Navien Error Code 736: What It Means and How to Fix It

If you have a Navien tankless water heater, you may encounter some error codes on the display panel that indicate a problem with the unit. One of these error codes is E736, which means there is an abnormality in cascade communication. This error code can prevent your water heater from functioning properly and may require professional assistance to resolve.

In this blog post, we will explain what cascade communication is, what causes error code E736, and how to fix it.

What is Cascade Communication?

Cascade communication is a feature that allows multiple Navien units to work together as a system to provide hot water for large applications. For example, if you have a large house or a commercial building that needs more hot water than one unit can provide, you can install two or more Navien units in cascade mode and connect them with a communication cable. This way, the units can communicate with each other and share the load of heating water.

What Causes Error Code E736?

Error code E736 indicates that there is an abnormality in cascade communication. This means that the communication cable between the units is either disconnected, damaged, or faulty. This can happen due to various reasons, such as:

• Improper installation of the communication cable
• Loose or corroded connections
• Physical damage to the cable
• Interference from other electrical devices
• Defective cable or unit

How to Fix Error Code E736?

To fix error code E736, you need to check the communication cable and make sure it is properly connected and in good condition. Here are some steps you can follow:

If you are experiencing error code E736 on your Navien tankless water heater, there are several steps you can take to troubleshoot the issue. The first step is to turn off the power supply to the units and unplug them from the outlet.

Next, locate the blue communication cable that connects the units. Check the cable for any signs of damage, such as cuts, frays, or kinks. If the cable is damaged, it will need to be replaced with a new one.

After checking the cable, inspect the connectors for any signs of corrosion, dirt, or looseness. If the connectors are dirty or corroded, clean them with a soft cloth and some contact cleaner. If the connectors are loose, tighten them with a pair of pliers.

Once you have checked the cable and connectors, plug the units back into the outlet and turn on the power supply. Check the display panel for any error codes. If error code E736 persists, try swapping the communication cable with another one to see if the problem is with the cable or the unit.

If swapping the cable does not solve the problem, you may have a defective unit that needs to be replaced. In this case, it is best to contact Navien technical support or a professional heater repairman for further assistance.

By following these troubleshooting steps, you can determine the cause of error code E736 on your Navien tankless water heater and take the appropriate steps to resolve the issue. Remember to always turn off the power supply before inspecting or working on the unit for your safety.

FAQs

Q: How do I know if I have cascade communication enabled?

A: You can check if you have cascade communication enabled by looking at the display panel of your unit. If you see a number followed by a letter (such as 1A or 2B), it means you have cascade communication enabled. The number indicates the position of your unit in the cascade system, and the letter indicates whether your unit is a master (A) or a slave (B).

Q: How many units can I connect in cascade mode?

A: You can connect up to 16 units in cascade mode using Navien’s Ready-Link® system. However, you need to make sure that your gas supply and venting system can support the total input of all units.

Q: Can I use any communication cable for cascade communication?

A: No, you need to use a specific communication cable that is compatible with Navien’s Ready-Link® system. The cable should be a CAT5e or higher grade cable with RJ45 connectors on both ends. The maximum length of the cable should be 328 feet (100 meters).

Q: What are some benefits of cascade communication?

A: Some benefits of cascade communication are:

• You can provide hot water for large applications without compromising efficiency or performance.
• You can save space and installation costs by using fewer vent pipes and gas lines.
• You can increase reliability and redundancy by having multiple units working together.
• You can monitor and control all units from one master unit.