High
E353 on Navien NCB300

Your boiler is temporarily unable to register the correct water pressure inside the system, which stops it from running safely.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Unable to detect or measure changes of water pressure

From this model's manual
Verified against the Navien/Navien Ncb300 Combi Service Manual30k 250328 Pdf installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like E353: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

E351View →E352View →E354View →

All 56 fault codes on the NCB300

Seeing a different code? Every code this model can display, in one place.

001003004004E012012E016016E030030E031046047109109E205302407515517593594615740782E001E003E004E012E016E030E031E046E047E109E110E205E218E302E351E352E407E421E439E515E517E593E594E598E615E740E782E783E787E788

Related guides you might find useful

What pressure should my boiler be?

1 to 1.5 bar when cold on most UK boilers, from the manuals.

Read →

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →