How to balance a load on two power supplies for one rig?

Understanding the Need for Load Balancing in Mining Rigs

When building or operating a mining rig, especially one that utilizes high-powered GPUs, power distribution becomes a critical factor. A single power supply unit (PSU) may not be sufficient to handle the load of multiple graphics cards, which is why many miners opt to use two PSUs connected to the same rig. However, simply connecting two PSUs does not automatically ensure an even distribution of power. To avoid overloading one PSU while underutilizing the other, it’s essential to balance the load effectively.

This guide will walk you through the technical steps and considerations required to balance the electrical load across two power supplies within a single mining rig setup.

Selecting Compatible Power Supplies

Before diving into wiring, it's crucial to choose compatible power supplies that can work together without causing instability or damage. Key considerations include:

• Matching wattage ratings: Use PSUs with similar output capacities to prevent one from being overworked.
• Matching voltage outputs: Ensure both PSUs provide consistent voltages on their rails, especially the 12V line, which powers most GPU components.
• Quality and reliability: Opt for reputable brands with good reviews in mining communities to reduce failure risks.

Mismatched PSUs can lead to uneven current sharing, overheating, or even system shutdowns due to overload protection triggers.

Physical Setup and Cable Management

Once the appropriate PSUs are selected, the next step involves physically installing them in your mining case or rack. Proper installation includes:

• Mounting both PSUs securely to prevent movement or vibration-related wear.
• Ensuring adequate airflow around each PSU to avoid thermal throttling or overheating.
• Using modular cables where possible to simplify connections and improve airflow.

Adequate cable management is vital. Poor routing can cause accidental shorts or strain on connectors, potentially leading to unstable power delivery or hardware damage.

Distributing Power Across Components

To balance the load between two PSUs, you must distribute the power draw evenly across all components. Here’s how:

• Connect half of the GPUs to one PSU and the remaining GPUs to the second PSU.
• If your motherboard requires significant power, consider splitting CPU and peripheral loads between the two PSUs.
• For systems with multiple PCIe risers, connect each riser to a different PSU to spread out the total power draw.

It's important to monitor the power draw per component using tools like HWiNFO or BIOS readings to ensure neither PSU exceeds its recommended load threshold.

Connecting the PSUs to the Motherboard

Most motherboards expect a single 24-pin ATX connector and possibly an 8-pin EPS connector for the CPU. When using two PSUs, you need to determine which PSU will power the motherboard and which will focus on the GPUs. Typically:

• One PSU connects directly to the motherboard via the 24-pin and 8-pin connectors.
• The second PSU does not connect to the motherboard but instead powers only the GPUs via PCIe cables or risers.

If you're using a motherboard designed for mining with multiple 24-pin headers or special power inputs, consult the manual before proceeding. Incorrect connections can result in short circuits or permanent damage.

Testing and Monitoring the System

After completing the physical setup and connections, boot up the system and begin testing. Monitor the following:

• Use software like GPU-Z or HWMonitor to check individual GPU power consumption.
• Observe temperatures and fan speeds on both PSUs during operation.
• Run stress tests such as FurMark or mining benchmarks to simulate real-world conditions.

During testing, pay close attention to any signs of instability, including unexpected reboots, screen artifacts, or dropped hashrates. These symptoms could indicate improper load balancing or insufficient power delivery.

Frequently Asked Questions

Q: Can I use two different brands of power supplies together?While it's technically possible, it's not ideal. Different brands may have varying voltage regulation and response times under load, which can lead to inconsistent performance or increased risk of failure. It's best to use identical models if possible.

Q: Is it safe to connect both PSUs to the same outlet?Yes, provided the outlet and circuit can handle the combined load. Most modern outlets support up to 15–20 amps. Calculate the total wattage drawn by both PSUs and ensure it stays below 80% of the circuit capacity to prevent tripping breakers or damaging wiring.

Q: Do I need a splitter or Y-cable when using two PSUs?No, splitters or Y-cables are generally discouraged because they can increase resistance and heat at connection points. Instead, connect each GPU or riser directly to a dedicated PSU port to maintain clean power delivery and reduce fire hazards.

Q: How do I know if one PSU is working harder than the other?Use software monitoring tools to track power draw per GPU. If one PSU powers more high-consumption GPUs, it will naturally work harder. Balance this by assigning equal numbers of high- and low-power GPUs to each PSU or by adjusting BIOS settings to equalize GPU clocks and voltages.