The National Product Standards Office announced the recall on Thursday, after laboratory tests found that a sensor inside Seorin Thermal Instruments’ TH-4 modules could warp in humid conditions and register too much heat. The devices are fitted to radiators in 612 apartment complexes, mostly in Seoul, Incheon and Daejeon.
Officials say the fault can push a household’s recorded heat use as much as 38% above its actual level. The ₩84 billion estimate is the total value of heating charges linked to affected devices since 2022, not a confirmed overcharge; a government review is now checking past bills before ordering refunds.
A cheap meter, a costly policy
The recall reaches beyond one manufacturer because the TH-4 became a common choice under the government’s 2024 Fair Heat Billing Programme. The scheme offered apartment managers rebates of up to ₩2.2 million per home to install individual heat controls, and officials listed the device as eligible after it passed certification tests.
“This is not a minor accounting error. It is a policy failure built into the monthly bill,” said Aleš Marković, a housing economist at the Seoul-based Civic Rental Institute. He estimates that tenants in the affected complexes may have paid several million won more than necessary over four winters, though the figure will vary sharply by flat and heating use.
When the state subsidises a meter, it cannot tell tenants to sort out the bill alone.
Aleš Marković, housing economist
Seorin said it would replace every affected module at no charge and pay for independent checks of disputed bills. Its public notice estimates that 61,000 households could qualify for adjustments, but it has not offered a total refund figure. The company says its engineers are still establishing when each device began producing unreliable readings.
Tenants face a long wait
Heat charges in many South Korean apartment buildings are collected through monthly management fees, alongside services such as lifts and cleaning. Renters often pay the building manager or landlord rather than receiving a separate heating bill, making it harder to spot a faulty reading or challenge an unexplained rise.
The Housing Energy Bureau has told building managers to preserve billing records and give residents itemised statements by 20 November. Kristel Fjodorova, an analyst at the Korea Housing Accounts Centre, said the deadline would be difficult for older complexes that changed management firms or kept records on paper.
“The dangerous part is the gap between a recall notice and a corrected bill,” Fjodorova said. “A tenant may move out before anyone works out what they were owed.” The government says it will publish a claims process next month, but has not decided whether managers or the manufacturer must make the first payment.
The recall also puts pressure on the government’s housing-efficiency drive, which was promoted as a way to cut energy use without forcing residents to pay for expensive building-wide upgrades. Vijay P. Dewan, a public-administration lecturer at Seoul Civic University, said officials had treated product certification as a substitute for checking how devices performed in occupied homes.
The bureau has paused rebates for the TH-4 and ordered checks of other models on its approved list. A parliamentary committee is due to review the programme’s certification rules in November. Until then, the dispute is likely to leave renters with a simple but costly question: whether the heat charge on next month’s fee is a measurement, or merely a number waiting to be corrected.
