December 3, 2014
The clocks not being accurate can be attributed to the frequency Hz output of the generator. Electric clocks rely on a constant 60 Hz to run accurately, most portable generators use a mechanical engine governor in order to regulate speed typically 3,600 RPM equates to 60 Hz, However most portable generator engines will vary in speed to some degree depending on the load. Lower engine RPM's will produce lower Hz causing the clocks to run slower while higher engine RPM's will cause clocks to run fast.
Furnaces, unlike consumer electronics, do not have a built-in regulated power supply They rely on a clean, consistent sine wave to power an IFC (integrated furnace control) and establish clock timing and synchronization of integrated circuits. A simple IFC may only control furnace functions such
as turning line or low voltage switches on and off, controlling fan-timing circuits, and monitoring flame rectification circuits. More advanced IFCs also control voltage to igniters, ECM and VFD
motors, and variable frequency drives. Even the simplest IFC may not operate when supplied with poor quality power. Furnaces have a minimum basic electrical requirement for voltage, frequency and power quality. The accepted standard is: 120 V ± 10 % (108 V to 132 V) 60 Hz frequency ± 3 % (57 Hz to 63 Hz) Harmonic distortion <5 % THD Furnaces supplied with voltages that have harmonic distortion greater than 8 % THD may not operate or will operate with possible damaging consequences for the electronic circuitry and components. It is common for standard generators to be in the 9% range and some to produce THD as much as 15%. I suspect that the THD of this generator is what is causing the problem you are having with your furnace. I would suggest that you contact your furnace manufacturer and ask what the power requirements are for your model in particular what the maximum allowable THD is. If it requires a THD of less then 5% then you may need to look into generators that have a THD lower then 5% or look into an inverter type generator. Hope this helps.
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