Steel panel radiators: how to choose the type and size for central heating
Steel panel radiators hold a significant share of the heating equipment market in Russia, Kazakhstan, Mongolia and other CIS countries — and that is no accident. A compact profile, even heat distribution, a wide range of sizes and a relatively low cost make them the standard choice for residential and commercial projects with correctly matched pressure parameters. Nevertheless, mistakes in selecting the type and size occur regularly — with consequences ranging from under-heated rooms to emergency situations on site.
Below is a practical guide for wholesale buyers, installation companies and designers: how to read the markings, calculate thermal output and understand when a steel panel radiator is suitable and when another type of appliance is the better choice.
Type markings: what the numbers 11, 21, 22, 33 mean
The numeric code in the designation of a steel panel radiator describes its construction — the number of panels and convector finned grilles (convectors).
Type 11 — 1 panel and 1 convector, depth approximately 63 mm (lightweight, minimal depth); type 21 — 2 panels and 1 convector, approximately 100 mm (medium output, more compact than type 22); type 22 — 2 panels and 2 convectors, approximately 100–105 mm (optimal balance of output and dimensions); type 33 — 3 panels and 3 convectors, approximately 155 mm (maximum output, large depth). Depth varies between manufacturers; check the technical documentation.
Type 11
One panel, one convector grille. The thinnest construction — the appliance fits well under panoramic windows with minimal sill space or in projects where appearance matters more than heat output. Thermal output is the lowest in the whole range. Application: corridors, bathrooms, small rooms with low heat losses, as well as a supplementary circuit to underfloor heating.
Type 21
Two panels, one convector grille. An intermediate solution: the depth is smaller than type 22, the output is higher than type 11. It is in demand where the width of the niche or a limited distance from the wall is important and the output of type 11 is insufficient. It is encountered less often — many installation companies prefer to move straight to type 22.
Type 22 — the most common choice
Two panels, two convector grilles. This is the market's workhorse: at the same height and width as type 11, type 22 delivers roughly 1.7–2 times the thermal output. The cost-to-heat-output ratio is optimal for most residential and office rooms. Under standard system parameters it is precisely type 22 that serves as the starting point for the initial calculation — and if necessary one moves up to type 33.
Type 33
Three panels, three convector grilles. The maximum thermal output in the line. Used for rooms with high heat losses: corner apartments, rooms with large glazed areas, buildings with insufficiently insulated enclosing structures. It is important to consider: the increased depth (about 155 mm) requires a corresponding distance from the wall, and the significant internal water volume increases the system's thermal inertia. For heat-pump installations with a low-temperature circuit, type 33 is one of the preferred options (more on this below).
Selection by thermal output: ΔT 50 and ΔT 30
A key mistake when choosing is to use the nameplate output without accounting for the real parameters of the system.
ΔT (delta-T) is the difference between the average temperature of the heat carrier in the radiator and the air temperature in the room. The European standard EN 442 rates thermal output at ΔT = 50 K (average heat carrier temperature 75 °C, air temperature 20 °C — that is, system parameters 80/70/20). It is precisely this value that is stated in catalogues as the "nominal output".
Example: a type 22 radiator, height 500 mm, length 1000 mm, can have a nominal output of 1644 W at ΔT 50. That is quite sufficient for a room of approximately 18–20 m² with standard insulation.
Modern systems with wall-mounted gas condensing boilers and, especially, heat pumps operate at lower heat-carrier temperatures — often 45/35 °C or 50/40 °C. Here the ΔT is already about 17.5–25 K, and the real output of the radiator is significantly below the nameplate figure. The recalculation is done with the formula Q_actual = Q_nominal × (ΔT_actual / ΔT_nominal)^n, where the exponent n for steel panel radiators lies in the range 1.30–1.35.
Practical conclusion: when moving from ΔT 50 to ΔT 30, the output falls by roughly 45–50%. This means that for a low-temperature system you need either to choose a more powerful size (longer, type 33) or to increase the number of appliances. Manufacturers operating to EN 442 are obliged to provide output tables at various ΔT values — request them at the procurement stage.
Working pressure and compatibility with the heating system
This is perhaps the most critical parameter when choosing the type of radiator — and the one an honest manufacturer is obliged to speak about directly.
The standard working pressure of a steel panel radiator is 6–10 bar (check the product passport). This makes them the optimal choice for closed systems with a wall-mounted boiler in private houses and low-rise construction; autonomous systems in commercial premises with an independent heating unit; and systems with weather-compensated control, where a panel radiator is most effective paired with a thermostatic valve.
For centralized district heating systems (DH), typical of multi-apartment buildings in Russia and the CIS, the pressure in the supply pipeline often exceeds 6 bar — and during hydraulic testing it can reach 12–15 bar and more. Steel panel radiators are not recommended under such conditions. The correct choice for district heating is steel tubular or sectional (cast-iron, aluminium) radiators with a working pressure from 10 bar and a test pressure from 15 bar. If the building is connected directly to the city heating network (without a heat exchanger), check the parameters with the heat-supply organisation and choose appliances with an appropriate margin.
Advice to the designer: the presence in the system of an individual heating point (IHP) with a heat exchanger that reduces the secondary-circuit pressure to 4–6 bar makes it possible to correctly use steel panel radiators even in multi-apartment buildings connected to district heating.
Certification: what a reliable supplier should have
When selecting a steel panel radiator for a project or a wholesale purchase, request the following documents.
CE / EN 442. The CE marking on steel panel radiators means a declaration of conformity with the EU Construction Products Regulation (CPR). The key condition: behind the declaration there must be a Notified Body with an assigned EU number — this guarantees independent verification of the thermal tests. Without a Notified Body, a CE certificate under the CPR is legally incomplete. Quality export radiators from major Chinese manufacturers are certified by accredited European Notified Bodies; the declarations are available for verification.
GOST. For supplies to the Russian market the manufacturer must hold valid certification to GOST requirements, including GOST 31311-2022 ("Heating appliances. General technical conditions"). Request a valid certificate — not scans without an expiry date.
ISO 9001 / 14001. Certificates of the quality management system and the environmental management system are a standard requirement for an export-level manufacturer. They do not replace product certification, but they demonstrate that production processes are systematically controlled.
Checklist for the buyer: what to ask the supplier
Before confirming an order, obtain answers to the following questions.
Type and size range. Which types (11/21/22/33) and sizes (height × length) are part of the standard supply? Are non-standard sizes available to order?
Thermal characteristics. Provide output tables at ΔT 50 and ΔT 30 (or the conversion formula). Are there test reports from an independent laboratory?
Working and test pressure. What are the values according to the product passport? Is the radiator suitable for the planned system?
Certificates. Provide the current CE declaration (with the Notified Body number), the GOST certificate (with the validity date), ISO 9001/14001.
Steel and coating quality. What is the thickness of the steel sheet? What type of powder coating (coating type, polymerisation temperature, adhesion)? Is it possible to apply RAL colours?
Logistics and minimum order. What are the MOQ, the production lead times, the packing conditions for transport (container, pallet)?
Warranty obligations. What is the warranty period? What is the procedure for handling claims?
About the manufacturer
Jiuding Radiator (Tianjin Jiuding Yangguang HVAC Co., Ltd.) has manufactured steel panel radiators since 2002 at a 45,000 m² factory in Tianjin. Production capacity is 500,000 sets per year. The products are exported to more than 20 countries; the company holds about 40% of the steel panel radiator market in Mongolia. Jiuding radiators are certified to CE / EN 442 (10 CPR certificates, Notified Body No. 2693), hold ISO 9001 and ISO 14001 certification, and also comply with the requirements of the Russian market (GOST 31311-2022). The company is a regular participant in international exhibitions: Aquatherm Moscow 2025, Aquatherm Almaty 2025, Aquatherm Tashkent 2024, BARILGA Mongolia 2024.
For wholesale supply, technical specifications and samples: website www.jdradiator.com, e-mail kevin@jdradiator.com.
This material was prepared by the technical department of Jiuding Radiator and is for information and reference purposes. The final choice of the type and size of the appliance must be made by the designer on the basis of the building's heat-engineering calculation and the parameters of the specific heating system.