Service technicians are often left playing the guessing game if they don’t have reliable and accurate electrical test meters.In the previous issue, we discussed the specialized test equipment required to work on heat-source appliances (fuel-burning boilers and heat pumps). This issue we will focus on test equipment needed for servicing and troubleshooting other parts of the hydronic system. This article is written for technicians in training and those that are qualified to work on HVAC equipment.
Electrical testing equipment
Without reliable and accurate electrical test meters, service technicians play guessing games and will often replace perfectly good parts until things start working again. Start-up and maintenance procedures require electrical testing to confirm that components are operating to specifications. My everyday go-to multimeter is a Fluke Model 16 (now 116), specifically designed for HVAC technicians. A number of manufacturers make similar models that measure AC and DC volts, ohms, micro-amps, and can be fitted with various temperature probes. The electrical test leads should come with detachable alligator clips. A max/min recording function is invaluable as is an easy to read back-lit display for poorly lit jobsites. If you can afford to upgrade, you might look at a similar model but with added smart phone capabilities, wireless probes, and data logging software.
Make sure to use pressure gauges for their intended purpose as you can ruin them if used improperly. For instance, the digital pressure gauge on the left shouldn’t be used for fluid pressure readings as water will destroy it.A clamp-on amp meter is another must for HVAC work, and most models will also give you volt, ohms, and continuity readings when used with plug-in test leads. If you aren’t testing micro-amps on flame rectification devices, a quality digital unit with these options may be the only meter you need for everyday use. If thermostats that have heat anticipator resistance wires are common in your work—a mini-amp meter in the zero to 1.2- or 1.5-amp range is a beautiful thing. Most thermostat heat anticipators have never been set properly. A mini-amp meter can show the correct adjustment, eliminating short cycling issues or wide room temperature swing problems. DC millivolt pilot generators are still common, and a dedicated meter with a zero to 1,000 millivolt range will help you troubleshoot from simple gas fireplaces to industrial equipment. Your digital multimeter may have settings for both of these tests but using single-purpose meters for these delicate readings is preferred.
Another nifty device to have in your tool pouch is a contact voltage detector. About the size of a mini flashlight, they light up and beep when you touch a “hot” wire, receptacle, or terminal. It’ll also help you figure out if some dangerous fool switched the neutral wire on you. Every circuit should be double-checked with a proper voltmeter before you start working on it. Stay away from really complicated, ultra-multi-function meters. They increase the risk that technicians might use incorrect functions, and most of us will never need or understand all that they can do unless we want to go deep into electronics. Revisit my note in the last article about “where to buy.” There are many makes and models of multimeters and you might purchase an accessory that is not compatible with your instrument if you choose the wrong supplier. Study what you are wanting to measure and talk to a knowledgeable vendor before you buy.
Temperature measuring
You can’t have enough temperature measurement equipment in the HVAC world. Hydronic system measurement needs vary widely. One thermometer just will not cut it. A versatile device for the ranges found in the HVAC world is a multimeter with a type K thermocouple input option. Look for one that accepts a variety of probes depending on what is being measured.
These are the three temperature measurement devices I use the most: an infrared camera, a Testo thermometer, and a glass mercury thermometer.For surface temperature readings, infrared temperature guns have come a long way and are quite affordable and useful as are infrared cameras. I have a Seek Thermal IR camera and use it all the time for troubleshooting, commissioning, start-up, as well as for illustrating system operation. High and low temperatures are shown in one shot—especially helpful in the hydronic world when detailing Delta T across various components. Infrared temperature measurement can be misleading because the emissivity of various components can lead to false readings. Some IR devices have emissivity adjustments but it’s best to confirm surface temperature with a dedicated surface temperature thermometer. I have a little Testo pocket unit that gives me instant readings at a touch. Most good multimeters will have surface temperature probe options including pipe clamp or strap, immersion, and insertion accessories. Look for purpose-built instruments for frequent use—much easier and less chance for error.
Fluid pressure
A hydronics technician should have a variety of fluid pressure gauges with lots of little fittings and adaptors to be able to connect them to piping systems. Old margarine containers seem to be the storage case of choice for the fittings, but the gauges should be kept in a padded hard case to prevent damage.
To deal with everyday wear and tear, I recommend high-grade oil or glycerin-filled gauges and suggest four-inch diameter dial faces for more precise readings. Choose units where the middle of the dial range is close to the pressures you normally want to read and be careful to avoid freezing temperatures after use. A female hose connector is really handy. I have a Lyncar Lazy Hand gauge that came with one out of the box and I use it often. If you are working with high head pumps, you will also want to get a combination gauge to measure vacuum as well as pressure.
These are some of the temperature measurement devices that I will regularly use on the job site.Your local plumbing wholesaler should be able to find you the gauges that best fit your needs. Ask them to order the exact ones you want if they don’t have them in stock.
Hydronic fluid testing
Hydronics specialists should be able to perform basic water quality testing during system fill or regular maintenance procedures. A refractometer for measuring glycol concentration is a must as well as pH test strips. If you use a particular brand of chemical treatment, you should get a test kit from that manufacturer to make sure whatever magic juice you are using is at correct concentrations and in good condition. A total dissolved solids meter is a good idea to see if fill water meets the boiler manufacturer’s max/min specifications.
Another really important point to make is to know what you are measuring and why. My number one troubleshooting rule is to leave your tools alone for at least a couple of minutes and take that time to look, listen, smell, feel and think. As you take a sensory and mental cruise around the boiler room, you will come up with questions that will lead you to reach for the appropriate diagnostic tool. For example, if you don’t think the system supply water seems hot enough, ask yourself: “How hot should it be and where should it be measured?” This will lead you to the temperature measuring device you should deploy.
Information technology
Don’t expect all temperature devices to read the same, there can be some variance between devices.If you are not familiar with a particular appliance or component and are not sure what to test for go and get more information. The biggest advantage for troubleshooting is using any of your smart devices to access I&O manuals. You can’t keep everything in your head, so never be shy about using outside resources. I once had a building owner rag on me for sitting down to read a boiler I&O manual. The information I needed was in the manual. I reached for my differential temperature meter, took the required measurement, confirmed the problem, and switched the pump from low speed to high. Problem solved and we got a lifelong customer.
Other great uses for smartphones include taking photos of rating plates, sketchy-looking installation details, and damaged components to send to your local support network. We are all in this together, after all.