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Case study

Powermax 155x Repair

A boiler and a hot water cylinder in one case. It is no longer made, and most London firms will not open one. Here is the work, in ten photographs.

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  • Discontinued appliances most firms will not open
  • Gas Safe and G3, so boiler and cylinder in one visit
  • Parts sourced for units long out of production
  • Ten photographs of the actual work, in order
No heating or hot water right now? Call 0203 868 6134. We will tell you the earliest realistic slot rather than the one you want to hear.

What a Powermax is

It is not a boiler. That is why everything else about it is different.
A Powermax is a boiler and a hot water store in the same case. It was sold under the Baxi, Potterton and Range names in the 1990s and 2000s. The boiler heats water held inside the unit. Your cold mains water passes through that store and comes out hot at the tap. It answered a real problem. It gave strong hot water to two or three bathrooms at once, at mains pressure, with no shower pump and no tanks in the loft. That is why so many went into London houses. They are no longer made, and parts are getting harder to find.
One thing worth knowing. Powermax is a Baxi appliance. That helps when you are ringing round, because the name on the front of the case is not the name most engineers recognise.

Why most firms tell you to replace it

Three things happen, and only the first is about the appliance itself.
Most firms will not open one. It is unfamiliar, it has been out of production for years, and it is two appliances in one case. No engineer wants to learn on a customer's floor, so turning the job down is the sensible thing to do. That leaves replacement as the only advice on offer. Which is fair enough from someone who cannot repair it. Then the quote arrives. This is the part most people do not expect. You cannot swap a Powermax for a boiler. The appliance is the cylinder. Replacing it means a new boiler, a new cylinder or unvented system, new pipework and a new flue position. You usually lose the mains-pressure hot water that made the house work. It is not a boiler swap. It is a new heating system. The repair on this job was a pump, a control board, a programmer and an expansion vessel. That is what the photographs below show.
Did you know Powermax units are discontinued and parts are getting harder to find, so a repair depends on the engineer knowing the appliance and being able to source the components. That is why most firms decline them. It is worth asking directly when you ring round, because an engineer who says they have not worked on one is telling you something useful.

The work, in order

Ten photographs from the job. Nothing staged and no stock images.
  1. Floor protection and Kamco Clearflow CF90 power-flushing equipment set up in a customer's hallway

    Protecting the property and setting up the equipment

    The hallway floor was covered with dust sheets and plastic before anything else. A Powermax sits inside the house, not in a garage, so the protection goes down first. The Kamco Clearflow CF90 power-flushing machine was set up ready.
  2. Kamco Clearflow CF90 connected to a microbore heating system after a radiator was removed

    Connecting to the heating system

    A radiator was taken off and the machine connected in its place. This is a microbore system, so the pipes feeding each radiator are much narrower than normal. Narrow pipes block up faster, which is why this kind of system needs a proper clean rather than a rinse.
  3. Kamco Clearflow CF90 power-flushing machine and twin magnetic filter connected in a protected hallway

    Power-flushing setup ready for circulation

    The CF90 and a twin magnetic filter, connected and ready to run. The filter catches the sludge coming out of the system. It means there is something to show the customer at the end, rather than just being told it went somewhere.
  4. Powermax 155x opened for circulation pump and isolation valve replacement

    Opening the appliance for repair

    The Powermax 155x opened up so the pump and isolation valves could be replaced. This is where most firms stop. What is behind the panel does not look like a normal boiler, and there is a tank of hot water directly behind it.
  5. Replacement circulation pump and isolation valves installed in a Powermax 155x

    Installing the replacement pump and valves

    A new pump fitted, with new isolation valves at the same time. The valves let the next repair be done without draining the system down. On an appliance where parts are getting harder to find, that is worth doing while it is open.
  6. Replacement control PCB being fitted inside a Powermax 155x

    Replacing the control PCB

    The replacement control board going in. Finding a board for an appliance that is no longer made is most of the difficulty with these jobs. It is usually the step that decides whether a Powermax gets repaired or written off.
  7. Replacement Powermax 155x control PCB and wiring connections before reassembly

    Checking the control connections

    Every connection to the new board checked before the case went back on. On an appliance this old the wiring has usually been disturbed a few times. A loose connector found now saves a second visit later.
  8. Reconditioned programmer/timer installed in a Powermax 155x control panel

    Installing the programmer

    A reconditioned programmer fitted into the control panel. New ones are not made any more. A reconditioned unit is often the only option, which is worth knowing, because a firm that only fits new parts has no answer here.
  9. Powermax 155x being tested after pump and control repairs

    Testing and reassembling the appliance

    The unit being tested after the pump and control work, before the panels went back on. Testing is done with the case open, so anything found can be dealt with there and then.
  10. Replacement expansion vessel installed for a Powermax 155x heating system

    Replacement expansion vessel

    A new expansion vessel for the heating side. When a vessel loses its charge the system pressure drops a little at a time. People top it up and carry on, and the topping up is what causes the damage.
The parts, in one line. A power flush, a pump and isolation valves, a control board, a reconditioned programmer and an expansion vessel. Compare that with a new boiler, a new cylinder, new pipework and a new flue.

Why we could do it

It comes down to qualifications.
A Powermax is a boiler and a pressurised hot water store in one case, so both have to be dealt with in the same visit. Gas Safe registration covers the boiler. It does not cover the stored water. That needs a separate G3 qualification, because unvented work has to be notified under the Building Regulations. Most heating firms hold Gas Safe and stop at the boiler. Most plumbers who hold G3 will not touch a gas appliance. Our engineers hold both, which is why unvented cylinder repair is a large part of what we do. That is the whole reason one firm says no and another says yes.
Related pages. The cleaning side is on power flush. How we diagnose a fault is on gas boiler repair. What decides whether a repair is worth doing is in our guide to repair costs. And because Powermax is a Baxi appliance, that page is the closest reference for the boiler half.
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Safety
If you smell gas: do not touch any switches. Open the windows, leave the property, then call the National Gas Emergency Service on 0800 111 999. That line is free and open 24 hours. Call them before you call us. If a carbon monoxide alarm is sounding: get everyone out immediately, then call 999 if anyone feels unwell. Do not go back in until the property has been ventilated and checked. If the boiler locks out repeatedly: try one reset. If it locks out again straight away, stop. Repeated resets hide a fault that is still there, and on a gas appliance that is not a risk worth taking. Under the Gas Safety (Installation and Use) Regulations 1998, only a Gas Safe registered engineer may work on gas appliances. Never open the boiler casing yourself.

Got a Powermax, or something else nobody will touch?

Tell us the make and what it is doing. If you have already been told it needs replacing, say so. The reason is often that the firm could not open it.
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