High
300 on Navien NCM 1130HH

Your boiler has detected that a key internal part is much colder than it should be, which safely shuts down the system to prevent damage.

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

Engine head control temperature less than TempHeadGridDisconnect degrees C when CX relay is energised. The default value of TempHeadGridDisconnect is 150°C.

From this model's manual
Verified against the Navien/Navien Ncm 1130hh 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.

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Related fault codes

301View →302View →

All 77 fault codes on the NCM 1130HH

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

96979899100102114116117118121122127157158164187253254257258259260261262263264265266267268269270271272273274275276277278280281282283284285286287288289290291292293294295296298299301302303304305306307308309310311319394395396397

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