Uploaded April 2020 | Updated September 2026, 2 weeks ago

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Wiring for frost thermostats on S plan, Y plan and combination boiler heating systems. This uses two thermostats in series, the first senses air temperature and the second the temperature of the return heating pipe, so that if activated, the boiler only stays on long enough for the pipes to be heated, rather than heating the whole building.

Many boilers have internal frost protection, but that only senses temperature within the boiler, which may not be sufficient if the boiler is located in a warmer part of the building such as in an upstairs room.

► Other videos in this series
S Plan: youtube.com/watch?v=V9rN5D-wQIc
Y Plan: youtube.com/watch?v=B7eAiiKUk2Y
Complete list of all heating videos: youtube.com/playlist?list=PLVsHvs2Suqmr5HtxgbInR4bXmH0kLseWc

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