Gledhill PULSACOIL explained

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GLEDHILL Pulsacoil explained

Understanding a Gledhill Pulsacoil and your options for replacement

Index Page > GLEDHILL Hot Water Storage > PULSACOIL Explained


How does a PULSACOIL work?

The purpose of section is to explain what a Gledhill Pulsacoil is and to explain in general terms how it works. It is not a definitive statement and you are advised to research whether a Pulsacoil will be suited to your needs. We hope this section will help you to understand the process that goes on behind the front panel to give you mains pressure hot water.

If you already own or have inherited such a unit you can obtain spare parts here in the event you have a malfunction. Simply give us a call.

Technical manual for -

PulsaCoil BP model:  (Discontinued)

Pulsacoil PCS Eco Stainless : Click here

PULSACOIL Product Sales: Click here


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 and in many models there isn't even a coil. 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?

Gledhill Pulsacoil BP unit

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 immersion heaters and stores it in an internal 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 the process of heat exchange. 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.

Why bother with a thermal store?

In a nutshell, thermal stores give you mains pressure hot water safely - because they're vented.

One of the biggest problems when creating hot water within a dwelling is delivering it at an acceptable pressure. A typical house with a gravity hot water system relies on water stored in a header tank (often located in the loft space) pushing down under the force of gravity to create the pressure we perceive. The higher the loft tank the greater the pressure.

For those who like a bit more tech info, a 33 foot (10 metre) head of water will generate 1 bar of pressure.

So if you apply this equation to any scenario where there is a gravity water system you can begin to appreciate how poor the water pressure can be. Simply measure the height differential from the header tank to the outlet point to appreciate this.

One way to overcome this problem is to install what is known as an 'unvented hot water cylinder'. This product is exactly what is claims to be - unvented. It is a pressure vessel which is directly fed and kept under pressure by the incoming water main. The contents of the cylinder are heated (either directly or indirectly) and when you open a tap the contents are forced out by the pressure of the incoming water - hence, mains pressure hot water.

Unvented cylinders do however carry with them an element of risk - the risk of explosion. If an unvented cylinder goes over temperature or over pressure (or both) the risk of explosion exists.

This might all sound great, but what does it actually mean? Have a look at the following clips to appreciate what an unvented cylinder can do if it goes wrong...



For this reason unvented cylinders are equipped with pressure release equipment which activates when the internal pressure exceeds a safe level. The problem is when the PR valve activates it can release scalding hot steam, so this needs to be piped to the outside of the building to vent safely into the atmosphere. The dangers associated with unvented hot water cylinders are addressed by Building Regulations - Section G3 (In England). A cylinder that contains in excess of 15 litres of hot water under pressure is subject to these regulations.

You might begin to appreciate why a thermal store offers an attractive alternative to an unvented system. As mentioned, a thermal store is open vented and as such cannot explode. Therefore, being inherently safe it is not governed by G3 Regulations as the only hot water under pressure is that contained within the heat exchanger. This is viewed as a huge advantage. Mains pressure hot water without any of the liabilities. Thermal stores do not require an annual service (unlike their unvented counterpart) making them doubly popular especially with landlords and do not require a vent pipe as the potential for high pressure steam simply does not exist (making them a favourite in buildings with multiple occupation).

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. For this reason and to denote the rise of the new unit each were allocated a 'BP' suffix. While retaining a similar look and name the product had changed internally. The Pulsacoil BP utilised an immersed heat exchanger coil (whereas earlier models had used a plate heat exchanger with micro processor controls for everything). The BP model required an external switching device for the immersion heaters.

Internals of earlier models of the Gledhill pulsacoil


The early model Pulsacoil (picture above 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 utilised a micro processor circuit board that can be seen near the top. The immersed heat exchanger of the BP model simply relied on a thermostatic blending valve to regulate output water temperature arguably a simpler method.


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.

Pulsacoil BP schematic


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 55oC).

Inside the Gledhill Pulsacoil BP


Early 2014 Pulsacoil changed yet again. Notably, where copper had been preferred as the construction material for the store now stainless steel would be used for the first time.

It could be argued that stainless is a little more resistant to corrosion and therefore the machine would be better suited to hard water areas. However, in reality the bulk of water in a thermal storage device theoretically doesn't go anywhere, the store is filled and that's that apart from a small amount of evaporation. So once the water from the initial fill has done its deed there is relatively little more going on. So, why stainless? Those who are a little cynical have attributed the change entirely to cost of material. Stainless is cheaper now than copper. There may be a slight advantage to the resilient nature of stainless but not the primary reason for the change.

The PULSACOIL STAINLESS could be described as a hybrid of all the earlier models - with the only exception being that of build material.

The PCS has re-introduced the use of a plate heat exchanger and associated control, although the switching of the immersion heaters is still a matter for an external device which is not part of the package you buy. Depending on which model you may be replacing you may or may not have the necessary off-peak controller already.

Pulsacoil Stainless - front cover off showing internals

Schematic diagram of the Gledhill Pulsacoil




The New Generation PULSACOIL ECO Stainless has arrived.

All the benefits of previous generations, but now incorporating a stainless steel thermal store and low energy hi efficiency components.

The Pulsacoil ECO Stainless still represents fantastic value for money and produces mains pressure hot water safely.

For more information please see section directly above - Pulsacoil Stainless - or refer to the Technical Manual

Need to replace your existing unit? Pulsacoil Sales

Need and installer? Please refer to our installers section.

Like to start a maintenance contract? Call us


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 modified throughout it's various guises.

Pulsacoil is 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).


Installation/retrofit of a Pulsacoil:

Pulsacoil is a product that has become a victim of its name. After all, what does it mean? The truth is that the Pulsacoil is a very simple machine. It is an open vented store of water (a bit like a bucket) heated by two electrical immersion heaters (exactly the same as an Economy 7 cylinder). So... why should you pay more to have a Pulsacoil fitted than a copper E7 cylinder? Yet, some plumbers would have you believe otherwise!

In short, Pulsacoil is delightfully easy to install. There are no special qualifications (G3) required for installation as the unit is open vented. The unit does not require annual servicing. Mains pressure hot water is achieved by a heat exchange process, which in reality is no issue as the machine is set up to work once the simple installation instructions have been followed.


PULSACOIL Value for money

Pulsacoil is offered by us at a very attractive price. So good in fact that there is nothing else on the market at present that can compete.


Alternatives to Pulsacoil

Pulsacoil is a thermal store. It gathers electrical/thermal energy and converts this to mains pressure hot water whilst remaining open vented itself. It is best suited to small properties such a apartments and flats. For bigger heavier applications you might consider Boilermate and Torrent Greenheat thermal stores.


It has been our objective to explain:

  • what a Pulsacoil is

  • what function it performs

  • how it performs said function

  • the advantage of a thermal store

  • the difference between new and older models of Pulsacoil

  • considerations when installing or replacing

  • general conclusions

  • alternative product advice

We sincerely hope we have succeeded by providing you with clear and objective information. This document has been produced to help you (the end user or installer) make an educated decision based on understanding.


You are always welcome to call our office for more advice if you would rather discuss your requirement further.


If PULSACOIL is the product for you please click here to go straight to the appropriate product section.






In principle the PULSACOIL remains the same in terms of operation. What has changed is the appearance.


The new PCS PULSACOIL is now cylindrical.



Constructed with a stainless steel water storage compartment, the function of the PULSACOIL remains the same. Mains pressure hot water from a thermal store that is heated electrically.


There are however a couple of variations to older versions above and beyond the shape.


The PCS PULSACOIL can now take heat from an alternative secondary source.



All models of the new PULSACOIL PCS are available handed Left or Right. In effect what this means is 'which side of the Immersion Heaters do you want all the pipework etc'?


The new cylinder sports a grey cover under which you will find all the stuff previously on show on earlier models - Plate heat exchanger, controls, pipe work etc. The grey cover also offers a degree of energy saving by insulating what was previous bare.


The optional handing places the grey cover (and therefore everything under it) to the right or the left of the immersion heaters. Strangely, Gledhill have decided to make the left hand (LH) version the standard (pictured above). If you don't ask for a right hand version you will simply get a LH model by default. BUT, older models would by a similar criteria be considered 'Right Hand' - where all the pipe work was on the right hand side of the unit. So, if you are replacing an older PULSACOIL and you want to minimise adaptation of existing pipe work you should bear this in mind.


The PCS is available in 3 sizes - PCS150, PCS180 and PCS 210. The two smaller models are supplied with a new attractive F&E tank that compliments the shape of the cylinder and sits neatly on top of it. The largest model still relies on an oblong F&E tank that is more often sat on a shelf above the cylinder.


It should be noted, the smaller circular F&E tank is not compatible with most float valves, so will need to be manually filled and periodically inspected to ensure there is water in it. Having a larger F&E tank, the PCS210 model can be installed with a live water feed to the F&E thereby fully automating the process of keeping the requisite water level. (A live feed will always require an overflow pipe from the tank).


A proprietary switching device will be required in every case to manage the electrical supply to the heaters.



Back to the Gledhill Pulsacoil PCS Stainless section






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