Inspection and Testing of Emergency Generators
NFPA 101(00), Sec. 188.8.131.52 requires that emergency generators be installed, tested and maintained in
accordance with NFPA 110, Standard for Emergency and Standby Power Systems. Chapter 2 of NFPA
101 references the 1999 edition of NFPA 110.
Buildings that fall under Chapter 18 of NFPA 101(00) and are equipped with or in which patients
require the use of life-support systems (e.g. hospitals, nursing homes with residents on ventilators)
must also meet the maintenance and testing provisions of the 1999 edition of NFPA 99, Standard for
Health Care Facilities [see NFPA 101(00), Sections 184.108.40.206, 220.127.116.11, 18.104.22.168 and 22.214.171.124].
Provisions dealing with maintenance and testing of emergency generators can be found in NFPA
99(99), Sec. 3-4.4. This section starts out by referencing NFPA 110, but also deals with such issues
- Testing intervals
- Test conditions
- Personnel qualifications
- Maintenance and testing of circuitry
- Maintenance of batteries
In order to follow the requirements in NFPA 99 and NFPA 110, you need to know the classification
systems used by those standards:
1. Let’s take a look at NFPA 99 first:
a. NFPA 99 treats emergency generators as part of an essential electrical system (EES), which is
defined as, “A system comprised of alternate sources of power and all connected distribution
systems and ancillary equipment, designed to ensure continuity of electrical power to
designated areas and functions of a health care facility during disruption of normal power
sources, and also to minimize disruption within the internal wiring system.” [see NFPA 99(99),
Chapter 2, Definitions].
b. NFPA 99 breaks essential electrical systems down into three categories – Type 1, Type 2 and
Type 3. Basically, the services provided by a facility determine the type of EES required as
- NFPA 99(99), Sec. 12-3.3.2 requires essential electrical systems in hospitals to conform to
Type 1 system requirements.
- NFPA 99(99), Sec. 16-3.3.2 requires essential electrical systems in nursing homes to
conform to Type 2 system requirements. By exception, however, Type 3 systems are
allowed in nursing homes that do not provide life support (e.g. ventilators).
c. For a more detailed description of these three types of systems, see Chapter 3 of NFPA 99(99).
If you’re unsure about which type of system describes your generator, the vendor that installed
and/or maintains your generator should be able to provide you with that information.
2. NFPA 110, on the other hand, treats emergency generators as part of an emergency power supply
a. There are two important definitions to keep in mind [see NFPA 110(99), Chapter 2]:
- Emergency Power Supply (EPS): “The source of electric power of the required capacity and
quality for an emergency power supply system (EPSS), including all the related electrical
and mechanical components of the proper size and/or capacity required for the generation
of the required electrical power at the EPS output terminals.”
A further explanation can be found in the Appendix [see NFPA 110(99), Sec. A-2-1]:
“For rotary energy converters, components of an EPS include the following: prime
mover, cooling system, generator, excitation system, starting system, control system,
fuel system, and lube system, if required.”
- Emergency Power Supply System (EPSS): “A complete functioning system of an EPS
coupled to a system that can consist of conductors, disconnecting means, and overcurrent
protective devices, transfer switches, and all control, supervisory, and support devices up to
and including the load terminals of the transfer equipment needed for the system to operate
as a safe and reliable source of electrical power.”
b. NFPA 110 breaks emergency power supply systems down into two categories – Level 1 and
Level 2. Once you know the NFPA 99 classification of your emergency generator (i.e. Type 1,
Type 2 or Type 3), that standard tells you where your generator fits into NFPA 110. NFPA
99(99), Sec. 3-126.96.36.199 specifies that:
- Type 1 and Type 2 essential electrical system power sources shall be classified as Level 1
generator sets per NFPA 110.
- Type 3 essential electrical system power sources shall be classified as Level 2 generator
sets per NFPA 110.
State licensure requirements
MSFC(07), Sec. 604.3 requires that emergency generators be maintained in accordance with the 2002
edition of NFPA 110. Fortunately, the provisions in this edition of the standard applicable to inspection
and testing are very similar to those found in the 1999 edition of the standard.
Maintenance and testing – Applicable standards
Requirements for routine maintenance and operational testing of emergency generators can be found
- Chapter 6 of the 1999 edition of NFPA 110
- Chapter 8 of the 2002 edition of NFPA 110
- Sections 3-4.4, 3-5.4 and 3-6.4 of NFPA 99(99)
Maintenance and testing – General
1. Maintenance and testing is critical to the continued reliability of your emergency generator and
must be performed in accordance with manufacturer’s recommendations, instruction manuals, and
the minimum requirements of NFPA 110 and the authority having jurisdiction (AHJ) [see: NFPA
110(99), Section 6-1.1; NFPA 110(02), Sec. 8.1.1].
2. Your facility should have at least two sets of instruction manuals for all major generator
components. One set should be kept in a secure, convenient location near the equipment. The other
set should be kept in a different secure location [see: NFPA 110(99), Section 6-2.1; NFPA 110(02),
Sec. 8.2.1]. These manuals must, at a minimum, contain the following:
- A detailed explanation of the operation of the emergency power supply system
- Instructions for routine maintenance
- Detailed repair instructions
- An illustrated parts list and part numbers
- Illustrated and schematic drawings of electrical wiring systems, including operating and
safety devices, control panels, instrumentation and annunciators
3. Special tools and testing devices necessary for routine maintenance must be available for use when
needed [see: NFPA 110(99), Section 6-2.3; NFPA 110(02), Sec. 8.2.3].
4. Routine maintenance, inspection and operational testing of the emergency generator and associated
components must be overseen by a properly trained person [see MSFC(07), Sec. 604.5; NFPA
99(99), Sec. 3-188.8.131.52(b)3; NFPA 110(99), Sec. 6-4.7; NFPA 110(02), Sec. 8.4.7]. Evidence of
such training should be kept in the designated employees’ personnel file. In the absence of a
properly trained person on-site, an outside vendor may need to be contracted to oversee the
performance of all or part of these services.
5. The standards do not establish a specific date and time of day for required testing. Those are to be
determined by management and are typically scheduled so as to provide minimum disruption of
To meet federal certification and state licensure requirements, healthcare facilities must inspect their
emergency generators weekly [see NFPA 110(99), Sec. 6-4.1; NFPA 110(02), Sec. 8.4.1]. At a
minimum, this weekly inspection should include a check of the following:
1. Fuel (check main and day tank fuel supply levels; day tank float switch; piping, hoses and
connectors; operating fuel pressure; and for any obstructions to tank vents and overflow piping
2. Oil (check for proper oil level and oil operating pressure; lube oil heater)
- Engine oil level can be checked with the unit stopped or running on many engines;
otherwise, it should be checked with the unit stopped
- Oil operating pressure should normally be above 40 psi
3. Cooling system (check coolant level, water pump(s), jacket water heater, belts, hoses, fan)
4. Exhaust system (check drain condensate trap and for possible leakage)
5. Battery system [look for possible corrosion; check specific gravity, electrolyte level (a level
between 1250 and 1275 is acceptable) and battery charger]
6. Electrical (conduct a general inspection of wiring and connections; check circuit breakers/fuses)
7. Prime Mover/Generator (Check for debris, foreign objects, loose or broken fittings; check guards
and components; look for any unusual condition of vibration, leakage, noise, temperature or
NOTE: This is not an all-inclusive list. The equipment manufacturer may have additional maintenance
requirements that will likely include monthly, quarterly, semi-annual and annual inspections and
1. To meet federal certification and state licensure requirements, healthcare facilities must exercise
their emergency generators under load at least monthly [see NFPA 110(99), Sec. 6-4.1; NFPA
110(02), Sec. 8.4.1]. There are a number of ways to comply with this requirement:
a. The base requirement is that generators be exercised for a minimum of 30 minutes* using one
of the following methods [see NFPA 110(99), Sec. 6-4.2; NFPA 110(02), Sec. 8.4.2]:
i. Under operating temperature conditions and at not less than 30 percent of the generator’s
nameplate kW rating. A 100 kW generator, for example, would need to be exercised under
a load of at least 30 kW to meet this requirement.
- Normal operating temperatures are set by the manufacturer. Something to consider
when scheduling your monthly tests is that your particular generator may not reach
operating temperature in 30 minutes* and that running the generator for short periods of
time may be harmful to the engine. You also want to make sure that the generator runs
long enough to ensure that all engine parts are properly lubricated.
ii. Loading that maintains the minimum exhaust gas temperatures recommended by the
manufacturer (it is unlikely that minimum exhaust gas temperatures will be reached if the
generator isn’t carrying a load equivalent to at least 30 percent of the generator’s nameplate
*Note: Warm-up and cool-down times do not count toward the required 30 minutes.
b. An alternate method is provided for diesel-powered generators that do not meet the testing
requirements outlined in 1.a above. This could occur when, for example, a large generator in
relation to the load is installed (e.g. either to account for the largest motor connected to the
generator or to accommodate future expansion of the facility). Such generators can be exercised
monthly with the available load and exercised annually with supplemental loads at 25 percent
of nameplate rating for 30 minutes, followed by 50 percent of nameplate rating for 30 minutes,
followed by 75 percent of nameplate rating for 60 minutes, for a total of 2 continuous hours
[see NFPA 110(99), Sec. 6-4.2.2; NFPA 110(02), Sec. 184.108.40.206].
c. For gasoline-powered, natural gas-powered or propane-powered generators that do not meet the
testing requirements outlined in 1.a above, it will likely be necessary to add more load to the
generator or conduct a load bank test to comply with testing requirements (a load bank is,
typically, a mobile piece of equipment that simulates the actual electrical load the generator is
intended to power). Where equivalent loads are used for testing, it’s important to note that such
loads are required to be automatically replaced with the emergency loads in case of failure of
the normal power [see NFPA 110(99), Sec. 6-4.2.1; NFPA 110(02), Sec. 220.127.116.11].
d. Where a generator set is used for peak load shaving or operated during a power outage, such
use is allowed to be substituted for a routine monthly test, provided the generator is operated in
accordance with the standards and the appropriate data are recorded. Another thing to keep in
mind, however, is that NFPA 99(99), Sec. 3-18.104.22.168(b)1 requires a minimum 20-day and
maximum 40-day interval between tests [see also NFPA 99(99), Sections 3-22.214.171.124(b) and 3-126.96.36.199(b)].
2. Load tests must include complete cold starts [see NFPA 99(99), Sec. 3-188.8.131.52(b)2; NFPA 110(99),
Sec. 6-4.3; NFPA 110(02), Sec. 8.4.3].
3. Time delays must be set as follows [see NFPA 110(99), Sec. 6-4.4; NFPA 110(02), Sec. 8.4.4]:
a. Time delay on start: 1 second minimum.*
Exception: Gas turbine cycle: 0.5 second minimum.
*Note: NFPA 101(00), Sec. 184.108.40.206 requires that emergency loads be picked up within
b. Time delay on transfer to emergency: none.
c. Time delay on restoration to normal power: 5 minutes minimum (to give the primary source
sufficient time to stabilize before retransfer of the load, a delay of between 15 and 30 minutes is
d. Time delay on shutdown: 5 minutes minimum.
It’s important to be prepared in case something goes wrong during testing. It is strongly recommended
that your facility have a policy in place that makes provisions for a portable generator or other alternate
power source for situations in which the emergency generator malfunctions or, worse yet, is out of
1. Transfer switches are required to be operated monthly [see MSFC(07), Sec. 604.3.3; NFPA
110(99), Sec. 6-4.5; NFPA 110(02), Sec. 8.4.5].
2. This monthly test must consist of electrically operating the transfer switch from the
normal/standard position to the alternate position and then a return to the normal/standard position
[see MSFC(07), Sec. 604.4.1; NFPA 110(99), Sec. 6-4.5; NFPA 110(02), Sec. 220.127.116.11].
- In many cases, a “Transfer Test” switch or button is provided and can be used to perform this
test. Where this feature does not exist, it may be necessary to manually disconnect normal
power in some fashion to the transfer switch (see “some words of caution on testing” below).
3. Transfer switches must also be inspected monthly to ensure that they are maintained free from
accumulated dust and dirt and to check for deterioration of the transfer switch contacts [see
MSFC(07), Sec. 604.3.3; NFPA 110(99), Sec. 6-3.5; NFPA 110(02), Sec. 8.3.5].
4. Because they are such a key component in the successful operation of your emergency generator, it
is recommended that you consider having infrared testing of your transfer switch(es) conducted
annually to check for loose connections.
Some words of caution on testing…
1. Shutting off power, especially shutting off the main breaker, can expose a person to possible shock,
electrocution and/or arc flash hazards. It is important, therefore, that anyone performing a test in
this fashion be adequately trained and take proper safety precautions, including the wearing of
proper personal protective equipment (PPE). To reduce the safety risks, it is strongly recommended
that facilities not already so equipped consider adding a switch for testing of their transfer
2. The explanatory information in NFPA’s 1999 Health Care Facilities Handbook to Sec. 3-
18.104.22.168(b)2, which addresses test conditions (including cold starts and appropriate automatic and
manual transfer of essential electrical system loads), provides more food for thought:
“Testing procedures might range from manually disconnecting power to the power sensors
on transfer switches to manually opening the main incoming feeder breakers. It is very
important that each test method be fully understood by all staff through appropriate notification
and that the consequences of each method (if something fails to function) be weighed carefully.
A procedure for returning to the normal power source should also be established in the event a
failure occurred during testing.”
“There is a false assumption that disconnecting a facility’s mains is the best method of
testing the standby generator(s) and essential electrical system. One has to always consider the
possibility that failure of the disconnecting means or some other unexpected contingency might
make it difficult or impossible to restore normal power. It is probably better to initiate engine
start by interrupting power just ahead of the transfer switch(es) on an alternating or rotating
basis in order to make sure each transfer switch has an intact engine start circuit.”
DOCUMENT your inspections and tests
NFPA 110(99), Sec. 6-3.3 requires the establishment of a written schedule for routine generator
maintenance and testing [see also: MSFC(07), Sec. 604.3.1]. A sample schedule can be found in
Appendix A of the standard [see Figure A-6-3.1(a)]** or may even be available from the equipment
manufacturer [see also: NFPA 110(02), Sec. 8.3.3 and Figure A.8.3.1(a); 1999 Health Care Facilities
Handbook Appendix C-3.2].
** Because there is a lot riding on the successful operation of a facility’s emergency generator,
it is strongly recommended that the schedule for Level 1 emergency power supply systems
be followed when establishing your maintenance schedule.
A written record of generator inspections, tests, exercising, operation and repairs must be maintained
on the premises and be available for review by the fire inspector on request. This record must, at a
minimum, include: the date of the report, name(s) of the person(s) providing the service, identification
of unsatisfactory conditions and corrective action taken (including parts replaced), and any testing of
repairs recommended by the manufacturer [see MSFC(07), Sec. 604.3.2; NFPA 99(99), Sec. 3-4.4.2;
NFPA 110(99), Sec. 6-3.4; NFPA 110(02), Sections 8.3.4 and 22.214.171.124].
- A sample inspection log can be found in Appendix A of NFPA 110(99) [see Figure A-6-3.1(b)]
or may even be available from the equipment manufacturer [see also: NFPA 110(02), Figure
- A sample testing log can be found in NFPA 110(02), Figure A.8.4.1(a) or may even be
available from the equipment manufacturer.
- As an alternate, sample inspection and testing logs have been developed to serve as a guide that
you can use in creating your own logs. Completed logs are provided to serve as examples of
how the logs are expected to be filled out.
It’s important that at least two people in your facility know where your logs are kept to increase the
likelihood that they can be readily provided if requested during an inspection. It is recommended that
these logs be maintained for at least three years.