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Powermax Repairs by Mike the Boilerman - Gas Safe Registered technician located on Berkshire/Wiltshire border. Call or text me on: 07866 766364

Replacing a Powermax:

The Powermax (in whatever flavour) is not a well regarded boiler within the heating industry. They are all prone to expensive and/or hard-to-diagnose failure and many technicians simply refuse to work on them. So my advice to anyone with a working Powermax is to replace it with a conventional mainstream style of boiler while it is still working, if you possibly can. This avoids you being caught in the impossible position of having shelled out a few hundred quid several times over for a series on unrelated breakdowns, and ending up still owning an old and unreliable boiler which is hard to get fixed despite having spent a sum of money approaching the cost of a new boiler. Did that make sense? :) 

Each time I explain this in a conversation with a customer, the natural question that results is "with what do you recommend I replace it?", and this page attempts to cover that question.

This is actually a surprisingly complex issue and breaks down into a series of more detailed questions:

Is there a new boiler which will be a straight swap and match the performance of my Powermax?

Sadly no. A new boiler will never be a 'straight swap' due to the following issues complicating things.

1) New boilers need new flues. The existing flue on your Powermax is obsolete and any new boiler will need new flue and air supply tubes to outside fitted, along with access panels for visual access for safety inspections. And it gets worse... The new flue on a new condensing boiler needs to be installed at a gradient rather than level your existing boiler's flue. It will need to slope at approximately 25mm per metre all the way from outside back to the boiler.  This means concealing it about the ceiling as before is difficult or impossible unless there is a huge gap above the ceiling boards, and a new flue route will need to be devised. 

2) New boilers are condensing, and need a drain connection. If you are lucky, your Powermax boiler will be fitted in a cupboard backing onto a bathroom or near a soil pipe so this drain connection can be installed. If not, then a condensate pump will be needed, or the new boiler installed in a different location near a soil pipe, e.g. in the kitchen.


3) A new boiler may need a new gas supply pipe from the meter. Should you choose a high performance combi, it is likely that a larger gas supply pipe will be necessary to supply the higher gas flow a combi demands. This can be a major expense if the meter is a long way from the boiler. Often the case with flats.

4) A correctly working Powermax delivers very high performance mains pressure hot water and this performance can only be matched in two ways with new equipment. One way is by a mains pressure hot water cylinder - and these require a safety discharge pipe which can often not be easily installed in flats, if at all, in full compliance with the Building Regulations. The second way is by a thermal store, for example a Gledhill Boilermate, which is usually as big as a Powermax and needs a separate gas boiler to heat it.

OK, so what do I recommend?

Tricky. It isn't straightforward. Assuming you want to stay with gas as your herating fuel, for simplicity and space-saving I'd suggest a combi boiler. For example one of the Vaillant EcoTEC 800 series of boilers. I am impressed by their reliability, in that I get virtually no calls to fix them (unlike most other brands of boiler), but hot water performance with a combi will be poorer than with your Powermax. Specifically, the maximum flow rate from the taps will be lower. This will also depend on your gas supply being big enough, or a route being available to fit a new gas pipe from the meter. There will also need to be a route for the condensate drain. Sometime this will mean fitting the boiler on the wall in the kitchen instead of in the airing cupboard where the old Powermax is fitted.

For equivalent performance to a Powermax, I'd recommend a separate gas boiler such as the Vaillant EcoTEC Plus 615 system boiler and a MEGAflo mains pressure unvented hot water cylinder. Location in the house or flat will depend on there being routes to install the condensate drains and safety discharge pipes as well as the new flue.

If space and performance requirements demand a new boiler in the same format as a Powermax, then the only product on the market at the moment to my knowledge is a Glow Worm Ultrapower SXi. It comes in two sizes, 100 litres and 170 litres of stored hot water, and is basically a condensing gas boiler and a mains pressure unvented hot water cylinder in a single case, just like a Powermax. I am wary of recommending it though, because like the Powermax, it is an unusual boiler and there are very few technicians around familiar with it for maintenance. Even I have encountered very few of them and have not built up a 'body of experience', so the chances are that any engineer attending will almost certainly be at the base of his learning curve, and learning at your expense.

So there really is nothing that will be a straight swap?

Nope. Nothing. Because of the disruption, complexity and cost of changing a Powermax, some customers elect to keep their old Powermax and to maintain and repair it regardless of cost. 

Why does gas have to be so complicated these days? Can I fit an electric boiler instead?

Yes you can. They are MUCH simpler to install as there is no flue or gas supply necessary, only a big fat electricity cable or two. Fuel cost is the issue here. Expect astronomical electricity bills. There are two types of electric boiler on the market. Daytime electric boilers and thermal store electric boilers. Daytime electric boilers are impressively cheap to buy and very compact, but burn daytime-price electricity so expect your energy bills to triple at best should you install one. Thermal store electric boilers are cheaper to run but large, complex and expensive to buy. They heat up at night using night rate 'low cost' (haha) off peak electricity (you'll need to have an Economy 7 meter installed) and store the 'low cost' heat for use the next day. With one of these you can expect your fuel bills to simply double, compared to gas :-/  A good example of a daytime electric boiler is the Amptec Electric Flow Boiler. The most common thermal store electric boiler is the Gledhill Electramate, now sadly discontinued (sadly for me, that is, as they went wrong so much and I earned such a good living mending them... not a good choice for you) There are several others on the market but none I’ve seen that I’d be happy suggesting here though, sadly.

One last, non-technical issue:

For flat owners there is usually a legal issue that needs taking into consideration. Most leases require the leasholder to obtain written permission from the freeholder to cut the fabric of the building. Drilling a new or holes through the outside wall for a new flue and air supply may be classed as cutting the fabric of the building so permission must be sought to comply with the lease. This permission is sometimes difficult to obtain and/or comes with a large administration fee attached. Best to check your lease for obligation to obtain permission to before embarking on a new boiler installation involving cutting a new flue and/or air supply hole to outside.


Mike Bryant, AKA Mike the Boilerman

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Copyright MICHAEL BRYANT 2022

First created 21st July 2009

Last updated 24th February 2022

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