Bradford White 25X78B N Series, Service Manual

Page: 7 / 28

F i g ure 6
O P EN C IR C UIT THERMO P ILE TE S TING
Step 1. Disconnect red and white thermopile wires from the wire harness leading to the gas control.
Step 2. Using a multimeter capable of reading millivolts, check across thermopile leads.
Step 3. Following the instructions located on the lighting instruction label or the lighting instructions located in the
installation and operation manual, proceed to light the pilot and allow the gas control to operate for three
minutes.
Step 1. Closed circuit testing is the preferred method for testing the thermopile. Following the instructions
located on the lighting instruction label or the lighting instructions located in the installation and operation
manual, proceed to light the pilot and allow the control to operate for three minutes.
Step 2. Using a multimeter capable of measuring millivolts, measure across thermopile connections at the
gas control (see Figure 6).
C LO S E D C IR C UIT THERMO P ILE TE S TING
T hermopi l e
Connections at g as
contro l
P a g e 7
F i g ure 5
Gas Contro l
K nob
S ERVI C E P RO C E D URE A G-I
Thermocoup l e Testin g and Rep l acement
F or M ode l s U sin g H oneywe ll Gas Contro l
NOTE:
I t may be necessary to ho l d the g as
contro l knob down in the “ PI LOT” position
continuous l y throu g hout this test .
NOTE:
I t may be necessary to ho l d the g as
contro l knob down in the “ PI LOT” position
continuous l y throu g hout this test .
I n a C LO S E D C IR C UIT test :
Any readin g over 300 mi ll ivo l ts
indicates g ood thermopi l e output .
F or readin g s under 300 mi ll ivo l ts
rep l acement of thermopi l e is
recommended .
I n an O P EN C IR C UIT test :
Any readin g over 4 00 mi ll ivo l ts
indicates g ood thermopi l e output .
F or readin g s under 4 00 mi ll ivo l ts
rep l acement of thermopi l e is
recommended .
7