Fireplace FAQs

There isn’t a single answer because the right kilowatt depends on a few different factors. To work it out, we use a common formula across the fireplace industry.

Start by measuring the area you want to heat:

Room length × width × height = cubic metres (m³).

Next, divide the room volume (m³) by 25, then add 2. That’s the kilowatt rating you’ll need. In simple terms, every 25 cubic metres of space requires about 1 kW of heat.

Of course, this formula is just a guide. Insulation, windows, outside temperature, and even your preferred room temperature can make a difference. In South Africa, most homes aren’t perfectly sealed, so these factors really matter. And if your ceilings are higher than 2.6 m, or if you don’t have a ceiling, you’ll need a higher output.

To spread heat more evenly, you can also use a ceiling fan or one of our Stovepro heat-powered fans. Some fireplace models even come with optional or built-in fans.

Every closed-combustion fireplace carries a kW rating, but the golden rule is that it’s safer to go slightly bigger and burn less than to go too small and overfire. Overfiring shortens your fireplace’s lifespan and can void the warranty.

If you’re unsure, feel free to contact us. We’re always happy to help you choose the best fireplace for your space.

The kW rating of a closed-combustion fireplace shows the ideal thermal output it can deliver while staying efficient and protecting the body and internal parts from damage.

Manufacturers usually publish figures that best suit their target market. For example, a fireplace rated at 10 kW with 75% efficiency might actually reach 14 kW during testing. At that level, however, the efficiency could drop to 70%. In simple terms, the fireplace can do more, but it burns less efficiently, so the manufacturer chooses to promote the 10 kW result.

Efficiency ratings are meant to measure how much of the fuel’s energy turns into usable heat for your room. Put another way, if a fireplace is 75% efficient, then 75% of the fuel heats your home, and about 25% is lost up the chimney.

These tests are done under controlled conditions, where a set amount of fuel is burned and the flue gases are measured for temperature and carbon content. The tricky part is that test conditions vary. Even in regulated countries like the UK, manufacturers can choose the type and quantity of fuel, how often it’s added, and the oxygen levels allowed during the burn.

This means “like for like” comparisons aren’t always straightforward. The best comparisons come from manufacturers who publish their test conditions and refuelling times, because you can then see how their results line up with others.

Your first fire is an important step in preparing your fireplace, and following these instructions carefully will protect your guarantee.

Before you begin:

• Don’t use your fireplace for the first 24 hours, as the waterproofing needs to dry.
• Make sure the firebox and ash pan are empty, and remove any tools, paperwork, gloves, or packaging. If you’ve self-installed, also remove anything stuck to the glass window.

When you light the first fire:

• Keep the door slightly open and leave the handle unlocked. This prevents the curing paint from sticking to the fire rope.
• The fire rope is made of specialised glass fibre (not asbestos). Leaving the door unlocked until the fireplace has cooled completely will protect it.
• Important: The installer’s newspaper demonstration does not count as your first fire.

What to expect:

• During the first burn, the paint cures, so you may notice some odour or light smoke. This is normal and will disappear after a few fires.

How to build the fire:

• Slide the lower primary and top secondary air controls fully open. If your fireplace has no bottom air vent, open the ash drawer by about 1 cm. Built-in models usually have vents under the door or window.
• Start with a small fire using a blitz and kindling. Once burning well, add two logs.
• Let the fire build gradually over 3–4 hours, increasing the temperature slowly.
• Once established, close the vents halfway to two-thirds, and refuel over time by adding one or two logs at a time.

Once your first curing fire is complete, you can move on to normal use. Here’s how to light and maintain your fire safely:

Before you start:

• Empty the ash pan and make sure the grate is unclogged (always do this once the fireplace has cooled down).

To light the fire:

• Fully open the bottom primary air vent, or open the ash pan by about 1 cm.
• Fully open the top secondary air vent.
• Place chopped kindling and a blitz starter block inside, light the fire, close the door, and let it burn until established.

To keep it going:

• Add 1–2 logs once the fire is burning well, then close the door. Always place logs carefully to avoid damaging the glass, fire bricks, or dislodging the baffle plate inside the chamber.
• Add more fuel only once the existing logs have burned down to a steady fire bed.

Adjusting the burn:

• Once you’ve reached a comfortable burn, partially close the air vents (by about one-half to two-thirds) and close the ash pan.

Important to note:

• Appliances like tumble dryers, extraction fans, or even open windows in the same room can affect the flue draft. This may cause poor burning conditions or even push smoke back into the room.

In short, a closed (or slow) combustion fireplace is a sealed metal stove that burns solid fuel more efficiently than an open hearth. By controlling the oxygen supply with adjustable air vents, the fire burns hotter and steadier, giving you up to 20–30% more heat while using less fuel.

With an open fireplace, much of the warmth is lost straight up the chimney. A closed combustion fireplace keeps more of that energy in the room, so you enjoy more heat, better regulation, and lower fuel bills over time.

Many models also come with technology that cuts down on emissions, making them kinder to the environment. Look out for fireplaces with SIA 2022 Eco-Design, DEFRA certification, or BLU technology. You’ll find these in the Charnwood and Northern Flame ranges on our website. Choosing closed combustion means more comfort, less waste, and a cleaner burn.

Closed combustion fireplaces are designed to get the very best out of your wood. Because they’re sealed with a door, the temperature in the combustion chamber gets much hotter than in an open hearth, which means the wood burns more cleanly and efficiently. Many models even use extra insulation, like vermiculite bricks or Accumote, to retain and reflect more heat back into your room.

The difference in performance is huge. An open fire achieves only about a 15% yield, with most of the warmth lost up the chimney. By contrast, a closed combustion fireplace delivers between 60–80% efficiency. And when it comes to emissions, the gap is even bigger. Open fires release around 15 times more CO₂ and 50 times more fine-particle pollutants than a closed wood-burning stove.

On top of that, today’s fireplaces often include advanced clean-burn technology that reduces emissions even further, making them a safer and more environmentally friendly choice. Look for models with SIA 2022 Eco-Design, DEFRA approval, or BLU technology. You’ll find plenty in the Charnwood and Northern Flame ranges on our website. Choosing closed combustion means more heat, lower fuel use, and a far greener way to enjoy your fire.

Cast iron and steel fireplaces both have their pros and cons, so it really depends on what matters most to you.

If time is important, think about how quickly you want the heat. Cast iron takes a little longer to warm up, but once it’s hot, it keeps radiating warmth even after the fire has died down. On the other hand, steel heats up fast, which is great for instant comfort, but it also cools down quicker.

In terms of control, many entry-level cast iron fireplaces don’t give you the same fine-tuned airflow as their steel counterparts. Because cast iron parts are moulded rather than cut, the fit isn’t always as precise as plate steel.

Design and budget also play a role. Steel allows for sleek, contemporary designs, which is why it’s so popular today. Fireplaces made from thinner plate steel (≤ 3 mm) are usually more affordable, though they won’t last as long as cast iron. Cast iron is tougher, but either option will give you years of use if you maintain it well and stick to burning dry wood.

These days, with advanced CNC technology, most manufacturers lean towards steel. That said, if you buy from a reputable brand, you’ll likely be happy with either. And if you want the best of both worlds, you can always go for a steel fireplace with cast iron internals and a cast iron door.

Primary air

Back in the 19th century, stoves were built as simple cast-iron boxes with a firebox at the bottom. Air entered at the base of the fire bed to get the fuel burning, and this became known as primary air. The idea is still used today in multi-fuel fireplaces, where a controllable vent at the bottom of the door feeds air under the fuel bed. Primary air gives a strong ignition for wood and coal, but if left wide open it can make the stove burn too hard. In earlier models, doors were solid cast iron because pyroceramic glass wasn’t yet available. As technology advanced, glass panes and secondary air systems were added to make burning cleaner and more efficient.

Secondary air (air-wash)

Secondary air comes in through vents above the door. It’s directed downwards across the glass and into the chamber, right where the gases rise toward the baffle plate. This stream of warm air ignites the gases for a secondary burn, giving more heat and fewer emissions. At the same time, it creates a warm “air curtain” that helps keep the glass clear. As the fire gets hotter, you can see the air-wash working as it visibly cleans the glass. On wood-burners, the secondary inlet usually becomes your main control once the fire is going. On multi-fuel stoves, you’ll use it in the same way, but may need to reopen the primary inlet when burning coal or if the fire isn’t burning strongly enough.

Clean burn (preheated secondary air)

Clean burn takes secondary air a step further by preheating it before it enters the chamber. The air is channelled up from the back of the stove, with some fed into the lower chamber and the rest flowing across the glass and into the firebox. Because this air is already hot, it burns off gases more completely and at higher temperatures than standard secondary air. The result is better efficiency, cleaner glass, and much lower emissions. If you look just inside above the door, you’ll see the same kind of channel on secondary and clean burn stoves, but clean burn models usually have their control at the base.

Tertiary air

Tertiary air is the third layer of control, usually found in Norwegian designs and contemporary fireplaces with big chambers. Air is drawn up the back of the stove and injected through small steel jets into the upper chamber. These jets of very hot air ignite the last of the gases that only burn at high temperatures. With dry, seasoned wood, this makes for a very clean burn with minimal emissions. Many fireplaces with tertiary systems carry the DIN plus standard for efficiency and low emissions.

What to look for

Modern closed-combustion stoves combine all these systems for maximum efficiency. For the cleanest performance, look out for models with SIA 2022 Eco-Design, DEFRA approval, or BLU technology. You’ll find these in ranges like Charnwood and Northern Flame on our website. Choosing a stove with these features means more heat, less waste, and a greener way to enjoy your fire.

For the best results, always use very dry, well-seasoned wood. To get the fire going, start with firelighters like Blitz and some chopped kindling. Wet wood should be avoided. It causes a smoky fireplace, blackened glass, up to 50% less heat, and nearly double the fuel consumption. Bluegum is a popular and cost-effective choice in South Africa.

What you shouldn’t do is just as important. Never use liquid fuels, tarred wood, shavings, fine coal, or pallet crates. And don’t treat your fireplace like a furnace for burning waste. It’s designed for heating your home, not for getting rid of rubbish.

Each brand has its own guarantee. Here’s a quick guide to what you can expect:

• Charnwood – 10-year limited guarantee on all fireplaces.
• Northern Flame – 2 year limited guarantee on built-in/inserts, and a 5 year limited guarantee on freestanding models.
• Invincible cast iron fireplaces & Earthfire ceramic pots – 10-year limited guarantee.
• Spartherm, Kratki, Invincible (plate steel), Hydrofire boiler fireplaces, Dovre, Godin – 5-year limited guarantee.
• Canature, Sentinel – 3-year limited guarantee.
• Hydrofire – 2-year limited guarantee on steel fireplaces, and a 5-year limited guarantee on cast iron units.
• Chad-o-Chef – 2-year limited guarantee.

Loose internal parts such as grates, ash pans, bricks, and baffle plates are covered for 1 year with Hydrofire, Dovre, Godin, and Invincible fireplaces, and for 2 years with Charnwood.

All guarantees are limited, which means they don’t cover consumable parts like glass, paint, or ceramic rope. These items naturally wear over time and aren’t included under warranty.

At GC Fires, we’ll repair or replace defective parts where possible, and labour for replacements is covered for the first year by the guarantee.

To keep your guarantee valid, your fireplace must be installed correctly, serviced annually, and used with the right fuel. Misuse, over-firing, water damage, or non-recommended fuels will void the guarantee.

Please also note that GC Fires cannot be held responsible for incidental or consequential loss, damage, or injury. To prevent overheating, we recommend using a stove thermometer to help manage your fireplace temperature.

If you ever need to make a claim, just send it to us in writing with photos and proof of purchase. We’ll do our best to make the process straightforward. And of course, nothing here affects your statutory rights.

Yes, we do,  outside of our peak season. You’re welcome to bring your unit to our warehouse for a free assessment and quote, or we can collect it for a fee in the Cape Town and Helderberg areas.

That said, we’re not miracle workers. Some units are simply beyond repair. If that’s the case, we’ll be upfront with you and recommend the best replacement option to suit your budget.