In those cases in which the demand for hot water sanitation and heating of our building or home is covered by mixed systems with centralized boilers (Boilers in series or in parallel), the operation of the and the percentage of the demand covered by each one of them. will depend on how the installation has been designed, in depending on whether these teams work in parallel simultaneously, or in series in a staggered manner.
How is the demand distributed in these mixed systems? centralized?
BOILERS IN PARALLEL:
When it comes to boilers running in parallel, the total demand is distributed simultaneously adopting a rate identical ignition to satisfy the load. In drawing 1 explains the process for responding to increased demand.
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BOILERS IN SERIES:
In this case as the load increases, the ignition rate of the first boiler is increased until the load demands a additional boiler. At this time, the second will start boiler, which becomes the modulating boiler. He Figure 2 explains the process for responding to increased demand.
In these systems the first boiler to come on functioning is called primary, while the following are secondary. This way it will always boot the one with the highest priority (primary) that will be the most efficient, before those with lower priority (secondary, less efficient).
We will carry out an example introducing two boilers of condensation in series, with a main or primary boiler of a power of 500 Kw, and a secondary of 400 Kw, both with a combustion efficiency of 98%. In this case the fraction of power contributed by each one is obtained dividing the power of each boiler by the total power that both generate.
1.-We define the first caldera, which will act as primary in the system, we mark mixed team of heating and ACS, and we define it as a boiler of natural gas condensation, we add.
2.-Obtaining the seasonal performance and the demand covered by the team . In the primary boiler defined, the power (500 Kw) and the efficiency of combustion (98%), its isolation and, if applicable, the volume of the accumulation tank in the lower zone of the display:
3.-Next we will obtain the real charge mean , which is the mean of the load fractions of the generator during its service time, click on the button question mark to the right of the actual mean load box, we place the fraction of total power provided by the boiler of 500 Kw, which will be 500/500+400= 0.56, and since this generator is the primary comes on load with a fraction of power 0, that is, it is the first boiler to start.
If we look at the window we have obtained a value of the seasonal or real average load factor of 0.24, as well as a fraction of energy contributed by this boiler of 0.95, therefore both is covering 95% of the demand for heating and ACS,. This value is used to then assign the percentage of demand covered by it.
4.-Then we accept and the value of the average real load as well as the average seasonal performance in ACS and heating of 94.5%, considering a boiler well isolated and maintained:
And in the window of the demand covered by the team we will introduce the previously obtained value of 95%.
We give the modify tab again to save us the changes, and thus we define the characteristics of the main boiler.
1.-We define the second caldera, which will act as secondary in the system, of the two that will meet our demand, we will indicate a new mixed team of heating and ACS, with type of generator by boiler of natural gas condensation and we add it.
2.-Obtaining the seasonal performance and the demand covered by the team . In the box "Seasonal average yield", the power is entered (400 Kw) and the combustion efficiency (98%), the insulation of the same and, if applicable, the volume of the accumulation deposit in the bottom of the screen:
3.-Next we will obtain the real load media , click on the question button on the real average load box, and we indicate the fraction of total power provided by this second boiler of 400 Kw, which will be 400/500+400= 0.44, and since this generator is the secondary, enters load with a fraction of power 0.56, that is, it starts when the installation is demanding more 56% of its total thermal power.
In this window we have obtained a load factor value seasonal or true mean of 0.44, as well as a fraction of energy contributed by this boiler of 5%, therefore it is covering the remaining 5% of the demand for heating and DHW.
4.-Then we accept and the value of the average real load as well as the average seasonal performance in ACS and heating of 96.2%, considering that the boiler is is well insulated and maintained:
And in the window of the demand covered by the team We will introduce the previously obtained value of 5%, being The demand is covered by this second boiler.
We give the modify tab again to save us the changes and in this way we have already defined our Mixed system with two centralized boilers in series for DHW and heating.
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Article prepared by José Luis Morote Salmeron (Technical Architect – Energy Manager – Profile from Google plus) Access to your website HERE, in collaboration with Follow us on Google+
