The principle of the inertia radiator is as old as heating. As soon as the men lit a fire to heat themselves, they never stopped keep the heat, in order to put the drudgery of refueling into perspective. One can think that the men of prehistory heated, in the blaze, large stones which continued to dispense their heat, well after extinction fires. The Scandinavian peoples who, from the Middle Ages, filled their heaters with volcanic stones had no other goal. Today, to obtain heat, it is enough to press a button, or better, to delegate this task to PLC. We operate, however, still thermal inertia materials or fluids, to gain comfort or to save energy, heavy for the balance of budgets and for the ecology of the planet.
This twofold observation is at the origin of the unprecedented development of inertial electric radiators, dealt with in this dossier.
Operating mode of the inertia radiator.
Inertia radiators are made with materials dense, which have the particularity ofstore heat. We can compare them to batteries for electricity or tanks for fluids. Inertia radiators, recover, then store, unused calories, to restore them gradually, when the energy source is cut. This characteristic applies equally to radiators with dry inertia or fluid inertia, but also to water or steam central heating radiators, to solar or geothermal system radiators, to gas radiators or, moreover, to all other heaters.
Performance of inertia radiators
The performance assessment of an inertia radiator is based on 3 main criteria:
- the power in Watts;
- the material type of the heating core;
- the type and functions of the controller or programmer.
Heating elements materials
The material constituting the heating body depends on the calorie storage capacity. Electric heaters, which exploit the inertia of fluids and dry inertia, share common advantages and disadvantages, although each brings its own peculiarities.
- gentle heat and comfortable delivered in a homogeneous, without drying the air;
- heat emission long after extinction the heating element;
- savings energy during operation;
- limited maintenance periodic dusting;
- rapidity and ease of installation;
- low cost installation, without degradation of the site;
- Very large choice of powers, models and finishes.
- price high purchase;
- apparatus heavy (weight increases with storage efficiency);
- poorly suited to rooms with intermittent use (bathrooms, toilets, laundry rooms, etc.);
- strong marketing promotion at the veracity sometimes
Advantages and disadvantages of fluid inertia radiators
In these devices, the storage member is the heat transfer liquid circulating in the heating body, generally in steel or in aluminium fusion. This is the system approaching, at best, central heating.
Advantages of fluid inertia:
- climb in temperature more fast ;
- weight less Student.
Disadvantages of fluid inertia:
- lower durability;
- heat transfer liquid fat, aggressive and not very ecological ;
- possible noises fluid circulation;
- lower reliability.
Advantages and disadvantages of dry inertia radiators
In these heaters, the heat is retained in the mass of inert and dense materials composing the heating body, i.e., by Ascending storage efficiency:
- aluminium fusion ;
- cast steel;
- natural stones (lava, granite, etc.);
- natural or composite refractory materials (bricks, ceramic, soapstone).
Advantages of dry inertia:
- big thermal stability ;
- slow restitution and progressive stored calories;
- reliability and durability exceptional;
- no noise Operating ;
- no risk for the environment ;
- only electrical devices are subject to aging.
Disadvantages of dry energy:
- climb in temperature more slow ;
- heavy to very heavy devices.
Dry inertia radiators sometimes have a front panel radiant heat emitter, ensuring a rapid rise in the temperature of the room.
Regulation of inertial radiators
Modern inertia radiators have a system of electronic regulation, often supplemented by a programmateur. They sometimes incorporate presence devices to automatically reduce the ambient temperature during periods of non-occupancy. Centralized or embedded, programmers are the main vector ofenergy savings. They are able to regulate the room temperatures, in steps of 1/10 ° C, hours by hour, room by room, on weekly or monthly periods. Some, GSM compatible, can be controlled remotely, using a simple telephone.
Ambient temperature probes deportees of the radiator are more efficient.
The power of the inertial radiator
The power, expressed in Watts (nominal power), corresponds to the maximum heat delivered each hour by the radiator. It compensates for heat loss of the room. The most efficient devices modulate this power, to better exploit the orders sent by the regulator (or the thermostat).
The nominal power of domestic inertial electric heaters ranges between 500 W and 3000 W, in steps of 250 to 500 W, depending on the manufacturer.
Choosing an inertia radiator
The choice of a heater does not cannot be dissociated of the’environment in which it is installed. The prohibitive operating cost prohibits the development of electric heaters for buildings that are poorly insulated and very permeable to air, the construction of which is prior to the thermic regulation (RT) of 1989. The revolution of the “all electric”, intervenes only with the RT 2005, limiting the heat loss of new buildings, in a modest way, to the energy consumption of 190 kWh / (m².year). The gentle heat of inertial radiators, only finds its real interest from RT 2012, limiting thermal consumption to 50 kWh / (m².year). Note, however, that some homes renovated or built before this date have comparable or better thermal performance.
Evaluating the heat losses of the room to be heated is an essential prerequisite for rigorously determining the power of the inertial radiator. The valid use, however, of empirical modes, based on the local climate, the level of insulation and the volume to be heated.
Simply estimate the power of the radiator, using the empirical method:
1 – poorly insulated building (<2005):
- 60 W / m3 for harsh climates (continental and low mountain);
- 50 W / m3 for temperate climates (oceanic and semi-oceanic);
- 40 W / m3 for mild (Mediterranean) climates.
2 – moderately insulated buildings (2005 to 2011):
- 50 W / m3 for harsh climates;
- 40 W / m3 for temperate climates;
- 35 W / m3 for mild climates.
3 – well insulated buildings (≥ 2012)
- 40 W / m3 for harsh climates;
- 35 W / m3 for temperate climates;
- 30 W / m3 for mild climates.
Example of estimated power of the radiator necessary to heat a moderately insulated room, located in Nice, of 4.00 mx 3.00 m and 2.5 m ceiling = (4 x 3 x 2.5) = 30 m3 x 35 = 1050 W,
Either, power reduced to the higher commercial power: 1250 W.