© EUROHEAT DISTRIBUTORS (H.B.S) LTD. July 2011
Instructions Part Number IN1231 Ed 1
8
1 System Requirements
The products of SHT Heiztechnik aus Salzburg GmbH are designed to work in combination with other components
of a heating system and to provide trouble free performance. The entire system should be designed to ensure
all components are compatible with each other and for the fulfilment of your heating requirements. For this
reason we recommend the system is designed by a qualified heating engineer who will be able to calculate
your heating load and be able to estimate reliably your expected fuel consumption.
Experience shows that a heating system is operated at rated load for a total of approximately 1500 hours
during a heating season. This is the total rated load and partial load hours added together. In this instance an
EVO 9 operating at 10kW for 1500 hrs. will produce 15000 kWh per year and burning pellets with a calorific
value of 4.8kWh/kg the annual consumption of pellets will be 15000 divided by 4.8 giving 3125kg.
1.1 Calculation of Heat Requirements
Choosing the right size of boiler to suit the specified heat requirements and the operating conditions is paramount
to ensuring satisfactory operation of the stove. For the stove to operate efficiently the boiler needs to be able
to produce heat at a minimum of 50% of its rated output for an operating time of between 1.5 to 2 hours or
higher at each burning cycle to ensure all tars and soot that may have been developed when the stove was
reaching its full operating temperature have been burned off.
The stove will need to dissipate aproximately 10% to 15% of its output to room and the remaining 85% to 90%
to be sent to the hydralic circuits. The heat generated in the boiler must be able to be discharged to the outside.
This is achieved to a lesser extent (approximately 10 to 15%) via the glass in the door and the outer shell of the
boiler. Most of the heat (85% to 90%) is transferred to the hot water circuit which is connected to the heating
system. Make sure that the system as a whole is also able to dissipate the amount of heat produced.
The heat requirements can only be calculated by taking the entire system into account. The system designer
is usually responsible for this task. Note that the boiler, connected to a buffer cylinder, must have a minimum
operating time of 1.5 to 2 hours running at least 50% of its rated output. This ensures the burner has time to
clear any tars and soot that may have been produced when the combustion chamber was below its normal
operating temperature and so maintain optimum efficiency.
1.2 Application Possibilities
As a main heating system: Operating as a central heating appliance in a low-energy requirement home.
As an additional heating system: Operating as an addition to other heat sources.
This distinction is important when designing the system especially when selecting components such as a buffer
cylinder or contemplating an additional thermal solar heating system.
Note: Domestic Water Heating in Summer Operation
The EVO AQUA is designed to give the majority of its heat output to its boiler and a minimum heating output
to the room of installation. At 9 kW the ratio is approximately 87% to boiler and 13% to room and at 15kW it
is 90% to boiler and 10% to room. However, as the output to room cannot be avoided entirely if it is to supply
domestic water heating during the summer months, undesirable room heating may occur. If this heating is
not required, we would recommend the addition of an alternative domestic water heating system such as an
electric immersion heater or a thermal solar heating system. Your heating engineer will be able to give you
suitable options.
