Generator Use & Safety

Spring is [hopefully] coming soon with expected turbulent weather.  A new hurricane season is also upon us.  Both are liable to cause disruptions to utility electrical power.  Annual ARRL Field Day is also approaching.  Time to think about auxiliary power generators.

Small gasoline-powered generators are relatively common and widely available for emergency or portable electrical power.  It’s a good idea for the prepared homeowner to have one, mainly to keep the fridge/freezer cold during times of sustained power outage.  The savvy radio amateur also recognizes the importance of communications capability in a blackout scenario as well.  Power is needed to make our radios work beyond what limited battery capacity we have, particularly in emergency situations.  Most EmComm groups include generators in their plan and have them on hand.  Not every ham does.

Honda Generator

Consider having a small generator for essential power when the lights are out for hours.  Having a generator is good; knowing how to use it safely is the focus of this topic.  We will look at four related safety considerations:

  1. Carbon Monoxide hazards— CO
  2. Fuel handling and storage (fire)
  3. Generator grounding
  4. Shock hazard

Carbon Monoxide (CO) is the primary hazard with generators, since  CO is produced in the exhaust of all gasoline and natural gas combustion engines. 


NEVER, ever run a generator inside a dwelling or garage where exhaust can seep into the occupied space.  CO is a colorless and odorless gas which can kill or injure humans and animals.   It can be detected only with chemical or electronic CO detectors; it’s wise to have detectors in every home.


Always operate a power generator outdoors in a well-ventilated area.


Fuel (typically gasoline) should be stored away from the generator and also out of any dwellings for fire safety.  Stored fuel should have a stabilizer/preservative mixed in to keep it usable beyond a few months.  Generally recommended to store the generator with an empty fuel tank and add fuel when power is needed.

Never fill a generator while it is running; switch off and cool down before refueling to avoid hot exhaust and/or electrical sparks from igniting fuel vapors.  It’s wise to have a Class BC (suitable for fuel and electrical) fire extinguisher handy near an operating generator.

Generator grounding is an important and controversial topic.  Equally authoritative sources have conflicting perspectives.

On one hand, many (most?) generator manufacturers specify to ground their portable generator to a suitable earth connection or ground rod, as do many EmComm and portable ham radio (Field Day) guidelines.  Grounding or bonding to earth is necessary when a generator is connected to building wiring.

On the other hand,  the US labor safety authority known as OSHA states that grounding a generator under the commonly used conditions introduces an increased risk of potential shock or electrocution hazard.

Gen Ground Hazard

Diagram taken from an OSHA Training Institute Monograph found on the ARRL electrical safety website (referred below).  The takeaway from this paper quotes chapter and verse from the US code of federal regulations and the National Electrical Code:

CFR Gen Ungrounded

The “following conditions” part is important because they lay out the situation where a generator is not required to be grounded.  Basically, when the loads are plugged into the generator (not hard-wired to building),  and  the receptacle grounding sockets have good electrical connection to the generator frame.  This would be the case for most common household and EmComm use of a generator (appliances and/or radio equipment, cord connected) .  

Further, the ARRL’s Introduction to Emergency Communication course EC-001 curriculum states that it is not required to ground a generator when loads are plugged in using cords:EC-001 GENERATOR GROUNDING

In summary, we have two conflicting positions on generator grounding.  Without taking a stance, this website is merely presenting both.  The reader should research the merits and consider how to apply one or the other to their own installation or use of a generator.  It may change from one situation to another.

The ARRL Handbook for Radio Communications (2013 edition, at least) speaks to this controversy in section 29.3.1, mentioning that there are hams on both sides of the fence.  The word “vigorously” is used.

To minimize electrical shock hazards, keep the generator sheltered (yet well ventilated) from rain and other moisture.  Do not touch the generator with wet hands.

More importantly, plug in a limited number of appliances directly to the generator using heavy gauge extension cords (not too long or undersized) in good condition .  If you choose to wire a [mid- to large-size] generator to the house wiring, make sure to disconnect the utility wiring first.


The issue here is that your generator will back-feed the area power lines if not isolated.  This can cause shock or electrocution of neighbors or utility workers who may be working on wires.  You could have a small but lethal generator energizing un-isolated power lines.  Also, when power is restored (exactly when, you cannot anticipate ), your generator is likely to be destroyed or damaged by incoming utility service.

Better yet, install a transfer switch to ensure that only one source or the other feeds the house wiring.

Sidebar note– if you have a mobile radio you already have a generator built into your vehicle.  The car battery can provide quite a bit of power with the engine switched off.  Once that gets low you can idle the engine for a while to charge the battery and power the radio and related accessories.

Make sure to follow the CO guidelines and run the vehicle outdoors; never in an enclosed area such as a garage.

Most modern ham radio equipment uses 12VDC power anyway.  For 120VAC to supply other appliances a power inverter can be used within reason.

Also consider that you have a potential source of fuel for your aux generator which could be siphoned from the vehicle, depending on which engine is most critical in the situation.

A few references on generators relevant to ham radio:

Red Cross

Portable Generator Safety Tips

Grounding Requirements for Portable Generators


Ham Universe


Harris County (TX) ARES Training (good stuff, a few discussions of generators)

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