Navien Error Code E302

What Does E302 Mean?

Error code E302 indicates that the system pressure is too low - typically below 1 bar. This is visible on your pressure gauge or the front display.

Quick Fix Guide

For NCB-CE or NCB300 Models

Step 1: Locate the Filling Loop

Find the metal braided flexible hose on the underside of the boiler. It has:

• One tap with a small blue handle
• One tap with a small black handle

Step 2: Re-pressurise the System

1. Open the black tap a quarter turn first
2. Open the blue tap slowly - you'll hear water entering
3. Watch the pressure gauge carefully
4. Stop filling when pressure reaches 1.0-1.2 bar
5. Close both taps - black first, then blue

For NCB500 or NCB700 with NaviFill Link

Step 1: Find the NaviFill Link

Look for the plastic and brass component with a green plastic lever underneath the boiler.

Step 2: Re-pressurise

1. Pull down the green lever gently
2. Listen for water filling the system
3. Watch the display/gauge until it shows 1.0-1.2 bar
4. Release the lever to stop filling

For LCB700 with Filling Loop

Step 1: Locate the Filling Loop

On combi models, find the metal braided hose near the top right with two small black tap handles.

Step 2: Fill the System

1. Open each tap a quarter turn
2. Listen for water entering the system
3. Monitor the gauge until it reads 1.0-1.2 bar
4. Turn both taps off completely

Important Safety Notes

Do Not Overfill

• Maximum safe pressure: 1.5 bar
• Optimal range: 1.0-1.2 bar
• If overfilled: Bleed a radiator to release excess pressure

Check for Leaks

If pressure drops frequently, you may have a leak:

1. Check all visible pipework
2. Inspect radiator valves
3. Look for damp patches around the boiler
4. Check the expansion vessel
5. Call an engineer if you can't find the source

Video Guide

For visual step-by-step instructions on re-pressurising NCB-CE and NCB300 models, watch our guide:

[Link to manufacturer video guide]

When to Call an Engineer

Contact a professional if:

• Pressure drops daily or weekly
• You can't locate the filling mechanism
• The error persists after re-pressurising
• You notice water leaks
• The pressure gauge reads zero

Prevention Tips

• Check pressure monthly - should be around 1.0-1.2 bar when cold
• Annual service to check expansion vessel and PRV
• Bleed radiators once a year to remove air
• Don't overfill - this can damage components

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Applicable Models: NCB-CE, NCB300, NCB500, NCB700, and LCB700.

Note: This is one of the most common and easily fixable Navien error codes. Most homeowners can resolve it themselves following the steps above.