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Gledhill Boilermate explained


 Thermal Stores

Gledhill Boilermate explained

Understanding Boilermate and your options for replacement


Know your Boilermate


Gledhill Boilermate

The product known as 'Boilermate' has been around for a long time. It has however changed during this time and if you are replacing an elderly unit (or for that matter planning to incorporate one in a new installation) you should be aware if fundamental differences between old and new models.

What is a Boilermate?

The answer to this rather depends on the age of the unit you are trying to describe as the function and appearance has somewhat altered over the years.

Pictured right you will see a Boilermate A Class OV - very different in appearance to a Boilermate II for example, or the new Boilermate BP shown below.

Essentially, the Boilermate is a Thermal Storage Unit. A thermal store, as the name suggests, is something that stores thermal energy. Thermal stores, as they are generically known, are available from different manufacturers and typically store their energy in a mass of water contained within the unit which is open vented - this is to say the water stored is at atmospheric pressure, not sealed or 'unvented' - rather like a massive bucket. Gledhill (the manufacturer of Boilermate) took the principle of an open vented thermal store (a concept favoured for it's safety when compared to unvented systems) and incorporated several functions into their unit and gave it a snazzy name.

As mentioned, the Boilermate unit has changed both in appearance and function due to product development (and other factors) over the years. The earlier models looked like a cylinder with various pipework, whereas the newer versions resembled a rather unassuming office cabinet with concealed pipework.

Gledhill Boilermate A Class with front cover removed exposing internals



What function does a Thermal Store perform?

The core function of a thermal store is to collect and store energy. Hence, a Boilermate is an energy store. But, the Boilermate (depending on model) utilises the stored energy to perform other domestic services. The most desirable function of a thermal store (and therefore a Boilermate) is to provide provide mains pressure hot water whilst remaining open vented. A contradiction you might think (mains pressure hot water from an open vented store?) but this is the somewhat clever part - heat contained within the store is simply imparted to mains pressure cold water passing through the unit. The method by which this operation is achieved marks the difference between products offered by manufacturers and indeed the different models within the Boilermate range.

What function does a Boilermate provide

Gledhill exploit the desirable characteristics of open vented thermal storage, package it with other useful functions and sell it as an 'all-in-one' branded product - The Boilermate.

The Boilermate developed into a hot water management system that took care of both heating and hot water requirements for domestic properties. Designed to work in conjunction with a boiler (hence the name 'Boilermate') the product soon became popular with major housing developers not only for it's performance but also for it's ease of installation - wheel it in, put it down, connect it up. Delightfully simple for the plumber, a full water management system in a single product - and no fiddly items of valuable stock for the developer to keep an eye on!

The Boilermate evolved from a cylindrical thermal store with a host of visible pipes and external components into a neat cabinet containing everything the unit needed to perform it's function concealed behind a removable front panel.

Mains pressure hot water, a fully open vented store (a great safety feature), central heating control, boiler control, all the pumps and gadgets needed to manage household requirements were incorporated into the Boilermate. As the product continued to develop (Boilermate 2000 and later) the unit saw the introduction of an optional 9kW electric boiler that could be used in emergencies if the main boiler were to breakdown. This feature became a standard fitment on the Boilermate 'A Class'. Little by little the unit became more and more 'clever'.

How do you get mains pressure hot water from an open vented thermal store?

The principle is simple, although achieving it is somewhat more complex. This contradictory scenario is achieved through heat exchange. Heat exchangers are utilised to take pre-heated water from the thermal store (which is open vented) and impart the energy into the mains pressure water passing through the unit. It's as simple as that. All of the dangers (risks of explosion) associated with unvented cylinders simply disappear because an open vented store cannot explode. So you get all the benefits of mains pressure hot water with none of the risks.

Reliability of the Boilermate

The Boilermate remains a good idea. To exploit elements that safely deliver mains pressure hot water without any of the dangers must be a good thing, but Boilermate hit a bit of a problem - it became too complex.

Boilermate had developed into a complex animal that required a brain. Although heat exchange technology is simple to achieve, stabilising output temperature opened up a whole new can of worms. In order to utilise a plate heat exchanger with a high flow potential AND achieve a stable output temperature the speed at which water from the store was pushed through the exchanger had to be regulated. This meant modulating pump speed to vary throughput in response to strategically placed temperature sensors monitoring output temperature. Control required a microprocessor which of course gave rise to the need for electronics and circuit boards. Electronics took over the control of all system functions. Unfortunately these complexities have proved to be expensive things to fix when they go wrong and of course like anything complicated it will go wrong.

Getting a Boilermate fixed

Getting somebody to work on a Boilermate has been an issue for many people over the years. Mention a thermal store to your average plumber and he'll look at you as if you were speaking ancient Hebrew. Mention Boilermate and you're lucky if they bother to close the door behind them as they run away. To most plumbers Boilermate is rocket science and there's never a scientist around when you need one!

In reality the function and principle of Boilermate is not all that complicated, it just needs a willing and open mind. Principles of thermal storage are in themselves fairly easy to grasp, but many plumbers either can't be bothered or become petrified at the thought of learning something new. Surround a thing with electronics that was already off-putting and you won't get a warm reception. For this reason owners of Boilermates around the country are happy as can be while they work, it's when they go wrong it becomes apparent that help is in short supply.

In short, models of Boilermate up to and including the 'Boilermate A Class' were good at what they were designed to do so long as they didn't go wrong. When they did (and continue to do so) it can be difficult to find a person who will understand and tackle a repair and spares can be a little pricey.

The new generation of Boilermate

Towards the end of the 2000 decade the Water Storage division of Gledhill that manufactured the Boilermate went into liquidation. It's reliance on the 'new build' housing market proved to be the downfall. Boilermate as we knew it ceased to be.

However.... Gledhill is made up of several divisions, so manufacture of the Boilermate range (along with others) transferred to the Building Products division. From then Boilermate would carry a 'BP' suffix.

The Boilermate BP

When the Boilermate product was transferred to the Building Products division of Gledhill it underwent quite a major change. Taking a positive view of the changes one might argue that the product was improved by removing all the complicated technology required to run to older model. But how you might wonder?

As mentioned earlier, the Boilermate had become complicated and required microprocessor control for time functions, pump speed modulation, switching etc etc. By utilising a different type of heat exchange mechanism (an immersed heat exchanger) the new BP model no longer requires pump control.

Furthermore, where the older model controlled DHW output temperature by varying the heat exchange process (by modulating pump speed) the new model simply uses a TMV (thermostatic mixing valve) on the outlet to limit the temperature that hot water can be delivered to taps. Genius you might think, but not really. Yes it is great that a simpler way to achieve mains pressure hot water had evolved, but it came at a price.

How does the Boilermate BP differ

The concept of Boilermate was (in the early days) a total water management system. A system that could deliver mains pressure hot water while remaining open vented itself. A great idea doing away with the dangers of unvented cylinders while retaining the performance. You simply needed to feed the unit with heat from a boiler and the unit would handle all domestic hot water (DHW) and central heating requirements. Furthermore, the DHW output flow potential was huge - up to 35 litres per minute. In reality very few domestic properties have the ability to procure 35 litres of water per minute, but the potential was within the capability of the Boilermate. The new Boilermate BP does not and cannot do the same.


There are several obvious differences:

(Please see Boilermate BP unit picture right - front cover removed)

Firstly, the new BP model does not contain any sort of control function. This is to say there are no programmers, switches or microprocessors in the unit. Any control function required must be provided externally.

Secondly, the Boilermate BP does not output to central heating. Whereas the older unit would send pre-heated water off to the radiators on demand the new one doesn't. There is no central heating function to the BP model.

Thirdly, the only function of the Boilermate BP is to provide mains pressure hot water while maintaining an open vented thermal store. That's it. The unit now installs to a heating system in the more traditional 'S' or 'Y' plan configuration.

New Boilermate BP unit with front cover removed. Note the simplicity of the connections!


Is the Boilermate BP suitable as a replacement for an older type?

In a word, Yes. But, you will have to bear in mind all that has been explained in the section. An older type Boilermate as you know managed central heating needs. The BP model doesn't.

If you compare the two pictures above you will see how very different the older A Class (top image) and lower BP model (black & white image) are.

Remember, the Boilermate BP is now a device that creates mains pressure hot water ONLY. You will need to make fairly minor alterations to existing pipework in the vicinity of the old unit, add an external programmer, zone valve/s and possibly a circulating pump in order to replace an old Boilermate with a new one. On a more technical level there are one or two other differences.

Firstly, earlier models of Boilermate did not have a heat exchanger (boiler coil) on the input from the boiler. Boiler water was circulated straight into the shell of the cylinder. Sister product to the Boilermate was the 'SystemMate'. This was a Boilermate with a boiler coil allowing a pressurised radiator circuit. The BMBP comes with a boiler coil as standard which is now the only way heat may be imparted to the unit. This of course means that the unit can be used on a sealed radiator (pressurised) system or a fully open vented system. Having a boiler coil means the BP model can also be used as a replacement for a System Mate (bearing in mind all the modifications/limitations mentioned that shall apply). There are no options available, the BMBP is a 'one type suits all' product and the unit will only accept one heat input.

Secondly, the hot water delivery rate on the BP is slower than the old models were able to manage. Instead of a colossal 35 litres per minute the new model delivers up to 18 litres per minute on the 125, 145 and 185 versions and up to 22 litres per minute on the 215 and 225 models.

Is the Boilermate BP as good as it's predecessors?

This really is a matter of opinion. Better, one might argue, if you consider the removal of components such as microprocessor circuit boards, pumps and a plate heat exchanger a good thing. After all, the more simple something is the less likely it is to break down. But then, is the Boilermate BP really a Boilermate at all? Boilermate used to refer to a clever box of tricks that would manage heating and deliver oodles of mains pressure hot water whilst maintaining an open vented thermal store. The new BP model delivers the hot water (albeit less of it) but does nothing else as it doesn't have anything to do with the heating. So in effect the Boilermate BP is now just a thermal store in a cabinet.

Alternatives to Boilermate

Now that Boilermate is simply a thermal store in a box, and because we know you will need to modify existing pipework during the process of replacement, you are of course no longer 'tied' as it were to the product. Replacement (if you wish to stay with the technology) will involve you buying a new thermal store (this is all a Boilermate is now) so you are at liberty to shop about.

In an attempt to keep things simple we will assume you wish to continue enjoying the benefits of mains pressure hot water together with the safety of an open vented thermal store. So which way should you go?

Top of the list must of course be to install a new type Boilermate BP. Perfectly understandable if you desire the cabinet style of the Boilermate BP. Just be sure you understand the differences between the new and old models and the alterations to plumbing and controls you will need to undertake. And remember, Boilermate BP is just a thermal store in a box. Nothing more.

If you are less concerned about 'the box' in which the Boilermate houses its store then you might like to look at a cylinder type thermal store.

There can be numerous advantages in considering a proper cylinder shaped thermal store. Not least is the fact that you can run heating directly from a cylinder type store should you wish in much the same way as the old Boilermate models used to. In short, cylinder type thermal stores are more versatile. Depending on the model you choose, cylinder type thermal stores will accept multiple heat sources simultaneously, provide mains pressure hot water AND remain open vented. They are therefore much more versatile than the Boilermate BP.

Which cylinder type thermal store should I choose?

Firstly you should take a look at the various options available to you. Gledhill (the manufacturer of Boilermate) make their own cylinder type thermal store called the Torrent Mulitfuel Store. Gledhill, in keeping with the company's propensity to brand their products with catchy names, have christened their thermal store cylinder with a name that describes the cylinder's function quite well. It is however only a thermal store and arguably does nothing more than other similar products.

You might also like to look at an alternative range of thermal stores that are available (follow the link for full info). These cylinder type thermal stores haven't been given snazzy names they simply perform the same function.

You might be interested to know that the Gledhill Torrent Multifuel store is available ONLY as described. The alternative cylinder however can be adapted and/or modified to customer specification and is available in cylinder and combination versions.

Thermal store cylinders can generally accept heat input from various sources such as solar, wood burners, AGA's, oil and gas boilers, air recovery and ground source heat pumps. The process is simultaneous, they remain open vented and all provide mains pressure hot water.

A thermal store is in some ways unique as it possesses the ability to accept heat from sources that are deemed 'uncontrollable' such as wood burners and AGA's. The inherently open vented nature of a store makes this possible without the risk of explosion.

Check them all out before you decide as there is often a price differential that cannot be ignored. You are always welcome to call our office for advice if the going gets a little tough!


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