This should help you with terminology related to boiler insurance. It includes the terms we use in our Terms and Conditions. The glossary is meant purely to help you understand some of the technical terms used on this website. That is, it is a ‘layman’s guide’ to the terms. It does not constitute a legal or policy definition of any word term or phrase. If you want a more detailed technical or definitive explanation of any term, please contact us and we will do our best to help you.

Bleeding the radiators

If air gets in the heating system, it can prevent the water circulating properly. A radiator that is warm at the bottom and cold at the top needs to be bled. By turning the radiators bleed valve (with a radiator key), the air will rush out until water spurts out of the bleed valve. The radiator is then bled. This should be done when the heating system is turned off; otherwise, more air can enter the system. This is not covered by the insurance as it is a maintenance matter.

Boiler insurance

The term used generically to describe the parts replacement insurance for boilers and central heating systems. The parts inside the boiler (and other specified parts) are what is covered by the insurance. The heating appliance as a unit is not covered for replacement as all boilers wear out so the need to replace a boiler is an eventual certainty and therefore not an insured risk.


Marsh Commercial.


British Thermal Unit. A unit of energy for measuring heat output. Domestic boilers typically range from 30,000 to 90,000 BTUs.

Casing (of boiler)

A boiler will have an outer casing the part of it you see whose condition is not essential to the working of the boiler. In other words, if it gets dented, the boiler will still work and the insurance won't pay to fix the dent.

Claim limit

The upper limit per claim that the insurance will pay. It does not mean every claim will automatically pay this amount. The insurance pays for repairing or replacing a faulty component/s up to the claim limit.

Combination boiler

A boiler that is turned on only when a domestic hot water tap is turned on or when the heating system is timed to go on. New combination boilers must now be condensing boilers which re-use the condensation from the flue gases.


When a boiler is beyond economical repair: usually an engineer will make this decision. The insurance will no longer pay for repairs after a boiler has been condemned.

Condensing boiler

Condensation from a boiler contains heat. That's why steam comes out of boiler flues. In recent years, boilers have been re-designed to capture that heat by condensing the flue gases. Legislation now requires that all new gas and oil fired boilers are the condensing type.

Condensing boilers will have two heat exchangers and will need an extra drain pipe to be fitted for draining away the condensed vapours. This fluid is extremely acidic and can erode through your pipes. As condensing boilers are more complex, they are more expensive to buy and insure.

Consequential loss

A term used in insurance policies to state that the insurance wont pay for losses suffered by the insured as a consequence of the failure or breakdown of the items that are insured. For example, in boiler insurance, the insurance will pay for the boiler to be repaired but not for the ten new kettles the customer bought to supply themselves with hot water while the boiler was not working. In boilerplus, the term consequential loss means losses or damage not directly covered in the term consequential loss means losses or damage not directly covered in the Terms and Conditions.

Conventional boiler

A boiler that heats hot water which is then stored in a hot water cylinder, as well as heating the water in the radiators. New conventional boilers must now be condensing boilers which re-use the condensation from the flue gases.

Conventional radiators

A radiator, standard in most homes, through which hot water circulates allowing the heat to disperse to the surrounding area. The radiator has one inlet pipe and one outlet pipe, both with shut-off valves. The material is metal. Radiators with special finishes (e.g. gold plated) are covered as standard radiators. Towel rails are not included.

Cooling-off period

When you take out the insurance, this is the period of time you have to change your mind and ask for a full refund. You can ask for this refund in writing, over the telephone or by email. If you make a claim during the cooling off period, you cannot receive a refund as you will have received the benefit of the insurance and will therefore be liable for the premium.


Damage caused by corrosion is long-term. It is not the result of a sudden and unexpected breakdown of a component. Where corrosion damages parts in a heating system, the insurance will not cover the cost.

Draining down (springing the system)

When the water in the central heating system is drained away (by opening the drain cock).

Faulty component

A component which is insured (see under Equipment Covered below) and which is destroyed or damaged by wear and tear or any accident or misfortune not excluded under any part of these Terms and Conditions.

Heat exchanger

A key component inside the boiler which holds slowly circulating water while the heat from the burner is transferred to the water. The design of the heat exchanger is a crucial part of making boilers more fuel efficient because the more heat that is transferred from the burner to the water, the less heat is wasted directly out the flue. As a result of this, heat exchangers are frequently re-designed and the one in your boiler may no longer be manufactured even if your boiler is relatively new. boilerplus protects you against the heat exchanger becoming obsolete with an age-related payment. So if your heat exchanger fails and cant be replaced due to it being obsolete, you will receive a payment that you can put towards a replacement boiler.

Heating appliance

The boiler.

Insured person

The person(s) or company whose name appears on the Certificate of Insurance insurers.


This policy is underwritten by the Inter Partner Assistance SA UK branch, which is fully owned by the AXA Assistance Group. Inter Partner Assistance is a Belgian firm authorised by the National Bank of Belgium and subject to limited regulation by the Financial Conduct Authority. Details about the extent of its regulation by the Financial Conduct Authority are available from us on request. Inter Partner Assistance SA UK Branch firm register number is 202664. You can check this on the Financial Services Register by visiting the website


Isolating valves

These are valves which allow the water supply to be cut off to a part of the heating system. For example, the water circulating pump should have isolating valves on either side so that if it needs replacing, the engineer shuts off the water to the pump, replaces the pump and then turns the water back on. Without isolating valves, the time and expense of draining down the system is required.

Normal working hours

9am to 5pm from Monday to Friday only (not including bank holidays) or the hours which your chosen engineer charges standard daily rates, whichever is longer. Engineers typically charge extra outside these hours and the insurance won't pay the increased rate.


The pipes that contain the water heated by the boiler.

Policy excess

The amount deducted from each claim which the policy holder has to pay. This is typically used in insurance to prevent frivolous claims which are costly to process and which drive up premiums.

Power flushing

When the central heating system has fresh water forced through it at pressure in order to force out sediment that has built up in the system. Sediment will impair the flow of water through the system which reduces the efficiency of the heating. Power flushing the system can restore a system to good working order but it can also force water through weak points in the heating system necessitating repairs. Power flushing is not covered by the insurance.


Putting water back in the heating system.


The fixing of a broken component which would otherwise need to be replaced. Excludes cleaning of or adjustments to components. A good way to know whether the work carried out on a part counts as a repair is if there are bits and pieces left over from the repair.


Damage caused by the build-up of lime scale in the heating appliance and central heating system. Scale will destroy components throughout a heating system and the insurance cannot cover this cost as it is not an unexpected cost due to breakdown but a certainty caused by untreated water in the system.

Service organisation

The industry-qualified firm that carries out the regular service and breakdown repairs.

System cover

Conventional radiators (including valves), thermostats, expansion tank and plastic oil tanks on oil fired systems (not contents). Conventional radiators (including valves), thermostats, expansion tank and above ground pipework on gas fired systems (not pipework under floorboards or in an attic or loft or steel pipework).

Water jacket

Another name for heat exchanger.