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MODEL OVERVIEW
About this model: Midea MGWH150OSNN
MGWH150OSNN outdoor natural-gas tankless heater: 12 verified codes, flow, frost and safe service guidance.
Verify the outdoor natural-gas variant
MGWH150OSNN is Midea's 150 MBH outdoor natural-gas tankless water heater. Its product record gives a 24,000–150,000 BTU/h input range and a 6.25:1 turndown ratio; the appliance heats flowing water rather than storing a tank of it. The linked manual cover lists four Outdoor Series models, including propane and 199 MBH variants. Match all letters on the installed rating plate, because that shared cover does not make the fuel types interchangeable. The exact product page calls this version noncondensing and outdoor. It lists a 14-inch width, 5.9-inch depth and 22.2-inch height, with a shipping weight of 31.3 pounds. These are identification and planning facts; a qualified installer still has to select a compliant location and connection design.
Understand flow before assuming a fault
The manual's specification table reports 0.81 UEF for this Outdoor Series and, for the 150 MBH class, about 6.6 gallons per minute at a 37°F temperature rise, 5.2 at 47°F and 3.7 at 67°F. The relationship matters: colder inlet water or a higher requested outlet temperature can reduce the available hot-water flow. The listing specifies 120 V, 60 Hz electrical power and a 15–150 PSI water-pressure range. The no-hot-water chart first asks whether the water shutoff valve and hot tap are fully open, whether the unit and utilities are on, and whether a pipe is frozen. It also notes that the burner can go out when incoming water flow is too small. These checks describe symptoms; they do not justify changing gas pressure or opening the casing.
Treat the outdoor setting as a safety condition
This is an outdoor-only appliance intended for a vertical wall, and the manual asks for professional installation. Its air intake and exhaust area need to remain unobstructed; shrubbery, debris or a confined location can affect combustion. Periodic inspection of burner, relief valve, water filter and venting belongs to personnel qualified in gas-appliance repair. The manufacturer also calls for monthly air-intake and cold-water-filter cleaning. For the filter it describes switching off and disconnecting power, closing the water supply, unscrewing the screen, rinsing it under running water and avoiding taps that can deform it. It recommends descaling every six months. If you do not have the correct isolation arrangements or access, arrange this upkeep with a technician instead of improvising around live gas or electrical parts.
Plan for freezing and normal fan purge
Outdoor placement makes the freeze warning especially important. The built-in electric warming system helps protect the unit only while power is available; it does not cover the inlet or outlet pipes, and the manual explicitly says not to rely on it in severe cold. If a long shutdown or freezing weather is expected, follow the manual's drain procedure or ask the installer to prepare the system. Do not run the heater with a frozen pipe. Separately, a fan that continues for about 10–15 seconds after a hot tap closes is documented as normal purging of unburned gas. That short run-on is different from a displayed E5 fan fault. Write down the display characters and the weather or flow conditions before reporting a problem, because those details help distinguish a protective stop from normal operation.
Read the two code pages and limit your reset
The rendered manual pages list E0 for the outlet-temperature sensor, E1 for accidental flame loss, E2 for a false flame signal and E3 for a thermostat fault. The continuation adds E4 overtemperature, E5 fan, E6 solenoid valve, EE timeout, C0 ignition, C1 residual flame, C4 vent blockage and F2 inlet-temperature sensor. C0 ends in the digit zero. For a displayed code, Midea says close the hot tap, switch the unit off, wait about five minutes, turn it on and reopen a tap. If the code remains, record it and follow the documented service route; for an unlisted code, close the tap, power off and call assistance. The table includes component replacement actions, but the warning expressly reserves gas piping, burners, vents, display and safety-device repairs for qualified personnel. Repeated resets are not a substitute for that diagnosis.
Verified model details
Exact 150 MBH natural-gas outdoor variant
Source for this detail12 codes checked on PDF pages 44–45
Source for this detailFreeze system does not protect external pipes
Source for this detailBrief fan purge after tap closure is normal
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Midea 150MBH Outdoor Natural Gas Tankless Water Heater MGWH150OSNN
Open official sourceIf there is a safety risk, stop using the appliance and follow the manufacturer’s instructions.