R e s i d e n t i a l H & V - 6 0 H z H F C - 4 1 0 A :
R e v : O c t o b e r 5 , 2 0 2 1
20
G e o t h e r m a l H e a t i n g a n d Co o l i n g
Water Quality Standards
OHM meter
Measuring Earth Ground Resistance
0.02
Building
Ground Rod
Well Casing
Measure the earth ground bond using an Ohm meter between the building's ground rod and the steel well casing.
The resistance measured should be zero Ohms. The NEC allows a resistance to ground up to 20 Ohms. Any
resistance above zero, indicates a poor earth ground which may be the result of a hot neutral line or that
conduc
�
ve water is present. Both of these may lead to electrolysis and corrosion of the heat pump piping. A check
for both should be performed and resolved.
Note if the well casing is plas
�
c, a conduc
�
ve path can be achieved by inser
�
ng a #6 AWG bare copper wire into the
well water. Remove the temporary conductor when
fi
nished.
