Attack Gasification Boiler User Manual
Attack Gasification Boiler
Operation Manual
June 2012
Attack DP25, DP35, DP45, DP75, DP95 Profi Gasification Boilers
The look of the DP Profi gasification boiler has changed as shown above. However
the changes are almost totally to do with styling with the exception of a pressure
gauge that now comes with the boiler, just under the control panel; and a flue gas
The working parts of the boiler are identical to the previous version.
Therefore the pictures and diagrams in this manual are still relevant even when the
older styling is shown.
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Table of Contents
Quick Guide ................................................................................................................... 4
How Gasification Boilers Work ....................................................................................... 5
Main Boiler Parts.................................................................................................... 6
How the boiler’s heat output is controlled ............................................................... 7
System Design ............................................................................................................... 9
Recommended Design........................................................................................... 9
Boiler Temperature Maintenance Valve (Oventroppe Regumat) ...........................10
Insulated Flue System...........................................................................................11
Buffer tanks...........................................................................................................12
Thermal Protection of the Boiler ............................................................................13
Combustion Air .....................................................................................................13
Commissioning ..............................................................................................................14
Before firing the boiler for the first time ..................................................................14
Firing the boiler .....................................................................................................16
Boiler Operation ............................................................................................................18
Heating .................................................................................................................18
Starting up the boiler .............................................................................................20
Cleaning ...............................................................................................................24
Servicing and Maintenance ...........................................................................................28
Trouble shooting ...................................................................................................28
Common Issues ....................................................................................................29
Maintenance .........................................................................................................30
Technical Information ....................................................................................................33
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1 Quick Guide
Burn Sequence
Start Up Phase
Light fire
Press start button for ½ second
When the boiler reaches 65°C the pump will start
Whilst boiler is heating up hot water will be retained in boiler circuit
Burn Phase
After 1 hour the boiler will start testing the flue gas temperature to see if heat is still
being produced.
When the boiler temperature gets near to the boiler setpoint the fan will reduce
If the boiler setpoint is exceeded the fan will stop until the temperature falls.
When the boiler is up to temperature the hot water will be sent to the buffer tank.
Shut Down Phase
If the flue gas temperature falls below the set temperature the boiler displays the
word ‘Fuel’.
If the boiler is refuelled and comes back up to temperature within 30mins of ‘Fuel’
being displayed the boiler will go back to ‘Burn Phase’.
If after 30mins the fire has gone out the boiler stops the pump and fan.
on / off
Shows boiler flow temp, (default),
also boiler setpoint, flue gas
setpoint and flue gas temperature
Out of fuel
indicator light
Flue gas
setpoint knob
– set to
Flow Temperature
Stop button stops
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Start button starts fan – if pressed
more than 3 secs >> manual mode
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2 How Gasification Boilers Work
When wood is heated to 200ºC to 300ºC it releases pyrolysis gases that are combustible and
can be burned like other combustible gases, hence the term gasification. When wood is
heated for long enough, in an oxygen free environment, all the pyrolysis gases are driven off
and all that is left is charcoal.
To make this work in a boiler we partially combust the wood to produce the heat needed to
drive off the pyrolysis gases, any charcoal that is left is also burnt in the partial combustion,
also known as reduction zone, which ensures that all the energy in the wood is used to
produce heat.
This gas is composed approximately of
 20% hydrogen
 20% carbon monoxide
 0% to 10% methane
 50% to 60% Nitrogen, a non combustible gas from the air used for partial combustion
The partial combustion and gasification zone is known as the primary combustion chamber
and the secondary combustion chamber is where the pyrolysis gases are burnt.
To get this working correctly the primary air supply has to be enough but no more than
necessary for partial combustion.
Gasification is really a controlled way of burning wood which is cleaner and more efficient
than burning in conventional ways.
To get the boiler running it is loaded with kindling and wood, the fire is lit, often using a blow
torch, and it runs automatically until it runs out of fuel. It can be stoked with more fuel whilst
it is going.
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Main Boiler Parts
The Attack DP Gasification boiler
1. Boiler body
2. Upper panel
3. Feeding door – to primary combustion
4. Ash door
5. Exhaust induction fan
6. Flue
7. Fire concrete moulding - jet for secondary
8. Fire concrete moulding – secondary
combustion chamber
9. Boiler thermostat
10. Reset button
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Flue gas thermostat (standard boilers only)
Flow temperature thermostat
On/off Switch
Flow temperature display
Thermostatic valve to control air damper (20)
Boiler cooling coil
Upper and lower cleaning covers
Flow connection
Return connection
Air intake damper
Pull rod for chimney flap
Room thermostat (Profi version only)
Flue gas sensor
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How the boiler’s heat output is controlled
Boiler control of pump
Once lit, the boiler controls the amount of heat given out, limiting it when there is low demand
and the boiler is getting too hot. The boiler controls the pump directly to make sure the
boilers temperature is maintained and that it is able to transfer heat away from the boiler
when it is producing heat. The pump comes on at a boiler temperature of 65ºC and goes off
if it falls below 60ºC. (These temperatures can be changed if needed.)
Use of flue gas temperature sensor
When a buffer tank is used and has been fully heated the water returning from the buffer tank
can exceed 65°C causing the pump to continue running even when the fuel is burnt out. This
will cause heat to be transferred back to the boiler from the buffer tank, and will result in
unnecessary heat loss from the connecting pipes and boiler; and unnecessary electrical
power use to run the pump.
To prevent this happening a flue gas sensor allows the boilers control system to detect that
the fuel has burnt out when the flue gas temperature falls below a set level after the fuel is
burnt. The boiler will then switch off the fan and pump until it is re-fuelled and restarted.
When the boiler is burning fuel the heat output is controlled by the following methods:
Flow temperature thermostat
The flow temperature setpoint will affect the amount of heat generated by the boiler, the
higher the temperature the more heat will be generated.
When the boiler flow temperature gets up to the setpoint the boiler’s combustion fan will slow
down to reduce heat output and eventually stop if the temperature keeps rising, and not start
again until it has dropped by 5ºC. This is the boilers primary means of controlling the flow
temperature from the boiler.
However even without the fan going the draught of the chimney can still result in a heat
output of up to 70% full output, depending on chimney design.
Thermostatic valve controlling air damper
Even when the fan is not working there will still be a natural draught due to the flue so the
boiler will keep producing heat even when the fan is off. If this results in the boiler getting too
hot the main air damper flap at the back of the boiler will be closed using a thermostatic
valve, below. It is essential that this thermostatic valve is set to the correct position
during commissioning.
Boiler cooling thermostatic valve
A secondary device to stop over-heating is a coil within the boiler body that can be cooled
using cold water admitted by a valve when the boiler reaches 95ºC. This valve is a separate
part to the boiler and needs to be ordered and fitted separately.
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As this too uses a non-electrical thermostatic valve it stops the boiler being damaged by
boiling dry even if there is a power cut.
The cooling water supply used can be either mains water supply, or a header tank if the
customer has a water pump which will also stop working if there is a power cut.
A drain needs to be provided for the cooling water discharged if the thermostatic valve is
Thermostatic Air
valve for boiler
valve rotates lever
to move chain up
and down to
control air damper
valve controlling
air damper
The valve rotates a
lever that is attached
to the flap by a chain.
The temperature the
damper closes at
needs to be set at
commissioning. This
provides overheating
protection even if
there is no power.
View of the back of
the boiler.
air damper
Chain from
valve to air
air damper
Air regulator
All connections to the boiler should be made in copper, not plastic composite as
shown in these pictures.
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3 System Design
Recommended Design
The following additional parts are recommended for a good quality installation and for good
performance from the heating system.
Boiler temperature maintenance valve, Regumat.
Insulated flue – to reduce condensation and creosote build up
Thermostatic valve for over-heating protection, Watts STS 20 or Danfoss equivalent
Buffer tank to allow boiler optimum operating conditions and reduce hands-on
attention to the boiler.
Given that the boiler is controlled by electrical and mechanical thermostatic means, and has
non electrical safety cooling, the boiler can be part of a sealed system with a maximum
pressure operating of 3 bar.
Key parts of a log boiler system
Insulated flue
To drain
Mains cold
valve (95ºC)
Buffer Tank
Cooling coil
cap for
mixing valve
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Boiler Temperature Maintenance Valve (Oventroppe Regumat)
Solid fuel burners burn more efficiently and cleanly when the boiler return temperature is kept
at least to 65ºC. This also prevents condensation corrosion in the heat exchanger. A
primary means of achieving this is to have the circulation pump controlled from the boiler so
that it doesn’t run unless the boiler temperature is above 65ºC.
The Attack gasification boiler uses this method, however when there is a large amount of
return water from a buffer tank or heating system the boiler is continually cooled with cold
water every time the pump goes on. To prevent this a boiler temperature maintenance
thermostatic valve is used. The Oventroppe Regumat available as an extra item with the
This is a mixing valve that keeps the return water to the boiler up to the temperature set on
the thermostatic valve. The operation is shown below.
Once the flow temperature
exceeds the thermostatic
valve setting some of the
flow is mixed with the return
to maintain the return
temperature at the set value.
When the whole system is up
to temperature and the return
water is hot enough no water
is diverted back to the boiler.
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Whilst the boiler is warming
up from cold all of the flow
water is diverted directly
back to the boiler.
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Using a thermostatic valve also ensures that the flow entering the buffer tank is always at a
higher temperature even when the return water from the buffer tank is cold.
We recommend the Regumat is set at 6 to maintain the correct temperature.
The Oventroppe
Regumat boiler
maintenance pump
valve adjustment
The temperature
gauges are also
handles for turning the
isolating valves
incorporated in the
Regumat unit.
valve sensor
There is also a check,
non-return valve, in the
flow side.
The thermostatic valve
should be set at 6.
Insulated Flue System
The need to keep the boiler warm extends
to the flue system where a cold flue leads to
condensation which can combine with
hydrocarbons in the flue to make creosote.
An insulated flue keeps the gases warm as
they go up the flue which also increases the
natural draught.
CHNZ supply the Therminox modular
insulated flue system from Poujoulat. This
has 32mm of rock wool insulation between
the inner flue and outer case. (50mm for
larger flues.)
The 200mm system recommended for the
boilers is certified for use in NZ according to
AS/NZS 2918.
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Buffer tanks
Buffer tanks provide two main functions in a log boiler system:
1. One is to allow the boiler to keep burning at optimum efficiency independent of the
variations in the load, leading to less fuel used and cleaner burning.
2. The other is to allow the boiler to be loaded and fired only once a day and all the heat
stored in the buffer tank to be used throughout the remaining 24 hours.
Both these functions require the buffer tanks to be sized in relation to the boiler’s firebox
volume which determines the amount of heat produced in one burn.
In practice the boiler may be sized so that it will provide enough heat on most days in the
winter but will need to be stoked more than once on cold days.
If the users want to wake up to a warm house it is important that the buffer tank can store
enough heat from the previous evening to heat up the house in the morning at the time of
day when the heat load is at its highest.
The amount of heat required per day depends on the insulation level of the house, the solar
gain on that day and the occupants lifestyle, whether they like high temperatures and the
amount of time they spend at home.
In practice buffer tanks will usually still be warmer than ambient temperature and need
further capacity to allow for a full burn of logs without over heating. For example the owner
might want to fire up the boiler over night so there is sufficient heat in the morning.
Corrosion Protection
As the buffer tank forms part of the central heating system and is steel, it is a
requirement to correctly dose the system water with a suitable anti corrosive inhibitor
such as Fernox. This corrosion protection should be checked on an annual basis and
maintained accordingly.
We recommend using Fernox CH-3 which is available in 25 litre containers. This needs
to be dosed at 1% solution. (10 litres of CH-3 for every 1000 litres of system volume)
It is recommended that the buffer tank is installed with isolation valves so that it is not
necessary to drain the buffer tank with its corrosion inhibitor if work needs doing on other
parts of the system.
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Thermal Protection of the Boiler
The coiling coil is to
protect the boiler by
stopping it from
boiling dry.
coil outlet
This valve should
always be supplied
with water and the
outlet should go to a
Thermostatic valve
temperature probe
coil inlet
If the supply of water to the cooling circuit is unreliable an open vented system may be used.
Combustion Air
The Attack DP gasification boiler is an open fanned flue boiler which therefore requires
permanent ventilation to be supplied to the room it is situated in.
There is no New Zealand guidance for the area of permanent ventilation needed so we
recommend using the UK govt guidance on this subject.
It should be noted that the dimensions given are for the total open area, or ‘free area’, of a
vent which means a vent with a mesh or louvres needs to be bigger to take account of the
area blocked by the mesh or louvres.
Total area of
vent (mm2)
Minimum Dimension of
square vent (mm)
Minimum Diameter of
round vent (mm)
Even under optimum conditions it is inevitable that some smoke will escape from the boiler
when the boiler door is open. Therefore the boiler should be placed in an area where that
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will not be a problem and apart from providing ventilation for combustion air it is good
practice to provide ventilation to clear any smoke.
This can be achieved by having ventilation at both high and low levels in the room where the
boiler is situated.
Ideally the boiler should be installed in a dedicated plant room either inside or outside the
house, with adequate ventilation for combustion and smoke clearance provided.
4 Commissioning
Before firing the boiler for the first time
Fill and Purge System
Eliminate air from the system as much as possible – once the boiler gets going there will be
a lot of heat to move and it won’t stop in a hurry if you find you have airlocks!
It’s a good idea to run the pump directly if you can to circulate the water round the system
and help purge it of air.
It is recommended that the system should be pressurised to 1 bar when cold. When first run
it there is likely to be air in the system which will lead to pressure increases when the system
starts to heat up. Continue to purge the system so that no water is lost due to over pressure.
Set the Regumat to 6.
Test thermostatic valve
Test the operation of the boiler cooling thermostatic valve and drain by pressing the red
button on the valve. Make sure the water is drained properly when full flow is established.
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Adjusting Dampers
Ignore the instructions on the back of the boiler: loosen the lock screws
and push both dampers fully in, and lock in that position.
Primary air
air damper
Main air cutoff flap
controlled by
valve at the
The ceramic ash tray should be pushed
back so there is no gap at the back of
the boiler.
Check position of ceramic ash tray
Check that the ceramic ash tray in the lower combustion chamber is pushed firmly to the
back of the boiler so that there is no gap and that the 2 halves are touching in the middle.
These can dislodge during transport and allow flue gasses to exit the boiler without
exchanging heat into the water jacket. This can cause excessive flue gas temperature and
fan failure, see picture above.
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Firing the boiler
Firing the boiler for the first time is part of the commissioning procedure during which you will
need to check the functionality of key components and set the thermostatic valve.
Load the boiler as described in the following Operation of Boiler section. It is advisable to
only use a half load at first so that if the boiler needs to be stopped to make any changes it
won’t take too long to burn out.
During the first one or two firings some paint may be burned off from inside the hopper, this
is normal.
Things to check during first firing
1. Check that the fan is running
2. Check that the pump starts when the boiler gets to the 65ºC.
3. When the pump starts check that the warm flow water is diverted back to the boiler from
the Regumat.
4. Keep an eye on the system pressure gauge
Setting the Air Flap Thermostatic Regulator
This is very important as it prevents the boiler producing excessive heat in the event
of a power failure.
The principle of the air flap at the rear of the boiler is that it should be fully closed at 85 to
90ºC. This should be confirmed during commissioning by running the boiler up to 90ºC to
check the flap is closed at that temperature.
Adjustment of the thermostatic valve is achieved first by lengthening and shortening the
chain between the thermostatic valve lever and the air flap, and then by turning the top of the
valve so it is closed when the boiler reaches 90ºC or a lower value if chosen.
The thermostatic valve with lever in correct position is shown below
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The lever is more or less horizontal when the boiler is not in
Air flap in approximate boiler
off position. Chain below flap
not attached to anything.
It is important to check that the flap closes correctly and if necessary put a weight on the flap
is there is any doubt that it will always close.
Once the valve has been set to the correct position tie the chain to the eye bolt at the back of
the boiler so that the chain is always the correct length and remove the top of the valve to
prevent anyone from changing the position of the valve.
Setting the flue gas temperature cut off
To prevent the pump running on after the boiler has run out of fuel it is necessary to set a
flue gas temperature below which the control system will know the combustion is finished.
If this is set too high the boiler may go off before the fuel is burnt out. If it is set too low the
pump will continue running long after the boiler has burnt out.
A temperature that works for most people is 100°C. This is set by turning the small knob at
the lower left corner of the control panel with the house and thermometer symbol below it.
(This knob can also be used for setting a room temperature sensor, hence the symbols.)
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To adjust the temperature turn the knob and the display will instantly change and show the
setting. When adjustment is finished the display will revert back to flow temperature after a
short period.
Setting other Service Parameters
There are numerous other parameters controlling such things as the temperature the pump
comes on etc which can be accessed by holding down the OK button for 3 seconds.
Changing service parameters
Hold down OK button for 3 seconds
Browse parameters using +/- buttons
Press OK to select a parameter to change
Alter value with +/- buttons
Confirm by pressing OK
To exit use +/- to find END and then press OK
A full list of parameters and their function can be found in the Appendix to the manual that
comes with the boiler. This is an A5 document separate to the manual.
5 Boiler Operation
Many perceived problems with the boiler have turned out to be caused by damp fire wood.
To ensure the wood is below 20% a log should be split and the moisture content tested by
sticking the moisture meter prongs into the side of the split into the wood that was previously
in the middle of the log.
This boiler is only designed to burn untreated, dry, wood fuel, preferably split wood with low
moisture content, 12% to 20%. Other fuels, such as coal or treated wood, will damage the
boiler, lead to corrosion and are more polluting than wood.
Higher moisture content fuel will not gasify correctly reducing efficiency and heat output, and
producing creosote.
Small proportions of sawdust and wood chips are allowed but should not block the air spaces
between the fuel wood.
Ideally the fuel will be almost as long as the primary combustion chamber and split to
minimise, but not block air gaps, and provide a high surface area of fuel.
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Control Panel of DP Profi
Shows boiler flow temp, (default),
also boiler setpoint, flue gas
setpoint and flue gas temperature
on / off
Out of fuel
indicator light
Flue gas
setpoint knob
Flow Temperature
Stop button stops
Start button starts
Out of fuel indicator light flashes and pump
and fan stop during start up phase.
If the flue gas temperature doesn’t reach the
set temperature after the set start up time
this light flashes and the boiler stops.
Reducing the flue gas set temperature can
start the boiler again if it is burning fuel.
Out of fuel indicator light on solid shows flue
temperature is below the set level and that
boiler will stop after a further set time.
(Default is 30 mins)
The boiler will stop after a set time unless the
fire is stoked and flue gas temperature
Information shown on display
Boiler temp (default)
> Boiler setpoint
C 80
> Flue gas set point
> Actual flue gas temp
> End – press OK to exit menu
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To see the other temperatures, apart from boiler temperature, press OK and use  and 
buttons. To exit go to ‘End’ and press OK.
Starting up the boiler
If the orange light is on indicating ‘out of fuel’ switch the boiler off then on again using the
power switch. Then check that the fan is running.
It is important not to block the slot at the bottom
of the primary combustion chamber as this is
where the gas flows through to the second
combustion chamber below. Leave a gap of 20
to 40mm for air to flow through the slot at the
bottom of the primary combustion chamber.
The fire should be constructed with a fire
starter such as newspaper or firelighters, under
kindling and then the main wood fuel.
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Shown here with only the back half of the
chamber loaded. This is typical Kiwi firewood
which isn’t the best shape for loading the
maximum volume of wood and minimising air
Air gaps are needed for the gasification
process but large air gaps mean less fuel is
loaded at any one time.
Before lighting the fuel flap knob at the front of
the boiler should be pulled out which opens a
port at the back of the combustion chamber to
let the smoke go straight up the flue. Once the
fire is going this should be closed again.
If the fuel flap is left open most of the heat will
go up the chimney instead of to the heating
system. This can also damage the combustion
The upper cleaning hatch has been removed to
show what is inside the back of the boiler.
Normally this is secured closed.
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The fire can be lit with matches, or a blow torch
for faster ignition.
This fire is going well after a 5 second blast
from a blow torch into the middle of the fire.
When the fire starts up there will be
condensation in the flue which will evaporate
once the flue warms up. This happens much
quicker with an insulated flue. This
condensation may leak out of the flue initially if
there are any unsealed parts.
Remember to close the fuel flap once the fire is going
Once the fire is going well the kindling and
paper burns down leaving room to put more
fuel in.
Opening the door during burning
If you want to look in the primary combustion chamber, or put more fuel in, first open the fuel
flap and leave for 15 seconds before opening the door a crack and leave for another 10
seconds and finally open the door very slowly. Rushing this process will lead to considerable
amounts of smoke coming out of the door.
Remember to close the flap again afterwards by pushing in the knob.
The boiler should not be run for prolonged periods at output below 50% as this will increase
the build up of creosote and soot. This will happen if fuel is loaded when the system is
already hot and there is no load, the air flap will close and output will be reduced.
Day to day operation
A key question is how often to run the boiler, and how much fuel to put in? In reality this will
be different for each user depending on the heat loss of the house and the amount of DHW
used,(if heated by the boiler), time at home and room temperatures set on thermostats.
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More of any of those factors means more fuel needs to be burnt. One of the biggest factors,
heat loss, is out of the users control as it is largely dependent on the outside temperature,
and the insulation levels of the house which don’t often change.
The decision on whether to reload the boiler and produce more heat depends on:
 What is the likely heat load in the immediate future? Depends a lot on the weather
and if the heating is going to be on or not.
 How much heat is already stored in the buffer tank?
If the user thinks there is enough heat in the buffer tank to meet the load in the future then no
more heat is needed.
The user will have to get to know their system and how much heat they need to meet
immediate demand.
More buffer tank capacity allows for more heat to be stored and for a bigger margin of error.
The coldest part of the day is just before and after dawn and this is generally when central
heating systems use most heat. Therefore it is a good idea if you know it is going to be cold
in the morning to burn some fuel in the evening or last thing at night to charge up the buffer
It is not necessary to fill the boiler with wood if only a small load is anticipated, such as in the
summer if there is only a hot water load it may make more sense to burn half loads.
How do you know how much heat is in the buffer tanks?
If you are using a Regumat it is possible to see the temperature at the top of the buffer tank
which is the same as the flow temperature as the boiler and what is shown on the Regumat
temperature gauge.
The return temperature gauge on the Regumat will show the Regumat’s set temperature
which is usually around 60ºC. Once the bottom of the buffer tank exceeds this temperature
the return gauge will also increase and show the temperature of the water coming from the
bottom of the buffer tank to the boiler.
If you have temperature gauges on the buffer tanks they will give a better picture of how
much heat is in the tank.
Radiator systems and DHW heating usually require operating temperatures of 70ºC to 80ºC
and so we want to charge the tank to temperatures in excess of that, particularly in colder
Underfloor systems run at lower temperatures but it is still good to charge the tank to a high
temperature as that way it holds more heat and has more potential energy for the heating
It is standard practice to charge the tank up to 90ºC at the top in order to hold as much heat
as possible.
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The boiler needs to be cleaned regularly when in constant use as ash/soot build up on the
heat exchanger surfaces will decrease the efficiency of the boiler. Frequency of cleaning
depends on the amount of wood burnt, but generally during the heating season once a week
is good practice.
Ash isn’t necessarily a bad thing when it sits on the ceramic liners in the primary and
secondary combustion chambers as it acts as insulation which is also what the ceramics are
doing. However when it starts to take up space it needs to be removed, and when it coats
any metal surfaces it reduces the heat exchanger efficiency.
Tar on the walls of the primary combustion chamber, log hopper, is normal in gasification
The flue gas temperature when the boiler is in normal operation should be around
200°C to 250°C. If the temperature is higher it is an indication that the heat exchanger
needs cleaning. Or possibly the fuel flap has been left open, or the lower ceramic is
not pushed to the back of the boiler.
Ashes should be put in a fire
proof container outside the
Scraper and brush provided with
the boiler for cleaning.
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Remove ash from upper and lower ceramics
if excessive amounts have built up.
Upper chamber shown right with ash starting
to build up.
Although it doesn’t look like much a bucket
of ash was removed from this boiler after the
picture was taken
The cleaned out chamber with more volume
available for fuel.
The ash in these pictures is not a problem
on the ceramic parts but the ash stuck on
the boiler walls, left and right, decreases
heat transfer to the boiler from the flue
The ash on the ceramics can be removed
using a dust pan and brush.
Dispose of ash in a fire proof container
outside the building.
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Scrape the ashes off the side of the heat
exchanger and generally clear the channel
between the ceramic and the heat
exchanger wall.
Using the scraper pull the ashes to the front
and clear the channel.
Remove the cleaning hatch at the rear of the
boiler, below to show inside of heat
exchanger, right
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Use scraper to remove ash stuck to flat
surfaces of the heat exchanger.
Use brush to clean ash from the fins and
other places not reached by the scraper.
Don’t push the brush too hard into any
spaces it doesn’t want to go or it may get
Replace hatch when finished.
Most of the ash will have fallen down to the
bottom of the heat exchanger and this can
be removed by taking off the rear bottom
cleaning hatch.
Use a brush to clear out as much ash as
Replace hatch afterwards.
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6 Servicing and Maintenance
Trouble shooting
If boiler exceeds 110ºC a safety thermostat locks out the boiler. This is reset by turning the
boiler thermostat to the left as far as possible.
In cold weather the boiler needs to be fuelled more often and run at a high temperature to
ensure maximum temperature output. To get maximum heat out of the boiler, make sure fuel
is dry, fill the fuel chamber and turn up the thermostat to maximum.
Fan comes on when starting and
then goes off again.
Start button held down for 3 seconds or more puts the
fan in manual mode which means it runs for a set
period of time and then stops.
To avoid this problem only hold the start button down
for half a second when starting the boiler.
Boiler runs OK for an hour after
starting and then stops
This can be caused by the boiler testing the flue gas
temperature to see if it still going and if that
temperature is set high it will go off at the end of the
start up phase as it thinks it is off.
Adjust the small knob on the lower left of the control
panel so that ‘100’ is shown on the display.
House is not warming enough
Check that your central heating controller is calling for
heat, may show a flame symbol when it is. If not turn
up thermostat and/or TRVs on radiators, or mixing
valve on underfloor manifold.
Boiler not getting to temperature
on thermostat
Check that there is enough fuel.
Check that fuel isn’t wet
Check the air regulation flap isn’t closing at too low a
Check all air intakes are free from obstruction
Fan may need cleaning.
Check that the boiler doesn’t need cleaning. If it does
need cleaning the heat exchanger works less
efficiently and more heat goes up the chimney
instead of into the heating system.
Fan not turning on
If not turning first try resetting the boiler by turning the
thermostat dial round to the left as far as it will go.
Check the motor condenser is not faulty
Check the motor isn’t faulty
Fan is noisy
The fan accumulates dust and soot over time so it
needs to be cleaned to prevent excessive build up
that makes it less effective.
E1 displayed on boiler: A
temperature sensor is faulty.
Call service agent
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Common Issues
Most performance problems encountered with the boiler are caused by the following factors
Wet wood: Wood fuel must be less than 20% Moisture which can be checked with a
moisture meter. Wood that is too wet is the most common cause of poorly performing boilers.
Wet wood: Wood fuel must be less than 20% Moisture which can be checked with a
moisture meter. Wood that is too wet is the most common cause of poorly performing boilers.
Wet wood: Wood fuel must be less than 20% Moisture which can be checked with a
moisture meter. Wood that is too wet is the most common cause of poorly performing boilers.
Flue draught: The boiler must have 23 Pascal’s flue draft when burning at maximum power.
This is checked by inserting a hole in the vertical part of the flue and using a digital
manometer. The DP35 and 45 require a minimum of: 200mm inside diameter insulated flue
at a height of 5.8m. However, local conditions prevail and if more flue is required then it
needs to be added until 23 Pascal’s is obtained.
Ceramic Ash Tray: Check that the ceramic ash tray in the lower combustion chamber is
pushed firmly to the back of the boiler so that there is no gap and that the 2 halves are
touching in the middle. These can dislodge during transport and allow flue gasses to exit the
boiler without exchanging heat into the water jacket. This can cause excessive flue gas
temperature and fan failure.
Dampers: Despite what the decals and install manual indicate, loosen the lock screws and
move the primary and secondary air damper adjusters to the fully ‘IN’ position. In the fully ‘in’
position, the boiler has the correct amount of primary and secondary air.
Flue gas temperature: Check that the flue gases at the flue outlet are between 200-250
degrees Celsius at maximum power. If flue gasses are hotter than this it indicates a dirty heat
exchanger or some other problem.
Return temperature maintenance: Position 6 on the Oventrop regumat maintains a return
temperature of 65 degrees Celsius to the boiler before sending heat out to the buffer tank. A
return temperature to the boiler of above 60 degrees is required for optimum fuel
combustion. Each number on the thermohead adjusts the temperature by 5 degrees.
When opening the door to refuel, pull the lever out and wait for 15 seconds, then crack the
door handle open and leave for a further 10 seconds before opening the door slowly.
Opening the door quickly causes a lot of smoke to come out.
Often when these items have been checked and rectified, the boiler and flue are left in
their previous sooted up state. Please ensure that after rectification of faults, that the
boiler and flue are fully cleaned to enable optimum performance.
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Clean fan unit to remove all soot.
Six monthly
Check door seals and adjust door if necessary
Check that thermostatic thermal protection valve is working
Clean flue using a suitable brush or hire professional
chimney cleaner
Check the Regumat is working correctly
Change ceramic moulding
If existing is worn out or
Changing the packing cord of the door
Dismantle the old packing cord with a screwdriver and clean the rabbet where it was placed.
Take the new packing cord and put its beginning on the horizontal parts of the rabbet. With
your hand or light knock of the hammer press it into the rabbet on the circumference of the
Adjustment of hinges
After some time the packing cord in the door gets deformed. To repack the door, it is
necessary to change the position of the door. The position is changed by tightening the
hinges of the door. Feeding door and bottom door are joined to the body with two hinges
which are attached to the door with a long pin. If we want to change the adjustment of
hinges, it is necessary to remove the pin and screw the hinge by turning it. Fit the door on
and insert the pin into the hinge.
Changing the Nozzle
The nozzle is the ceramic piece with a slot between the primary and secondary combustion
chambers. This is sealed by a glass fibre packing cord.
To remove, dig the packing cord out with a screwdriver and pull out the nozzle. Clean out
any residues where the nozzle is seated.
Put the new nozzle in place with the shorter part at the back pushed up against the back of
the boiler. The gap between the sides of the nozzle and the boiler must be the same on
each side.
Lightly knock the packing cord into the gap until it is flush with the top of the nozzle.
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Changing the lower heat proof moulding
Remove the damaged moulding and clear and residues from the boiler surface.
Put the rear part, 1, into the lower chamber by putting it in sideways and then turning it.
Push it up against the steel plate at the rear. Insert one side piece and then the other by
turning it to fit through the door and then rotating to the correct position. (2 & 3)
Push the two side parts together and push them to the back to join up with the first piece of
the moulding.
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Wiring Diagram
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7 Technical Information
10 - 25
14 - 35
18 - 45
30 - 75
40 - 95
Fuel chamber capacity
Fuel chamber door size
Depth of fuel chamber (front to back)
Max. length of logs
Heat output
Recommended fuel
Dry wood of 15-17 MJ/kg calorific value, water content min
12%, max 20%, 80 – 150mm diameter
Chimney draught
Maximum operating pressure
Volume of water in boiler
Flue outlet diameter (OD)
Boiler height
Boiler width
Boiler depth
Minimum size of buffer tank
Thermal efficiency
Flue gas temperature at full power
Flue gas mass flowrate full power
Maximum noise level
Boiler power – not including pump
Electrical supply
230 VAC 50Hz
Operating temperature range
65 - 95
Range of room temperature (Profi)
10 - 27
Current rating of boiler relays
1.5A 230V AC
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