Viljandi Metall PELLE STI20TPV Guide

CENTRAL HEATING BOILER PELLE
Installation and user instructions

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Technical specification
Thermal rated power 20 kW
Operating pressure up to 2.5 bar
Test pressure 3.25 bar
Max. temperature of boiler water up to 95°C
Power efficiency over 0.9
Water space 0.165 m3
Weight (empty) 145 kg
Fuel light fuel oil, gas, wood pellets
Boiler external dimensions 1500 x 635 x 600 mm
Assembly set: a boiler including control and protection
devices, gauges, an ash pan, installation and
user instructions
Chimney draft (in case of pellet burner) from 4 till 8 Pa
Cross-section of the chimney 120 x 240 mm or Ø 200 mm
Installation instruction
The boiler must be installed in a boiler room with a floor made of non-combustible materials
meeting the requirements of EPN 10.8 set forth for boiler houses and boiler rooms. The
boiler may be lifted only supported from the bottom frame.
Connect the exit/return water pipe located on the boiler with a heating system by means of a
quaternary mixer or a special collector.
Connect the fire tube with the chimney with a smoke flue as short as possible, with an angle
upwards.
The boiler is suitable to be used with closed and open fuel systems and for heating water
with appropriate distribution/regulation system supplying floor heating and city water.
A burner to be selected according to recommendations of the specialised sales company will
be installed on the furnace door [1] (see the scheme) following the installation instructions of
the burner. The standard opening in the furnace door is meant for the pellet burner. For
installing an oil burner, use an intermediate plate with a special opening [2].
When installing the boiler “Pressurised equipment safety regulations” and decrees and
instructions related to these have to be followed.
Problems occurring during assembly of the boiler, equipment and devices have to be solved
in cooperation with a heat engineering specialist.

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After installation we recommend to conduct a boiler test to determine suitable operation
regimes and thermal efficiency.
User instruction
The boiler is designed to burn wood pellets or light fuel oil. The boiler operates without
permanent monitoring by the operator.
The boiler is equipped with an automatic pellet or fuel oil burner used in accordance with the
burner user instructions.
In order to ensure maximum efficiency, the boiler is designed to be used with turbolators [4].
Selection of turbolators is made based on the chimney structure and draft (see
recommendations).
Water operation pressure must not exceed 2.5 bars.
Control and protection devices, gauges
Switch [5] – switching it on energises power equipment of the boiler.
Operation thermostat [6] – turning the handle from 0 position to the position of the boiler
water temperature activates the burner. From the point of view of efficiency we recommend
using boiler water temperature 90º C.
The safety switch in the boiler connection circle has to be 6A for oil and gas burners and
10A for pellet burners.
The red indicator lamp [7] switches on when the boiler operation is stopped and the
maximum temperature thermostat is activated.
Furnace door limit switch [8] – stops operation of the burner when the furnace door is
opened.
Maximum temperature thermostat [9] – stops operation of the burner, when the boiler
water temperature achieves the value of 95°C. Operation of the burner can be continued
when the water temperature has lowered and the thermostat has been manually reset to the
operation position.
Safety valve [10] – opens, when the water pressure in the boiler exceeds 2.5 bars. To
ensure operational order of the safety valve open it manually from the handle.
Manometer [11] – shows the pressure of boiler water.
Boiler water thermometer [12] shows water temperature in the boiler.
Flue gas thermometer [13] shows flue-gas temperature exiting from the boiler.

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Supply plug [14] is meant for connecting the power system of the boiler with power network.
It has to be connected in a socket with three-pin earthing and with a fixed neutral.
Burner connection plug [15] is assembled with the burner.
Maintenance of the boiler equipped with a pellet burner
In case of burning pellets, move a rapper lever [16] to clean the fire tube and turbolators.
This may be done when the boiler is operating. Turbolators have to be cleaned approx. once
per month. To ensure normal operation of the boiler clean the grate and furnace of the
burner and empty the ash pan [3] approx. after burning of 500 kg of pellets. For this
procedure you have to stop the boiler.
We recommend carrying out more thorough maintenance of the boiler once per month. The
boiler has to be stopped for this. To clean heating elements open the upper hatch [17],
shake off loose ash deposited on the turbolators, remove axes of the rapper, pull out the
turbolators and clean with a brush. First push soot and ash deposited in the flue-gas
chamber down through the pipes into the furnace and thereafter remove ash deposited in the
fire tubes with a special brush. In connection with cleaning the furnace, clean the grate of the
burner and empty the ash pan.
When burning pellets, the boiler has also to be cleaned in case the temperature has
exceeded over 230ºC or the draft has weakened remarkably.
In order to ensure normal operation of the burner follow the recommendations and
instructions of the manufacturer.
In the end of the winter heating season the boiler has to be thoroughly cleaned to avoid
sintering of soot on the heating elements.
When burning light oil, clean the boiler once per year after the end of the heating season.
The possessor of the boiler is responsible for safe operation of the boiler, and is obliged to:
•ensure that the boiler room is clean and in order;
•ensure that the connection joint of the boiler and the chimney meets the requirements;
•ensure that the chimney is in order.
It is absolutely forbidden to:
•heat the boiler with no water inside;
•to fill a hot boiler with water, which has been left dry;
•to store combustible materials in the boiler room

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Electrical connections
The device can be connected to the power outlet only by a qualified electrician. Use a flexible
cable with a cross-section of 3/5 x 1.5mm2. The device is designed to be connected to 230 V
power outlet. Use a fuse with a minimum value of 10 A.
Colours of cables:
Neutral conductor – blue
Phase conductor – black
Earthing – yellow / green
Principle circuit diagram of the boiler:
F
ront pane
l
o
f
t
h
e
b
o
il
e
r
Wall socket
Main switch
Switch of the furnace door
Maximum
temperature
thermostat
Regulating
thermostat
Plug

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Recommendations for the choice of a turbolator
As turbolators in “Malle” and “Pelle” convection tubes are the main sources of aerodynamic
resistance, it is reasonable to choose these based on consumer’s chimney parameters.
A “Pelle” boiler with a pellet burner and a turbolator no. requires draft of the chimney 10 Pa
(1 mmVs) in output value of 20 kW and 20 Pa in output value of 30 kW. In case of bigger
draft more powerful turbolators are recommended. As draft of the chimney depends on very
many factors, it is always recommended to measure it and to choose proper turbolators
according to the measuring result.
The following table is necessary for making the preliminary choice of the turbolators and is of
help to the boiler installer. Turbochargers are manufactured in four different aerodynamic
resistance values. The bigger the number of the turbolator, the bigger is the resistance value.
A turbolator with bigger resistance value ensures bigger efficiency of the boiler.
USED FUEL
OIL PELLETS
CHIMNEY
TURBOLATOR NO.
Half brick flue
14 x 14 cm 2 1
1-storey
building Full brick flue
14 x 27 cm 3 2
Half brick flue
14 x 14 cm 3 1
2-storey
building Full brick flue
14 x 27 cm 4 2
In case draft of the boiler provided with a turbolator based on this table is not sufficient, use a
turbolator with a smaller number.

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1. Furnace door
2. Burner opening door
3. Ash pan
4. Turbolator
5. Switch
6. Operation thermostat
7 Indicator lamp
8. Furnace door switch
9. Maximum temperature thermostat
10. Safety valve
11. Manometer
12. Boiler water thermostat
13. Flue gas thermometer
14. Supply plug
15. Burner connection plug
16. Turbolator rapper lever
17. Upper hatch
* A burner with a connection plug is not included in the
boiler set. The producer has the right to change the
here presented scheme.
A scheme of the central-heating boiler STI20TPV “Pelle”
Fire
Burner
Smoke flue
City water
heater
Furnace
Emptying
Electric
heater
element
opening
Heating
water in Cold water
Heating
water out Hot city
water