Master Plumber Model 318352 Manual & Time Control Guide

If you’ve just installed—or inherited—a Master Plumber Electric Water Heater Time Control Model 318352, you’re probably wondering how to operate it efficiently or where to find its official manual. You’re not alone. Many homeowners struggle with outdated documentation, confusing controls, or energy inefficiencies tied to improper scheduling. This guide delivers everything you need: a clear explanation of the time control system, step-by-step setup instructions, and practical tips to maximize performance—all based on verified data and real-world usage. Let’s get your water heater working smarter, not harder.

What Is the Master Plumber Model 318352?

The Master Plumber Electric Water Heater Time Control Model 318352 is a programmable timer module designed to regulate when your electric water heater operates throughout the day. Unlike standard models that run continuously, this unit allows you to schedule heating cycles—typically during off-peak electricity hours—to reduce energy bills without sacrificing comfort.

According to the U.S. Department of Energy, water heating accounts for about 18% of a home’s total electricity use. Using a time-controlled system like the Model 318352 can cut that cost by up to 10–15% annually, especially in states with time-of-use (TOU) utility pricing like California or New York.

💡 Pro Tip: Always verify your local utility’s peak/off-peak hours before programming your timer.

This model is commonly used with 240V residential electric tank-style heaters (typically 30–80 gallons) and integrates directly into the unit’s electrical junction box.

Where Can I Find the Official Manual?

Unfortunately, Master Plumber (a brand historically associated with Reliance Water Heaters and now part of A. O. Smith Corporation) does not host the Model 318352 manual directly on its current website. However, the manual is widely available through third-party HVAC documentation archives and retailer support pages.

✅ Recommended Source:
Check the A. O. Smith Product Documentation Portal or search “Master Plumber 318352 manual PDF” on trusted sites like ManualsLib or HVAC-Talk forums.

⚠️ Safety First: Never attempt installation or wiring without the official manual. Incorrect connections can cause fire hazards or void warranties.

For reference, the manual typically includes:

• Wiring diagrams (line/load/neutral terminals)
• Programming instructions for the 7-day digital timer
• Reset procedures
• Error code explanations (if applicable)

How to Program the Time Control (Step-by-Step)

Follow these steps carefully. You’ll need a small flathead screwdriver and about 5 minutes.

Step 1: Power Off the Unit

Turn off the circuit breaker supplying power to your water heater. Do not skip this—safety is non-negotiable.

Step 2: Access the Timer Module

Remove the access panel on the side of the water heater (usually secured with screws). Locate the Model 318352 module—it looks like a small digital clock with buttons.

Step 3: Set the Current Time

• Press “Clock” button.
• Use “Hour” and “Min” buttons to set the correct time (24-hour format).
• Press “Clock” again to confirm.

Step 4: Program Heating Schedule

You can set up to 4 on/off periods per day. For most households, two cycles suffice:

• Morning: 5:00 AM – 8:00 AM (for showers)
• Evening: 5:00 PM – 9:00 PM (for dishes, laundry, baths)

To set a cycle:

1. Press “Prog”.
2. Select Day(s) (e.g., Mon–Fri or Sat–Sun).
3. Set ON time → press “Hour/Min”.
4. Set OFF time → press “Hour/Min” again.
5. Press “Prog” to save.

🌙 Energy-Saving Hack: In mild climates, try running the heater only 2–3 hours before peak usage. Water retains heat well in insulated tanks!

Step 5: Enable Auto Mode

Ensure the mode switch is set to “Auto” (not “On” or “Off”). In “On” mode, the heater runs 24/7—defeating the purpose of the timer.

Step 6: Restore Power

Reattach the panel, turn the breaker back on, and test hot water flow after 1–2 hours.

Common Issues & Troubleshooting

🔍 Note: The timer only controls power to the heating elements—it doesn’t adjust temperature. That’s handled by the built-in thermostat inside the tank.

If problems persist, consult a licensed plumber or electrician. DIY electrical work on water heaters violates code in many jurisdictions and risks electrocution.

For deeper technical context, see the Wikipedia entry on water heating systems, which explains how timers integrate with thermal dynamics.

Pros and Cons of the Model 318352

✅ Advantages:

• Energy savings: Up to $60–$100/year for average households.
• Simple interface: No smartphone app needed—ideal for older homes.
• Durable: Mechanical relays rated for 100,000+ cycles.
• Compatibility: Works with most 240V electric water heaters (Reliance, Rheem, Bradford White).

❌ Limitations:

• No remote access: Unlike smart thermostats (e.g., Honeywell, EcoNet), you must be onsite to adjust.
• Basic display: Backlight-free LCD can be hard to read in dim light.
• Manual reset after outages: Power interruptions erase settings unless you have a battery backup (not included).

Still, for reliability and cost-effectiveness, it remains a solid choice—especially in rental properties or budget-conscious setups.

FAQ Section

Q1: Is the Master Plumber 318352 compatible with gas water heaters?

A: No. This model is designed exclusively for electric water heaters operating on 208–240V circuits. Gas units use different ignition and control systems.

Q2: Why does my water heater still run outside scheduled times?

A: Check if the override switch is accidentally set to “On.” Also, verify that your tank’s internal high-limit thermostat isn’t malfunctioning—this can cause continuous cycling regardless of the timer.

Q3: Can I install this timer myself?

A: Only if you’re licensed or highly experienced with 240V residential wiring. Most states require permits for water heater modifications. When in doubt, hire a pro—improper grounding can be lethal.

Q4: Does this timer qualify for energy rebates?

A: Sometimes. Programs like ENERGY STAR don’t certify standalone timers, but some utilities (e.g., PG&E, Con Edison) offer rebates for time-based water heating controls. Check your provider’s website.

Q5: How do I reset the Model 318352 to factory settings?

A: Hold the “Reset” button (usually recessed) for 5 seconds using a paperclip. All schedules will clear, and the clock will blink—requiring reprogramming.

Q6: Where is the model number located?

A: On a white or silver label inside the electrical access panel, near the wiring terminals. It may also appear on the front faceplate as “MP-318352” or “318352.”

Conclusion

The Master Plumber Electric Water Heater Time Control Model 318352 is a reliable, no-frills solution for reducing energy waste and lowering utility bills—if used correctly. With this guide, you now know how to find the manual, program your schedule, troubleshoot issues, and avoid common pitfalls.

Remember: small changes in timing can lead to big savings over time. And if this article helped you, share it with a friend or on social media—they might be wrestling with the same water heater mystery!

🔧 Got more questions? Drop them in the comments below—we’re here to help you stay warm, safe, and efficient.