Excel Tankless Water Heater Troubleshooting
On this page (7 sections)
The Short Answer: Most Excel heaters are compact propane units rated around 1.6 gallons per minute, lit by battery-powered spark. When they pass cold water, the usual causes are an empty or closed propane cylinder, dead batteries, too little water flow to trigger the burner, or an oxygen-depletion sensor (ODS) shutdown. A unit without a vent connection should only be run outdoors.
Where an unvented propane heater can run
The small Excel units are sold without a flue connection, and some listings describe them as vent-free. This site treats any propane water heater without a vent connection as an outdoor appliance: never in a house, garage, basement, RV, camper, van, tent, shower enclosure, or any other enclosed or partly enclosed space. The oxygen-depletion sensor shuts the burner off when oxygen drops. It does not measure carbon monoxide, and it is not a substitute for venting. For other compact propane units, see Camplux troubleshooting. Larger Excel “Pro” models are built to connect to a flue and should be installed by a qualified gas installer according to their instructions.
Why it is running cold
| What happens | Likely cause | How urgent |
|---|---|---|
| No click or spark when water flows | Dead or reversed batteries, or flow too low to trigger the unit | Owner check |
| Clicks but never lights | Cylinder empty or closed, regulator frozen, or air in a new hose | Owner check, then service |
| Lights, then goes out after a short time | ODS trip from poor air supply, wind, or a failing ODS | Stop if it repeats |
| Lights but water is only warm | Flow higher than the unit can heat, or very cold inlet water | Expected limit |
| Yellow, smoky flame or soot | Combustion problem | Stop using it; service |
| Water dripping from the cabinet | Leaking fitting or a freeze-damaged heat exchanger | Stop using it |
What you can check safely
- Propane: the cylinder valve is open, the cylinder is not empty, and other propane appliances on the same supply work. A regulator covered in frost in cold weather can starve the burner.
- Batteries: replace them with fresh ones in the orientation marked in the battery box.
- Water flow: the unit lights only above a minimum flow. Open the hot tap fully, then reduce it if needed. Clean the inlet screen only if your manual tells the owner how.
- Temperature controls: both the gas and water knobs on the front change the output. Higher water flow means lower temperature rise.
- Location: the heater should be outdoors with open air around it, away from wind gusts that can blow out the flame.
Do not loosen hose or pipe fittings to “check for gas,” and do not tamper with the ODS.
How much hot water to expect
A unit in this size class can raise the temperature of roughly one low-flow shower’s worth of water. On a cold day, with 45 to 50 °F inlet water, a full-flow shower head may only come out lukewarm even when everything works. Turning the water flow down raises the temperature. If you need several fixtures at once, a heater of this size is the wrong tool.
What the technician will check
A gas technician confirms the supply and regulator pressure against the rating plate, inspects the burner and ODS pilot for spiders, dirt, or damage, and checks the spark electrode and gas valve. They also check for water leaks inside the cabinet, which usually come from freeze damage.
Repair or replace
Parts and authorized service for compact imported units are limited. Fresh batteries, a new regulator, or a cleaned burner are worthwhile. A cracked heat exchanger, a failed gas valve, or a unit that has been overheated is usually replaced rather than repaired.
Frequently Asked Questions
Q: Why does my Excel shut off after a few minutes? A: The most common reason is the ODS reacting to poor air supply or wind disturbing the pilot flame. Make sure the unit is outdoors in open air and out of strong wind. If it keeps shutting off, stop using it and have it inspected.
Q: Can I use an Excel heater in my camper or shower house? A: Not an unvented unit. Run it outdoors only. For RV hot water, use an appliance designed and vented for RV installation, such as the units described in Girard tankless troubleshooting.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
- CPSC: carbon monoxide fact sheet (opens in a new tab)Carbon monoxide hazards and emergency response.
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