This review is for the Intergas Rapid boiler but all the intergas boilers are built in the same way but with additional bells and whistles. The Rapid is at the budget range, costing around £800 with 3 years warranty while the Xclusive is their flagship appliance, 10 years warranty at £1,400.

The Intergas brand is not as well known as a Worcester or a Baxi as it’s a relatively newcomer in the UK. It is a Dutch manufacturer and only opened a UK head office in 2008. However it is well-established in their home country for over 80 years! Until recently, spare parts were not easily available but this has gradually changed.

A review of the Rapid is not possible without understanding its innards as these are what make the Intergas brand so unique. If you’re used to a Worcester, Baxi, Vaillant and the likes, be ready for a shock as all the boilers across the Intergas range are built differently. They all have a 2-in-1 or bithermic heat exchanger for heating and hot water and don’t have a secondary plate to plate heat exchanger as a result. This also means that the diverter valve and motor will be missing. What you get is still the same though: hot water and heating.

Now that we know what’s inside, let’s get the pros and cons rolling.

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One boiler to rule them all

As a result of this 2-in-1 heat exchanger, we get a 4-in-1 boiler. This means the same boiler can be used for heating only, hot water only, as a system boiler or a combi boiler. If the boiler isn’t going to used to provide domestic hot water, then those pipes in the boiler can simply be left opened and unused.

This is a very useful feature to have if a property may be extensively modified in the future, perhaps with the addition of an extension or additional bathroom. If the combi version cannot keep up with the new hot water demands, it can be turned into a system boiler to heat an unvented hot water cylinder without having to change the boiler at all. Or perhaps you move into a new property and need a new boiler urgently whilst you plan to get rid of the cylinder further down the line to create more space. Stick an Intergas boiler in place to be used as a system boiler and turn it into a combi later when the cylinder is removed. No new boiler is needed and it’s as simple as updating the boiler settings.

What other manufacturer can boast of this feature?

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Large waterways in the heat exchanger

The heat exchanger is made of aluminium which is an excellent heat conductor. Copper pipes carrying water go right through it such that the water is never in contact with the aluminium. Those pipes are quite large and they are unlikely to get blocked, especially with sludge on the heating side. In fact the pipes are so large that they can remain empty of water whilst the boiler is firing and the heat exchanger won’t be damaged by the extreme heat. This is after all 3 of its 4-in-1 possible states explained above, for instance as a heat only boiler.

Usually boilers firing with a heat exchanger full of air can damage it severely.

It just purrs

The boiler in operation has an extremely quiet fan to the extent that it’s not always apparent whether the boiler is running or not. If you plan on having your boiler installed in a living space such as a bedroom, the Rapid should be at the top of your list for this reason.


All Intergas boilers come with Opentherm connections as standard. This is another great advantage as any Opentherm control can be fitted to them, giving a large choice and range of prices instead of being stuck with proprietary controls solely provided by the manufacturer. Another great plus for Intergas in my book.

Value for money

Given all of the above advantages described – a quality heat exchanger, opentherm connections, very quiet operation, multiple boiler configuration – the Rapid comes at a very reasonable price at around £800 currently. It comes with only 3 years warranty compared to 6, 7 or 10 for other boilers but they all contain the same main components, so you get the same quality.

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Manual air vent

Having got rid of diverter valve and motor which are often sources of leaks, Intergas also got rid of the dreaded automatic air vent. The manual air vent is located externally on top of the boiler so any water coming out will stay outside.

Cable leads

The boiler comes supplied with electrical cable leads so the installer only either needs to fit a plug to the end or stick it in a fused connection unit. Job done. Not a deal breaker by all means but a little help along the way.

External filling loop

Another small plus for me that’s meant as a cost-cutting exercise for the manufacturer on this budget range. I’m a big fan of standardisation so if all boilers had the same filling loops, then they would be cheaper and easier to fix when needed. Sadly their top of the range boilers come with their own integral filling loop.

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Combined PRV and condensate pipe

This is certainly a great advantage during installation and it also means one hole less to damage the fabric of the building. However, if the PRV ever leaks for whatever reason, it won’t be visible at all and a fault may go unnoticed for a while. Is it worth it? Depends who you ask…

Settings options

There are plenty of parameters that can be used to fine-tune the boiler, including range-rating. However, there isn’t even a fault history, not on the budget Rapid, nor on the flagship Xclusive…

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Only 4 moving parts

This is meant as an advantage in that there are fewer things that can go wrong. No diverter valve to leak, no diverter motor to break down for instance. However, this is assuming that this 2-in-1 heat exchanger design doesn’t create its own issues elsewhere. More on this in the next section.


Burner seal requires replacing every two years

When Baxi doesn’t put a time limit on their plain black rubber burner seal and Vaillant now requires their graphite seal to be changed only once every 5 years, having to change the burner seal on any Intergas boiler every two years seems over the top. It doesn’t inspire confidence that they trust their seal to last only 2 years.

Many people don’t have their boiler serviced regularly, if at all. Should they not expect their appliance to last longer than 2 years then? Perhaps Intergas should invest in better materials or just ask Baxi how they do it!

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Casing is hard to remove

Intergas is on a parr with Worcester Bosch when it comes to who has the most frustrating boiler casing. The two screws at the bottom are hidden deep in their plastic casing and don’t align easily with their holes. Additionally, the edge clips on the casing which allow the screws to bite in frequently move out of alignment or fall out. The worst is this hasn’t changed on the newer models.

What a faff just to get started on that boiler!

Thou shall not pass – EV lies in the way

If and when you do manage to remove that casing, you’ll find the expansion vessel blocking the way of most components. To get around this, it is possible to unclip the EV and swing it out of the way by design. But it does keep swinging back and can only swing as far as the flexible hose will allow. Better not pull too hard on that.

Also, it swings to the left so if you’re trying to access it from this side because the boiler is in a corner, it doesn’t help much.

Another similar but more minor issue is the gas valve facing to the right, again, due to space restrictions most likely. If the boiler is in the same corner, not only do you have the EV to contend with but the gas valve is now facing away from you. Accessibility is clearly not a priority here.

On the bright side, if there’s ever an issue with the EV, it’s going to be right there in the face, easy to work on.

The Rapid and the rest are still an improvement on the HRE boiler which doesn’t even come with an expansion vessel! Looks like they gave up trying to fit one in.

The reason for this clumsy design is that there isn’t much space within the boiler for the EV because the heat exchanger is so massive. Which brings us to the next issue.

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It’s built like a tank

Just have a look at the dimensions below. The Rapid was never meant to be a cupboard fit and not because it wins points on looks. That fancy bithermic heat exchanger is so massive that the boiler just cannot be any smaller and also weighs a mighty 42 kg. Better make sure there’s a sturdy wall to hold it.

Rapid 25Dimensions (mm)
Weight (kg)42

Bithermic heat exchanger design

Yes, I’ve listed it as a con while Intergas make it into a pro. Well, I did list it under Pros too but it was the heat exchanger itself, not the design.

First of all, there’s nothing wrong with the other design that all other boiler manufacturers use: a primary heat exchanger that diverts the heated water to a secondary heat exchanger for hot water at the taps. These boilers are all very efficient. Yes, the secondary heat exchanger gets blocked, but that’s because of sludge and limescale.

Even the Intergas Rapid boiler will have its heat exchanger blocked eventually if it is installed in a hard water area as limescale builds up inside. An electrolytic inhibitor should be used to prevent this, but those secondary heat exchangers that get blocked due to limescale should also have electrolytic inhibitors fitted.

To be fair, the manufacturers are not to be blamed at all here. But from the customer’s point of view, it’s going to be much cheaper to replace or clean a secondary heat exchanger than replace this massive 2-in-1 heat exchanger. The secondary heat exchanger design means it can take the hit for failure/blockage and be cheaper to fix/replace whereas the Intergas heat exchanger may take longer to get blocked but when it does, it gets very expensive. In a clean system, neither design takes the hit.

This is only going to be an issue if the boiler is installed in a hard water area AND an electrolytic inhibitor is not used but in the real world, this happens regularly…

To pick up on a previous point made, although the Rapid has only 4 moving parts and therefore fewer things that can go wrong, the heat exchanger takes up a lot of space, is heavy and when it does go wrong, costs can quickly add up.

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Heat losses

Still on the subject of the bithermic design, it’s not as heat efficient as it’s claimed to be. When the boiler is operating in DHW mode, it’s also heating the pipes containing water for the heating system and the flow and return pipes near the boiler will warm up. This is acknowledged by the manufacturer as the installation instructions advise to fit a non-return valve to prevent this.

With the primary and secondary heat exchanger design, all of the heated water from the primary heat exchanger gets diverted to the secondary heat exchanger to heat DHW.

When looking at the required flow rate for a 35 deg temperature rise, it’s 10.5 L/min for the Rapid 25, an average figure. Iin other words, the secondary heat exchanger method is just as efficient.

Flue test points

Is it possible to make that into a con? Yes, when they are mounted on the elbow instead of the turret. If the flue goes sideways through the wall, then the elbow also has to turn around and the flue test points are only accessible from the side. If that side is blocked with a cupboard, wall or panel, then access becomes limited.

This is why a good design will always have the test points mounted on the turret and facing forward no matter what the orientation of the flue is.


The Rapid is not one to fit daintily in a cupboard, so if that’s not a deal-breaker, then to me its main disadvantage is that the burner seal is a bit of a let-down. It wasn’t always like this – it’s only their “progress” in materials science that brought out a new seal with a 2 year lifespan!

So if we can look past that and the heat exchanger design that is no better or worse than the other one, we get a very quiet boiler which can operate in multiple configurations and offers OpenTherm connectivity. If you look after the heat exchanger, it will look after you for a long time. Overall, the Rapid is a robust boiler offering great value for money and some room for improvement.

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