1. The brew boiler of G3028A is made of SUS304 stainless steel.
2. The water-contacting pipes inside the steam thermoblock are made of 304 stainless steel.
3. The parts that transport water from the boiler/ thermoblock to the group head/ steam wand are made of food-safe PTFE (Teflon) material.
4. The water tank is made of ABS plastic.
5. The exterior of the G3028A is primarily made of SUS430 stainless steel.

OPV (Over Pressure Valve) is a key component in an espresso machine’s brewing system. It sets the maximum brew pressure, preventing over-extraction or potential machine damage.

When pump pressure exceeds the preset limit, the OPV diverts the excess to maintain stable brewing pressure.

G3028A Coffee Machine Default Settings (All Adjustable): 

- Automatic coffee time: 25 s
- Water flowing to coffee bed time: 2 s
- Soaking time: 2 s
- Coffee temperature: 199 °F
- Steam thermoblock temperature: 293 °F
- Milk frothing temperature: 140 °F
- Automatic steam mode: S-1
- Default OPV Valve Setting: Tighten fully counterclockwise

1. Purpose of the OPV
The Over-Pressure Valve (OPV) is designed to regulate the maximum brewing pressure, thereby preventing over-extraction and protecting the machine from potential damage.

2. Recommended Pressure Setting
The ideal brew pressure range is 9–12 bar. Note that actual pressure can be influenced by factors such as grind size, coffee dose, puck density, and the overall extraction system.

3. Dual-Mode OPV Overview
The G3028A is equipped with a dual-mode OPV that supports both preset and manual pressure control, offering flexibility for users at all experience levels.

4. Tips for Beginners

Before adjusting the OPV, ensure your grind size is calibrated to reach approximately 9 bar under default settings.

Avoid lowering the pressure below 6 bar during extraction.

Keep in mind that while proper OPV settings help achieve extraction stability, final flavor is also affected by grind quality, coffee beans, and brewing technique.

For further guidance, please watch the "OPV User Guide" video tutorial:
https://www.youtube.com/watch?v=oU_J6_7VPBc

Spraying from a bottomless portafilter is common during espresso extraction. When pressure builds, water naturally flows through the weakest or uneven spots in the coffee puck, resulting in channeling or spray.

Ways to reduce spraying:

1. Use a distributor/leveler to ensure an even coffee bed.
2. Check for clumps — break them up to avoid channeling.
3. Use proper dose, grind size, and extraction parameters (use 58mm basket):
- Coffee powder is 17~20 g
- Coffee brewing temperature 194~205 °F
- Group head pressure 9~12 bar
- Extraction time 25±5s
- Powder-to-liquid ratio 1:2~2.5

1. 【Mode 1: Pre-Set Pressure Before Brewing】(Beginner-Friendly)
You can set the maximum extraction pressure before brewing, and the machine will maintain it automatically.

- Advantages: Simple operation, easy to achieve stable extraction, ideal for beginners;

- Example procedure: 
Loosen OPV → Place cleaning disc on the empty portafilter and lock it to the group head → Start extraction → Turn OPV counter-clockwise to reach desired pressure → Stop adjusting. 


2. 【Mode 2: Manual Pressure Control During Brewing】(Advanced Users)
Adjust the pressure in real time during extraction to fine-tune flavor according to bean characteristics.

- Advantages:
Achieve precise control over the extraction process to meet your custom requirements for different coffee beans and flavors. Enables personalized and professional-level extraction. Ideal for advanced users and coffee enthusiasts.

3. Tips For Beginners: 

① Confirm grind size reaches 9 bar with default settings before using OPV. 
② Avoid adjusting the pressure below 6 bar during extraction.
③ Proper OPV settings help achieve stable extraction, but the final flavor also depends on grind size, bean quality, and barista technique.

Steamed Milk Frothing Tutorial: 

1. Choose the right milk:
Use cold, refrigerated whole milk (approx. ≥3.6% fat, ≥3.2% protein). This produces smoother, creamier microfoam.

2. Steam wand position:
The wand has a temperature probe and a steam tip. Submerge the temperature probe under the milk surface, with the steam tip just below the surface
roughly at the depth shown in the reference image (milk covering the red line). No need to insert too deep.

3. Observing Foam Thickness:
- Too Thin Foam: The steam tip is too deep → no air enters → only heats the milk without frothing.

- Too Thick Foam: The steam tip is too too shallowly to the surface → too much air enters → too thick, bubbly foam.

- For detailed instructions, please refer to the "Milk Frothing" section of the G3028A "Make a Perfect Coffee" tutorial video: 
https://www.youtube.com/watch?v=JmX5b2onmyI- For detailed instructions on frothing milk, please refer to the G3006 "Steam Function Tutorial" video tutorial:
https://www.youtube.com/watch?v=HcmfhWZYeNU

How to Reset the OPV: Tighten fully counterclockwise to reset.

For detailed instructions, please refer to the "OPV Reset" section of the "OPV User Guide" tutorial video: 
https://www.youtube.com/watch?v=oU_J6_7VPBc