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Is it worth replacing an old Alpha gas boiler?


I've recently moved to a house where the central heating system is run via a 14 year old Alph gas boiler. My meter readings seem high. Is this down to the age of the boiler? It has been regularly maintained. I'm wondering whether to replace it or not.
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Best answer by Transparent 12 April 2018, 11:28

Hi @aphrabenn
Your first Forum posting I notice! :8

Although 14 years may sound a long time ago, I would still expect the boiler to be rated SEDBUK "A". Type the model number into a search engine to confirm this.

"A"-rated can only be achieved if it is a condensing boiler with a condensate drain leading outside or to a waste pipe. It is certified to operate up to 95% efficiency under a predetermined set of operating conditions.

I also happen to know that Alpha boilers of about that age could have an optional GasSaver heat-recovery unit mounted on top to remove even more of the energy which would otherwise be wasted through the flue. Does yours have one?

Next, are you making a fair comparison with the boiler in your old house? The main issue is whether each of them was a Combi style.

Even if you understand this, for the sake of others reading this topic in future, can I define Combi as a boiler which not only provides heating (radiators) but also a direct supply of Domestic Hot Water (DHW) when you turn on a hot tap. A Combi boiler does not have a hot-water cylinder which it maintains at a preset temperature. Instead it fires up a few seconds after water flows from the hot tap.

Once you give me that background info, I'll be in a better position to advise where you are losing efficiency, resulting in higher than expected gas bills.

Oh... and please fill out your user-profile. I read this to better refine my answers on the Forum. Thanks.

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Hi @aphrabenn
Your first Forum posting I notice! :8

Although 14 years may sound a long time ago, I would still expect the boiler to be rated SEDBUK "A". Type the model number into a search engine to confirm this.

"A"-rated can only be achieved if it is a condensing boiler with a condensate drain leading outside or to a waste pipe. It is certified to operate up to 95% efficiency under a predetermined set of operating conditions.

I also happen to know that Alpha boilers of about that age could have an optional GasSaver heat-recovery unit mounted on top to remove even more of the energy which would otherwise be wasted through the flue. Does yours have one?

Next, are you making a fair comparison with the boiler in your old house? The main issue is whether each of them was a Combi style.

Even if you understand this, for the sake of others reading this topic in future, can I define Combi as a boiler which not only provides heating (radiators) but also a direct supply of Domestic Hot Water (DHW) when you turn on a hot tap. A Combi boiler does not have a hot-water cylinder which it maintains at a preset temperature. Instead it fires up a few seconds after water flows from the hot tap.

Once you give me that background info, I'll be in a better position to advise where you are losing efficiency, resulting in higher than expected gas bills.

Oh... and please fill out your user-profile. I read this to better refine my answers on the Forum. Thanks.
Thank you for your reply with information. Most interesting. My Alpha boiler is a Combi boiler. It is an Alpha CB28X. The boiler in my previous house was a two year old Combi, a Worcester, but I can't remember which model.
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Thanks @aphrabenn.

I've just checked online: the CD28X is a non-condensing gas Combi-boiler which was manufactured between 2000-2005. Spare parts are readily available from several suppliers.

It's SEDBUK D rated at 80.1% efficiency (Central-heating mode on first firing-up). So although it clearly falls outside of current minimum standards, it's not in a bracket which I would label "condemned".

As you're new to this property you may not yet know how reliable it is, nor how often it's previously required spare parts to be fitted. Without knowing the average annual maintenance costs over the last 5 years it isn't possible to evaluate when it is cost effective to replace it.

Personally I would try to get it serviced by a local Heating Engineer who currently fits Alpha boilers. I employed one from Plymouth to install an Alpha in a renovation property a couple of years ago, which I was very pleased with. However I don't know where you are in the country (please fill out your Forum Profile!!)

You could check online to find the nearest Alpha trade-supplier in your area, and then phone them to ask the names of three installers they regularly supply. They're bound to tell you because it means more business for them and their trade customers in the future!
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Sorry, I should have added a comment about whether the type of Alpha boiler is likely to be the source of your higher-than-expected gas bills.

In short... yes, it's likely to have an impact. But I would question whether that makes it financially viable to spend £1500-plus on replacing it with a new model.

For most situations, the two factors most likely to give rise to high gas bills with modern boilers are:
  • that it's a Combi (no hot-water cylinder)
  • that the return water from radiators is still at a high temperature

Both of these factors take the boiler out of condensing mode within a short time after it fires up. So the SEDBUK "A" rating is meaningless because it's then certainly no longer running at 90% efficiency or better.

Simply replacing your existing Alpha Combi boiler with a modern condensing type doesn't alter either of these two predominate factors.

Now if you were asking me a different question:
"What about replacing the Alpha CD28X with a non-Combi condensing boiler, and installing a hot water tank with the option to later add a solar-thermal input?"
then I would be far more likely to say "Go for it!"

And if you then said you'd like to run underfloor-heating as well (instead of radiators), then there's no doubt you would get greater boiler efficiency. UFH has a much lower temperature for return-water to the boiler. This means it could stay in condensing mode.

So in a nutshell, I'd tend to retain your existing Alpha boiler at the moment...

... but give some thought to the medium-term possibility of a hot-water tank and (partial?) UFH because that's where you'll really increase boiler efficiency.

Finally, before anyone else points it out - yes, I know I've mentioned nothing about the differing levels of insulation between the old and new properties. That's another whole subject!
Thank you so much for your in depth reply. I've taken on board your Alpha repair man advice. I've already had to call out a local plumber at a cost £60 to replace a part (the boiler stopped working). I bought the house off a relative, and I've just looked at the service history. British Gas were contracted to service the boiler for a number of years, and there have been issues. I'm looking into having it replaced under the Government's Green Energy Scheme, or something akin. I live in the Chesterfield area of Derbyshire.
i had a similar alpha boiler. alpha is acutally a spin off company of British gas, suprised.

my boiler was loosing pressure, tried re-pressure the expansion vessel and replace the prv. still didnt resolve. so went down the route of a new combi...

ideal vogue C32 with nest smart thermomstat and adey magnaclean pro 2 filter.

that meant a 10 year warranty. please read up on opentherm technology and get a boiler tgat supports this protocol. it will. save you money in the long run.
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Thanks for that, @og567.

So that other readers can follow this, may I just give a layman's explanation of the nouns you've used?!

1. I wasn't aware of any corporate connection between Centrica/British-Gas and Alpha. I know that Alpha are a supplier to BG, but their Companies House registration shows that they are part of the Italian-based Immergas Group.

2. Expansion Vessel = a cylinder connected to the heating circuit with a rubber membrane between its two chambers. One side is filled with the heated water, which pushes against the membrane, thereby compressing the air on that side. The air-pressure can be pre-set using a valve at the end connected to a pump (like a car-tyre pump).

There is a "correct" pressure for this pre-charge, which will be listed in the boiler specifications. If this Vessel is inside the sealed boiler casing, then of course you must be Gas-Safe Registered to get to it.

A leaky rubber membrane means that the water pressure isn't properly regulated, which is why @og567 headed for this unit.

3. PRV= Pressure Relief Valve. A safety device connected to every central-heating system which will open if the water pressure exceeds a preset value - usually around 3 to 4 Bar. Often it is combined with an over-temperature device.

The PRV may or may not be within the boiler. If it is... then Gas-Safe registration applies, as above.

4. Magnaclean filter: most boiler manufacturers now insist on the installation of a magnetic filter in order to support their Guarantee. The filter sits within the pipeline close to the boiler and any iron particles (usually from within radiators) are attracted to it.

The filter can periodically be cleaned out using the valves either side to isolate it. The amount of deposit inside it is a good measure of the status of the radiators and whether the anti-corrosion inhibitor is working.

5. Nest is one of several Smart-Home range of heating/lighting controls. There is an ongoing battle between the smart-system suppliers to sign up as many customers as they can. As the smart system components are usually incompatible, the proportion of market-share is indicative of their likelihood to survive.

6. OpenTherm is a system originally designed by Honeywell that allows 2-wire communication between boilers and thermostats. The two wires carry both power (up to 225mW) and data signals. It is an open standard allowing boilers and thermostats from different manufacturers to be connected.


In closing, can I point out that many of these "smart" technologies need to be weighed against the forthcoming functionality offered by the SMETS2 smart-meters. Within the UK, the government has legislated that energy supply (gas & electricity) is to be monitored intelligently and governed by communication signals sent from the Energy Suppliers (like OVO). All houses must have smart meters by the end of 2020.

This will, for example, enable a boiler to communicate with a Smart Meter, acting as an Auxilliary Load Control Switch (ALCS). This can allow houses to maintain steady preset temperatures whilst being fed with energy when it is cheapest.

So a house occupied by an elderly couple might have it's gas boiler switched off an hour earlier in the morning than is set by the time-clock because the weather-forecast has shown a rapid temperature rise soon after 9am. There's no point wasting gas between 8-9am raising the air temperature to 20degC if the sun is about to raise it to 23degC for free!

There are no ALCS-aware boilers yet on the market, but it's something to be aware of before committing oneself to one of the several incompatible smart-home systems.
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