How Hot Is It?

By Bob "Hot Rod" Rohr

Radiant expert

In the hydronic business, comfort is the product we sell and provide. The measurement we use to design, size, operate, service and troubleshoot is temperature.

This month, I will share some of the tools I use to start-up, adjust, document and troubleshoot hydronic systems.

Most boilers ship with some sort of temperature indicator. Long ago, most boilers came equipped with the tridicator-a gauge that measured temperature, pressure and the corresponding distance above the boiler the water will reach at various pressures. Most boiler manufacturers provide a tapping into the boiler for this multipurpose gauge, and some provide a tee and bushing to add it to the near boiler piping. I've found that the accuracy of these gauges is directly related to its selling price. On occasion, I have received the boiler and gauge with both indicator needles lying in the bottom of the window, no longer attached to the stems. It is getting hard to find a quality tridicator or temperature-pressure gauge anymore-at least the gauges that are shipped with the boiler.

If you have jumped on the mod con (modulating/ condensing) boiler bandwagon, you have no doubt noticed the trend to use digital temperature gauges. Often, this is incorporated into the control module on the face of the boiler. Most will allow you to read various parameters such as supply and return temperature at the boiler header, flue gas, and with an outdoor sensor, outdoor temperature. My experience has shown these to be accurate, easy to read and homeowner friendly.

Furthermore, you probably have a combustion analyzer if you service and install mod cons. These also have a temperature sensor in the probe for flue gas or air temperature.

Following are some options for testing and trouble shooting systems.

Point-and-shoot infrared temperature guns are popular and affordable. Some are equipped with a laser pointer to help narrow in on the target. However, theses guns can be fooled by shiny surfaces. New copper pipe, some ceramic tiles and other surfaces may produce a false reading. It may help use a black marker or to apply black friction tape to the copper pipe. While they look cool and impress the customer, be careful with what they tell you. Check out the new MicroRay IR-100 from Ridgid.

One of my current favorite digital thermometers is the dual-temperature Azel DS-60. It runs on a small, flat, internal watch battery, or can be conveniently powered by a 24-volt AC power source. This clever and affordable unit uses strap-on thermistors for sensing and can be used with leads up to several hundred feet long. It reads 32 - 248F. It also has a centigrade readout option. It will capture and store high and low temperatures until it is manually reset. These thermometers are great for reading delta T across supply-and-return pipes at boilers, radiant loops or manifolds, and indirect tank piping. I also include them on my outdoor wood boiler installations-I hang one sensor outside to read outdoor temperature and I install the other on the outdoor wood boiler supply tap to allow the homeowner to monitor the temperature from inside the home. You will likely find dozens of uses for this gauge.

Another favorite is the temperature sensing attachment for my Field Piece stick meter. This head reads two temperatures, -50 - 400F, and will also display the delta T number. The leads are fairly short, but it is a nice attachment to add to a multimeter.

For quick-and-simple readings, the Stick-temps from Watts Radiant are peel-and-stick strips that show temperature by color and small readout numbers. With a range from 100 to 260, these work nicely for temporary applications. I've found they work well for a year or so depending on the temperature they are reading. The higher the temperature, the shorter the working life of the strip. Keep a sheet of these in your glovebox.

Another must-have is the HOBO data logger. This tiny box reads multiple of locations and records the readings. Mine, shown here is a 4 channel. PICTURE You need the "Boxcar" software and a computer to use this tool. You can program the channels, temperature range and sampling interval on your computer or laptop, then disconnect and take the device to a jobsite. It is battery powered and can record temperatures over several days. Then, plug the unit back into your computer and download the data. You can print cool-looking graphs that illustrate the temperature action. In addition, it is easy to send these files via e-mail. The graph here shows a Paxton 4 way reversing valve at work in my shop.

When all else fails, use your hands. With experience I can feel a PEX or ferrous pipe and make a ball-park guess at its temperature. Also, PEX becomes supple at elevated temperatures. Your sense of smell can give you a clue, as well. PEX or rubber tube running at or above 160 tends to emit an odor. Just as an experienced plumber or pipe fitter can guess the length of a piece of pipe within an inch or so, you're experience will help you make good temperature estimates. Certainly, you could determine if a floor heat loop is warm enough to deliver some heat to the space.

Bob “Hot Rod” Rohr is particularly interested in “hybrid” radiant systems – systems that utilize solar and wood energy in addition to, or in place of, fossil fuel. Also, systems that incorporate different methods of heat delivery. He owns and operates Show Me Radiant Heat and Solar, Inc. in southwest Missouri. Reach hot rod at hotrodradiant@aol.com or by phone at (417) 753-3998.