Motor Rewinding in Bomet

What 1,959 m does to a frame size. IEC 60034-1 rates a motor for installation up to 1,000 m. Bomet sits 959 m above that datum, and thinner air carries less heat away from the windings — the conventional allowance is about 1% of output per 100 m, so roughly 10% here. A motor selected on its nameplate alone is therefore already working closer to its thermal limit before the driven load is considered.

And what 27.7 °C does to the rewind. The rating datum is a 40 °C ambient, leaving about 12.3 °C of headroom at Bomet before the motor generates any heat of its own. Insulation life is governed by temperature and the accepted rule is that every 10 °C of sustained overtemperature halves it, so at this ambient the insulation class and the cooling arrangement decide how long a rewind lasts far more than the winding wire does. Voltage imbalance compounds it: a few percent of imbalance produces a disproportionate rise in rotor heating, and on a site already short of thermal headroom that is what turns a rewind into a repeat rewind.

Moderately warm. At 27.7 °C design ambient the thermal penalty is modest — roughly 1.1% — and standard radiator packages have margin in hand. What deserves attention instead is the gap between the 24 °C typical day and the 29.2 °C peak: an installation sized for the average will be the one that trips on the hottest afternoon of the year, which is usually also the afternoon you most needed it.

What this does to windings. Insulation life is governed by temperature: the accepted rule is that every 10 °C of sustained overtemperature halves it. A motor at Bomet starts from a 27.7 °C ambient before it generates any heat of its own, so the insulation class and the cooling arrangement decide how long a rewind lasts far more than the winding wire does. Specifying a higher class than the minimum is usually the cheapest life extension available at this ambient.

Load profile. Bomet sits in the middle band for population, where demand is concentrated in a handful of towns rather than spread evenly. In practice that means standby duty for institutions and commercial premises, where the machine sits idle for weeks and then has to start and take load without argument — which makes exercise regime and battery condition matter more than peak-output arguments.

Getting there. Bomet lies about 184 km west of our Embakasi, Nairobi workshop in a straight line — road distance is longer. Our mobile workshop covers all 47 counties, so visits here are planned rather than improvised — we confirm the fault description in advance so the right parts travel with the engineer.

How to read these figures. Altitude and temperature are for Bomet, the Bomet County headquarters — counties span wide ranges, so these are county reference points, not your site values. The figures derived from them are planning indications, not a substitute for a site survey and measured readings. Elevation: GeoNames, via the Open-Meteo Geocoding API. Temperature: Open-Meteo ERA5 reanalysis, 2025 daily maxima. Both CC BY 4.0, retrieved 2026-08-08.