High
980 on Viessmann Vitodens 100-W B1HF-11

Your boiler isn't getting enough water flowing through it to heat your hot water tap supply, so it has paused hot water heating until the flow improves, though your central heating may still work.

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

Minimum flow rate not achieved before the start of DHW heating: Shut-off or too much constriction; Scaling or sludge; Incorrect hydraulic configuration; Circulation pump faulty, air in the heating circuit; System pressure unstable or too low

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 100 W B1hf B1kf 6167586 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 980: 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

F.22View →F.10View →

All 151 fault codes on the Vitodens 100-W B1HF-11

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

78111213141516293049505758596263646567686970717273747577788789919295100102103104142161162163176182183184185299345346347348349350351352353354355357359361364365366367368369370371372373374375376377378379380381382383384385386387388395396399400401402403404405406408410416417418425446447448449451452453454455456457458461462463464467468471474477517527528540544545574575576577578579682683684694738766767799979981982E10E12

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on a combi.

Read →

Hot water works but heating does not

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

Read →

Banging, kettling or whistling noise

Each noise points to a different fault.

Read →