3.5. Water Cooling

Water cooling is available as an option on water-cooled MagnaDC power supply models. On water-cooled units, chilled water at or below the rated inlet temperature must be supplied to the product’s water inlet. An internal on-off solenoid controls the flow of water, opening only when cooling is needed (see Solenoid Operation), so that chilled water flows only when required; this improves efficiency and limits condensation buildup inside the product. Extensive temperature monitoring through thermal sensors mounted directly to the heatsinks ensures that the power semiconductors do not overheat in the absence of water.

Magna-Power Electronics water-cooled DC power supplies are built with copper and brass fluid paths; PEX tubing is also used in some cases where a central manifold distributes water to multiple products or internal assemblies. Because of these metallurgies, deionized (DI) water must not be used — it is highly corrosive to copper and brass, leading to premature wear and damage. Instead, follow the guidelines below to maintain water quality, ensure proper heat transfer, avoid scale buildup, and minimize corrosion or biological growth. These recommendations draw upon Magna-Power Electronics’s experience with best practices for water cooling systems.

Refer to your product’s specifications for the maximum inlet water temperature, minimum flow rate, maximum inlet pressure, and water connection type.

3.5.1. Solenoid Operation

During normal operation, the SLx Series MagnaDC power supply controls the water solenoid automatically based on internal temperature, using two strategies that run together:

• Condensation control (default). The firmware compares the hottest internal heatsink temperature against the product’s internal ambient temperature. The solenoid opens when the hottest heatsink rises roughly 5 °C above ambient and closes again once it falls roughly 5 °C below ambient. This hysteresis admits chilled water only while the product is warmer than its surroundings, minimizing the risk of internal condensation in cooler or humid environments.

• Over-temperature protection. If any monitored temperature approaches its protection trip threshold (about 90% of the trip point), the solenoid is forced open regardless of the condensation logic. Once all monitored temperatures fall back below about 85% of their trip points, control returns to the condensation strategy above.

When the load is disabled or power demand drops, cooling output ramps down gradually rather than switching off abruptly. The current solenoid state (open or closed) is reported by the solenoidStatus bit of the status register.

For maintenance, draining, and verifying actuation, the solenoid can be cycled manually from the front panel under Maintenance → Cycle Solenoids. Entering this mode disables the output and places the product in standby with a Maintenance status; the firmware then energizes each solenoid and fan in turn at full output for 60 seconds, repeating the sequence continuously. Fan-speed settings have no effect and the output cannot be enabled while the mode is active. Listen for the solenoid to click and confirm the open state using the solenoidStatus bit of the status register. Power-cycle the product to exit the mode and return to normal operation.

Warning

Allowing water to flow in a low-temperature or humid environment can cause condensation inside the product, leading to corrosion or electrical faults. Damage related to condensation or unapproved cooling practices is not covered under warranty.

3.5.2. Cooling System Types

Open-loop systems typically draw water from an external source (such as municipal water, a cooling tower, or another reservoir) and then discharge it after use. Ingestion of hard water can lead to scale formation. Scale can impede water flow, coat the interior of copper/brass lines, and cause the solenoid valve to seize. Air contact and continuous water makeup can introduce dissolved oxygen, minerals, and biological contaminants, increasing corrosion and biofouling risks. More frequent treatment and monitoring are needed to manage hardness, corrosion, and microbial growth.

Closed-loop systems continuously recirculate the same volume of water through the product’s heat exchanger with minimal makeup. Although closed loops are inherently less prone to contamination from outside water, leaks or inadequate pretreatment of makeup water can still introduce hardness, contaminants, or microbes. Closed-loop systems usually operate at low dissolved oxygen levels, which helps reduce corrosion. However, stagnant areas or dead legs can harbor microbial growth. Proper filtration, corrosion inhibitors, and periodic checks are essential to maintain water quality over time.

3.5.3. Water Quality and Treatment

Softened water is generally preferred to reduce hardness. Excess hardness deposits (calcium, magnesium) are the main culprit behind scale plugging small flow paths and solenoid valves. Partially demineralized or RO-permeate blends may be acceptable if they are conditioned with the proper corrosion inhibitors and pH buffers. Avoid pure DI water; it can leach metals from copper/brass and cause severe corrosion.

Keep total hardness (as CaCO₃) under 10 ppm in a closed loop if possible. In open loops, continuous monitoring and chemical treatment are critical to ensure scaling does not occur.

Copper and brass components benefit from azole-based inhibitors (e.g., tolyltriazole or benzotriazole), which form a protective film on copper-based alloys. Mild steel or cast iron piping (if present) can be protected with nitrite or molybdate inhibitors. These also help buffer pH in a closed loop. Regularly test inhibitor residuals and keep them within the ranges recommended by your water treatment supplier.

For copper and brass, a pH range of 7.0–9.0 is typically acceptable — going too high can risk localized corrosion on brass, and going too low accelerates copper corrosion. In a closed loop, it is easier to maintain the pH setpoint; in an open loop, you may need continuous monitoring to adjust feed chemistry as water quality fluctuates.

Microbial growth (algae, bacteria, fungi) can form biofilms that impede heat transfer and foster under-deposit corrosion. Apply non-oxidizing biocides periodically (e.g., glutaraldehyde, isothiazolone), or oxidizing products for remedial action (e.g., chlorine dioxide), if microbial counts rise. Consider side-stream filtration and routine draining or flushing of stagnant segments to prevent microbial buildup.

3.5.4. Preventive Measures and Maintenance

Side-stream or in-line filtration helps remove suspended solids that cause fouling or block narrow cooling passages. Aim for 1–5 micron filtration, especially in closed loops, to capture fine particulates. Monitor the pressure differential across filters and change or clean filters when the differential rises (e.g., 10 psi above baseline).

Schedule annual inspections of the product’s cooling path, looking for scale or debris around the solenoid valve and fittings. Clean any buildup promptly: flush the system with softened water plus a compatible cleaner, or follow your water treatment supplier’s recommended cleaning and passivation procedure.

In a closed-loop system, track daily or weekly water makeup using a flow meter. Losses beyond expected drift or minor maintenance are a sign of leakage. Excessive makeup in an open loop can rapidly degrade water quality, introducing hard water and contaminants.

Periodically verify flow in all piping segments (including seldom-used branches or bypass lines). Stagnant areas promote corrosion and microbial growth. Consider rerouting or installing a bypass line to keep flow continuous through rarely used piping.

3.5.5. Pressure Monitoring

Magna-Power Electronics recommends monitoring inlet water pressure so the product operates only under adequate water supply conditions. Choose a pressure switch that provides a dry contact for a simple permissive, or a pressure transmitter (analog to a controller) if you need visibility and logic. Place the device on the supply line feeding the product inlet.

Integrate the signal into the product’s interlock so the loop is closed when healthy and opens on fault. With a switch, wire its normally closed contact in series with other safety devices; with a transmitter, have the controller drive a relay that opens the interlock on fault. Commission the system by recording normal readings at your installation and verifying that simulated low-pressure conditions open the interlock and command a safe shutdown.

• Setpoints: Trip thresholds 10–20% above the product’s minimum pressure; optional high-pressure trip at 90–95% of the product’s maximum.

• Timing: 0.5–2.0 s running delay before tripping to avoid nuisance events.

• Reset: Prefer manual reset; if auto-reset is used, require 5–10 s of healthy readings before re-enabling.

3.5.6. Preparing for Shipping or Storage

Before transporting or storing a water-cooled MagnaDC power supply, clear all internal water passages of residual fluid. Trapped water can freeze, spill, or promote corrosion during transit and prolonged storage.

Warning

Disconnect AC power from the mains and confirm 0 Vac before connecting or disconnecting water lines. Control power is required only for the brief steps that command the solenoid, as noted below.

To empty the water path:

1. Shut off and disconnect the external chilled-water supply from the product’s water inlet.

2. Connect a regulated source of clean, dry compressed air (approximately 40 PSI) to the water inlet.

3. With control power applied, enter Maintenance → Cycle Solenoids from the front panel. The product enters its maintenance cycling mode (output disabled, Maintenance status), repeatedly opening the solenoid in 60-second intervals; the applied compressed air clears liquid from the water path each time the valve opens. Confirm the open state using the solenoidStatus bit of the status register and continue until no more water exits the outlet.

4. Once the path runs dry, power-cycle the product to exit maintenance mode, then remove control power and disconnect the compressed air.

Cap or plug the inlet and outlet fittings to keep the cleared passages dry until the product is reinstalled.

3.5.7. Cleaning the Water Path

In the event of a stuck solenoid caused by deposit buildup, or after prolonged storage, Magna-Power Electronics suggests circulating a mild acidic solution to dissolve deposits. The recommended procedure is:

1. Prepare a 5-gallon container with a solution of 5% acetic acid and 95% filtered water.

2. Use a small water heater set to its highest temperature and keep the container covered to retain heat.

3. With control power applied, recirculate the heated solution through the unit for up to 24 hours. Periodically enter Maintenance → Cycle Solenoids to actuate the valve through its full travel and help work deposits loose; power-cycle to exit the mode when finished.

Note

The SLx Series MagnaDC power supply solenoid does not permit reverse flow. Always circulate the cleaning solution in the normal inlet-to-outlet direction; do not attempt to reverse the flow direction through the unit.

Following this method helps restore solenoid operation by removing accumulated deposits, minimizing downtime and the need for solenoid replacement.