Digital Zeus™ HVAC Tool & Instruments Journal

The Fieldpiece® HVACGuide™ Models HG1 | HG2 Full Field Manual and QuickStart Guide have been added to Zeus’ File Box. Lower right column black box. Feedback on this instrument is appreciated.

External Static Duct Pressure

- Using your Combustion Air Analyzer to determine External Static Pressure -

Probably one of the most frequently ignored factors in setting up a duct system is the external static duct pressure (ESP).

In years past the temperature rise or drop across the coil or heat exchanger could verify that the air flow was in the ‘ballpark’, but with the higher efficiencies, particularly of air conditioning systems and heat pumps, air flow becomes absolutely critical. In fact, if the air flow is not per manufacturers recommendations, it is impossible to even get the refrigerant charge correct.

Ironically, measuring ESP is a fairly simple procedure and, in all likelihood, will result in increasing customer satisfaction with the system’s performance, comfort and efficiency as well as find more work on a jobsite. Several studies have concluded that most heat pump and air conditioning systems have duct systems that are inadequate to supply sufficient air flow.

To correctly measure ESP, a static pressure tip is used in conjunction with a pressure gauge capable of reading in the hundredths of a water column inch. Bacharach’s electronic instruments which measure differential pressure (typically used for draft measurements), can measure ESP.

The two Bacharach combustion test instruments commonly used to measure ESP are the PCA 25 (and higher series) or the Fyrite Pro 125.

PCA 25

Fyrite Pro 125

In the photo’s above, the differential pressure taps are the two on the right hand side, the port on the left hand side is for sampling combustion gases.

This Article provided courtesy Bacharach® Instruments. For the rest of this Article: http://hvacprotech.forumwise.com/hvacprotech-post-11130.html#11130

The Need To Test With Digital Instruments

Today, most oil fired equipment is still being serviced and adjusted with traditional manual combustion efficiency test equipment [wet kits] for field service and seldom is testing done on gas, coal, or wood burning equipment. These kits generally consist of a stack thermometer, draft gauge, wet chemical CO2 gas tester, slide rule and smoke pump. Although this equipment has served the industry well over the years, faster, more accurate, real time flue gas analysis is necessary.

Many service technicians are reluctant to utilize digital instruments; there is a certain comfort in using what we are used to, and in some cases we figure if we don’t know, we cannot be held responsible. Nothing could be further from the truth. Failure to test does not absolve you of liability. Information is power whether it used for you or against you.

With digital equipment many errors with the measurement process are eliminated. Analog measurement errors can be the result of interpolation errors, calibration errors, poor repeatability of the measurement and most importantly not having a procedure in place to consistently repeat the measurement process.

Tuning a system should happen in real time, not “after the fact” with a very highly “averaged” sample. [Each squeeze of a wet kit bulb represents a different snapshot of the flue gas. A traditional test blends all those snapshots together into one reading.]

Only digital analyzers allow you to take real time tests. You cannot do a real time test with a a wet kit; it is physically impossible to take the sample fast enough and do the slide rule calculation.

Today testing is not an option, but rather a necessity on every gas, oil, wood or coal equipment that you might service. The truth is digital instruments are faster, more accurate, more reliable and have a higher repeatability than most analog tools. Digital instruments stay in calibration, allow trending, allow more complex functions and save time. Digital instruments allow data to be recorded and reported without human error, and provide accurate results for you and your customers. Data can be recorded much faster than any technician could ever do the calculations and data can also be recorded whether or not the technician is there to see it [eg. using features like online mode on a Testo® 330]. In most cases, the data is an un-editable record, so what you see is what was measured at the jobsite. Permanent records allow the user to track system changes and determine if the system is operating within the design parameters or if changes have taken place.

The Article above is an excerpt from the Testo® Combustion Applications Guide: For Residential and Light Commercial Appliances [A Measurements Reference for the Advanced Technician]. Authored by Jim Bergmann. Learn more about combustion analysis, combustion analyzers or talk to Jim Bergmann at The Technicians Forum: HVAC PROTech.com® http://www.hvacprotech.com

Combustion Testing: ON a Viessman CT3-46 (Sealed Combustion)
Using a Testo® 330-1 combustion analyzer and Easy Heat™  software, observed the combustion over time in high and low fire. The stability of the combustion is being affected by changes in CAZ (Combustion Air Zone) pressure due to intermittent loss of draft through the appliance due to the negative fluctuating mechanical room pressures. This was observed during the draft readings, CO readings, stack temperatures and O2 readings. Due to the instability of the combustion process, both boilers will require re-commissioning after the ventilation air issues are resolved. Although no CO was produced during operation as the technician left the boiler, changes in building pressures could result in CO formation and pose grave danger to the building occupants. 

Using a Combustion Analyzer to Test Heat Exchanger Integrity: http://hvacprotech.forumwise.com/hvacprotech-thread4956.html