Removing & Replacing Element Assembly Service Bulletin EP-23 PowerStar AE115 & AE125

Removing & Replacing Element Assembly Service Bulletin EP-23 PowerStar AE115 & AE125
Service Bulletin EP-23
Models: AE115, AE125, RP17PT, RP27PT
Removing & Replacing Element Assembly
PowerStar AE115 & AE125
Powerstream Pro RP17PT & RP27PT
NOTE: This bulletin is only for heaters with polymer heating
modules. Element replacement is not possible for units
with copper heating modules.
NOTE: Models AE115/RP17PT will have 4 white insulated wire
NOTE: Models AE125/RP27PT will have 6 white insulated wire
CAUTION: The wires must be re-installed in the same sequence
as the original configuration. Improper installation of these
wires will result in the unit not operating properly.
Figure 1
Electricity is EXTREMELY Dangerous.
all circuit breakers are off before
Tools required
Philips head screwdriver
Flat head screwdriver
Wire cutters
Wire ties
Socket wrench with extension bar and 8mm socket.
Needle-nose pliers
1.Turn off circuit breakers supplying power to the water heater.
2.Close installer supplied shutoff valves.
3. Open a hot water fixture to allow water to drain from water lines
and heater.
4. Remove front cover from heater.
Removing element assembly
1. Remove gray circuit board cover on lower right side of heater.
Cover is secured with one screw. Remove neon light from clip
inside cover.
2. Note color and position of wires with white insulators on control
board as shown in Fig. 1.
control board
control board
3. Remove the wires with white insulators from the circuit board
using needle nose pliers.
4.Using wire cutters, cut the cable ties on the wire bundles
leading from the circuit board to the element assembly being
5.Separate the disconnected wires from the wire bundle.
6.Unscrew the slotted screw(s) with washer(s) to remove the
wire(s) from the left side of the thermal cut out (TCO). (Figure
2, pos. A) AE125 and RP27PT models have 2 wires, AE115 and
RP17PT models only have 1 wire. DO NOT remove wire(s) from
right side of thermal cut out (TCO).
1 2 | EP-23 | AE115, AE125, RP17PT, RP27PT
Service bulletin
Figure 3
7. Remove the 2 screws and washer that mount the TCO and
ground wire to the element assembly (Figure 2, pos. B). Pull the
TCO and attached wire(s) free from the element assembly.
Figure 2
Top View
Rear of Heater
Front of Heater
Note: only relevant wiring shown
for clarity purposes
8. Remove the 6 hex head 8mm screws from the element assembly.
(Figure 2, pos. C)
9. Remove the element assembly from the polymer module. It may
be necessary to use a slotted screwdriver to carefully pry them
apart. (Figure 3, pos. A))
10.Inspect the elements for scale buildup. If scale is present, water
must be treated to prevent damage to the elements. Consult
local water treatment professional for recommendations.
This is not a defect or warranty issue but is related to water
hardness (mineral content).
Replacing element assembly
1. Discard the old o-ring between the element assembly and
polymer module.
2.Liberally apply lubricant to the new o-ring, inner lip of element
assembly and outer lip of polymer module. We recommend
using Dow Corning 111 Valve Lube and Seal.
3. Insert the new o-ring into the top of the element assembly,
ensuring it is even and fully seated on the ledge approximately
1cm (⅜") in from the mating surface. Do not install o-ring on
4. Install the element assembly into the polymer module. Orient
the assembly with TCO mounting towards the front of the
module. Press down until the assembly is evenly and fully
seated on the module.
5. Reinstall the 8mm hex head screws and tighten by hand until
may strip the threads in the module. (Figure 2, pos. C)
Data subject to change without notice | Printed in the USA | 06.2008 revA
(Wiring not shown for clarity)
6. Open a hot water fixture and slowly turn on the water supply to
the heater and check for leaks. Turn off the water supply. If no
leaks, proceed to the next step.
7. Remount the TCO to the top of the element assembly being sure
to secure the green and yellow striped ground wire under a
mounting screw head. (Figure 2, pos. B)
8.Connect the short wire(s) from the new element assembly to the
left side of the TCO. On AE125 and RP27PT models, the wire
from the bridged terminals mounts to the lower left terminal of
the TCO.
9.Connect the wires from the elements to the circuit board in
correct order. (Figure 1)
10.Bundle the wires together with new wire ties.
11.Clip the light to the inside of the circuit board cover and reinstall
the cover.
12.Reinstall heater cover.
13.Turn on a hot water fixture and open shut off valves to heater to
allow water to flow through heater.
14.Once water has been flowing for at least 30 seconds, turn on
circuit breakers. Light should come on and water should heat.
Bosch Thermotechnology Corp.
50 Wentworth Avenue
Londonderry, NH 03053
Tel: 1-866-642-3198
Fax: 1-603-584-1681
Bosch Thermotechnology Corp.
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