

 ow even though 

fl

 ow through the 

fi

 lter 

system will vary depending on how dirty the 

fi

 lter is.

For most installations, an external bypass valve 

is not needed in the heater water piping. This is due to 

the large size of the heater's internal bypass valve. If 

the pump 

fl

 ow rate is known to exceed 125 gpm (7.9 

l/s), an external bypass may be needed to assure proper 

heater operation.

Water 

fl

 ow should be con

fi

 rmed upon start-up of 

the heater and in most servicing situations. If the 

fl

 ow 

is not normal, corrections must be made to the pool 

system. Flow is evaluated by determining the water 

temperature rise through the heat exchanger.

Before checking the temperature rise, make sure 

that the pool 

fi

 lter is clean and that gas supply and 

manifold pressures are correct. If necessary, clean 

all components of the 

fi

 lter system. Temperature rise 

is measured in the return header of the Legacy.  To 

measure the temperature rise, turn off the 

fi

 lter pump 

and remove the plastic plug protruding through the 

cabinet on the return header side of the heater.  See 

Figure 20. With the plug removed, install the special 

thread adapter and Pete’s Plug

®

fi

 tting and insert a 

pocket thermometer. A temperature rise measurement 

kit is available through your Jandy distributor. See 

Section 11 of this manual for the correct kit number.

The internal bypass can be adjusted by means of 

a screw on the right-hand side of the header. To adjust 

the temperature rise to within the ranges speci

fi

 ed in 

Table 6, proceed as follows:

1.   If the piping system has an external bypass valve, 

close it.

2.   Turn the heater control panel to OFF.

3. Start 

the 

fi

 lter pump.

4.   After three minutes, note and record the 

thermometer reading. This is the pool water 

temperature.

5. 

Start the heater by turning the controller to ON. 

Allow the heater to operate for 

fi

 ve minutes 

or more. Note and record the thermometer 

reading. Subtract pool water temperature from 

this reading. This difference is the temperature 

rise. Refer to Table 6. If your measured tempera-

ture rise is within the range designated for your 

heater, skip steps 6 through 8.

6.   Locate the bypass adjustment screw on the right-

hand side of the header (see Figure 20). Loosen 

the nut so that the screw can be adjusted. A slight 

water leak past the nut may be expected. Turn the 

screw counterclockwise to decrease the tempera-

ture rise, and clockwise to increase the tempera-

ture rise as needed to achieve the ranges in Table 

6. After the adjustment, tighten the nut so that no 

leaks occur.

7.   If the temperature rise is too low and cannot be 

raised by means of the adjustment screw, the 

fl

 ow 

is in excess of 125 GPM (7.9 lps). An external 

bypass will need to be installed, or if one already 

exists, open the external bypass valve gradu-

ally until the temperature range in Table 6 is 

achieved.

8.   If it was necessary to adjust the external bypass 

as outlined in step 7, scribe a line on the bypass 

shaft and case to mark the correct adjustment 

position. Wire or remove the valve handle to 

prevent tampering.

BYPASS 

ADJUSTMENT 

SCREW

THERMOMETER WITH 

PETE'S PLUG

Figure 20. Temperature Rise Measurement