Powermax boiler repair across London
We repair Powermax units still in use. Ring us, day or night.
- Powermax HE and Range Powermax repaired
- All our engineers are Gas Safe registered
Makes we repair
How does booking a Powermax repair work, and what does it cost?
Booking: ring us any time, day or night, or send your details and we ring you back. We'll ask what the Powermax is doing, and its model and any code on the display if you can see them. You don't need to know what's wrong. Finding the fault is the engineer's job. Then we tell you when an engineer can come, anywhere in Greater London.
What it costs: a repair's price depends on the part it needs, how long the job takes and when it's done. Our rates are higher in the evening, overnight and at weekends. Once the engineer has found the fault, the rate for the repair is agreed in writing before any work starts.
What happens on a Powermax repair visit?
A repair visit has three stages.
1. Before anything is touched
The engineer covers the floor around the Powermax and asks what you have seen and heard since you rang.
2. Finding the fault
The engineer tells you which part has failed, whether they have it with them or must order it, and how long the work should take. No work is done until you say yes.
3. The repair
The engineer fits the part and checks the Powermax runs as it should before leaving. The repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
What goes wrong on Powermax boilers most often?
The problems the Powermax's own documents deal with are these:
- Losing pressure. On a Powermax HE the P reading flashes as the heating pressure falls, then the boiler stops with A 15. On a sealed Range Powermax the gauge falls to zero, and the boiler won't run. A Powermax HE that needs topping up often should be looked at for leaks.
- Not lighting. A 01 on a Powermax HE, or the red lock-out light on a Range Powermax.
- Pressure too high when hot. P 3.0 or more on a Powermax HE, which points to its heating expansion vessel.
- Water or steam from the safety pipe. On a Powermax HE, hot water or steam from the tundish may mean a fault on the cylinder side. Switch the boiler off and ring us.
- A blocked or frozen condensate pipe. On a Powermax HE it is among the causes of A 01 and E 20. The outside pipe should be kept from freezing.
- The programmer. On a Powermax HE, a blank display can point to the fuse, and a clock alone means a remote programmer is fitted.
- Limescale. In hard water areas, the documents for both Powermax ranges call for the water to be treated.
- The mains wiring. Live and neutral reversed in the electricity supply can stop a Range Powermax sensing its flame. On a Powermax HE it shows as E 21.
- The flue and condensate connector. Powermax HE boilers made from 2001 to 18 November 2005 are covered by Safety Alert 013. What Safety Alert 013 says about the connector.
Sources: Potterton's instructions for the Powermax HE, and the householder and technical FAQs for the Range Powermax.
Worth knowing
Two appliances share the Powermax name. The Potterton Powermax HE is a condensing boiler with an unvented hot water cylinder, and the older Range Powermax is a gas-fired thermal store. Neither is made now, and we still repair both.
Powermax codes and lights, and what they mean
Powermax codes come from the Powermax HE's red display, as a letter and a number:
- An A code is a lock-out, with the red lock-out light on. It needs the Reset button.
- An E code is an error.
- P with a figure is the heating pressure in bar, usually a reading rather than a fault.
The Range Powermax shows lights instead. The meanings below are from the 2004 issues of the Powermax HE's manuals. The first issues, of 2001, gave some codes other meanings. We'll ask for the code when you ring.
A 01A 01: the burner did not light (Powermax HE)
What it means: A 01 means the Powermax HE's burner didn't light, and the red lock-out light is on. Before showing it, the boiler repeats its lighting sequence by itself.
Possible causes, as the manual lists them:
- the fan, or the boiler control that powers it
- no gas at the valve, from the gas supply, the overheat thermostat, the boiler control or the gas valve itself
- the gas valve's setting
- the spark
- a blocked condensate trap
- the gas supply from the meter
If the burner lights for 3 seconds and goes out, the manual points to the ionisation probe and its lead.
What you can do:
- See that the gas is on.
- Press Reset.
- See that the condensate outlet isn't blocked.
In a frost, a frozen condensate pipe outside at ground level can be thawed with warm, never boiling, water. If A 01 comes back, ring us. The rest of the manual's chart is engineer work. We'll ask whether the burner lit for a moment before it went out.
A 15A 15 or P 0.1 to 0.4: the heating pressure is lost (Powermax HE)
What it means: A 15 means the Powermax HE's heating pressure has been lost, or its pressure sensor is faulty. Below 0.5 bar the boiler shuts down for safety and shows P 0.4 or A 15, with the red light on. A flashing P reading of 0.5 to 0.9 is the early warning.
Possible causes, as the manual lists them:
- the pressure sensor, if the dial gauge still reads 1 to 2.9 bar
- a heating relief valve letting water out, if the gauge is low too
- the charge of the built-in heating expansion vessel
What you can do: top up, as the user's instructions show.
- Pull off the bottom front panel.
- Fit the filling loop to the valve on the cold inlet.
- Open both valves slowly. Close them once the pressure has risen to 1.0 to 1.5 bar with the system cold.
- Take the loop off and refit the panel.
- Press Reset.
If A 15 comes back, or the pressure keeps dropping, ring us. A leak, a relief valve letting by and a flat vessel are all engineer checks. We'll ask how often it has needed topping up.
P 3.0 to 3.5P 3.0 to 3.5, or E 01: the heating pressure is too high (Powermax HE)
What it means: P 3.0 to 3.5 means the Powermax HE's heating pressure is over 3 bar, and the boiler has switched off. The installer's manual also lists E 01 for heating pressure that is too high.
Possible causes: the built-in heating expansion vessel, which needs checking, setting or renewing.
What you can do: if the display reads P 3.1 or more with the boiler at its normal running temperature, switch it off. Ring us straight away. The vessel is an engineer's job. We'll ask what the display read with the boiler hot.
A 03/E 03A 03 and E 03: an overheat lock-out, the flow too hot (Powermax HE)
What it means: A 03 means the Powermax HE has locked out because the water overheated or wasn't circulating. E 03 means the flow temperature is abnormally high. The A is a lock-out, which needs the Reset button, and the E an error.
Possible causes:
- the pump
- the 3-way diverter valve
- low heating pressure
- air in the system
What you can do:
- Switch the boiler off for 10 minutes.
- Look at the pressure, and top it up if it is low, as the user's instructions show.
If the code comes back, ring us. The pump and the valve are engineer work. We'll ask whether the pressure was low when the code showed.
A 40A 40 (A 02 in the user's instructions): a system response fault (Powermax HE)
What it means: A 40 means the Powermax HE has a system response fault. The user's instructions list A 02 with the same meaning, and the installer's manual adds A 41, a system flow fault.
Possible causes:
- the pump not running or at the wrong speed
- the by-pass or other valves shut
- the 3-way valve
- air in the heat exchanger
- the control not reading the flow and return sensors
What you can do: open any radiator valves that are shut, then press Reset, as the user's instructions show. We'll ask whether any radiator valves had been turned off.
E 20/A 20E 20 and A 20: a flame sensed with the gas valve closed (Powermax HE)
What it means: E 20 and A 20 both mean the Powermax HE has sensed a flame while its gas valve is closed. E 20 is an error, and A 20 a lock-out.
Possible causes:
- the ionisation probe or its cable
- a blocked condensate outlet or vent tube
- for A 20, a gas valve that isn't closing fully
What you can do:
- For E 20: switch the boiler off for 10 minutes, and see that the condensate outlet isn't blocked.
- For A 20: switch the electricity off and on, and press Reset.
In cold weather, keep the outside condensate pipe from freezing. A frozen pipe at ground level can be thawed with warm, never boiling, water. If the code comes back, ring us. The gas valve and the probe are engineer work. We'll ask where the condensate pipe runs.
Red lightThe Range Powermax's red lock-out light
What it means: The Range Powermax's red lock-out light means the burner failed to light.
Possible causes:
- Possibly a minor one, such as a dip in the gas supply.
- A burner that lights, but whose flame the control can't sense. The likeliest cause is reversed polarity on the incoming mains, when the green light stays off though the flue is warm.
What you can do:
- Switch the boiler off.
- Wait 10 seconds.
- Switch it back to its timed setting, with the programmer in an on period.
The boiler then tries 5 times to light. We'll ask whether the green light came on at all.
MoreEvery other Powermax HE code, in one list
Every other Powermax HE code is in this list, with the readings that aren't faults. The list comes from Potterton's installation and servicing instructions (September 2004) and user's instructions (February 2004). Where a code is in one of the two documents and not the other, the list says so. A code the installer's manual doesn't list means a faulty boiler control.
A 04The overheat thermostat has opened, or the gas valve has failed
Possible causes
The wiring, the overheat thermostat, or the gas valve's coils
A 05A safety relay inside the boiler's control has failed
Possible causes
The boiler control, if switching off and on and a reset don't clear it
A 07A fault in the heat exchanger's monitoring
Possible causes
The gas valve's setting, the combustion, the ionisation probe, or the control's reading of the flow and return sensors
A 09 to A 12An internal control failure (in the user's instructions, not the installer's manual)
Possible causes
The boiler control, if switching off and on and a reset don't clear it
A 18A control or sensor failure (in the user's instructions)
Possible causes
The control or a sensor
A 19A flame detection or gas valve fault
Possible causes
A gas valve slow to close, or a fault in the electricity supply
A 33The fan's speed is wrong
Possible causes
The fan's wiring or connections, the fan, or the boiler control
A 41A system flow fault (in the installer's manual)
Possible causes
The pump or its speed, or the by-pass valve shut
E 04The flow sensor's circuit is open
Possible causes
The sensor, its cable or its connections
E 06The flow sensor has a short circuit
Possible causes
The sensor or its cable
E 07The hot water sensor's circuit is open
Possible causes
The hot water sensor or its cable
E 08The hot water sensor has a short circuit
Possible causes
The hot water sensor or its cable
E 13, E 16, E 19An internal control error (in the user's instructions)
Possible causes
The boiler control, if switching off and on doesn't clear it
E 21The live and neutral are reversed in the electricity supply
Possible causes
The supply's wiring
E 22The electricity supply isn't at 50 Hz
Possible causes
The electricity supply
E 29A fault in a link on one of the control's plugs (the user's instructions call it a boiler circuit fault)
Possible causes
The pressure sensor's cable assembly, or its connections
E 40The return sensor's circuit is open
Possible causes
The sensor or its cable
E 41The return sensor has a short circuit
Possible causes
The sensor or its cable
E 42An internal control error
Possible causes
The boiler control
P 0.5 to 0.9, flashingThe heating pressure is low
Possible causes
Low water pressure, which needs a top-up, a look at the dial gauge and any leak found
P 1.0 to 2.9A normal pressure, warm or hot
Possible causes
Not a fault
U, c, t, b and 0 00Readings. U and a temperature is the hot water setting, and c and t are the heating and hot water flow temperatures. The display shows b while the cylinder reheats, and 0 00 on standby.
Possible causes
Not faults
Any other codeA faulty boiler control
Possible causes
The boiler control
The Range Powermax: its lights, in one list
The Range Powermax shows its state with lights, and none of its maker's pages lists a numbered code.
Red (lock-out)The burner failed to light, and the boiler has locked out
Possible causes
Possibly a minor cause, such as a dip in the gas supply. A flame the control can't sense is another, most likely from reversed polarity on the incoming mains.
GreenThe gas burner is running
Possible causes
Not a fault. If it stays off while the flue is warm, that points to reversed polarity on the incoming mains.
OrangeThe power is on
Possible causes
Not a fault
Pressure gauge at zero (sealed versions)The heating pressure has gone, and the boiler won't run
Possible causes
Not given in the FAQ, which shows how to refill to 0.8 bar
Programmer flashing "switch on" when first set upIts battery back-up switch hasn't been turned on
Possible causes
Not a fault
Other makes number their codes their own way. The fault codes of every other make, explained code by code.
Sources, read on 10 October 2026: Potterton's installation and servicing instructions for the Powermax HE (5106226, issue 07, September 2004) and its user's instructions (5106228, issue 04, February 2004), Baxi's statement on Safety Alert 013 (November 2013), and the Range Powermax's householder and technical FAQs, in the Internet Archive's copies of the makers' own websites.
Which Powermax do you have, and how does it show a fault?
Powermax is the name of two different appliances, and each has its own faults, controls and safety rules. The Potterton Powermax HE is a condensing boiler with an unvented hot water cylinder built in. The older Range Powermax is a gas-fired thermal store. Neither is made now, and we still repair both. We'll ask which you have, and what it shows, when you ring.
Not every reading is a fault. A Powermax HE's display also shows:
- P 1.0 to 2.9: a normal pressure, warm or hot
- U and a temperature: the hot water setting
- c and t: the heating and hot water flow temperatures
- b: the cylinder is reheating
- 0 00: standby
Other things are normal too:
- the pump runs for a few seconds each day
- the burner fires below 5°C to protect against frost
- a white plume comes from the flue on a cold day
- the outside condensate pipe may drip
- the heating pauses for about 10 to 15 minutes after a bath is run, because the hot water comes first
Safety Alert 013: the Powermax HE's flue and condensate connector
Safety Alert 013 is Baxi's alert, issued with Gas Safe in November 2013. It covers Powermax HE boilers made from 2001 to 18 November 2005, which were built with an aluminium flue and condensate connector. Baxi's statement says that in very extreme cases, with several factors at once, carbon monoxide above normal levels could escape. Baxi calls the chance of that very low.
Baxi recommended changing every original aluminium connector for a black composite plastic one, whatever its condition. Baxi also said many had already been changed during services. The alert is about the Powermax HE, not the Range Powermax.
Baxi advises every Gas Safe registered engineer who works on a Powermax HE to follow the alert's inspection procedure. An engineer should check which connector yours has. All our engineers are Gas Safe registered. Ring us, and we'll ask for the serial number and the model. Both are on the data plate under the white front panel.
The Powermax HE's hot water cylinder
The Powermax HE's hot water cylinder is unvented and fed from the cold mains. Its safety parts are an engineer's work:
- The temperature and pressure relief valve. Fitted at the factory, and not to be removed except by the maker's own authorised staff. It discharges through a tundish, also fitted at the factory. The tundish drains into a metal pipe that falls all the way to a safe place where it can be seen.
- The inlet control group. A stop valve, a pressure reducing valve, an expansion relief valve and a strainer, on the cold supply. No valve is allowed between it and the cylinder.
- Two expansion vessels. One for the hot water, supplied separately, and one built in for the heating.
Fitting a cylinder like this comes under Part G of the Building Regulations. It must be done by a competent person, as Approved Document G3 defines one. Our engineers hold the G3 unvented qualification.
Hot water or steam coming from the tundish or the safety pipe may mean a fault. Switch the boiler off and ring us. Normally nothing comes out, and the outlet should be kept clear and safe for children.
For a leak on the hot water side:
- Switch the boiler off.
- Turn off the water at the mains stopcock.
- Catch the water, which may be very hot.
For a leak on the heating, switch the boiler off to stop the pump. Then ring us.
Hot taps may leak because of the mains pressure. The optional immersion heater has its own safety cut-out. The cause of any overheating must be looked into before it is reset. Our unvented hot water cylinder repairs.
Sources: Potterton's installation and servicing instructions and user's instructions for the Powermax HE.
How do you reset a Powermax?
Each Powermax resets its own way:
- Powermax HE: note the code, then press the Reset button on the control panel. The same button steps the display through the pressure, the hot water setting and the heating flow temperature.
- Range Powermax: switch the boiler off and wait 10 seconds. Switch it back to its timed setting, with the programmer in an on period. It then tries 5 times to light.
Reset once. If the code or the red light comes back, ring us, and we'll ask for the code and the serial number.
The pressure on a Powermax HE should read 1.0 to 1.5 bar with the system cold. A reading from 1.0 to 2.9 is normal when warm or hot.
- A flashing reading of 0.5 to 0.9 means it is low.
- Below 0.5 bar the boiler stops and shows P 0.4 or A 15.
- At P 3.1 or more when hot, switch it off and ring us.
The user's instructions show how to top up:
- Pull off the bottom front panel.
- Fit the filling loop to the valve on the cold inlet.
- Open both valves slowly, and close them once the pressure has risen.
- Take the loop off and refit the panel.
- Press Reset.
On a sealed Range Powermax, the maker's FAQ shows how to refill when the gauge reads zero:
- Switch the boiler off.
- Lift off the loose cover on top, and unscrew the red cap on the automatic air vent.
- Open the filling loop slowly until the gauge reads 0.8 bar, then close it.
- Put the cap back loosely, and the cover on.
- Switch back to timed, with the programmer on.
The green light should come on, and the boiler takes about 20 minutes to be fully working. The filling loop is then disconnected, as the regulations require. A Powermax HE that keeps needing a top-up should be looked at for leaks.
No heat and no code? The Powermax HE's user's instructions list the simple causes:
- the gas, water or electricity off
- the amber mains light out
- the programmer outside an on period
- a thermostat or radiator valve not calling for heat
A blank display can point to the fuse. We'll ask about each when you ring.
In a frost, keep the Powermax HE's outside condensate pipe from freezing. A frozen pipe at ground level can be thawed with warm, never boiling, water, then the boiler reset. When a boiler won't fire up, and frozen condensate pipes.
Sources: Potterton's user's instructions and installation and servicing instructions for the Powermax HE, and the Range Powermax's householder and technical FAQs.
Is your Powermax still under guarantee?
A Powermax is no longer under its maker's guarantee. Every one is long past its standard cover.
When new, the Powermax HE's guarantee covered the boiler, not the pipework, radiators or valves. Its cylinder had a guarantee of 10 years. The Powermax HE was off Potterton's floor-standing list by January 2008, so the cylinder's cover has ended too. The Range Powermax came with one guarantee for the whole system.
Baxi Genuine Parts, Baxi's parts business, aims to support a product for at least 10 years after it is discontinued. The Powermax HE passed that point years ago, so no maker's promise covers its parts now.
Parts can be hard to find. The engineer tells you about the part before any work starts, and says honestly whether a repair or a new boiler makes more sense. The choice is yours. What fitting a new boiler involves.
Ring us for a Powermax repair. We are an independent firm, with no connection with Powermax.
What does a Powermax service cover?
A Powermax HE service is an inspection every year, with a full service every second year, recorded in the Benchmark log book. Each year the engineer:
- cleans the ionisation probe
- releases trapped air
- checks the ignition, the flame and the combustion
- tests for gas leaks
- looks after the cylinder's safety side
On the cylinder's safety side, the strainer and the pressure-reducing cartridge are cleaned, and both expansion vessels' charges are checked. The expansion relief valve and the temperature and pressure relief valve are opened by hand. The discharge route is checked, and both valves are seen to reseat.
Every second year the burner, the combustion chamber and the heat exchanger are inspected and cleaned as well. Baxi advises that any work on a Powermax HE follows Safety Alert 013's inspection procedure.
We service every Powermax model, and give you the rate on the call. What a boiler service includes, check by check.
Sources: Potterton's installation and servicing instructions for the Powermax HE.
15% off a new boiler, fitted
The 15% comes off the price of a new boiler installation. We quote from photos of your old boiler, or after a free survey visit. Now is the time to replace an old or discontinued boiler.
Terms: 15% off everything in the price we quote for a new boiler installation. That means the boiler, its flue and controls, and the fitting. The offer is for installations booked by 31 December 2026. One offer per home, and not with any other offer.
Do you cover my part of London?
Yes: we travel all over Greater London, day and night, to repair Powermax units in every borough, north and south of the Thames. Pick your side of the river to see the areas.
North of the river
Every borough north of the Thames: Barnet and Enfield at the top, Hillingdon in the west, Havering in the east, and central London in between.
South of the river
Every borough south of the Thames: Richmond and Kingston in the west, Bexley in the east, and down through Croydon to Sutton and Bromley.
The other makes we repair
Every main make, combi, system and regular. Pick yours for its common faults, its codes and how we repair it.
Questions about Powermax units
Do I need to know what's wrong with my Powermax before I ring?
No. Ring and say what the Powermax is doing, or what you can see or hear, and we'll ask the rest. Finding the fault is the engineer's job.
Do you charge more in the evening or at weekends?
Yes. Our rates are higher in the evening, overnight and at weekends.
Can you repair an older Powermax?
Usually, yes. It depends on the Powermax's condition and whether its parts are still made. We'll ask for the model when you ring.
Is my Powermax worth repairing?
Often, yes. Age alone doesn't decide it. What decides it is the rate for the repair against a new boiler, and how often the boiler has failed. The engineer gives you the rate for the repair, and the choice is yours. When a new boiler makes more sense.
Do you fit Powermax's own parts?
Yes, the maker's own parts wherever they are available. Each repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
How much does a Powermax repair cost?
The cost of a repair depends on the part, how long the job takes and when it's done. The rate is agreed in writing before the repair starts. How our rates work.
Is my Powermax a Range Powermax or a Powermax HE?
A Powermax with Potterton and Powermax HE on its control band, and a red display showing letters and numbers, is a Potterton Powermax HE. It was made in 85, 115 and 150 litre sizes. The Range Powermax, the older one, shows lights rather than codes: red for a lock-out, green while the burner runs and orange for the power. Its models are the 140, 155x, 157 Propane and 185. We'll ask what the front shows when you ring.
Does Safety Alert 013 apply to my Powermax HE?
Safety Alert 013 covers Powermax HE boilers made from 2001 to 18 November 2005, built with an aluminium flue and condensate connector. Baxi recommended changing each for a black composite plastic one, and many were changed during services. Baxi calls the chance of carbon monoxide escaping very low. The alert doesn't cover the Range Powermax. An engineer should check which connector yours has. Ring us, and we'll ask for the serial number from the data plate.
Can I top up the pressure on my Powermax myself?
Topping up a Powermax HE is a step its user's instructions show:
- Take the bottom front panel off.
- Fit the filling loop to the valve on the cold inlet.
- Open both valves slowly until the pressure reads 1.0 to 1.5 bar on a cold system, then close them.
- Take the loop off, and press Reset.
On a sealed Range Powermax, the maker's FAQ shows how to refill to 0.8 bar with the boiler switched off. If a Powermax HE needs topping up often, ring us to have it looked at for leaks.
Are Powermax boilers still made?
Powermax boilers are no longer made. Neither the Range Powermax nor the Potterton Powermax HE is sold now, and the Powermax HE was off Potterton's floor-standing list by January 2008. We still repair both, and we'll ask for the model when you ring.
Who made Powermax boilers?
Powermax boilers came from one line of companies. The Range Powermax came from RSA Waterheating. That company was called IMI Range until 1994, and IMI Waterheating until 1998. RSA Waterheating became part of the Baxi Group in November 2000, and passed its trade to Baxi Heating UK on 1 January 2002. The Potterton Powermax HE was made from 2001 under the Potterton name, a trading division of Baxi Heating UK. Today's Range Cylinders is a separate company, with no stated link to Powermax. We are an independent firm, with no connection with any of them.
Don't know what has failed? You don't have to.Ring and say what you can see or hear. Finding the fault is our job.
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A real person answers and gives you the rate on the call. No work starts until you say yes, and repairs are guaranteed for 12 months: parts, labour and any return visit.
