Excel Tankless Water Heater Troubleshooting (Complete Guide)

The Excel tankless water heater is perfect for small spaces like hunting cabins and RVs. With a ventless design, the unit can deliver 96 gallons within an hour. Moreover, it can function with exceptionally low water pressure (2psi to 120 psi).

However, the tankless water heater model is not without a few faults. 

You may have to fix leaking gas valves, replace a poor temperature regulator, or change the outlet fitting. Fortunately, many of these are easy to fix ourselves. All you may need is a reset or a couple of additional parts.

This article will explore common problems in Excel tankless water heaters and outline how to solve them yourself.

Common Problems with Excel Tankless Hot Water Heaters

Like all appliances, the Excel tankless water heater may develop some faults after a few years. Excel users may experience one or more of the following problems—luckily, we’ve listed the solutions:

No Standard Outlet Fitting

The standard brass fitting for an outlet is often ¾ inch. This large pipe size allows for better flow and more hot water supply. 

However, the Excel tankless water heaters come with a ½” inch outlet fitting, which is rather small and inconvenient for most users. 

According to these owners, it is not cost-effective to return the unit to the manufacturer, as Excel manufacturers charge shipping fees for returned units. 

However, you can use a shark-bit plastic thread to adapt the fitting to the standard size. Ensure that you get the right plastic thread size to prevent water leaks from forming around the fitting. 

Does Not Turn Off Even When No Water Flow

In this situation, the heat exchanger will stay lit despite cutting off the water flow. With no water to cool it down, the exchanger will heat up and start melting other components within the unit. No doubt, this is a fire hazard.

A defective thermal switch or flow sensor is responsible for this error. In the 1.6gp Propane B08DHDX3DT unit, Excel did not use a conductive thermal paste between the thermal switch and the tubing in the heat exchanger. 

Because of this design choice, the thermal switch does not cut off the current to the exchanger, placing it at risk of overheating.

The best option is to add a safety switch to cut off the electric current to the fuel solenoid. Better still, add your own solenoid valve inline. 

Keep in mind that this solution may void the unit’s warranty. If possible, consult a technician for guidance.

Difficult to Install

For first-time users, it is pretty challenging installing this unit. In fact, most RV users complain of misplaced components in the unit. Incorrect installation can create a fire hazard, so it’s vital to install it properly.

The best way to do so is to contact a repairer to install the unit for you. Furthermore, ensure the power output is compatible with the unit. 

To install correctly, use a 3A fuse to regulate the electric current input. After installation, insert the battery into the unit. 

Turn the unit upside down to allow the magnet to move freely and spark the pilot light. Uninstall the unit if the magnet is stuck.

Lastly, install the exhaust for forced exhaust models like Excel JSQ20-20V.

excel tankless water heater

Unit Creates Yellow Flames and Smoke

Excel models like the JSQ20-20V will produce smoky yellow flames due to these reasons:

  • Too high or low gas pressure
  • A blocked exhaust tube
  • Blocked burner
  • Blocked heat exchanger.
  • High air pressure
  • Half-opened gas valve

A smoky yellow flame indicates incomplete combustion and will rapidly deplete your gas supply. As such, you’ll want to get on this problem ASAP.

First, start by checking if the gas valve is fully opened. If it is, test the gas pressure regulator. Gas leaks give off a distinct smell. If you smell propane or natural gas, it’s time to replace the regulator. 

All regulators also have a date rating and become less effective over time. If you need to replace the device, contact a licensed repair technician. 

You should also contact a licensed technician to repair blocked burners or heat exchangers.

Water Heater Does Not Ignite

In most cases, a faulty thermocouple is behind this issue. The thermocouple works by opening the gas channel to the burner when you switch on the pilot light. But, a defective one will shut off the gas supply to the burner.

Follow these steps to replace a lousy thermocouple in Excel tankless water heaters:

  1. Shut off the gas supply valve and ensure the handle is at a right angle to the pipe.
  1. Move to the back of the unit and unscrew the nut holding the gas and thermocouple line.
  1. Pull out the entire burner assembly, including the old thermocouple.
  1. Unscrew the other end of the thermocouple from the burner assembly.
  1. Replace it with a new thermocouple of a similar length and size.
  1. Slide the burner assembly into the unit and re-attach the thermocouple and gas supply line.

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Abnormal Noises When Ignited

Maybe your unit does ignite, which is good—but does it create loud backfires or grinding noises when you do so? If so, you need to check out the exhaust or burner. Debris or sediments may be blocking the unit’s exhaust.

You can either call a licensed repairer or follow these steps to do it yourself:

  1. Turn off the gas supply valve.
  1. Put on a dust mask
  1. Connect an extension to a vacuum cleaner.
  1. Verify that the vent hood is removable
  1. Insert the vacuum extension.
  1. Start vacuuming to remove all debris in the exhaust.


You don’t need much technical know-how to fix some of the common problems in Excel tankless units. Increasing the lifespan of your Excel tankless heater can be as simple as cleaning out debris or replacing a small part.

Following the steps outlined above, your appliance should be back to normal in no time.