Bosch GWH 260 PN Service Bulletin Booklet page 2

THERMOCOUPLE AND PILOT TEST
MODELS: 1000P, 1600P,
260PN, 425PN
Before replacing the thermocouple, please test the
thermocouple safety circuit and the pilot as follows.
A. Pilot does not stay lit when the button is
released.
1. When lighting pilot, ensure the gas valve button is fully de-
pressed and held down for at least 15 seconds after pilot is
lit.
2. Pilot flame should be a shar p blue flame that fully engulfs
the thermocouple tip. If pilot doe s not look this way, please
see bulle tin 'CT-22 Cleaning pilot assembly' for instr uctions
on how to clean pilot a ssembly and or ifice.
3. If heater is equipped with an AQ4 power vent kit (models
1600P and 425PN only), press reset but ton on power vent
spill switch to c heck if it is tripped. NOTE: r unning the heater
without electrical power to po wer vent fan will trip the spill
switch. Also check the AQ4 safety circuit connections for
corrosion or loose connections. Consult AQ4 manual for par t
locations.
4. Check the electromagne t connections. The electromagnet
is located on the back side of the gas valve. The electromag-
net connection from the thermocouple is a 5 mm brass nut
tha t screws into a 17 mm aluminum nut. Tighten both nuts
snugly but do not over tighten.
5. Check if connections at both temperature limiters (ECO) are
loose or corroded. Cle an any corrosion with very fine sand
paper or an eraser and reconnect leads.
6. If cleaning the terminals attac hed to the ECO's does no t fix
the problem, choose one EC O and remove tw o wires at-
tached. Connect a jumper wire between the two wires re-
moved from the ECO. Try to relight the pilot. If the pilot
flame now remains on, the ECO may be defective. If the
pilot still goes out, remove jumper, r econnect wires leads
and perfor m the same step wit h the other ECO.
Note: Never attempt to operate heater for normal
use with jumper wire connected!
7. Replace ECO.
8. Have a licensed gas technician verify the proper operation of
the thermocouple. To test the thermocouple, disconnect wire
from the thermocouple where it connects to the upper ECO
(located top right side of the heat exchanger). Insert a multi-
meter probe into the ther mocouple lead and attach or hold
the other probe to the metal chassis of the heater (DC com-
mon). Light the pilot flame and hold button while obser ving
the me ter reading. If the reading is 24mVDC or more the
thermocouple is good.
©BBT NORTH AMERICA CORPORATION
Bosch Group
W W W W W ARNIN ARNIN ARNIN ARNING G G G G
ARNIN
LP & N LP & N G ARE EXTREMEL G ARE EXTREMEL
LP & N LP & NG ARE EXTREMEL LP & N G ARE EXTREMEL G ARE EXTREMELY FL
T T T T T AKE EXTRA PRECA AKE EXTRA PRECA AKE EXTRA PRECA AKE EXTRA PRECAUTIONS WHEN
AKE EXTRA PRECA
PERF PERFORMIN PERF ORMIN ORMIN G ANY W ORMIN G ANY W G ANY W G ANY WORK T
PERF PERF ORMIN G ANY W
B. Pilot goes out during use
1. Light the pilot and allow it to warm the ther mocouple tip for
2 minutes.
2. Perform dr op test by blowing out the pilot flame and listen
for the electromagnet to close. This closure will make a dis-
tinct clunk noise as it shuts. The time between blowing out
the flame and the electromagnet closing should be between
20 and 30 seconds. Units equipped with an AQ4 power vent
kit have drop times between 10 and 15 seconds.
3. Repeat drop test several times to confirm it is consistent
4. If drop times are not within specifica tions, then follow steps
2-7 in section A . After each step, repeat drop test. Proceed
to the next step until drop test is within specifications.
C. Pilot goes out during use and drop test is
within specifications.
1. Check the vent size and length. Vent should be 5 inches in
diame ter for the 1600P and 425PN and 4 inches in diameter
for the 1000P and 260PN. The heater mus t have a rise of 1-
foot before any elbo ws in the vent system, at least 6 feet
vertical in length and terminate through the r oof. Any reduc-
tion in vent size or the presence of an elbow directly on the
top of the unit may cause the flue gas sensor to trip the pilot
safety circuit. Please see t he venting section in the manual
for more de tailed information regarding the required venting
for this heater.
2. Inspect the draft hood and heat exchanger fins for signs of
soot build-up or any other foreign material such as spider
webs. Clean out an y debris found in the vent hood. Signs of
soot indica te insuf ficient combustion air or exhaust draft.
Check for vent assembly bloc kage or combus tion air block-
age on the underside of the unit. Ensure combustion air
requirements are being met as specif ied in the installation
manual.
3. Measure the outgoing temperature of the hot water exiting
the unit. Temperature in excess of 160F may trip the pilot
safety circuit. The heater must not be supplied with w ater in
excess of 90F. Preheated water may cause the heater t o
overheat t he outlet water and shut down as a safety precau-
tion.
340 Mad River Park, Waitsfield, VT 05673
Y FL Y FL AMMABLE SO AMMABLE SO
Y FL Y FLAMMABLE SO AMMABLE SO AMMABLE SO
UTIONS WHEN UTIONS WHEN UTIONS WHEN
UTIONS WHEN
ORK T ORK T ORK TO THE HEA O THE HEATER O THE HEA O THE HEA TER TER TER
ORK T O THE HEA TER
Bosch Water Heating
CT-02
page 1 of 1
rev 10/06