Power consumption
The maximum electrical power consumed by the boiler during operation. For non-electric models (see Energy source), this power is usually low, as it is required mainly for control circuits and it can be ignored. Regarding electric boilers, it is worth noting that the power consumption in them is most often somewhat higher than the useful one since part of the energy is inevitably dissipated and not used for heating. Accordingly, the ratio of useful and consumed power can be used to evaluate the efficiency of such a boiler.
Efficiency
The efficiency of the boiler.
For electric models (see "Energy source"), this parameter is calculated as the ratio of net power to consumed; in such models, indicators of 98 – 99% are not uncommon. For other boilers, the efficiency is the ratio of the amount of heat directly transferred to the water to the total heat amount released during combustion. In such devices, the efficiency is lower than in electric ones; for them, a parameter of more than 90% is considered good. An exception is gas condensing boilers (see the relevant paragraph), where the efficiency can even be higher than 100%. There is no violation of the laws of physics here. It is a kind of advertising trick: when calculating the efficiency, an inaccurate method is used that does not take into account the energy spent on the formation of water vapour. Nevertheless, formally everything is correct: the boiler gives out more thermal energy to the water than is released during the combustion of fuel since condensation energy is added to the combustion energy.
Max. gas consumption
Maximum gas consumption in the boiler with the corresponding energy source (see above). Achieved when the gas heater is operating at full capacity; with reduced power and consumption, respectively, will be lower.
Note that boilers of the same power may differ in gas consumption due to the difference in efficiency. While the more fuel-efficient models tend to cost more, the price difference pays off in gas savings.
Expansion vessel capacity
The capacity of the expansion tank supplied with the boiler.
The expansion tank is designed to drain excess water from the heating system when the total volume of liquid increases as a result of heating. It consists of two parts connected by a flexible membrane: in one, hermetically closed, there is air under pressure; in the other, excess water enters, compressing the membrane. In this way, a catastrophic increase in pressure in the heating circuit is avoided. The optimal volume of the expansion tank depends on several system parameters, primarily the volume and composition of the coolant; detailed recommendations for calculations can be found in special sources.
Gas supply
The diameter of the pipe for connecting the gas supply pipe in the boiler with the corresponding type of power supply (see "Energy source").
Diameters are indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size. The most common options are
1/2" and
3/4".
Central heating flow
The diameter of the pipe for connecting the pipe through which the heated water enters the heating system from the boiler.
Diameters are indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size. Among which models stand out for
3/4",
1",
1 1/4" and
1 1/2".
Central heating return
The diameter of the pipe for connecting the pipe through which the cooled water returns from the heating system to the boiler.
Diameters are indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size.
