![background image](http://html1.mh-extra.com/html/graco/therm-o-flow-243698/therm-o-flow-243698_instructions-manual_2251035009.webp)
Installation
309213G
9
Installation
Check the Resistance Between
the Supply Unit and the True
Earth Ground
Have a qualified electrician check the resistance
between each supply unit component and the true
earth ground. The resistance must be less than
0.25 ohms. If the resistance is greater than 0.25
ohms, a different ground site may be required. Do
not operate the system until the problem is cor-
rected.
NOTE:
Use a meter that is capable of measuring
resistance at this level.
Checking Resistance
You can check the resistance of the supply unit's heat
sensors and heaters.
NOTE:
Check resistance at ambient room temperature
(63° -77°F).
Sensor Resistance Checks
To verify the RTD sensors to be used with the 2- or
4-zone heat control box, refer to the tables below.
RTD Sensors - 2-Zone Control
RTD Sensors - 4-Zone Control
An ohm meter can be used to check the resistance
between the terminals indicated. To check the sensor
resistance:
1.
Make sure the power is off and that the disconnect
switch is in the OFF position.
2.
Make electrical resistance checks for the compo-
nents.
3.
Replace any parts whose resistance readings do not
comply with the ranges listed.
WARNING
FIRE, EXPLOSION, AND ELECTRIC
SHOCK HAZARD
To reduce the risk of fire, explosion, or
electric shock the resistance between the
supply unit components and true earth
ground must be less than 0.25 ohms.
WARNING
ELECTRIC SHOCK HAZARD
Do not open the electrical control panel,
unless you are a trained professional.
Before opening the control panel, make sure
that all power has been removed from the
control panel.
WARNING
ELECTROCUTION HAZARD
To reduce risk of injury or damage to
equipment, conduct these electrical checks
with the main disconnect OFF.
Zone
Component
Terminals
Value Range
1
Dispense
Hose 1
1091 & 1101
108 + 2%
ohms
2
Dispense
Gun 1
1161 & 1171
108 + 2%
ohms
Zone Component
Terminals
Value
Range
1
Dispense
Hose 1
1161 & 1171
108 + 2%
ohms
2
Dispense
Gun 1
1231 & 1241
108 + 2%
ohms
3
Dispense
Hose 2
1301 & 1311
108 + 2%
ohms
4
Dispense
Gun 2
1371 & 1381
108 + 2%
ohms