WW
WW
W
ARNINARNIN
ARNINARNIN
ARNIN
GG
GG
G
LP & NLP & N
LP & NLP & N
LP & N
G ARE EXTREMELG ARE EXTREMEL
G ARE EXTREMELG ARE EXTREMEL
G ARE EXTREMEL
Y FLY FL
Y FLY FL
Y FL
AMMABLE SOAMMABLE SO
AMMABLE SOAMMABLE SO
AMMABLE SO
TT
TT
T
AKE EXTRA PRECAAKE EXTRA PRECA
AKE EXTRA PRECAAKE EXTRA PRECA
AKE EXTRA PRECA
UTIONS WHENUTIONS WHEN
UTIONS WHENUTIONS WHEN
UTIONS WHEN
PERFPERF
PERFPERF
PERF
ORMINORMIN
ORMINORMIN
ORMIN
G ANY WG ANY W
G ANY WG ANY W
G ANY W
ORK TORK T
ORK TORK T
ORK T
O THE HEAO THE HEA
O THE HEAO THE HEA
O THE HEA
TERTER
TERTER
TER
CT-06
page 1 of 1
rev 10/06
Bosch Water Heating
340 Mad River Park, Waitsfield, VT 05673
©BBT NORTH AMERICA CORPORATION
Bosch Group
OVERCOMING FLUCTUATING
TEMPERATURES
MODELS: 1000P, 1600P, 1600H
260PN, 425PN, 425HN
Introduction
Temperature fluctuations from hot to cold during use is typi-
cally caused by a back pressure on the water flowing through
the tankless water heater. This decreases the flow rate through
the tankless water heater below the required activation flow
rate and shuts the heater down. Follow these instructions step
by step to overcome this phenomenon.
Clean faucet aerators and shower heads
Check for restrictions in outlets, which would limit hot water
demand and may assist in de activation scenario. For sinks,
remove faucet aerator on end of sink. Flush and clean screen
and reinstall. For showers, remove showerhead and flush. If
plugged with mineral deposits, clean according to
manufacturer’s suggestions or replace. (Note: if showerhead is
wand style/hand held, corrugated tube connecting to head may
be too restrictive. Enlarging tube or using a normal showerhead
may be the solution.)
Clean Inlet filter screen
Inlet filter screen is located in bottom of the water valve near
the cold water connection side (right) at t he rear of the unit.
Please see bulletin
CT-12 Cleaning inlet f ilter for more detailed
instr uctions.
Check for plumbing crossover
A plumbing crossover can be caused by a failed cartridge at a
single lever faucet, incorrect plumbing or a faulty mixing valve
in the piping. The crossover will create a back pressure on the
water heater and prevent an a dequate flow of w ater through it.
Close installer supplied cold water shut off valve to the heater
(if none installed, install bef ore proceeding). Open all hot wa-
ter taps supplied by the heater. Wait 5 minutes and check all
taps. Water running is a sign of a plumbing cross-over. Consult
a local plumber or service person for help in correcting a plumb-
ing crossover.
Confirm water pressure
Water pressure should stay above 30psi during operation. If on
a well system, we recommend a pressure setting of 40-60psi.
Lower temperature
The temperature can be lowered by moving gas slide control to
the left. On models 1600H and 425HN, turn power adjustment
knob clockwise. See bulletin
CT-07 Lowering temperatures for
alternative methods of lowering output temperature.
Confirm activation rate of the heater
1. Turn flow control knob on the front of heater fully clockwise.
2. Fully open one hot water tap.
3. Return to heater and shut cold water supply valve.
4. Slowly open cold water supply v alve until the burners ignite.
5. Return to hot water tap and measure flow rate by timing
how long takes to fill a quart container. A fill time of 30
seconds indicates a proper activation rate of 0.5 gallons per
minute (GPM)*. See Table 1 for other flow r ate conversions.
6. Repeat steps 4 and 5 a few times to check the accuracy of
test.
* A fill time less than 30 seconds indicates an activation rate
above the required 0.5GPM and a possible problem within
the heater’s water valve. Periodic maintenance is required
on this water valve. Visit our website for parts and service
bulle tins for this procedure.
GPM
Quar t Jar
(in Secon ds)
Ga l l o n Ju g
(in Seco nds)
.50 30 120
.75 20 80
1.00 15 60
1.25 12 48
1.50 10 40
1.75 8.5 34
2.00 7.5 30
2.50 6 24
3.00 5 20
3.50 4.25 17
4.00 3.75 15
TABLE 1
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