Understanding The 15-120-15 Pressure Gauge Ordering Code

When many people first see the string of numbers “15-120-15” on the pressure gauge case or outer packaging, their subconscious reaction is: Is this a range? For example, measure vacuum on the left and positive pressure on the right?

To be honest, if you really follow this logic to place an order, you will fall into a trap if you keep it accurate. This three-paragraph number combination is, to put it simply, a set “internal code” (order number) created by the manufacturer for the convenience of its own shipments. It’s neither a standard industry term nor does it allow you to see at a glance how much pressure this watch can withstand.

What exactly are these three numbers “implying”?

In circles like air conditioning, refrigeration, or refrigerant, there are many codes that look like “brothers”, such as 15-100-100 or 15-120-30.

Don’t look at them, they look quite similar, and the meaning may be a hundred and eighty thousand miles different. According to the unspoken rules within the row, these three groups of numbers usually represent the dial size, mounting method (whether it is connected below or behind), and range range, respectively. But the problem is that the seating order is different for each manufacturer! If you don’t open the manufacturer’s ordering manual that is as thick as a brick to check, even if you are a master craftsman who has been working for more than ten years, it is easy to “grab blind” just look at this string of numbers.

And there’s one most overlooked “hard flaw”: this string of encodings is usually unsuffixed. This means you have no idea how large its connector threads are, nor do you know whether the scale unit is PSI or MPa, or even whether it is for R-134a or other refrigerants.

Why can’t I “see code recognition table”?

Many manufacturers try to save trouble and just throw it into the “refrigeration control” category, but this does not mean that it is the kind of refrigerant manifold meter you are looking for. The manufacturer divides it into major categories, just telling you that it can mix in this field. As for whether it can withstand the actual medium pressure you have, you still have to look at the detailed parameter table in black and white.

The principle is actually quite intuitive: to accurately describe a table, it must have a reference pressure (whether it is gauge pressure or absolute pressure), range start and end values, accuracy level, and unit. It’s simply unrealistic to try to cram so much core information into three numbers. If you confuse “maximum permissible pressure” with “scale limit”, it will be a safety accident.

Those pits about “positive and negative tables”

In refrigeration equipment, the low-pressure section often uses a type of pressure gauge with zero in the middle “composite pressure gauge”. The pointer of this type of table can measure vacuum to the left and positive pressure to the right, making it very suitable for systems where pressure fluctuates during operation.

But don’t assume that the code 15-120-15 appears in the manual and you must be a composite table. The numbers themselves do not contain any information about vacuum or positive pressure intervals. Want to confirm what number of roads it is? We still need to honestly check the manufacturer’s comparison table to see which part of the pressure section it covers.

Pit avoidance guide: How to avoid buying the wrong one?

If this is all you have, don’t rush to place your order yet. The following steps are the safest to take:

• Search the dictionary: First search for the manufacturer’s name, find the corresponding order number manual, and fill in these three numbers to take the corresponding number.
• Pick at the details: Confirm whether it is gauge pressure, differential pressure or compound pressure; see if the unit is Bar, PSI or something else. If this unit is wrong, the range will be completely messed up.
• For the interface: Check whether it is radial (connection below) or axial (connection behind), and whether the thread specifications are correct.
• Want environment: Is the medium temperature high? Is the environment corrosive? The joint material must be able to withstand it.
• The last truth: 15-120-15 is at most a “treasure hunt clue” and should never be used directly as a specification. Take it as a starting point, complete the suffixes, and align the parameters. This is the way to truly understand the selection table.