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Boiler service mode, by make and model

How to put a boiler into service mode to take combustion readings at maximum and minimum rate. 1,255 models from 542 manufacturer manuals across 22 makers, written out step by step with the manual page for each.

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Alpha35 models, 18 manualsAriston34 models, 20 manualsAtag41 models, 10 manualsBaxi153 models, 52 manualsBiasi71 models, 29 manualsChaffoteaux21 models, 16 manualsFerroli32 models, 27 manualsGlow-worm107 models, 57 manualsHalstead10 models, 5 manualsHeatline14 models, 8 manualsIdeal182 models, 66 manualsIntergas10 models, 5 manualsJohnson Starley11 models, 10 manualsKeston12 models, 10 manualsMain17 models, 10 manualsPotterton83 models, 28 manualsRemeha13 models, 6 manualsSime48 models, 15 manualsVaillant100 models, 31 manualsViessmann39 models, 13 manualsVokera66 models, 38 manualsWorcester Bosch156 models, 68 manuals

What service mode is for

A modulating boiler won't sit still at one rate on its own. Service mode forces it to a fixed rate, normally maximum first and then minimum, long enough to take a stable flue gas reading and compare the CO₂ and CO against the figures in the manual. It drops back to normal running on its own after a set time, anywhere from 5 to 30 minutes depending on the boiler, so have the analyser ready before you start it.

The name changes by maker. Worcester and many Baxi ranges call it chimney sweep mode, other Baxi and Potterton ranges call it calibration mode, Vaillant puts it under the installer level as check programmes (P.01 maximum load, P.02 minimum load), Glow-worm lists test modes, and Ideal shows SH and SL for service high and service low. It's the same job on all of them.

Why the steps come with a page number

Each procedure is taken from that boiler's installation and servicing manual, and shows the page it came from. Button names and sequences change between generations of the same range, so check the manual's front cover matches the boiler, and go to the page if anything on the display doesn't match.

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The whole manual, not just this page

Service mode, gas valve settings, combustion figures and fault codes for the boiler in front of you, plus Ask Flint for anything the manual covers.

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Service mode and combustion checks are work for a competent, Gas Safe registered engineer. These procedures are taken from the manufacturers' manuals and inform your judgement; they don't replace it. Always work to the manual for the exact appliance, its data badge and the current standards.