OSO Unvented Water Heater

OSO Unvented Water Heaters

Part of A/S OSO, the largest water heater manufacturer in Norway, OSO Hotwater UK is the company’s British arm and provides customers throughout the UK with access to OSO’s wide range of hot water heater models. OSO water heaters run the gamut from unvented models to specialty solar-powered options for those who want to make their home greener. The company also guarantees their cylinders to last up to 25 years, provided they are professionally serviced every year. At EasyFlow, we provide OSO unvented water heater repairs and annual service to customers throughout Manchester, Liverpool and Leeds.

Control switch on OSO water

OSO cold inlet and hot outlet

OSO unvented water heater

OSO Unvented Water Heater Models

OSO Hotwater UK has become one of the primary suppliers of hot water heaters to homes and businesses throughout the UK, offering a range of models to suit different usage needs and installation requirements. The company’s OSO Super S line includes units with capacities ranging from 120 litres to 300 litres. They also manufacture a Slimline model, as well as a super-compact under-sink model designed for commercial use with sinks that are not tied to the main hot water lines. Notably, the Slimline RD150 is the slimmest domestic cylinder on the market in the UK, and capable of being installed in some of the tightest spaces imaginable.

The Super S line of hot water heaters are available in both direct and indirect (gas) versions, but both are unvented, meaning that they rely on pressure created during the heating of water to supply hot water to the taps, rather than mains pressure as with a thermal store hot water heater or a conventional gravity feed system.

OSO dataplate

OSO Hot Water

OSO unvented water heater

OSO Water Heater Faults

While OSO Hotwater UK is regarded as a pioneer in the industry, as well as one of the greenest hot water heater manufacturers in the world, the fact remains that their products are not trouble-free. As they age, they are subject to experiencing a number of faults. While some of these can be diagnosed and even repaired by the average homeowner, others cannot, and some are dangerous to attempt. We have listed some of the most common faults for OSO unvented water heaters below.

No Hot Water: If the unit is not heating water, there could be a number of problems. The most common issue is that the safety cut-out has been activated because an immersion heater thermostat or tank thermostat has failed. It is also possible that the thermostat is set too high, and the temperature tripped the cut-out feature. Homeowners can attempt to reset the cut-out with the manual reset button within the electrical box. However, if the fault persists, an EasyFlow technician will need to service the unit.

Hot Water Discharge in the Tundish: If very hot water is being discharged through the tundish, it is a sign that something is wrong. It is possible that the pressure relief valve has malfunctioned, but it could also be a problem with the thermostat or with the thermal cut-out. Homeowners should immediately isolate the unit from the power supply and call EasyFlow for service.

OSO Direct RD

OSO Direct RD

Stopcock and PRV

Intermittent Discharge through the Tundish: If you are noticing a slow or intermittent discharge of warm or cold water into the tundish (but not very hot water), the most likely culprit is the expansion vessel. If the expansion vessel loses its pressure, the system will periodically discharge water. The vessel must be recharged to 3.5 bar to alleviate the problem. An EasyFlow technician can handle this service quickly.

No Water from the Hot Taps: If you open the hot tap and no water comes out, it means either there is a blockage at the mains, which is unlikely, or the hot water heater’s strainer has become blocked. The strainer will need to be removed and cleaned to restore water flow to the hot water taps.

At EasyFlow, we specialise in servicing a broad range of hot water heaters, including models from OSO Hotwater UK. Whether you’re experiencing intermittent discharge, no hot water or something completely different, one of our experienced technicians can help.

If you need assistance with any hot water heater repairs, to schedule hot water heater maintenance, or to install a new hot water heater, call EasyFlow at 0800 433 4043

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Find out more about EasyFlow Maintenance Plan

Our maintenance plans are designed to ensure our customers enjoy peace of mind, and constant hot water. We keep your hot water flowing while minimising your costs and eliminating stress. Let our experts identify and correct water heater faults, while you enjoy low monthly payments.