Glow-worm boiler fault codes
Glow-worm have been part of the Vaillant Group since 2001, and every boiler they have sold since about 2014 — Energy, Ultimate, Easicom, Betacom3 and 4, Compact — runs group electronics and shows the group F.xx code set. That is stated plainly here because pretending otherwise would be silly: the Energy7 installation manual prints the same forty-odd rows an ecoTEC does, down to the note that "since the code table is used for various products, some codes may not be visible for the product in question". What is not shared is everything around the table. Glow-worm publish their fault codes by range on a trade website written for engineers, and a much shorter homeowner page covering eighteen codes; the reset limits, the pressure thresholds and the user-guide permissions come from Glow-worm operating instructions that differ from range to range. And before the group platform there were three Glow-worm code systems of their own — the F1 to F77 of the Ultracom, Flexicom and Ultrapower, the two-digit F00 to F86 of the Ultracom2 and Betacom2, and the flashing temperature scale of the Betacom c — none of which owes anything to Vaillant, and the boilers that carry them are still in a great many homes. These pages quote what Glow-worm printed for your range and then say what it means.
Where the code shows on a Glow-worm
Work out which display you have before you read a code, because the same characters have changed meaning three times. Energy, Energy7, Ultimate3, Easicom3, Betacom4 and Compact show a code with a full stop — F.22, F.28 — on a small LCD, and if several faults are present they alternate every two seconds; the Compact splits it, showing F. then 22 then the pressure in turn. Ultracom2 cxi and sxi, the Ultracom2 35 Store, the Betacom 24a and 28a and the Betacom2 show a two-digit code without a stop — F00, F22, F28 — and the Betacom2 guide describes it as a flashing, alternating F and number; on those boilers F20 is an overheat, F26 and F77 are gas valve motor faults and Err is the user interface. Ultracom cxi, hxi and sxi, Flexicom cx, hx and sx and Ultrapower sxi show a one- or two-digit code, again a flashing F and number, from a shorter list in which F1 is an ignition lockout after five attempts, F4 is a flame failure, F5 an overheat, F6 the flow thermistor, F9 the pressure sensor and F22 low pressure; their 2001 to 2006 predecessors — 24CI, 18SI, 30ci Plus, Xtramax HE, Xtrafast — show the number, the letter F and a flashing red light. The Betacom 24c and 30c have no F codes at all: the temperature scale flashes at a value, and 30 means the heating thermistor, 40 the hot water thermistor, 50 the outside sensor, 60 low system pressure, 70 the air pressure switch, 80 an open overheat circuit and 90 a flame or gas failure. An early Betacom with only a red and a green light, and the Micron, Ultimate FF, BF and CF, Hideaway, Space Saver, Swiftflow, Energysaver and Fuelsaver before it, have no code system: a lit neon or a red light is all the boiler can tell you, and the page for those is the hub you are reading.
How to reset a Glow-worm
Each generation quotes differently, so use the line for your boiler. Energy7: "Press the reset button for one second. The product makes another ignition attempt. If you have been unable to eliminate the ignition fault after three reset attempts, consult a competent person." Ultimate3 and Betacom4 say the same with "press the button", and all three arrive at F.28 only "after three unsuccessful ignition attempts", so a lockout you can see has already been retried. Compact: "Press and hold the on/off button in the basic display for longer than three seconds to reset the product (maximum five times)" — rE appears while it resets and flashes rapidly once the five are used up. Betacom2: "Press the reset button, then wait 5 secs. Should a fault be indicated, a further 2 more attempts can be made"; the Betacom 24a installation manual is blunter — "never press reset more than 3 times". Ultracom, Flexicom and Ultrapower: press the reset button; for F5 the guides say allow the boiler to cool first. 24CI, 30ci Plus and their contemporaries have no reset button: "Turn the On/Off switch to 0, wait for five seconds. Turn the On/Off switch to I, the boiler is reset." Micron: if the reset neon is lit, turn the control knob to 0 and back again. Stop and call a Gas Safe registered engineer when the same code returns after the resets your guide allows, when the code is one the guide reserves for a competent person — on the current ranges that is every code except F.22, F.28 and F.83 — when you can smell gas, or when a carbon monoxide alarm has sounded; a gas smell is for 0800 111 999 before anyone touches the boiler.
Most common Glow-worm faults
The Glow-worm codes people look up most.
- F.28Get it checkedThree ignition attempts have failed and the boiler has locked out. Glow-worm's guides let you check the gas supply and the condensate pipe and reset three times before calling anyone.
- F.22Get it checkedGlow-worm's low-water-pressure shutdown, and the one code every Glow-worm user guide lets you clear yourself by topping the system up. The threshold differs by range.
- F.75Get it checkedGlow-worm's own documents give this code three different cause lists — pressure switch only, or sensor, pump or lack of water — and the fullest one is the Compact's eight-way diagnostic.
- F1Get it checkedOn Ultracom, Flexicom and Ultrapower boilers F1 is an ignition lockout after five failed attempts, and Glow-worm's guides let you reset it. On Energy and Ultimate boilers F.01 is the return sensor instead.
Every Glow-worm fault code
50 published codes. Filtering happens in the page — every one is in the HTML.
Showing 50 of 50 codes
Glow-worm models
Codes can differ between generations. Check yours.
- 24CI, 18SI, 30ci Plus, Xtramax HE and Xtrafast2001–2006
- Betacom 24c and 30c2007–2010
- Betacom3 and Betacom42016+
- Compact2019+
- Easicom, Easicom2 and Easicom32016+
- Energy, Energy2 and Energy72014+
- Flexicom cx, hx and sx2008–2013
- Micron, Ultimate FF/BF/CF, Hideaway, Space Saver, Swiftflow, Energysaver, Fuelsaver
- Ultimate, Ultimate2 and Ultimate32015+
- Ultracom cxi, hxi and sxi2006–2010
- Ultracom2, Betacom 24a/28a and Betacom22009–2015
- Ultrapower sxi 100 and 1702008–2012
Guides that help with Glow-worm faults
Boiler fault codes explained: what they actually tell you
Codes look like diagnoses and are not. Understanding which family a code belongs to turns a meaningless number into a genuinely useful starting point.Read the guideHow to repressurise a boiler
The five-minute job that resolves more no-heating calls than any other. Here is how to do it properly, and how to tell when topping up is the wrong answer.Read the guideWhat a Gas Safe engineer actually checks in a boiler service
Most people pay for this once a year and stand in another room while it happens. Here is what should be going on, which test cannot be faked, and how to tell a real service from twenty minutes and an invoice.Read the guideWhat to do when your condensate pipe freezes
The single most common winter boiler fault, and one of the few you can genuinely fix yourself in fifteen minutes with a kettle and some patience.Read the guide
Looking for Glow-worm’s own support? www.glow-worm.co.uk. We are not affiliated with Glow-worm.