A draft gauge is essentially a manometer used to measure draft of low gas heads, such as draft pressure in a furnace, or small differential pressures of less than 1 psi. These instruments are suitable for checking flue pipe, chimney, fire box, smoke hood, smoke pipe draft, draft regulator, oil burner firing rate, and basement ventilation.
Manifolds are used to monitor and charge HVAC systems. These units will have multiple ports for different refrigerant types. The majority of these units are simple analog instruments. However, there are many digital manifolds on the market today that enable the user to perform other complex operations such as calculating superheat and subcooling, linear adjustment of the pressure sensors, and micron measurements via a built-in micron gauge.
This video demonstrates the Fieldpiece SMAN4. It is a 4-port, wireless digital manifold with a large 3/8" port for faster evacuations and recovery. This is just one of the digital manifolds available from TEquipment.
Gauges are simply used to monitor HVAC systems. The vast majority of gauges can be used to measure pressure of any type of refrigerant, however the temperature scales located on the inner rings of the gauge are based on pressure-temperature data for specific refrigerants. If you are looking to get pressure-temperature data from your gauges, make sure they are marked for the refrigerant you use.
HVAC gauges can range from simple analog gauges to digital vacuum gauges with built in high and low pressure alarms and integrated timers to record how long the system has maintained a deep vacuum. Digital gauges have several advantages over analog gauges. Primarily, digital gauges are more accurate. The typical accuracy for digital gauges is 0.5% of full scale, although it can range anywhere from 0.35% full scale to 1% of full scale. It is important to remember however that the accuracy of a digital gauge can vary with temperature. Digital gauges also feature better display resolution than analog options. Most digital gauges have a resolution of 0.1 psi and can display pressures through their entire range in increments of 0.1 psi. The best analog gauges show increments of 5 psi.
This video demonstrates the Fieldpiece SVG3 Digital Micron Vacuum Gauge. This gauge is an affordable digital option that incorporates alarms, a stopwatch, and display resolution of 1 micron.