Step-by-step Karma Gamatka Installation – Procedure and Requirements

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Installing the Karma Gas Heater Step by Step – Procedure and Requirements

The Karma gas heater is one of the most widespread local air heaters on the Slovak market. Correct installation is the foundation of reliable and safe operation – and also a condition for the manufacturer to accept any warranty claim. In practice, we see many installations where a seemingly minor detail was underestimated during installation: incorrect mounting height, insufficient space for air circulation, an inadequate electrical connection, or an improvised flue outlet. These mistakes then result in malfunctions, increased gas consumption, or – in the worst case – a safety risk. This article therefore gives you a complete technical procedure for installing the Karma gas heater, from the first measurement to the final start-up.

If you are still deciding which model to choose, we recommend first reading the other articles in this Knowledge Center: How to choose the right Karma gas heater for your space and What output do I need for my gas heater – calculation based on room area. Here we assume you have already chosen the model and output, and we go straight to the installation.

What is the Karma gas heater and how does it work – a brief technical overview

A "gamatka" (also called a "wall-mounted gas heater" or "gas convector") is a gas-fired warm-air heater that burns natural gas or propane directly in the room, while exhausting the combustion gases outside through a wall duct. It draws combustion air either from the room (so-called open combustion chamber, type C0) or from outside via a coaxial intake (sealed combustion chamber, type C1/B2). The Karma BETA 2C series works with a sealed combustion chamber – combustion air comes from outside and exhaust gases leave to the outside, which increases safety and allows installation even in less ventilated spaces.

The heat generated by combustion is transferred to the flowing air through a heat exchanger, which is cooled by a fan. The warm air is blown into the room and circulates naturally. The difference between individual models (for example Karma BETA 2C 01 and Karma BETA 2C 02) lies primarily in the output and type of control – this is discussed in more detail in the article Karma BETA 2C vs. BETA 2E – difference between types and when to choose which.

Required tools, materials and prerequisites before starting

Installing the Karma gas heater is not a job "for every DIYer". Gas appliances are regulated by law in Slovakia – specifically by the decree of the Slovak Chamber of Building Surveyors and standards STN EN 1020, STN EN 13611 and related regulations. The gas connection and pipework may only be carried out by a person with a valid authorization to install gas appliances (a certified gas fitter under §7 of Act No. 51/1988 Zb., as amended). The electrical connection (230 V) must be carried out by a qualified electrician. A layperson can help with preparatory work – drilling the hole for the flue outlet, mounting the brackets – but the final gas and electrical connection must be professionally completed and handed over to the customer along with an inspection report.

List of required tools and materials

Drill and hammer drill, masonry/brick drill bits with a diameter of 60 mm or 80 mm (depending on the model)
Angle grinder (or a chisel and hammer for a brick wall)
60 cm spirit level
Measuring tape, pencil, plumb line
Torque wrench, pipe wrenches (various sizes), flat screwdriver, cross-head screwdriver
Gas tightness tester (manometer test kit or an electronic gas detector)
UV- and frost-resistant silicone for sealing the flue outlet on the outside
Masonry filler / plaster to finish the opening in the wall
Mounting bracket (usually included in the package), anchor screws for concrete (Ø10 mm anchor, min. 60 mm length)
Flexible gas hose or copper pipe, suitable fittings and a shut-off valve
Flue extension (if the wall exceeds the standard depth) – for example Gamat 471 Flue Extension or Gamat 473 Flue Extension

Step 1 – Choosing the location and preparing dimensions

Choosing the right spot on the wall is the most important step. A mistake here cannot be easily fixed – an opening in the exterior wall is a permanent intervention. Follow these principles:

Location of the heater in the room

The Karma gas heater is mounted exclusively on the exterior wall of the building, because the coaxial flue must pass directly through the wall to the outside. The ideal location is below a window or in the corner of the room next to the exterior wall, where you achieve the most even heat distribution. The heater must not stand behind furniture, behind curtains, or in a narrow space – air circulation must be unobstructed by at least 30 cm on the sides and 50 cm in front of the heater.

The mounting height of the flue axis from the floor depends on the model; the manufacturer states it in the technical data sheet. For most models in the BETA 2C series, it ranges from 200–400 mm from the floor. The lower it is, the better for circulation – cold air is drawn in from below and warm air rises upward.

Minimum clearances and safety distances

From the ceiling: min. 400 mm (for maintenance and filter replacement)
From a side wall: min. 150 mm
From flammable surfaces (wooden panelling, parquet flooring, curtains): min. 500 mm on all sides where warm air is discharged
From existing gas piping: min. 50 mm
From electrical wiring: min. 30 mm

Step 2 – Drilling the hole for the coaxial flue

This is the physically most demanding step. The diameter of the hole depends on the specific model and accessories. For most models in the BETA 2C series, the coaxial flue diameter is 60 mm, in some cases 80 mm – always check the technical data sheet for your model. The hole is drilled horizontally, or with a slight downward slope of 3–5 mm towards the outside (so that rainwater does not flow inside).

Drilling procedure:

Mark the center of the hole on the interior wall according to the calculated flue axis height. Use a spirit level and a plumb line.
On the exterior wall, mark the corresponding point (taking into account the wall thickness and the required slope).
Drill gradually from both sides using a core bit or a hammer drill to avoid chipping the plaster.
For thick walls (over 40 cm), consider using a flue extension. The range includes several variants – for example VYD60 Flue Extension for a 60 mm diameter, or Gamat 471 Flue Extension and Gamat 473 Flue Extension for other variants. A separate article discusses selecting the right extension: Gamat flue extension – which diameter and length are suitable for your type.
After drilling the hole, clean it out, or smooth it manually with a grinder or chisel if needed.

Important notice: Before drilling, always check that there are no hidden electrical wires, gas pipes, or other utility lines in the wall. Use a hidden-wiring detector.

Step 3 – Mounting the bracket and hanging the heater

The Karma gas heater is a wall-hung appliance – it hangs on a steel bracket that must be firmly anchored to the wall. The bracket is usually included in the package.

Bracket mounting procedure

Hold the bracket against the wall and level it horizontally using a spirit level. Do not rely on old plaster – always use a spirit level.
Mark the position of the anchor holes. The bracket is anchored at a minimum of 4 points; the spacing of the anchors depends on the bracket manufacturer.
Drill holes for Ø10 mm anchors, min. 60 mm deep, into solid masonry. For hollow bricks, use special anchors designed for hollow masonry.
Insert the anchors and tighten the screws. Check the firmness of the bracket – it must not move even a millimeter when pulled.
Hang the heater on the bracket. Most models have a hook strip on the back that fits precisely onto the bracket.
Check the horizontal alignment of the heater with a spirit level after hanging.

Step 4 – Installing the coaxial flue

The coaxial flue is a double-walled pipe – exhaust gases exit through the inner wall, while fresh combustion air enters through the outer wall. This is a critical part of the installation, both in terms of safety and efficiency.

Basic flue installation procedure

Insert the coaxial pipe into the prepared hole in the wall. The pipe must protrude at least 30–50 mm beyond the outer facade to ensure free exhaust and air intake.
Direct the pipe slightly downward toward the outside (a slope of 3–5°) – this design prevents condensate and rainwater from entering back into the appliance.
Fill the gap between the pipe and the wall opening with heat-resistant mineral wool (not PU foam, which burns), then seal from both sides with cement filler.
On the outside, fit the outer grille/flue cover – it is included in the package or as an accessory. The grille prevents insects, birds and debris from entering, but must not restrict airflow. Never cover the flue with a mesh with openings smaller than 5 mm, as it could become clogged.
On the room side, slide the flue onto the appliance's spigot. Secure the joint with locking clamps according to the manufacturer's instructions.
If the wall is thicker than the standard length of the supplied pipe, an extension must be used – the correct selection is described in the article Gamat flue extension – which diameter and length are suitable for your type.

Prohibited practices for the flue: Never direct the flue into a shaft, a wall cavity, under a balcony, or into any other enclosed space. The flue must terminate in free outdoor air. The minimum distance between the end of the pipe and an opening window is 500 mm, and 1,000 mm from an adjacent opening (another window, passage, entrance).

Step 5 – Connecting to the gas supply

This is legally and safety-wise the most critical step. To reiterate: it may only be carried out by a certified gas fitter.

Technical requirements for the gas supply

A shut-off ball valve (tap) accessible without tools must be installed upstream of the heater – for emergency shut-off. This valve must not be located behind the heater or behind furniture. The sizing of the gas pipe depends on the heater's output and the length of the pipework – for appliances up to 6 kW (typical medium-sized heater), a DN 15 (1/2") connection is sufficient, while for more powerful models (10–12 kW), DN 20 (3/4") is recommended.

The heater is most commonly connected to the gas supply using:

A flexible steel-braided hose – simple installation, maximum permitted length 2 m, must not pass through a wall or be hidden under plaster
A copper pipe – a more permanent solution for fixed installations, with soldered or crimped joints

After connecting the gas, the gas fitter must carry out a pressure tightness test using a manometer test set (test pressure of at least 150 mbar for 10 minutes without a drop), or an electronic gas detector at each joint. The appliance may not be put into operation without proof that the pressure test has been carried out.

Step 6 – Electrical connection

The Karma gas heater (BETA 2C series) requires a 230 V / 50 Hz power supply for the fan motor, ignition, and thermostat electronics. The power consumption of the fan and control electronics is low (usually 20–80 W), but it must come from a proper socket with a protective conductor (PE), protected by a circuit breaker of at least 10 A.

The socket must be within reach – most heaters have a power cable 1.0–1.5 m long.
The socket must not be on an extension cord or a splitter – it must be a permanently wired wall socket.
If the heater has a room thermostat or timer control (depending on the model – see the article Mechanical vs. electronic control of the Karma gas heater – which is better), the external thermostat is connected to the terminal block on the heater according to the enclosed diagram.
Disconnecting the heater from the mains when working on the gas supply (e.g. during a service intervention) is mandatory.

Step 7 – First start-up and setup

Once the installation is complete, the pressure test has been carried out, and the electrical connection has been made, you can proceed with the first start-up. The first start-up is always a delicate moment – there may be residual air in the pipework, and the appliance may take a moment to "find" the flame before the burner locks in.

First start-up procedure

Open the gas shut-off valve upstream of the heater.
Set the heater's thermostat to the maximum temperature (to ensure the thermostat does not cause the burner to shut off prematurely).
Press the ignition button and hold it according to the instructions (usually 3–5 seconds). If the burner does not ignite on the first attempt, wait 1 minute and repeat – the air in the pipework needs to be purged.
Once the burner ignites, check the visibility of the flame through the inspection window (if the model has one).
Monitor the first 15–20 minutes of operation – there must be no smell of gas, and the heater must not make unusual noises (crackling outside of ignition, knocking).
Check the exhaust outlet outside – warm air must be coming from the outer grille, and in winter, a slight vapor (condensate) as well.
Set the thermostat to the desired operating temperature (we recommend around 20 °C for the first start-up) and verify that the heater correctly switches off and re-ignites as the temperature is reached/drops.

Detailed instructions on setup and optimizing consumption can be found in the article How to properly set up and operate the Karma gas heater to save energy.

Documentation, inspection and handover of the installation

Once installation is complete, the gas fitter must issue a certificate of handover for the gas appliance – the so-called tightness and operability test report. This document is important for several reasons:

It is a prerequisite for claiming a warranty from the manufacturer
It is required by the insurance company in the event of a claim
It may be required by the gas distributor when inspecting the supply point
It serves as documentation for the service technician in case of a future repair

Also keep the original installation and operating manual, the warranty card, and the invoice. You will need these documents for any service intervention. It's a good practice to photograph the rating plate on the heater and save the photo on your phone – this is very practical when ordering spare parts or accessories (such as a flue extension).

Typical mistakes in practice – what most often goes wrong during installation

Over years of working with customers in the heating technology field, we see recurring mistakes. We list them here not to scare anyone, but so that you can avoid them in advance:

Flue hole drilled too high: The flue axis is more than 500 mm above the floor. The heater still works, but the cold air is not heated efficiently and the room has cold feet.
Insufficient bracket anchoring: The bracket loosens over time, the heater tilts, and the coaxial pipe separates from the spigot. Result: exhaust gas leaks into the room. Extremely dangerous.
Missing flue seal in the wall: The gap between the pipe and the opening is not sealed. In winter, cold air blows through it and heat loss increases significantly.
Flue directed toward an opening window: In summer, with the window open, exhaust gases enter the interior. This violates both installation regulations and health safety.
Flexible hose longer than 2 m or run behind plaster: Violation of installation regulations; the insurance company may refuse to pay out in the event of damage.
Missing shut-off valve: A heater without a valve upstream – in an emergency, there's no way to quickly shut off the gas without intervening in the house supply line.
Incorrect flue slope: The pipe rises slightly toward the outside. Rainwater flows into the appliance and damages the heat exchanger. Always slope slightly downward.

If you're wondering whether your old installation was done correctly, or if you're taking over a property with an existing heater, pay attention to the article Common Karma gas heater faults and how to fix them as well as Maintenance and servicing of the Karma gas heater – what you can do yourself and when to call a technician.

Installation in different types of walls – specifics

Not every wall is the same. Here are practical notes for the most common types:

Solid brick or concrete (thickness 25–50 cm)

Standard coaxial pipes supplied with the heater are 300–400 mm long. For walls thicker than 350 mm, an extension is required. Anchors should be installed in the solid part, not in the plaster – for wall depths over 30 cm, request a construction drawing or measure the depth with a probe.

Aerated concrete (Ytong, Siporex)

Aerated concrete is a brittle material – drill without hammer action! Hammer drilling will crumble the material and the anchor won't hold well. Use masonry drill bits without activated hammer action or special bits for aerated concrete. The anchor must be a special type for lightweight building materials – a chemical anchor or an expansion anchor designed for aerated concrete.

Double-skin facade panels or sandwich walls

This is the most complicated case. The cavity between the inner and outer skin must not remain open – a gas-tight sleeve must be used, and the entire space in the cavity must be filled with non-combustible thermal insulation. If in doubt, contact a technician.

Timber-frame construction

Installation in a timber-frame building is possible, but requires special attention when routing the flue through wooden load-bearing elements (risk of weakening the structure) and when sealing the flue (flammable material near the hot exhaust pipe). The distance between the hot exhaust pipe casing and the wood must be at least 20 mm, or thermal insulation separation must be used.

Operation in and out of season

A properly installed heater requires no special preparation for the winter season. Before the first start-up after a summer break (when the heater has not been running for several months), it's a good idea to:

Check the outer flue grille – to make sure there's no insect or bird nest inside
Visually inspect the flue seal in the wall – to check for cracks caused by temperature changes
Start the heater and monitor it for the first 10 minutes – any odor may be from dust on the heat exchanger, which is normal and will disappear after a while

During prolonged non-use (e.g. a cottage that is only occasionally heated), leave the gas valve closed. Before leaving an unheated building in freezing weather, remember that the heater does not protect against frost in spaces where it is not operating – there is a risk of other pipework freezing.

Frequently Asked Questions (FAQ)

Can I install the Karma gas heater myself without a gas fitter?

You can carry out the preparatory work yourself (drilling the hole, mounting the bracket) if you have the skills and the right tools. However, connecting to the gas supply, performing the pressure tightness test, and the first start-up must be carried out by a certified gas fitter with a valid certification. Without proof of professional installation, you have no right to a warranty claim, and the insurance company may not accept liability in the event of damage. The electrical connection must be carried out by a qualified electrician.

What diameter hole do I need for the flue of the Karma BETA 2C gas heater?

For models in the BETA 2C series, the standard coaxial flue diameter is 60 mm. Drill the wall opening to a diameter of 65–70 mm to allow space for thermal insulation sealing and pipe installation. Always verify the exact dimensions in the technical data sheet for your specific model – dimensions may differ for other series.

What if my wall is thicker than the standard flue pipe?

In that case, you'll need a flue extension. For a 60 mm diameter, for example, the VYD60 Flue Extension is suitable. For other diameters, the Gamat 471 Flue Extension or Gamat 473 Flue Extension are available. It's important to observe the maximum total length of the coaxial system specified by the manufacturer for the given model – if the flue is too long, efficiency drops and ignition problems may occur.

At what height from the floor is the heater mounted?

The height of the flue axis (and thus the height of the lower edge of the heater) depends on the model. For most heaters in the BETA 2C series, the flue axis is placed at a height of 200–400 mm from the finished floor. Always verify the exact dimension in the enclosed installation documentation, as each model has a different shape and dimensions. Mounting it too high reduces heating efficiency – cold air remains near the floor and circulation is uneven.

Can I connect the Karma gas heater to propane-butane instead of natural gas?

Yes, but the heater must be structurally prepared or converted for this. Gas heaters are sold either for natural gas (G20) or for propane/LPG (G30/G31) – these two versions are not interchangeable without replacing the nozzles and adjusting the burner. Some models are sold with a conversion kit, while others need to be professionally converted. Never run the heater on a different type of gas than stated on the rating plate – there is a risk of explosion or carbon monoxide poisoning.

How long does it take to install the Karma gas heater?

An experienced gas fitter with an assistant can complete a standard heater installation (drilling, bracket, flue, gas connection, start-up) in 3–5 hours. If it's a masonry wall thicker than 40 cm, or if a new gas pipeline needs to be run, expect a full working day. Electrical work (if it involves more than just plugging into a standard socket) will add further time. Always include the sealing and finishing of the flue in the facade in the price of the work – customers often underestimate this task, but poor flue sealing is a source of heat loss and condensation problems.

Conclusion – what not to forget

Installing the Karma gas heater is a technically relatively straightforward process if the correct sequence is followed and legal requirements are observed. Summary of the most important points:

Exterior wall, correct height, sufficient space for circulation
Opening with a slight outward slope (3–5°), correct diameter, thorough sealing
Bracket firmly anchored into solid masonry, heater hung level
Coaxial flue directed into free outdoor air, at least 500 mm from any opening
Gas connection carried out exclusively by a certified gas fitter with an inspection report
Shut-off valve upstream of the heater, accessible without tools
Electrical connection to a proper 230 V socket with a protective conductor
First start-up supervised by a professional, installation documents carefully kept

If you have doubts about any step, or if you encounter a non-standard situation (thick wall, timber-frame construction, combination with another heating system), contact an experienced technician. A properly installed heater will serve you reliably and safely for many years with minimal maintenance requirements – read more about this in the articles Maintenance and servicing of the Karma gas heater – what you can do yourself and when to call a technician and Frequently asked questions about the Karma gas heater.

Do you have a question on this topic?

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