Characteristics
Las características de un termo son las siguientes:[4].
Nominal capacity
It consists of a value in liters, normally in accordance with the commercial capacity in liters of the appliance. The thermoses have the following commercial capabilities.
Thermoses are grouped within these capacities conventionally accepted by manufacturers. Unlike vehicles, which each can have the power they consider, thermoses are grouped into these capacities that are oriented to a number of users and a specific function. Thus, 10 and 15 liter thermoses are not designed to work in toilets as a source of hot water for showers.
actual capacity
The real capacity is a data that expresses the exact volume of the thermos. The existence of parts inside the boiler usually means that the nominal and actual capacity do not coincide. Actual values may be lower or higher than nominal values. The standards generally indicate that the nominal and actual capacity must be similar, so that a consumer can compare characteristics between two thermoses from different manufacturers.
Rated power
The nominal power is the instantaneous power of the thermos in electrical terms. It is related to the power of the resistor(s) it houses. The nominal powers on the market vary between 750W and 6000W.
The water heaters must be installed in lines of 16, 25 or 32 amps depending on their nominal power, so it is not a plug and play appliance, that is, unpacking and plugging in like a washing machine can be, for example. The washing machines, in their case, have not reached the maximum power allowed by the electrical line on which they are connected, so until now they are appliances that can generally be unpacked and connected, except in cases of old installations without protection or with cables with a section less than 2.5mm2.
The thermoses must work on lines of 2.5mm2, 4mm2 or 6mm2 depending on the operating characteristics. This operation must be carried out by an authorized technician.
Strain
The electrical voltage for which it is designed. The water heaters are prepared to operate with a service voltage and frequency. In the case of Europe, the values are 230 Vac with 50Hz frequency.
High-capacity water heaters with high electrical energy consumption have the option for three-phase connection, which is 400V alternating voltage.
Current
The current of a water heater is the amperage consumed by the water heater in normal operating conditions. It is a value that is related to resistance. Thus, a thermos with a power of 2000W has an amperage of 8.69 amps, the result of dividing the power by the nominal voltage, which in this case we have taken as 230Vac.
Connection to the electrical network
The lower amperage water heaters incorporate a connection cable with a standard plug for the grounded region. In certain high-capacity models, the device may not come with a plug, but rather a connection strip or a cable to connect the network.
Network connection indicator
Some water heaters have an indicator that allows you to verify that the electrical network is connected and active.
Heating indicator
In some thermoses, there is a light indicator that allows you to see when the resistance is connected, therefore, knowing when the thermos is heating the water.
Thermometer
A thermometer is available in some thermos models, to check from the user's point of view the actual temperature of the water and compare it with the selected temperature.
There are mechanical and digital thermometers. Mechanics offer a rough measurement with a less precise reading. Digital ones are of two types. With LED reading, indicating the temperature level with LED diodes, or microprocessor-based thermometers, with a high precision reading offering the data on alphanumeric screens.
Some thermoses do not have a thermometer of any kind.
Regulator
In thermoses with external regulation, a mechanical wheel, a couple of buttons or a touch screen are the most common versions to control the water temperature. The regulation takes place between the minimum and maximum temperature value. This variation is known as dynamic range and has a critical determination when calculating the production capacity of mixed hot water at 40 °C. A water heater with regulation at 60 °C and a water heater with regulation at 90 °C will have very different hot water production capacities.
ΔT °C /Inlet temperature
Temperature increase. The thermos has values measured by the manufacturer, indicating how long it takes to make a thermal jump. The thermal jump is the rise between the network inlet temperature and a higher value, normally 45, 50 or 55 degrees above. The temperature of the network is a data that in Spain is available statistically in the Technical Building Code, which in its volume HE, collects the values of water temperature in different provinces and months of the year. The minimum values are 5 degrees Celsius in January and the maximum 21 °C in July and August. The value provided by the manufacturer is from an inlet temperature value to a water temperature value after the jump. This result is offered in minutes or hours and varies depending on the thermos between 15 minutes and 8 hours.
Losses at rest. Thermal dispersion
Thermoses with accumulation heating have a parameter that describes the losses at rest of the appliance. This is the energy that needs to be provided to the thermos in 24 hours, to maintain the temperature set by the user. It is generally offered in kWh/24h and is related to the time that the resistance must operate at rest so that the water does not lose heat energy.
Dispersion losses are due to the fact that the insulating wall of the thermos is theoretically considered an adiabatic surface, which means that it does not allow heat to pass through it. The reality is different and all surfaces, regardless of the material, even in a vacuum, allow heat to pass through them. To a greater or lesser extent.
Interpretation.
Dispersion losses of 1.5kWh/24h means that a 750W resistor must be connected for 2 hours of time in a 24-hour interval to maintain the temperature.
The manufacturer offers these values at a standard temperature of 65 °C. At a temperature of 90 °C this figure is higher, and can reach 1.5 times the offered value.
The thermal dispersion follows the following equation.
q=A*k*dT/dL.
Where.
A is the exchange area.
k is the thermal conductivity in W/mK of the material between the water and the outside air.
dT is the temperature increase between the outside of the thermos and the inside of the thermos in degrees Kelvin.
dL is the thickness of the insulation in meters.
The larger the heat exchange area or the thinner the insulation thickness, the greater the amount of losses documented in the thermoses.
Thermal dispersion is a figure that depends entirely on the boundary conditions, that is, on the temperature of the room in which the thermos is located. At a point where the thermos is colder than the room, the dispersion will be a negative value and it will behave like thermal storage, that is, absorbing heat from the room instead of providing heat.
Resistance connections.
An internal parameter that is not offered by the manufacturers is the way to restore the energy lost in the normal operation of the thermos.
These connections occur thousands of times during the life of the thermos, so it is important to minimize the minimum number of connections to avoid breakdowns, ensuring stability of the boiler temperature. Depending on the number of connections we make, we achieve a thermal stability of between ±0.6 °C and ±5 °C.
Number of boilers
One of the characteristics of a thermos is the number of boilers it contains. A conventional thermos has a boiler. Certain models of thermoses between 30 and 100 liters have two boilers, which are connected in series to improve the speed and intake of cold water.
Each boiler has its independently controlled resistance, to offer a higher overall value than a thermos with a single boiler.
The inlet boiler receives the cold water, while the outlet boiler is designed so that it is not affected by the cold water from the previous boiler.
Connection sockets for compatibility with solar thermal installations
A water heater can have connections to function as an interaccumulator support for a solar thermal installation. These installations, different from photovoltaics, capture the heat of the sun and convert it into hot water that circulates through a closed-circuit installation. This energy in the form of heat can be transferred to a thermos that serves as a storage tank, to allow the use of hot water even when the sun has gone down. The sockets for connection with solar thermal installations are usually on the side of the thermos. Water heaters with outlets to function as solar accumulators have a single boiler and an internal coil through which heat is exchanged. The use of these connections reduces the electricity bill. Thermoses with these connections have an internal coil that exchanges heat, a piece that increases the empty weight of the thermos. Thermoses do not normally include this coil, which is only available on selected models.
The thermos resistors are resistors with high heat dissipation. They are classified using the materials that make them up, and the Watts for which they have been designed, without mentioning the resistive value that characterizes them.
They can be made of copper, ceramic, enameled. In all cases it is a material through which a very high current circulates, raising the temperature of the air or water, depending on the element used as an interface.
They are usually submerged in water, which sometimes causes their calcification with subsequent breakdown.
Thermoses designed to work in hard water areas have a resistance separate from the water, which dry heats the boiler, in such a way that there is no contact with the water and limescale is not deposited around it, so the thermos works in better conditions.
The resistors can be shielded which prevents water from damaging them.
Some resistances are interchangeable with the thermos filled, having a jacket that separates the boiler from the resistance.
Facility
The water heaters have different types of possible installation. Vertical Only, Horizontal Only, both or floor installation. The geometry and construction of some thermoses prevent them from working vertically or horizontally. Even in horizontally positioned thermoses, they can determine that the outlets are on the right or left. Others can operate interchangeably in both positions, altering their efficiency and hot water production. Other thermoses, due to their high capacity, can only work installed on the ground.
Hot water production. V40
Domestic hot water is standardized at 40 °C and 60 °C. Manufacturers certify their products with a production of hot water at 40 °C that depends on the actual capacity, the thermostat, the room temperature, the water temperature, as well as the insulation of the boiler. The figures can vary around 150% of the nominal value of the thermos, although much higher values can be achieved when the boundary conditions are favorable for the thermos, that is, inlet water above 15 degrees, room temperature at more than 20 degrees and a thermostat with high dynamic range. Two thermoses with the same nominal capacity and thermostats with different dynamic ranges will have different V40 water production values.
Hydraulic connections
Depending on their capacity and flow rate, the water heaters are connected to the water network with DN15-1/2", DN20-3/4" or DN25-1" sockets, depending on the capacity of the water heater. The smaller capacity water heaters usually have DN20 - 1/2" sockets, the intermediate capacity water heaters connect through DN20 - 3/4" sockets. The large capacity water heaters connect through commas. DN25 - 1".
The inlets can be at the top of the thermos, at the bottom, on both or on the side. Depending on the location of the inlets, the water heater is designed to operate in special environments such as under the sink, whose inlets are above the water heater. To operate above the sink, the outlets are lower.
Weight
Weight is a relevant factor for some thermoses, if the walls are not strong enough. This information is offered in the catalogue, both empty and filled with water.
Measures
The measurements of a thermos are the geometric dimensions that define it, having mainly two variants. Diameter and length, for the thermoses of a boiler. Or height, width, depth, for thermoses with two boilers and thermoses of less than 25 liters.
The so-called Slim thermoses usually have capacities of up to 100 liters and allow installation in low-depth cabinets with diameters of around 350mm. The 300 and 500 liter thermoses usually have heights greater than 1.5 meters resting on the ground.
smart functions
Thermoses with smart functions make it possible to avoid unpleasant situations for the user and save on the overall operation of the thermos.
Antibacterial function. The thermos generates high temperature peaks to eliminate germs, bacteria and any type of life that comes from the water network.
Anti ice function. This function prevents the thermos from freezing in the event of untimely frosts.
Anti dry heating function. This function prevents the thermos from heating the heating element dry.
Calculation of time until the next shower is ready. Indicates in minutes/hours the time needed for the next shower to be ready.
Calculation of showers available until the end of hot water.
Smart water heaters calculate the optimal temperature ranges to heat the necessary water, saving energy.
Smart thermoses have a screen that reports on the operation of the entire device.
Night rate
Some water heaters implement energy/economic improvements when recharging at night, avoiding overloading the network at peak times.
Energy class
Thermoses, like all household appliances in Europe, are grouped into energy classes. The smallest models of 10 and 15 liters normally qualify as class A, those with intermediate liters qualify as class B, while those with larger liters qualify as class C. There are class D models.
The efficiency of electric hot water heaters by storage is lower than that of instantaneous electric heaters without accumulator, since they must keep the water hot for 24 hours, while instantaneous heaters heat it at the time of use, obtaining class A in most cases.
Load profile
The load profile is proposed by the manufacturer and confirmed by the certifying agency through flow tests, measuring the liters of hot water that the thermos can provide over the course of a day in an instrumented and calibrated installation.
It has several possible values, XXS, XS, S, M, L, XL, XXL.
T°C out of the box
The "out of the box" temperature is the so-called optimal operating temperature. Many manufacturers define optimal operating temperature as the maximum temperature of the appliance. Others offer an intermediate range as the optimal operating temperature.
ERP/AEC consumption
The ERP or AEC consumption (Annual Energy Consumption) is the energy used by the water heater under normal conditions, after normal use at the end of the year. This figure varies between 482kWh/year for those with lower capacity and 4,404 kWh/year for those with greater capacity. Actual consumption may or may not correspond to these estimates depending on the use of the water heater, temperature selection, charge/discharge cycles and boundary conditions. The presence of energy saving mechanisms, in the so-called Smart thermoses, the load profiles mean that several thermoses with different capacities obtain identical annual consumption figures, offering ERP data that does not vary between 50, 80 and 100 liter thermoses.
The dispersion losses of the thermos can reach values between 248kWh/year and 1314 kW/h/year at 65 °C, slightly higher as the operating temperature increases. This figure represents in some cases 30% of the annual consumption of the thermos.
Operating pressure
The nominal operating pressure for which the thermos is designed. It is expressed in bars. The thermoses incorporate a safety valve set at a pressure lower than the nominal pressure of the thermos, so that in the event of overpressure it opens the safety valve before structural damage occurs to the thermos.
Electrical protection
Electrical protection indicates what degree of protection the thermos offers against events such as water dripping on the thermos or splashing water.
The following protections are offered in the different models on the market.
IP24
Protection degree IP24 - the digit "2" indicates the level of protection against the penetration of solid external agents with a diameter greater than 12.5 mm, the digit "4" indicates the level of protection against splashes of water. Heating appliances with IP24 protection are suitable for heating bathrooms and other wet rooms as long as the operating instructions are followed.
IP25
Protection degree IP25 - the digit "2" indicates the level of protection against the penetration of solid external agents with a diameter greater than 12.5 mm, the digit "5" indicates the level of protection against pressurized water of 12.5 liters/minute.
In general, the IP2X grade corresponds to the mechanical security necessary to not be able to insert a finger or a pen, scissors or similar into the part that is under tension.
IPX1
Protected against dust in all its forms and against water poured onto the thermos.
IPX3
Protected against dust in all its degrees and against water mist spray.
IPX4
Protected against dust in all its degrees and against water jets of 10 liters/minute.
EAN code
The EAN code identifies the item in an online sales system. The existence of very diverse codes and references with letters and numbers could cause one thermos to be confused with another, so EAN codes eliminate the possible discrepancy by uniquely identifying the thermos.
Warranty
Thermoses generally have 3 different guarantees. A general one for the product, which is 2 years according to law. One for spare parts and/or electronic parts that varies depending on the manufacturers, and may not even exist beyond two basic years. A third warranty for the boiler, which some manufacturers extend annually following an anode inspection program, reaching up to 10 years.