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Published by Mo's Plumbing and Heating
How to Reset a Worcester Boiler
Worcester is the most common boiler on Glasgow walls, and the reset control is not in the same place across the range. On some models it is a button, on others a dial you turn and release, and on the compact models it is neither of the things people go looking for. Find your model first and the rest is thirty seconds.
The Short Answer
On most Greenstar models the reset is either a dedicated button marked with a flame or reset symbol on the front panel, or the central dial turned anticlockwise to a reset position and released. Hold or turn for around five seconds, then wait up to two minutes while the boiler purges and attempts ignition. Note the fault code first, because resetting clears it. If it locks out a third time, stop.
Find Your Model First
This matters more on Worcester than on most makes, because the Greenstar range has run for a long time across several generations and the controls changed between them. Advice written for one generation genuinely does not apply to another.
The model name is on a sticker, usually behind the front flap or on the underside of the case. You are looking for something like Greenstar 25i, 30i, 24i Junior, 28CDi, 30CDi, Si Compact or Ri. Photograph it rather than trying to remember it.
Broadly, the older i and CDi models tend to have a physical reset button on the fascia. The Si Compact and later models more often use the central control dial, turned anticlockwise past the minimum to a reset position and then released. Some have both, where the dial does the reset and a button does something else entirely.
If you have hunted for a button and there is not one, that is the answer: yours resets on the dial. That is the single most common reason somebody concludes their Worcester has no reset.
Worcester publish the manual for essentially every unit they have made and it is free to download. For thirty seconds of looking it removes all of the guessing on this page.
The Procedure
Once you know which control you have, this is the same on all of them.
- Note the fault code showing on the display and photograph it. It disappears on reset and it is the most useful thing you will have if this recurs.
- For a button: press and hold for around five seconds rather than tapping. For a dial: turn it anticlockwise to the reset position, hold a few seconds, and return it to its normal setting.
- Wait. The boiler runs a purge cycle before it attempts ignition, so expect fans and no flame for up to a couple of minutes. Do not press it again during that.
- Watch what happens. Firing and settling into normal operation means it cleared. Locking out again straight away means the fault is still there.
- If the display shows a code again, note whether it is the same one. A different code the second time is worth mentioning, because it usually means something else.
- Worth knowing what normal looks like on these, since it makes an abnormal display obvious. In ordinary operation a Greenstar display generally shows the flow temperature, a number in the sixties or seventies while the heating runs, sometimes with a small flame or radiator symbol alongside it. A short alphanumeric code in place of that temperature is the boiler reporting rather than measuring, and that is the difference worth recognising at a glance.
The Codes You Are Most Likely to See
Worcester uses alphanumeric codes and there are a great many of them, so the ones below are the common lockout causes rather than a complete list. Your manual has the full set for your specific model, and the code on your display should always be read against that rather than against a list assembled for a different unit.
Low water pressure is among the most common and it is not a repair. The gauge will confirm it, and topping up to about 1.2 bar and resetting is the whole job. It has its own guide in the boiler pressure cluster.
Ignition failure or flame loss is the other frequent one, and it has several possible causes ranging from the trivial to the real: no gas at the meter, a frozen condensate blocking the flue path, a dirty electrode, or a gas valve issue. The order to check is meter first, condensate second, then it is an engineer.
Overheat codes mean the boiler detected a temperature it will not run at, which usually points at poor circulation: a stuck pump, a closed valve, a sludged system, or air in the circuit. Resetting repeatedly through an overheat code is the least useful of all, because the condition is still there each time.
Fan or air pressure switch codes point at the flue or the fan itself, and in a cold snap a frozen condensate can present this way too.
The Two Free Checks
Before deciding a Worcester needs an engineer, two things account for a large share of what we get called to and both cost nothing.
The pressure gauge. Worcester units lock out on low pressure like any other sealed system, and the fix is the filling link rather than the reset button. Worcester uses an integrated keyed filling link on the underside rather than an external braided loop, which is a genuine difference and the reason people cannot find one. That has its own guide.
The condensate pipe in cold weather. Worcester boilers are condensing appliances like every modern boiler, and a frozen external condensate run produces a lockout on a boiler that is otherwise entirely healthy. Thaw it with a warm cloth, never boiling water, and reset.
Between them those two explain a lot of winter Worcester callouts, and both are things you can settle in five minutes before phoning anybody.
Warranty and Who Should Touch It
Worth knowing because Worcester warranties are often long and people are reasonably cautious about affecting them.
Resetting the boiler is user operation described in the manufacturer's own instructions. It is not an intervention in the appliance and it does not affect a warranty. Neither does topping up the pressure or thawing a condensate pipe.
What matters for a Worcester warranty is that the appliance was installed by a suitably qualified registered person, registered with the manufacturer within the required period, and serviced annually with the record kept. A missed service is the common way cover lapses, rather than anything a householder does with the reset button.
Work inside the case is a different matter and is not a customer job on any gas appliance. We are manufacturer certified for Worcester Bosch, which is handy to know if the boiler is still in its warranty period, since who carries out the work can matter to a claim.
Why So Many Glasgow Flats Have a Worcester
The practical consequence of Worcester being the most fitted brand in this city is that a close often holds several of them from different years, and the reset control is not the same on all of them. Neighbours give each other confident and wrong advice about it more than with any other make, precisely because they both have a Worcester and assume that settles it.
That is worth resisting. A Greenstar fitted during a 2008 refit and one fitted in 2019 are different generations with different controls, and the flat downstairs having a button does not mean yours does. Check your own sticker rather than the neighbour, which sounds obvious and is the single most common shortcut people take on this.
The other Glasgow specific is where the boiler sits. A great many are inside kitchen wall units, boxed in during a refit, and on a Worcester the front flap has to open to reach both the reset control and the model sticker. Where a cupboard door or a shelf blocks that, people end up resetting by feel without ever seeing the fault code, which is the piece of information worth having. If yours is boxed in awkwardly, it is worth finding out now how the flap opens rather than at ten on a January night.
And the cold snap pattern applies with particular force to this brand here simply because there are so many of them. A hard frost produces a wave of Worcester lockouts across the city that are overwhelmingly frozen condensate rather than appliance faults, and the flats affected tend to be the same ones each winter, because the condensate was run externally when there was no internal route available.
When to Call Someone Out
Call after the third lockout, or immediately if the code points at overheating, which means poor circulation rather than anything the reset button addresses. Have the model name from the sticker and the fault code ready, because between them they usually identify the problem before anyone arrives and they let the right part come on the van rather than being ordered after a look. Mo and Muhammad are Gas Safe registered for domestic work and we are manufacturer certified for Worcester Bosch, which matters if the appliance is still under warranty. If you smell gas or suspect carbon monoxide, get out and ring 0800 111 999 first.
Boiler Repair in GlasgowCommon Questions
On older Greenstar i and CDi models it is usually a physical button on the front fascia. On the Si Compact and later models there is often no button at all: the central control dial is turned anticlockwise to a reset position and released. If you have hunted for a button and found none, that is almost certainly why.
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