Are digital gauges necessary? This is a question that comes up a lot, and there are a wide variety of opinions. After all, the HVAC industry doesn’t seem to favor one style over the other. Why is one any better than its alternative?
Most HVAC technicians should keep at least two sets of gauges, and potentially three depending on their exact work. Different types of HVAC units may be more compatible with different gauges. Consequently, there isn’t really a clear answer to the question of which gauge type is superior, if at all. Let’s take a closer look at both types and their potential applications to find the right answer for your situation.
Different Types for Different Work
You need two, possibly three, sets of gauges depending on what you are doing. Some techs like to have one set for 410 refrigerant machines and another for R22 machines. However, we have so many different types of refrigerants now it’s not practical to have a set of gauges for each. One set of digital gauges and one back up set of analog gauges is all most people will ever need.
Using Digital vs. Analog Gauges
Digital gauges are far superior for testing and adjusting the charge, and they’re absolutely imperative if you want accurate superheat and subcooling readings. Digital gauges have temperature clamps that connect to the liquid line and suction line and have built-in pressure-temperature charts. You simply tell the gauge set what refrigerant you are testing, hook up the hoses and temp clamps, and get live instant readings of superheat and subcooling. The margin of error is remarkably low.
If you use analog gauges to perform critical charging, you will have to read literally between the lines of the needle and the gauge lines. Once you guess the pressure reading, you must then use a pt chart to obtain the temperature equivalent. After you get that number, you have to actually take a temp reading of the appropriate line and subtract those two numbers. Along the way, chances are you will either misread something, make a mistake in the math, make a pt chart conversion mistake, or several of the above. Even if you manage to get all that correct, there’s a good chance that the system pressure or temperature changed between all the readings. This change alone will lead to inaccuracies of four to five degrees. When you are talking about subcooling number targets of 10 or 12 degrees and you miss it by six, that’s a significant margin of error.
What Do Industry Professionals Prefer?
Some brand manufacturers require the dealers to charge with digital gauges if they want to continue and sell that brand. Usually, these policies exist because manufacturers have received warranty returns due to improper charging methods rather than actual problems. Consequently, the requirement for digital gauges is a (generally successful) attempt to combat these warranty returns and preserve business.
Analog gauges have their place, however, especially if you are working on a system that has a bad burn out and has turned the oil into acid. You will not want to pull this into your $400 digital gauge set, so you whip out the trusty analog set. The analog is also a great back-up set when your digital set goes out.
Pro Tip: Different brands of digital gauges may have varying features, but overall, they all work about the same. Just find the brand with features you like the most.
Neither is Always Better
To summarize, there is no way to state for certain which type of gauge is better. While digital gauges are more convenient and generally preferred by HVAC professionals and manufacturers, sometimes an old-fashioned analog gauge works just as well or even better. The ultimate deciding factor is preference. To make sure you always have the type you or a client prefer, maintain a set of each type of gauge just in case.
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