How to choose manifold gauges

Manifold Gauges

This article is to introduce some basic knowledge of analog manifold gauges and how to select them properly.

It’s essential for a HVAC/R technician to use manifold pressure gauges as a diagnosis and service tool. It requires some specific knowledge to choose the proper manifold gauges.

1. Application of the gauge

The gauges show the pressure of liquids/gases in a cooling system and the vacuum pressure in the process of testing or charging the device. The gauges with different pressure scope are designed for different refrigerants. A common gauge is designed for various refrigerants such as R410A, R22, R32, R134a and R407c with a large pressure scale 0-800 psi (high pressure, left side, blue) and 30-500 psi (low pressure, right side, red). To be more precise, people may also need a gauge for R134a only with pressure scale 0-400 psi/0-140 psi. Besides the basic function of pressure check, the gauges are also used to remove contaminated or unknown blend refrigerants from the ac systems, reducing the possibility of cross-contaminating.

2. Material of the gauge

The manifold body can be made of brass or aluminum. Although brass looks better and more expensive in cost, the aluminum body has an unbeatable feature: It has a sight glass in the middle to observe the flow of the refrigerants during operation.

3. Digital gauge

Nowadays people can find more and more digital gauges in the market. The numerical reading is accurate but the tool itself is quite complicated and much more expensive. An experienced tech may like the traditional analog gauges anyway.

4. Key points for gauge selection

After introduction of the basic information about the manifold gauge, you should understand some key points to select a proper gauge:

  • The refrigerant in use. You may choose MG-2-R134a for R134a only or MG-4-R410A for R410A only. For multi-refrigerants, MG-2-R410A is designed for R410A, R22, R32, R134a and R407c and MG-2-R22 can be used for R22, R134a, R404A and R407C.
  • The gauge diameter. There’re two popular sizes for the gauge: 68 mm and 80 mm and the former is more common.
  • Digital gauge needs professional training besides its high cost. Due to its simplicity the analog gauge is more popular.

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