How to Choose the Right Karma Heater for Your Space

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How to Choose the Right Karma Gas Convector Heater for Your Space – A Complete Buying Guide

Karma gas convector heaters ("gamatky") are a proven solution for local heating and ventilation that have earned loyal users across Slovakia and neighbouring countries over decades of use. Still, a large share of customers come to us with the same question: "Which gas convector heater should I choose?" There's no single answer, because it depends on several factors – the room's floor area and ceiling height, the building's installation setup, flue gas exhaust requirements, the type of control, and, last but not least, your budget. This article will walk you through all the key decisions, show real-world examples, and help you avoid the most common mistakes when choosing.

What Is a Gas Convector Heater and Why Choose Karma?

A gas convector heater is a gas convector with a sealed combustion chamber that draws combustion air from outdoors and exhausts flue gases directly outside through the wall or facade of the building – not through a traditional chimney flue. This solution is called a "balanced flue" or "turbo" system, and it offers several key advantages over older appliances with vertical chimneys: it doesn't require chimney modifications, doesn't pollute the room's air, and is safe even in well-sealed new buildings.

The Karma brand has a long tradition, its products meet European standards for category C gas appliances (sealed combustion chamber), and on the Slovak market it benefits from a wide service network, availability of spare parts, and a good supply of accessories – including flue extensions for various wall thicknesses.

Basic Types of Karma Gas Convector Heaters – What Are BETA 2C and BETA 2E?

In the Karma range, you'll mainly encounter two main lines: BETA 2C and BETA 2E. The letter after the number indicates the type of control and regulation:

BETA 2C – mechanical (classic) control with a thermostat and gas valve block. The thermostat is either built-in (integrated into the unit's body) or external. Output is set manually. Typical customer: cottage, holiday home, occasionally heated space.
BETA 2E – electronic control with a modulating burner, digital thermostat, and generally higher energy efficiency. More suitable for permanently occupied spaces, where you'll appreciate more precise temperature control and the option to program a weekly schedule.

For a detailed comparison of both lines, we recommend the article Karma BETA 2C vs. BETA 2E – the difference between the types and when to choose which in the Knowledge Center.

In this category, you'll find for example Karma BETA 2C 01 and Karma BETA 2C 02 – these models differ mainly in nominal output and the dimensions of the unit body, which directly relates to the heated area.

Output – The Most Important Selection Parameter

If we had to pick a single parameter that determines whether a gas convector heater will work properly, it would be the heat output in kilowatts (kW). A unit that's too weak won't fully heat the room during hard frosts; one that's too powerful will run briefly, switch off, and switch back on (so-called "cycling"), which shortens its lifespan and increases gas consumption.

Rough calculation: for well-insulated spaces, count on 70–90 W/m²; for older low-energy buildings with weaker insulation, 100–130 W/m²; and for renovated original buildings without insulation, up to 140–160 W/m². Take ceiling height into account with a correction factor: for ceilings of 3 m or more, add 10–15 % to the calculated output.

Real-world example: a customer had a 22 m² kitchen in a new building (well-insulated walls, triple glazing), with a 2.6 m ceiling. Calculation: 22 × 80 W = 1,760 W ≈ 1.8 kW. Since most gas convector heaters start at 2–2.5 kW, they chose a model with 2 kW nominal output – and it heats the space without any problems even at –15 °C outside.

You'll find a more detailed calculation procedure, including correction factors for room orientation, glazing, and construction type, in the article What Output Do I Need for My Gas Convector Heater – Calculation by Room Area.

Type of Control – Mechanical or Electronic?

After output, the second most important decision factor is the type of control. Karma gas convector heaters come in two basic control configurations, which have a major impact on operating comfort, energy efficiency, and appliance price.

In practice, a simple rule of thumb applies: if you're dealing with a holiday home that you only heat on weekends and don't need precise temperature settings, the mechanical BETA 2C type will suffice. If you live permanently in an apartment building or house and value comfort and low gas bills, electronic regulation will pay for itself in savings relatively quickly – with continuous operation, we're talking about 10–20 % gas savings compared to classic on/off control.

A detailed comparison is provided in the article Mechanical vs. Electronic Control of the Karma Gas Convector Heater – Which Is Better.

Where in the Room Should the Gas Convector Heater Be Placed?

The placement of the gas convector heater significantly affects heat distribution in the room as well as the building requirements for installation. The unit must be placed against an exterior wall (since it needs a direct passage through the wall for the coaxial flue outlet and air intake), ideally below a window.

The reason for placement under a window is purely physical: the window is the coldest point of the perimeter wall, creating a so-called cold draft (downdraft), which flows downward along the glass and spreads across the floor into the room. A gas convector heater placed under the window captures this cold draft, warms the air, and directs it horizontally (or via an angled outlet) into the space – evenly heating the entire volume of the room.

Under the window – ideal position, even heat distribution.
In a corner against an exterior wall – acceptable, but there's a risk of less even heating and possible condensation near the window.
In the middle of an exterior wall without a window – technically possible, but thermal comfort is slightly lower.
Against an interior wall – not possible without a long flue extension, which is complicated and usually technically unsuitable.

Coaxial Flue Outlet and Flue Extension – A Key Installation Element

Karma gas convector heaters use a coaxial (concentric) outlet, where the inner pipe carries flue gases out and the outer sleeve brings in fresh air from outside. This system is sealed off from the room – so the units don't need air supply from the heated space.

The diameter of the coaxial outlet depends on the specific model of the gas convector heater – most Karma BETA 2C models use a diameter of 60 mm (outer sleeve) or 80 mm. The standard length of the wall-through kit is designed for a wall thickness of around 25–30 cm. If you have a thicker wall (masonry + insulation + facade can be 50–60 cm), you'll need a flue extension.

The range includes several extension variants:

Flue Extension Gamat 471 – suitable for a specific diameter and wall length, consult with an installer before ordering
Flue Extension Gamat 473 – alternative length/diameter, suitable for other types of wall passages
Flue Extension VYD60 – specifically for 60 mm diameter units, popular for renovations of older buildings

You'll find a detailed guide to choosing the right extension – including compatibility tables with unit types and wall thicknesses – in the article Gamat Flue Extension – What Diameter and Length Are Right for Your Type.

Wall Thickness and Outlet Direction – What to Measure Before Buying

Before ordering any Karma gas convector heater, measure the following:

Wall thickness at the planned passage location – you'll be drilling a hole directly through the entire perimeter wall, including any insulation and exterior plaster.
Distance from the floor to the center of the opening – Karma gas convector heaters are typically installed so the center of the outlet is at a height of 20–35 cm above the floor. An outlet installed too low can be a problem with snow drifts in winter.
Wall material – brick, concrete, aerated concrete, or timber-frame construction each have different drilling requirements. A core drill with a diameter of 65 mm (for a 60 mm outlet) or 85 mm (for an 80 mm outlet) requires special core bits; most customers have this done by a professional.
Outlet direction – the standard outlet is rearward (horizontally through the wall). Some models also allow a side outlet, which is handy for corner installations.

Gas Type – Natural Gas or LPG?

Karma gas convector heaters are supplied as standard for natural gas (category G20, 20 mbar pressure). For LPG (G31, 37 mbar pressure) or propane from a tank (G31), conversion kits are available – so-called nozzles and regulation accessories. Conversion may only be carried out by a certified technician; DIY conversion violates standards and endangers safety.

When purchasing, always state what type of gas you have available. A typical real-world situation: a customer in the countryside has a propane tank (a large plastic tank by the house) – in this case, they must either order a special propane version of the unit, or receive a natural gas unit with a conversion kit that the technician installs during setup.

Gas Pressure and the Distribution System – What to Check Before Installation

One of the causes of a gas convector heater malfunctioning after installation is inadequate gas pressure or undersized piping. Karma gas convector heaters require a pressure of 20 mbar for natural gas – if your supply pressure is lower (for example, due to old regulators or an unsuitable pipe diameter), the unit won't reach its nominal output and the thermostat will keep "hunting".

The technician should always measure static and dynamic gas pressure before starting the unit. If you have multiple gas appliances at home (boiler, stove, water heater) and are planning to add a gas convector heater, have the supply capacity calculated – the pipe diameter must be sufficient for the combined consumption.

Gas Convector Heater Dimensions and Space Constraints

Karma BETA 2C gas convector heaters have relatively compact dimensions, but minimum clearances from the floor, side walls, and furniture must still be observed during installation. Typical minimum clearances:

From the floor: minimum 10 cm (a standard-installed unit has legs or a bracket at a height of 10–15 cm)
Side clearances from the wall or furniture: minimum 15–20 cm on each side
Space in front of the unit (for warm air outlet): minimum 30 cm of free space – no curtain, furniture, or other obstruction may be present
Above the unit: minimum 60 cm of free space (for air circulation and service access)

Typical mistake: a customer buys a gas convector heater and wants to build it into a wooden cabinet niche under the window. Wood in close proximity to a gas appliance is a safety hazard, and most manufacturers directly prohibit this in their installation manuals. The correct solution is either an open niche made of non-combustible material, or placing the unit freely against the wall.

Electrical Connection

Even mechanical BETA 2C models usually require an electrical power supply – generally for 3 reasons: the flue gas exhaust fan (which ensures pressure-independent operation even without natural draft), the ignition system, and possibly an external thermostat. Electrical power consumption for gas convector heaters is typically in the range of 20–60 W – negligible compared to the heat output, but you need a 230 V outlet nearby.

The power cable must not be routed near hot parts of the unit, and the outlet must be accessible without dismantling the unit (in case of a power outage). Some models offer backup piezoelectric ignition, which works even without an electrical supply – suitable for cottages with an unstable power grid.

Purchase and Installation – What You Handle and What a Professional Handles

Under Slovak legislation, gas convector heaters are category I gas appliances – their installation, initial start-up, and inspection may only be carried out by a person professionally qualified to work with gas equipment (a certified gas fitter with valid authorization). An inspection report is mandatory, and without it the appliance has neither legal operating status nor insurance coverage.

What you can arrange yourself:

Choosing the right model according to this guide
Measuring the room and wall
Ordering the unit and accessories (flue extension)
Preparing the space (clearing under the window, plastering if needed)
Communicating with the gas fitter about the installation date

What a professional must do:

Drilling the passage through the wall (recommended – not technically mandatory, but requires special equipment)
Connecting to the gas supply
Initial start-up, pressure setting, and combustion check
Preparing the inspection report

You'll find a detailed step-by-step installation procedure in the article Installing the Karma Gas Convector Heater Step by Step – Procedure and Requirements.

Energy Efficiency in Operation – What You Can Influence Through Settings

Choosing the right gas convector heater is just the beginning. How you operate it plays a major role too. From experience, we know that customers with electronic control who set night and day temperatures according to their schedule consume 15–25 % less gas than those who let the unit run at full capacity 24 hours a day. Basic rules for economical operation:

Set night-time setback temperatures (12–15 °C) rather than turning off completely – reheating a cold room costs more gas than maintaining a minimum temperature.
During longer absences (holidays), set a frost-protection mode (8–10 °C) instead of switching off.
Ventilate by briefly opening and closing windows – a short, intense airing (a "draft" for 5–8 minutes) loses less heat than leaving a ventilation gap open for a long time.
Don't cover the unit's outlet with curtains, furniture, or decorations.

You'll find a complete guide to setting schedules, setback temperatures, and correct operation in the article How to Correctly Set Up and Operate a Karma Gas Convector Heater for Energy Savings.

The Most Common Mistakes When Choosing a Gas Convector Heater – Real-World Examples

Over years of selling and installing Karma gas convector heaters in Slovakia, the same mistakes keep recurring. We've collected the most common ones:

Mistake 1: Underestimating the required output. A customer buys a 2 kW unit for a 30 m² room in an old, uninsulated brick house. Result: in January, the unit runs continuously and still can't heat the room above 17 °C. Solution: calculate the correct output before buying (see the article What Output Do I Need for My Gas Convector Heater).

Mistake 2: Ignoring wall thickness. A customer orders a unit but forgets that their wall consists of a brick wall + 10 cm EPS insulation + facade = 52 cm total. The standard outlet is designed for 30 cm. This is discovered only during installation, requiring an extension, which delays the installation by several days.

Mistake 3: Wrong gas type. A customer without a gas main connection wants a gas convector heater because their neighbours have one – forgetting to ask, they find out the neighbours use LPG, while they're waiting for the gas network extension. Solution: always state the gas type and pressure when ordering.

Mistake 4: Planning an installation without a professional. A customer thinks it's enough to connect a hose to the gas pipe like a garden hose. Gas installation requires threaded or crimped joints with a professional inspection – this is not a DIY hobby project.

Mistake 5: Buying a mechanical model for permanent living. A customer wants to save on price and buys a cheaper mechanical model for a year-round occupied house. After a year, they find that with fluctuating outdoor temperatures they must constantly adjust the thermostat manually, and their gas bill is higher than it would be with an electronic model. The price difference would pay for itself in 2–3 seasons.

Frequently Asked Questions (FAQ)

Do I need a chimney for a gas convector heater?

No. Karma gas convector heaters are category C appliances with a sealed combustion chamber. Flue gas exhaust and air intake take place through a coaxial pipe directly through the building's exterior wall. You don't need a chimney flue – this is actually one of the biggest advantages of a gas convector heater compared to a classic gas boiler with a vertical chimney.

Can I install a gas convector heater in any room?

You can install a gas convector heater in any room that has an exterior wall suitable for drilling a passage. Restrictions apply to rooms with combustible surfaces in close proximity (wooden paneling), damp environments (units are not intended for bathrooms or laundry rooms), and spaces where the outdoor outlet would open into an enclosed courtyard or below another apartment's balcony (due to flue gas dispersion).

How much does it cost to run a Karma gas convector heater per year?

It depends on the unit's output, the number of operating hours, and the price of gas. Rough example: a 3.5 kW unit in a 30 m² room, operated 8 hours a day during the October–April season (about 180 days), at an average output of 60 % of nominal (modulation) = 3.5 × 0.6 × 8 × 180 = 3,024 kWh of gas per season. At a gas price of around €0.08–0.10/kWh, that comes to about €240–300 per year for heating one room. Electronic control can reduce this amount by 15–20 %.

How long does installation of a gas convector heater take?

An experienced gas fitter can complete the installation of a Karma gas convector heater, including drilling the passage, installation, and initial start-up, in 3–5 hours, if the gas connection is nearby and the wall isn't extremely thick. Under more complicated conditions (thick concrete wall, distant gas connection, need for an outlet extension), installation can take a whole working day.

What should I do if the gas convector heater stops igniting?

The most common causes are: a dirty ignition electrode, a clogged nozzle, or a gas pressure problem. Some simple tasks (visual inspection of the electrode, cleaning the surface of the unit) you can handle yourself, but any intervention in the gas section or combustion chamber must be done by a service technician. You'll find a detailed overview of common faults and their solutions in the article Common Faults of Karma Gas Convector Heaters and How to Fix Them.

Is it worth buying a newer gas convector heater if I have an old unit that still works?

It depends on the age and condition of the old unit. If the appliance is more than 15 years old, its efficiency is very likely lower (older type without modulation), spare parts are hard to find, and an inspection technician may take it out of service for failing to meet current standards. A new unit with electronic control has higher efficiency, meets current emission standards, and typically saves 20–30 % of gas compared to an old appliance. The payback period for continuous operation is 4–7 years.

Summary – What Not to Forget When Choosing

Choosing the right Karma gas convector heater isn't rocket science, but it does require thinking through several basic parameters before ordering. If you remember just one thing from this article, let it be this: start with the output calculation. A correctly sized gas convector heater is the foundation for the entire system working efficiently, safely, and reliably over the long term.

Then choose the type of control based on how you'll use the space. Measure the wall thickness and select the appropriate flue extension accordingly. Plan the installation with a certified gas fitter and have an inspection report prepared. And finally – set up operation correctly so your gas convector heater serves you for years without problems and with minimal gas costs.

You'll find the complete range of Karma gas convector heaters, including accessories, at atria.sk/gamatky-karma/. If you're not sure about your choice, check out more articles in the Knowledge Center or use the technical parameters of individual models directly on the product pages – they list nominal outputs, dimensions, outlet types, and compatible flue extensions.

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