As a professional HVAC trainer, I help HVAC service technicians and contractors get better at their jobs and earn more money. That includes the facility maintenance staff, too! Many of my live classes are well attended by facility maintenance pros from apartment complexes, resorts, hotels, municipalities, and large office buildings and factories. Frequently, I get asked questions about gear in general and test instruments in particular.

I decided to give you a bonus with my top three test instruments a facility maintenance technician should have:

1. A good digital multimeter.

A good quality digital multimeter should be on the top of every technician’s tool list. Hands down it is the most valuable instrument in the tool crib. With so many choices and price points available, how should you choose? Here is my advice:

-Get a good quality all in one meter. All in one meters combine the features and functions of a digital multimeter (DMM) with an amp clamp meter. These meters can measure all the necessary voltages and Ohms as well as current without breaking the circuit. Additional features like non-contact voltage detection, frequency, capacitance, temperature, and DC micro-amps are often included. Look for units that feature a soft carrying case and good quality test leads. Expect to spend between $150 and $250 for a good quality meter. Brands such as Fluke, UEI, TPI, Fieldpiece, Klein, Extech, and Ideal all make good units.

2. A dual input digital thermometer.

Even though the digital multimeter you have may also measure temperature, nothing can take the place of a good dual input digital thermometer. Measuring two temperatures at once is important when working on HVACR equipment. For example, you may need to measure the inlet and outlet temperature of a water heater at the same time. Dual input thermometers make it easy to measure the temperature difference across a heating or cooling coil. Digital thermometers can be calibrated to be extremely accurate and they also respond very quickly to changes in temperature.

Some units will also log temperature over time which is very handy if you are monitoring a troublesome walk in freezer or some other thing that has intermittent problems. The UEI DT302 is a great choice as is the Amprobe TMD-53.

I like to have a separate thermometer apart from the multimeter because I often need to measure temperature and electric simultaneously. For example I made need to know what is the boiler supply temperature when the aquastat closes.

3. A Carbon Monoxide Tester

Carbon monoxide may be the biggest indoor environmental hazard we face in our society today. Carbon monoxide is a colorless, odorless, poisonous gas that is a byproduct of burning fossil fuels. Acute exposure symptoms range from headaches and nausea for medium level exposure to unconsciousness and death for high level exposure. Long term exposure to low levels of carbon monoxide can cause a wide range of mysterious health problems and ailments.

All fuel fired appliances are potential sources of carbon monoxide. Gas and diesel engines and generators are too. If your facility has any natural gas, propane, fuel oil, wood, gasoline, or diesel fired equipment, you building is subject to possible carbon monoxide infiltration. Close proximity to loading docks or parking structures can also allow carbon monoxide to enter your facility.  I recommend that every mechanical room be equipped with a stationary carbon monoxide alarm. These units are similar to a smoke alarm but designed to detect carbon monoxide. Further, Facility HVAC personnel should be able to make spot tests using a proper carbon monoxide ambient tester.

The UEI CO71A, the Testo 317-3 and the fieldpiece SCM4 are all good instruments for measuring carbon monoxide in the ambient air. They can also be used to narrow down the source such as a water heater draft diverter or a burner. These instruments will fit in your shirt pocket and display a measurement of carbon monoxide in parts per million (PPM), and they are reasonably priced. ($180 – $220) If CO is detected, I recommend you contact the utility provider, the fire department, or your HVAC contractor to find the source of the problem with their meter. (Professional meters will cost between $400 and $700.)

For more information about carbon monoxide including testing and detection, visit

Including a good digital multimeter, a good digital thermometer, and a carbon monoxide tester in your tool kit will get you well on your way to doing more work in house and relying on outside contractors less. If you aren’t sure how to use these tools, or need some additional training, make sure you are on my mailing list to get regular training session updates. Just a reminder, I also provide private in house training for facility maintenance crews to address these issues and more!

To Your Success,

Eric Shidell
HVAC Service Mentor