The dead zone is a section of the heating element that does not give off heat. It is located directly at the heater head. Its task is to protect the seals and the head from overheating.

If the radiator remains partially cold despite the heater working, and also makes unusual noises like hissing, gurgling, or water sloshing, it is almost certain that it is air-locked. Venting will be necessary to avoid damaging the heater, ensure optimal and correct radiator performance, and maintain the required room temperature.

If an electric heater is installed in the radiator and a hissing sound is heard during its operation, it can be assumed that the cause is an oversized electric heater (installed power is too high) or the tubes forming the heating element are touching each other or the radiator, leaving no space for the heating medium (water) to circulate. Check how to choose a heater for a radiator?

The IP (Ingress Protection) rating determines the tightness of an electrical device's casing against the ingress of foreign objects (dust) and water.

This is the amount of heat given off to the room by the radiator, expressed in Watts (W). It determines how much thermal energy the radiator can provide at specific parameters to maintain the desired room temperature.

Radiator power is often given for 75/65/20°C parameters, but many manufacturers also provide them for other heating water temperatures, e.g., 70/55°C and 55/45°C. These parameters are favorable for condensing boiler and heat pump operation.

For example, a 2-panel radiator, type 22 with a height of 500 mm and length of 1000 mm, achieves a heating power of 1497 W.

The same radiator in the same room, at lower inlet temperatures, achieves lower power.

Radiator power also depends on the ambient temperature – the required temperature in the heated room. The lower the room temperature, the more heat the radiator can give off. Or conversely, the lower the temperature needed in a room, the smaller the radiator that can be used.

These are the standard parameters for which the thermal power of radiators is given:
75°C – inlet water temperature,
65°C – return water temperature,
20°C – indoor air temperature.

How much time is needed to heat a 120-liter water tank to 70°C using a 2kW heater?

This can be done using the formula:
t = [m · Cw · (t2 - t1)] : P where:
Data:
m = 120l = 120kg – mass of water in the tank [kg]
Cw = 4189.9 [J/kg*°C] – specific heat of water
delta T = t2 - t1
t2 = 70°C – temperature to which the water is to be heated [°C],
t1 = 10°C – initial water temperature in the tank [°C],
P = 2kW = 2000W = 2000J/s - heater power

We are looking for:
t = water heating time [s],

Solution
t = [m · Cw · (t2 - t1)] : P =
t = [120kg * 4189.9 [J/kg*°C] * 60°C] : 2000J/s =
(after simplifying units)
t = 120 * 4189.9 * 60 * 1s : 2000 =
t = 15083s = 251min = 4h 11min

Help:

specific heat - the heat required to increase the temperature of a unit mass of a substance by one unit,
the initial water temperature in the tank (t1) is 10°C (it is assumed that the cold water flowing into the tank has this temperature)

Heaters must not be used in stainless steel tanks because electrolytic (galvanic) corrosion occurs, destroying the heater's coating (the heater corrodes and burns out). Therefore, in a relatively short time (depending on the chemical composition of the water, usually 2 to 6 months), pitting appears on the heating element, causing it to leak and rendering it unusable.

Using a heating element made entirely of the same material as the tank also does not solve the corrosion problem; it only extends the time before pitting appears by a few months.

Pitting on the heating element reduces wall thickness. This manifests as a high leakage current – in other words, the residual current circuit breaker trips, or in its absence – the heating element cracks.

In stainless steel tanks, a magnesium anode should be installed and periodically replaced (every 12 - 18 months). If there is a magnesium anode in the tank and it is periodically checked, a heater can be installed.

A magnesium anode installed in stainless steel boilers is designed to protect the entire system from galvanic corrosion. In an electrolyte environment, different materials in contact form galvanic cells, and the less noble metal (anode) corrodes. The material forming the cathode in such a pair does not corrode or corrodes very slowly. When combining stainless steel with copper, stainless steel is the cathode, which can cause the copper heater to corrode.

This is prevented by introducing a more anodic material, like magnesium, which forms an electrochemical pair with stainless steel and corrodes faster than copper, thus protecting the copper heater. The condition of the magnesium anode should therefore be checked and replaced periodically. Installation in tanks with a small amount of water (e.g., ladder-style bathroom radiators) is permitted.