Radiator FAQs
Common questions about radiators and heat distribution.
Why does my radiator have cold spots?
Cold spots at the top of a radiator usually indicate trapped air, which can be resolved by bleeding the radiator. Cold spots in the middle or at the bottom are typically caused by sludge (magnetite) build-up inside the radiator, which reduces its heat output. Persistent or widespread cold spots throughout multiple radiators suggest the whole system needs a power flush.
What are TRVs and should I have them fitted?
TRVs (Thermostatic Radiator Valves) regulate the flow of hot water to each radiator independently, allowing you to set different temperatures in different rooms. They are a cost-effective way to reduce heating bills and improve comfort. Building Regulations require TRVs to be fitted in all rooms except the room containing the room thermostat when replacing a boiler. Halo Heating fits TRVs as standard on new boiler installations.
How often should I bleed my radiators?
You should bleed radiators whenever you notice cold spots at the top, or at least once a year at the start of the heating season. If you find yourself needing to bleed radiators frequently (every few weeks), this indicates air is repeatedly entering the system — possibly due to a failing pump, a micro-leak, or a problem with the pressure relief valve.
Can sludge damage my radiators permanently?
Yes. Over many years, sludge build-up causes internal corrosion that can eat through radiator panels, causing pinhole leaks. Once a radiator has corroded through, it typically needs to be replaced rather than repaired. Maintaining inhibitor in the system and fitting a magnetic filter significantly slows this process.
How do I know if my radiators are the right size?
Radiators are sized to match the heat loss of the room they serve. An undersized radiator will struggle to heat the room even on full; an oversized one will heat the room quickly but cycle on and off frequently. Heat loss calculations take into account room dimensions, insulation levels, window area, and external wall area. We carry out room-by-room heat loss calculations for all new boiler and heat pump installations.
Can I add a new radiator to my existing system?
Yes, additional radiators can usually be added to an existing system. The key considerations are whether the existing boiler has sufficient output capacity for the extra load, and whether the existing pipework can supply adequate flow. We'll assess the system and provide a quote for installation including any necessary pipework.
Should I replace old radiators when I get a new boiler?
You don't necessarily need to replace all radiators with a new boiler, but it's worth having them assessed. Very old radiators may have reduced output due to internal corrosion or external damage. If upgrading to a heat pump, some radiators may need to be replaced or supplemented to deliver sufficient heat output at the lower flow temperatures. We'll advise specifically after a site assessment.
Are decorative or designer radiators as effective as standard ones?
Designer and column radiators can be highly effective if correctly sized for the room. Their heat output is determined by their surface area and the number of columns, which must be matched to the room's heat loss calculation. Some decorative radiators with very slim profiles may have lower outputs than their footprint suggests — always check the BTU/watt output specification when choosing.
Why is one radiator in my house always hotter than the others?
This is usually a system balancing issue. In an unbalanced system, radiators closest to the boiler receive more hot water flow than those furthest away. Balancing the system involves adjusting the lockshield valves on each radiator to equalise flow distribution. A balanced system heats all radiators evenly and is more efficient.
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