Pulsacoil explained

This section is intended to explain in general terms what a Gledhill Pulsacoil is and how it works. The Standard Pulsacoil is heated by two immersion heaters. A newer addition to the range incorporates a solar input to further reduce running costs where a 'wet' solar collection system is available.

PULSACOIL

The name 'PULSACOIL' is simply a name invented by the manufacturer Gledhill. It is not entirely clear where the name originated as there doesn't seem to be anything pulsing within the unit. One thing is for sure though, when you open the cupboard and discover a unit with such a grand name you can be excused for feeling intimidated by it. In fact this can be the problem when it comes to getting one fixed or replaced - very few people fully understand quite how this product works! As such, you are likely to fall prey to the unscrupulous who will often blind you with 'science' and overcharge because they can tell you anything they wish. After all, if you don't understand it on what grounds will you object?

What is a PULSACOIL and how does it work?

Pulsacoil is a thermal store. To be more precise, a Pulsacoil is a DIRECT thermal store. A thermal store (as the name suggests) is a device that stores heat. It generates thermal energy with electrical heaters that are immersed a store of water. The store of water is open vented. This is to say it is under no pressure - at atmospheric pressure (rather like a bucket of water). This is a key feature of a thermal store. Being at atmospheric pressure it is entirely safe (unlike unvented devices that can explode if they malfunction and go 'over temperature or pressure'). The clever yet simple thing with a thermal store is the way it creates high performance hot water for your domestic use whilst remaining open vented. It does this by employing a heat exchanger. The heat exchanger enables stored heat (in the thermal store) to be imparted to mains pressure cold water as it passes through the unit. This simple process enables a vented store of hot water to make mains pressure hot water.

Replacing a Pulsacoil

Simple? This rather depends on what you are replacing. Although Pulsacoil remains simple in principle the way the unit does its job has changed over the years. This affects installation requirements if you are replacing an older unit.

The origins of Pulsacoil

Pulsacoil used to be made by the Water Storage division of Gledhill. A few years ago this division went into liquidation. Although Gledhill continue to make Pulsacoil they do so now through their Building Products division. While they have retained the name and the look the product has changed internally. The newer model is identified by a BP suffix.

The early model Pulsacoil (picture right) used to use plate heat exchanger technology to create mains pressure hot water. This required a pump to circulate hot water from the store through the exchanger. Water temperature was regulated by modulating the pump speed according to feedback from temperature sensors. This function and others of switching and timing needed control, so a micro processor circuit board became necessary. On the newer BP model heat exchange is performed by a different method, one that does not rely on such complicated control.

The new PULSACOIL BP

The Pulsacoil BP utilises an immersed heat exchanger (unlike the plate heat exchanger on the earlier type that was situated within the cabinet but outside the store). This is to say the heat exchanger is immersed within the hot water in the thermal storage compartment.

How Pulsacoil BP works

Mains pressure cold water is passed through the immersed heat exchanger, is rapidly heated and exits as hot mains pressure water. Temperature control is achieved using a thermostatic mixing valve (TMV) on the outlet that limits the maximum temperature water can emerge (usually set to approx 55^oC).

Simplicity at it's best

Hopefully you can appreciate how simplicity in method requires a much less complex control. The Pulsacoil BP has been stripped of all control functions (an important point to consider if you are replacing an older unit). When you purchase a Pulsacoil BP your installer must add all necessary controls (such as Economy 7 and boost switching) externally.

Conclusions about Pulsacoil

A safe vented unit producing mains pressure hot water must be considered a good thing. Pulsacoil is presented in a smart little cabinet (looking a bit like a filing cabinet) which is pleasant in appearance. No requirement for a high pressure vent pipe to atmosphere makes them simpler to install and less obtrusive. However, since it's conception it has been substantially simplified placing the newest 'BP' model in direct competition with other 'Thermal Stores'.

Pulsacoil is now just a thermal store in a steel cabinet. The cabinet only performs an aesthetic function and the internals only do what all other direct thermal stores do (vented, 2 heaters, cold in, hot out). All the clever more useful bits such as switching, timing and the higher performance plate heat exchanger technology have gone (see picture right). Keeping something simple is however arguably better as the more complex something is the more prone to breakdown it becomes. The loss of complicated electronics and controls that can be costly to repair is no great shame.

The bare truth remains that the Pulsacoil is now nothing out of the ordinary - just a thermal store. Whether you are replacing an older unit or installing new, you will need to add external control gear - just like with any other thermal store.

You might also consider maintenance before making your decision. For example, immersion heaters for the Pulsacoil cost in excess of £50 each to buy. The equivalent replacement heater for other makes costs £44 (prices at Summer 2012) and they perform exactly the same function. Hummm!

Lastly, there is a matter of availability. Pulsacoil can be difficult to obtain quickly. Lead times frequently range up to 3 or 4 weeks. When you or your tenants have no hot water this borders on ridiculous. 3 to 4 weeks without hot water is not only mind blowing to contemplate in this day and age but might meet with an angry response!

Alternatives to Pulsacoil

As mentioned, the new Pulsacoil BP is just a thermal store in a metal box. Hopefully the above information will have helped to dispel the mystique surrounding the product which in effect leaves you free to make your own choice.

Thermal stores are readily available from numerous manufacturers. Indeed, Gledhill are prolific in the manufacture of thermal stores but they attach wonderful names to their products which serves to protect the true function of a unit unless you're 'in the know', such as Boilermate and Torrent Multifuel - both thermal stores.

However, now you have been enlightened your new found understanding means you are no longer shackled to a product name simply because you or your plumber didn't know what it did.

If you need an alternative to Pulsacoil (for whatever reason) you can begin your search here. Pictured right you will see what a thermal store looks like without a cabinet. The one in the image is a 'combination' version (meaning the F&E tank [needed for all thermal stores to work] is incorporated on the top but there are normal 'cylinder types' available too (that require a remote F&E tank). These are quality thermal stores configured in the same way as a Pulsacoil BP, they just look different.

Now available with SOLAR input