High
1 flash green on Baxi 600 Heat

Your boiler has detected that the water inside it is getting too hot, too quickly, or is unable to circulate properly, so it has shut down 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

Temperature protection: Maximum flow temperature exceeded, Flow temperature rise rate too high, Excessive difference between flow and return temperature

Shared across the 600 Heat range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s 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 1 flash green: 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

E110View →E119View →

All 18 fault codes on the 600 Heat

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

1 flash1 flash red2 flashes2 flashes green2 flashes red3 flashes3 flashes green3 flashes red4 flashes4 flashes green4 flashes red5 flashes5 flashes green5 flashes red6 flashes6 flashes green6 flashes red

Related guides you might find useful

Hot water works but heating does not

On a combi it is usually the diverter valve. On a system boiler, the motorised valve.

Read →

No hot water but heating works

Almost always a stuck diverter valve on a combi.

Read →

Banging, kettling or whistling noise

Each noise points to a different fault.

Read →