Rheem MHD85245 - User Manual

Questions and Answers

M
Mr. Rodney CoxAug 7, 2025
Why is my Rheem Water Heater not producing enough hot water?
- M
  Misty MedinaAug 7, 2025
  If you're not getting enough hot water from your Rheem Water Heater, it could be due to several reasons. Your water usage might have exceeded the heater's capacity, so wait for it to recover. A fuse might be blown, or a circuit breaker tripped, so replace the fuse or reset the breaker. The electric supply to the water heater may be off, so ensure the power is on. Also, check that all hot water faucets are closed, as leaks can reduce hot water availability.
G
gsteeleAug 15, 2025
Why is the water from my Rheem MHD85245 Water Heater too hot?
- V
  Victor BridgesAug 15, 2025
  If the water from your Rheem Water Heater is too hot, the thermostat might be set too high. Also, check if any covers or insulation are missing and reinstall them, if needed.
K
Katherine WellsAug 23, 2025
What to do if the relief valve on my Rheem Water Heater is popping or draining?
- B
  Bryan McdanielAug 23, 2025
  If the relief valve on your Rheem Water Heater is producing a popping noise or draining, it's likely due to pressure build-up from thermal expansion in a closed system. This is an unacceptable condition and must be corrected. Contact the water supplier or plumbing contractor on how to correct this. DO NOT plug the relief valve outlet.
C
Christopher ColonAug 29, 2025
How to fix a rumbling noise in my Rheem MHD85245?
- M
  Melissa MiddletonAug 29, 2025
  A rumbling noise in your Rheem Water Heater is likely caused by a build-up of scale or mineral deposits on the heating elements due to water conditions. Remove and clean the heating elements. Contact a qualified service technician.

Summary

Important Safety Information

Water Temperature and Scalding Risks

Discusses dangers of high water temperatures and provides a time/temperature scald chart.

General Safety Warnings and Requirements

California Installation Requirements

California law requires bracing for water heaters due to earthquake risks.

Water Heater Installation Guide

Local Installation Regulations

Requirements for installation based on local codes, utility codes, and NEC.

Location Selection Criteria

Guidance on choosing a suitable location for the water heater installation.

Installation Procedures

Thermal Expansion Management

Explains thermal expansion in water systems and potential issues like closed water systems.

Vacuum Relief Valve Installation

Details the function and importance of the factory-installed vacuum relief valve.

Installation Details

Relief Valve and Drain Pan Installation

Instructions for relief valve installation and drain pan requirements.

Connection and Filling

Water Supply Connections

Guidance on connecting hot and cold water supply lines.

Filling the Water Heater

Step-by-step instructions on how to properly fill the water heater.

Installation Overview

Typical Installation Diagram

Illustrates a typical water heater installation setup with key components.

Electrical Setup

Electrical Connections Guide

Details on making proper electrical connections, including circuit sizing and grounding.

Electrical Sizing and Diagrams

Branch Circuit Sizing

Guide for sizing branch circuits and wire sizes based on National Electric Code.

Wiring Diagrams

Visual representation of electrical wiring for the water heater.

Installation Accessories

Insulation Blanket & Pipe Insulation

Information on insulation blankets and pipe insulation installation.

Operating the Water Heater

Operational Safety Precautions

Essential safety precautions to follow during water heater operation.

Safety Controls and Temperature Setting

Explanation of safety controls and how to adjust water temperature.

Thermostat Adjustment Procedures

Setting Water Temperature

Step-by-step guide on how to adjust the water heater thermostat.

Care and Cleaning

Draining and Maintenance

Procedure for draining, routine maintenance, and extended shutdown.

Troubleshooting Common Issues

Problem Resolution Guide

Common problems and their solutions to help diagnose issues before calling for service.

Replacement Parts Illustration

Element Replacement Instructions

Warranty Period and Claims

Warranty Period Details

Outlines applicable warranty periods for different installation types.

How to Make a Warranty Claim

Step-by-step process for submitting a warranty claim.

Owner Record Keeping and Product Registration

This document is a Use & Care Manual with Installation Instructions for Light Duty Commercial Electric Water Heaters, specifically for Double Element Models with 75, 85, and 105 Gallon capacities. It serves as a comprehensive guide for both installers and owner-operators, covering installation, operation, safety, maintenance, and troubleshooting.

Function Description:

The device is an electric water heater designed for light-duty commercial use. Its primary function is to heat and store water for distribution in commercial settings. It utilizes double heating elements to achieve the desired water temperature. The manual emphasizes the importance of proper installation and maintenance to ensure safe and efficient operation.

Important Technical Specifications:

Capacities: Available in 75, 85, and 105 Gallons (63, 71, and 88 Imperial Gallons, respectively).
Dimensions (Height x Diameter):
- 75 Gallon: 62 5/8" H x 28 1/4" D
- 85 Gallon: 70 1/4" H x 28 1/4" D
- 105 Gallon: 70 3/4" H x 30 1/4" D
- Note: Height includes factory-installed Temperature and Pressure Relief Valve.
Approximate Full Weight (when filled with water):
- 75 Gallon: 748 lbs
- 85 Gallon: 843 lbs
- 105 Gallon: 1,028 lbs
Electrical Requirements:
- Voltage: 240 Volt
- Wattage options: 3,000 W, 3,800 W, 4,500 W
- Recommended Over Current Protection (fuse or circuit breaker amperage rating) for 240V:
  - 3,000 W: 20 Amps
  - 3,800 W: 20 Amps
  - 4,500 W: 25 Amps
- Wire Size AWG (Based on N.E.C. Table 310-16 (75°C)) for 240V:
  - 3,000 W: 12 AWG
  - 3,800 W: 12 AWG
  - 4,500 W: 10 AWG
Thermostat Settings: Factory set at 120°F (49°C) for US models and 140°F (60°C) for Canadian models. The water heater is capable of supplying outlet water temperatures greater than 180°F (82°C) when both thermostats are set to high.
Temperature and Pressure Relief Valve: Must comply with ANSI Z21.22, have a pressure rating not exceeding 150 psi (1034 kPa), and a BTUH rating not less than the water heater's input rating (1 watt = 3.412 btu/h).
Vacuum Relief Valve: Factory installed on the cold water inlet to prevent tank failure due to negative pressure.
Water Connections: Cold water inlet and T&P relief valve use 3/4" NPT connections. Hot water connection uses either 3/4" or 1" connection depending on unit size, utilizing rubber seal rings for a watertight connection.

Usage Features:

Thermostat Control: The water temperature is regulated by adjustable surface-mounted thermostats located behind jacket access panels. Dual element heaters have two thermostats (upper and lower).
Temperature Adjustment: Instructions are provided for adjusting thermostat dial pointers using a small screwdriver. To increase temperature, adjust the bottom thermostat only. To decrease temperature, adjust all thermostats to a lower setting.
Safety Controls (ECO): Equipped with a combination thermostat and temperature limiting control (ECO) that breaks the power circuit if water temperature becomes excessively high. It must be manually reset after activation.
Scald Prevention: Emphasizes the danger of water temperatures above 125°F (51°C) causing severe burns. A time/temperature relationship chart for scalds is provided. Recommends lower thermostat settings for locations with small children, disabled, or elderly persons. Mixing valves are recommended for reducing point-of-use water temperature.
Installation Location: Should be in a clean, dry area near the greatest hot water demand, protected from freezing, and away from high-temperature appliances. The floor must be strong enough to support the full weight of the water heater. NSF International requirements for commercial installations (restaurants) include weather sealing to the floor, a raised base, or elevation for clearance.
Thermal Expansion Control: Discusses the importance of addressing thermal expansion in "closed water systems" by installing an expansion tank in the cold water line to prevent premature failure of the relief valve and the heater itself.
Filling the Water Heater: Crucial to ensure the unit is completely full of water before turning on electrical supply to prevent "dry firing" and voiding the warranty.
Wiring: Requires a separate branch circuit with copper conductors, overcurrent protection, and suitable disconnecting means. Wiring must conform to local codes and the National Electrical Code ANSI/NFPA 70 (or Canadian Electrical Code for Canadian models).

Maintenance Features:

Routine Preventative Maintenance: A routine program is suggested, including periodic inspection of operating controls, heating elements, and wiring by qualified service personnel.
Draining the Water Heater: Detailed instructions are provided for draining the unit, which is recommended monthly to clean the tank of hard water deposits.
Temperature and Pressure Relief Valve Check: At least once a year, the lever handle on the T&P relief valve should be lifted and released to ensure it operates freely, allowing several gallons to flush through the discharge line.
Vacuum Relief Valve Replacement: Recommended every six years due to potential mineral deposit buildup.
Insulation Blankets: External insulation blankets are generally unnecessary as the water heater meets Energy Policy Act standards. If local codes require them, specific cautions are given to avoid covering labels, access panels, or the top of the heater.
Element Replacement: Detailed, step-by-step instructions are provided for replacing heating elements, including safety precautions (turning off power, draining water), proper removal and installation, and tightening specifications. Emphasizes using elements of the same power rating as factory installed and ensuring the correct element for the upper or lower port.
Extended Shut-Down: For long idle periods or in freezing locations, power and water supply should be turned off, and the unit drained to prevent freeze damage.
Troubleshooting Tips: A chart is included to help diagnose common problems like rumbling noise, relief valve popping/draining, not enough hot water, or water being too hot, along with suggested solutions. Users are cautioned against attempting electrical repairs themselves.