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Potterton Promax SL Heat 24kW Regular Gas Boiler


Despite its discontinuity, the Promax SL Regular Boiler is still valid today. Of course, as the years went by, manufacturers have designed more efficient boilers with better features. Nonetheless, it might be a reasonable option if you’re looking for a quick fix.

With a general output rating of 24kW, the Promax SL Regular Boiler can handle small and medium-sized households with relatively low demand for hot water and central heating.

Continue reading for more on the Potterton Promax SL Heat 24kW Regular Gas Boiler.

Potterton Promax SL Key Features

  • It’s a condensing boiler.
  • It has an overall 88.80% efficiency rating (SEDBUK Band B-rated).
  • It’s ErP A-rated for hot water production.
  • It has hot water and a central heating max output of 24kWs
  • It can serve up to 15 radiators.
  • It has a hot water flow rate of around 10 litres per minute.
  • Offers a modulating power output for more convenient temperature control
  • It has an external filling loop.
  • It offers extensive flue options of up to 75 meters.
  • It comes with a wall plate and pre-plumbing jig.
  • It’s compatible with twin-horizontal and vertical flue systems.
  • Compatible with Megaflow Eco Solar Cylinders.
  • Compact dimensions of 600mm Height by 390mm Width by 280mm Depth
  • It weighs 26kgs.


The Potterton Promax SL Regular Boiler features a classic design. We’re particularly pleased with the amount of steel on its casing. Not only does it look great, but it also ensures durability. Also, its controls and knobs are well-hidden behind the grey plate at the bottom of the unit. In our opinion, it gives the boiler a neat presentation.

Sizewise, the boiler is compact enough to fit in a standard kitchen cabinet. Also, it doesn’t require compartment ventilation.

Unfortunately, this boiler doesn’t come with an LCD. Therefore, fault identification might be tricky.

Fuel and efficiency

Indeed, this Promax SL Regular Boiler runs on natural gas. Unlike modern boiler models, this one doesn’t come with LPG-supporting variants.

Honestly, its 88.80% efficiency rating is quite impressive for a boiler of its age. By today’s standards, it easily earns the SEDBUK B-Band rating. Also, it’s ErP A-rated for central heating and hot water production. Because of this, it will help keep your fuel costs to a minimum.

With this boiler, you’ll not have to worry much about your carbon footprint. It has achieved the best class 5 for minimal NOx and CO emissions. On top of that, you have the option of installing Megaflow Eco Solar cylinders that will help you save money and reduce toxic emissions. No wonder it secured an Endorsement from the Energy Saving Trust.

Power output rating

An output rating of 24kW is still acceptable even by today’s standards. The Potterton Promax SL Regular Boiler will comfortably supply heat and hot water for households with 2 to 3 bedrooms and one bathroom.

Generally, it will work for small and medium-sized households. If yours has two bathrooms, you might want to consider other boilers in the SL product range. There is a 30kW-variant of the same model.

Even for small households, you have to be careful. Remember, unlike combi boilers, regular systems require tanks and cylinders. This might be a problem if you’re running low on indoor space. Ideally, regular boilers suit households with low mains water pressure and old-style radiators.

Installation and servicing

Unlike most regular boilers, the Promax SL doesn’t require a pump overrun. Therefore, it’s much easier to install. The installers will not have to lift carpets and floorboards. Additionally, it offers a wide range of flue options and is compatible with vertical and horizontal systems.

Finally, it has front and side accesses that don’t require special tools to open. This makes maintenance and servicing that much easier.

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