Alliance Appliances Pty Ltd RAPID 26 Operating instructions

Continuous Flow Gas Water Heater

26 Litre Series

Service Instructions

Page 1Alliance Appliances Pty Ltd

Rapid 26

Rapid Continuous Flow Gas Water Heater

26 Litre Series

Service Instructions for:

This manual covers the normal servicing required

on the above models.

KEY TO MODEL NUMBERS

R=RAPID

26 = 26LPM @ 25ºC temperature rise.

N = Natural Gas

P = PROPANE Gas (Australia only, not universal LPG)

Natural Gas

RAPID R26N

Propane Gas

RAPID R26P

Page 3Alliance Appliances Pty Ltd

Rapid 26

26LPM CONTINUOUS FLOW

HOT WATER SERVICE MANUAL

DESCRIPTION OF OPERATION

The Rapid 26 range of Continuous Flow Gas Hot Water Services (CFGHW) are Gas ﬁred

Forced combustion hot water heating appliances.

The unit is powered and active at all times. When hot water is required, signalled by turning

on a hot tap in the home (to the desired ﬂow rate), the unit senses ﬂow via the ﬂow meter,

and after some safety checks initiates an ignition cycle.

IMPORTANT: THE WATER FLOW RATE WILL BE AUTOMATICALLY REDUCED

MOMENTARILY TO ENSURE FAST HEAT UP AND TO MINIMISE WATER WASTAGE.

When the water approaches the correct temperature the unit will then resume the

desired ﬂow.

If there is air in the line or for some reason ignition does not occur, the controller attempts

again for 5 more attempts. It will then lock out. The unit is reset only when the water is

turned off for 2 seconds and then back on again. Switching the power off and on again,

without interrupting the water ﬂow, will NOT reset the unit. Only when the tap is closed

and opened again will the ignition cycle be re-started.

After a successful ignition attempt, and immediately the unit senses ﬂame at the burners,

the control unit (ECU) calculates how much gas is needed to ensure that the water is at the

correct temperature for that ﬂow rate. It then switches on 1, 2 or 3 packs of burners using

3 solenoids provided. As well the ECU unit polls the outlet temperature sensor many times

per second and ﬁne tunes the gas ﬂow via a gas modulating valve. This valve is the blue coil

on top of the main gas control valve. The unit adjusts the gas to suit the water ﬂow and the

desired temperature, thereby supplying water at the correct temperature.

The unit also reacts to changes in ﬂow rate, (e.g. another tap being turned on) and starts to

re-adjust the temperature almost immediately.

If the desired temperature cannot be attained because the user has opened water taps

too far or has too many on at one time, (Excessive ﬂow rate) the unit will adjust the water

ﬂow down internally so that the desired temperature will be maintained. (This is called

Temperature Priority).

The unit also includes a safety shut down if the water gets too hot, which requires a

water ﬂow shutdown and reopening of a tap to reset. This fault however is not common and

indicates a problem with the unit. If it recurs call a service agent to correct the fault.

Also included is a safety shutdown and re-ignition if the sensor loses ﬂame contact during

use. It repeats this 5 times and then locks out. Reset is again by a 2 second interruption to

water ﬂow.(Turn tap off and then on after 2 seconds.

COMPONENTS DESCRIPTION

GAS TRAIN AND CIRCUIT

1. GAS VALVE. This valve is a SIT Components 845 Sigma model with 2 main solenoids and

an additional (Blue, low voltage) ) Modulating Valve to adjust gas rate for ﬁne adjustment.

The Rapid unit has a special inlet ﬁtting provided with a gas test point that is ﬁtted outside

the case underneath the unit to allow for easy checking of the inlet gas pressure. The gas

outlet (burner) pressure is easily read using the gas manifold test point provided on the

front of the burner box assembly.

2. VALVE TO BURNER PIPE. This is a short copper pipe formed to transmit gas from the gas

valve outlet to the gas manifold which is integrated into the burner box assembly. The pipe

uses ﬂat rubber washers at each end for gas sealing.

3. THE GAS MANIFOLD is a cast component that has a stamped plated steel cover and

gasket and distributes gas to 3 separate Solenoids (Fig A Item 3). These solenoids deliver

gas to the packs of 3, 5 or 9 of the 17 burners, plus a combination giving 3,5,8, 12 and

17 burners. The solenoids, under the control of the main electronic controller, (ECU Fig

A) allow rough cut supply of gas to approximately suit the desired temperature and water

ﬂow. The modulating valve as described in point 1 above, is also under the control of the

ECU and allows ﬁne tuning of the gas pressure at the burner injectors to precisely match

the desired load. A multi stepped gas rate is therefore provided. There is provided a gas

pressure test point on the manifold for checking of burner gas pressure.

4. BURNERS There are 17 small burners in the unit and these are made of stainless steel

and would normally not need servicing.

5. GAS INJECTORS are located in the cast alloy manifold and can be accessed after

removal of several screws. See instructions.

6. HEAT EXCHANGER The hot gases from the burner array pass vertically upward through

a box type copper heat exchanger which has helical cold water pipe soldered to the

outside of it. This scavenges heat and supplies pre-warmed water to the main ﬁnned heat

exchanger. Across the top of this box there is a ﬁnned copper serpentine heat exchanger

that takes most of the energy from the ﬂue gases and transfers it to the water ﬂowing in

the pipes, prior to the cooled gases being exhausted from the stainless steel ﬂue outlet.

WATER CIRCUIT

7. INLET WATER FITTING. This ﬁtting is connected to the cold inlet mains water (or the

warm outlet of a Solar Pre-heater tank. (70C model only.)) It has a screw off combination

ﬁlter/drain ﬁtting that incorporates a stainless gauze water ﬁlter. Only under extreme

conditions is this ﬁlter expected to become blocked. The drain is useful for draining the

unit if it is to be left in a cold area with no power available. (Freeze Protection.) This ﬁtting

also has pockets for the inlet water temperature sensor and a small heating resistor for

freeze protection.

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Rapid 26

Page 5Alliance Appliances Pty Ltd

Rapid 26

8. INLET WATER VALVE. This valve is located just inside the case bottom and is an extension

of the inlet water ﬁtting. It is electrically controlled by the ECU to adjust the ﬂow rate of the

water so that the desired temperature can be achieved even if the user has fully opened

up several taps.(Thereby exceeding the possible heat input from the unit.) The inlet water

valve also incorporates the ﬂow sensor turbine that allows the ECU to detect water ﬂow

above 3LPM and initiate the ignition cycle. The ﬂow meter also provides information to the

ECU to ﬁnely adjust the gas to give the desired temperatures. The outlet of this valve is

connected to the inlet pipe of the copper heat exchanger described above.

9. HEAT EXCHANGER. This as described above in (6).

10. OUTLET WATER FITTING. This is located under the lower left hand side of the heater

and incorporates a pressure relief valve and drain assembly. It connects with the outlet

pipe of the heat exchanger and is connected through the case to the delivery pipe into

the house.

ELECTRICAL COMPONENTS

11. ECU. This is located at the lower left hand front of the unit and has all the electronics

needed to control the gas and electrical components to ensure ignition, temperature

and safety aspect all perform as designed. The electronic components should never be

touched by hand as static electricity can destroy the electronics.

12. SENSORS. Water TEMPERATURE. There are 2 temperature sensors, one in the

incoming water valve and one in the outgoing water ﬁtting. These are wired back

and plug into the PCB. Each has an O-ring and small screw bracket.

13. TRANSFORMER. MAINS POWER SUPPLY. There is provided a mains power

transformer to supply all the electrical loads required for the various components.

14. PRESSURE SWITCH. Fan Proving. This is located at the lower RH end of the case

and is connected via a silicone rubber tube to the fan outlet. This switch senses fan

air pressure and allows the ECU to ignite the unit in the knowledge that the fan is

operational. The other side of the pressure switch is connected to a short hose that

connects with the air inlet vents to balance the air switch under wind conditions.

15. FAN (COMBUSTION). This is approx 100 mm diameter and is located behind the ECU

PCB. It is mounted from the bottom of the burner box assembly. The fan assembly can

only be removed after the heat exchanger is removed. However, the fan motor and fan

wheel component can be removed from the fan scroll by removing 3 screws visible on

the front of the fan assembly, saving much disassembly to change a fan over..

16. OVER-TEMPERATURE CUT OUT. This is ﬁtted at the top RH side of the heat exchanger

on the pipe work and is of the auto reset type. This will only open circuit if the main ECU

fails to operate properly. WARNING: THIS ITEM IS CONNECTED TO 240V MAINS

POWER AT ALL TIMES.

17. ANTIFREEZE. This is an array of ceramic power resistors IN SERIES which are clipped

onto the water carrying pipes or are imbedded into the water valves and ﬁttings. They are

all connected with ﬁbreglass wiring and are 240V MAINS POWERED AT ALL TIMES,

providing the unit is plugged in and power switch is on.

The frost sensor is attached to the outlet of the heat exchanger at the top LH side of

the unit. It is recommended that power be left on to this unit even when the home is

vacant, (such as at holiday time) to ensure that the risk of damage from frozen pipes and

components is minimised.

CAUTION: Power must be applied at all times for this heater circuit to effectively

protect the unit in frosty conditions.

18. DRAIN The unit can be drained (if it is desired to switch off all power to the unit)by

removing the inlet water ﬁlter AND the outlet pressure relief valve on the hot water

outlet ﬁtting.

19. THERMAL FUSE. A thermal fuse is ﬁtted on the rear of the heat exchanger in a ﬁberglass

sleeve. This must only be replaced with a genuine part from Alliance.

Page 6 Alliance Appliances Pty Ltd

Rapid 26

Page 7Alliance Appliances Pty Ltd

Rapid 26

SERVICING THE UNIT

DISASSEMBLY OR REMOVAL OF COMPONENTS.

CAUTION: ENSURE ALL WATER, POWER AND GAS SUPPLIES ARE ISOLATED PRIOR TO

REMOVING FRONT COVER.

FRONT COVER. This is removed after removal of 2 screws at the top ﬂange and 2 at the

bottom ﬂange. The cover lifts straight off but care must be taken to not break or lose the thick

rubber gasket from around the ﬂue spigot at the top. If it comes off retain it and ensure that

it is reﬁtted upon re-assembly. A balance tube is ﬁtted between the pressure switch and the

front cover, care must be taken to replace this tube if disconnected.

CAUTION: The unit will NOT perform correctly without the front cover and balance pipe

in place.

MAIN CONTROL PCB. Remove all plugs, wires and ignition cable and remove 2 screws

from underneath the unit and the PCB, in its box ,will come out of the unit. All plugs are

polarised and are different so re-assembly is straightforward. The cold water sensor and

hot water sensors are combined into a 4 pin plug to avoid errors. The individual sensors

are connected to the 4 way plug with 2 polarised in line connectors with different polarity to

avoid mix ups.

TRANSFORMER. The main power transformer is secured by 2 screws through the

case. All low voltage connections are already disconnected but 240V connections must

be disconnected prior to removal/replacement. Reﬁt unit in reverse order ensuring all

connections are correctly made.

INJECTORS. If access to the gas injectors is required the gas manifold must be removed.

DO NOT REMOVE THE FRONT PLATED STEEL COVER AS THIS IS PART OF THE GAS

TRAIN. Note position of wiring to the 3 solenoids and disconnect. Undo the main brass nut

at the manifold end of the valve to burner pipe and ensure that the ﬂat washer is not lost.

Remove the gas manifold taking care to not damage the rubber sealing strips that seal the

manifold to the burner box. Re-assemble to burner box in reverse order. ENSURE THAT

IGNITION WIRE AND FLAME SENSOR WIRES ARE STILL CONNECTED. Re-connect

solenoid wires.

MAIN GAS VALVE. ENSURE GAS IS OFF at the isolating valve. Unplug 2 wires from the

blue modulating coil on the front of the gas valve. These are not polarised and can go on

either way. Unplug the main wiring connection from the gas valve body. Remove the Union

from the gas inlet isolating valve and remove the combination gas ﬁtting /gas pressure test

point. Remove 2 screws adjacent to the inlet gas spigot. Remove the valve to burner pipe

ensuring that the ﬂat rubber gasket is not lost. Remove Gas valve.

Reassemble in reverse order ensuring that all gaskets and sealing rings are in place and all

wiring connections are well made. Adjust gas valve settings as per instructions below.

IGNITION ELECTRODE AND FLAME SENSOR. These are located on a small plate at the

front of the combustion chamber. Remove the thick ignition wire from the electrode and from

the ignition coil on the PCB to prevent excessive strain on the wiring connection. Remove the

ﬂame sensor wire from the other electrode. Mark or otherwise ensure that the wires go back

onto the correct electrode when re-assembled. The ignition lead is on the left looking at the

unit. Remove the single screw at the centre of the plate and gently remove the plate, ceramic

felt gasket, the 2 ceramic electrode holders and the electrodes from the unit.

THE HOLDERS ARE KEYED AND CAN ONLY BE RE-FITTED ONE WAY. TAKE CARE TO

ASSEMBLE THE ELECTRODES CORRECTLY.

Re-assemble and screw ﬁrmly into place. Check gasket and do NOT over-tighten.

WATER INLET FITTING. This item should not need to be removed except where the inlet

water valve needs to be replaced. The ﬁtting is removed (after disconnecting the water

supply pipe,) by removing 2 screws through the ﬂange on the ﬁtting from underneath the

unit. The ﬁtting will then separate from the inlet valve inside the unit. DO NOT LOSE THE “O”

RING or damage the sensor.

WATER INLET VALVE. This incorporates the motorised valve and the water ﬂow sensing

turbine. After removal of the inlet water ﬁtting, undo 2 screws from underneath the unit case

and also 2 screws that retain the valve to heat exchanger cold water pipe. The valve should

then lift out. Take care to not lose the “O” Ring. The cold water sensor also ﬁts into the side

of this valve with a screw and small plate. It has a mall O ring to seal.

WATER OUTLET FITTING. This ﬁtting is removed by removing the 2 screws from under the

unit and undoing the brass nut that retains the hot water pipe from the heat exchanger. Do

not lose the washer. The pipe can then be pushed backwards out of the way and the ﬁtting

removed. Note that this ﬁtting also has a pocket for a frost protection resistor and also water

outlet sensor. A single screw and bracket hold both the sensor and the heater.

FAN, COMBUSTION. The fan motor and fan blade of this component can be removed by ﬁrst

removing the 3 screws that hold the motor to the fan scroll. This is the most convenient way

to replace the fan if faulty. The fan scroll itself can only be removed after the heat exchanger

and burner box assembly is removed.

HEAT EXCHANGER (AND BURNER BOX) ASSEMBLY. This is removed as a complete

assembly. Disconnect/ Unplug all connections and remove PCB by removing 2 screws

from under the outer case , Disconnect and remove valve to burner pipe, transformer, and

disconnect overtemperature sensor on top RH corner, disconnect anti frost connections from

mains terminal block, and water connections from Cold inlet water valve and Hot water outlet

ﬁtting. The frost protection heaters and thermostat (top LH side) will come out still clipped to

the pipework of the heat exchanger.

CAUTION: Mains power is connected to the antifreeze protection circuit at any time

power is connected to unit.

Remove 4 mounting screws from the brackets under the gas manifold and 4 screws from the

brackets either side of the ﬂue outlet at the top, and lift heat exchanger assembly free of the

case. The fan scroll and fan motor will came out as part of this assembly.

The heat exchanger is not to be serviced separate from the burner box. This component is

only available as a factory sealed and assembled unit for safety reasons.

Page 8 Alliance Appliances Pty Ltd

Rapid 26

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