Pulsacoil Repairs

I’m Mike Bryant, also known as Mike the Boilerman. I specialise in repairing old or unusual boilers and Pulsacoils are a good example. I keep a full stock of spares for Pulsacoil in the van. Much of my work is in Wiltshire, Berkshire, north Hampshire, Oxfordshire, Surrey but I’m happy to travel further if necessary, but I no longer travel into London, sorry. The further you are from me (near Hungerford) the higher the cost will be, but I'm happy to do the travelling.

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How does a Pulsacoil work?

Firstly, Pulsacoils are 'thermal stores', which work in a different way from ordinary hot water cylinders and water heaters. Differently enough to to mystify many heating engineers when it comes to fixing them, it seems. Pulsacoils are not particularly difficult to understand but the later versions can look intimidating with the cover removed and without background knowledge, many heating engineers understandably struggle to diagnose and repair them.

With a Pulsacoil (and with thermal stores in general) the main tank is filled with very hot water at very low pressure, and this is not the hot water that comes from your hot taps. The water inside a Pulsacoil never changes, it is the same water today as when it was first installed, or last drained down and refilled by technician. The header tank on top of a Pulsacoil is there only to replace water lost from minor leaks and evaporation. This is the fundamental difference between a Pulsacoil and an ordinary hot water tank.

The water inside the a Pulsacoil is being used to store heat energy rather than to feed the hot taps, hence the term ‘thermal store’. This very hot, very low pressure stored hot water is then used as the heat source to heat high pressure cold mains water in ‘real time’ on its way to the hot taps, showers etc. It does this using a heat exchanger, in much the same way that a gas combi boiler uses a heat exchanger. So mains water passes through the Pulsacoil, entering cold and high pressure, then exiting hot and high pressure, just a second or so later. The point of this is to take advantage of the high water pressure in the street mains water supply, to deliver high pressure HOT water to the shower in particular, without the use of pumps.

Why do we have Pulsacoils?

Showers fed from ordinary hot tanks don’t really work very well (or at all). The conventional alternative is a “mains pressure unvented hot water cylinder”. The mains pressure cylinder is generally known amongst plumbers as a “Megaflo”, which is the trade name of the market leader in these devices. A “Megaflo is a tank of hot water at high pressure and contains a lot of energy, and if things go wrong can be a serious safety risk so installation is governed by law to those qualified to fit them, similarly to gas. The most onerous aspect to fitting one is a requirement for a metal safety discharge pipe capable of carrying away steam to outside under fault conditions. Architects often specify thermal stores when installation of this safety discharge pipework is not practical, e.g. when the airing cupboard is in the centre of an apartment and not near an outside wall. This is why so many modern town centre apartments have Pulsacoils installed - in a nutshell to make the showers work!

There have now been quite a few versions of Pulsacoil made by Gledhill over the years and there are pages here describing each in a bit more detail along with what goes wrong with them and the possible solutions. If these don't help, I'm happy to give advice to anyone wanting it via my Gledhill Repairs discussion forum (it's here) or by text, WhatsApp or email. Gledhill themselves also offer telephone technical support during normal office hours but it's expensive - 60p per minute last time I checked. Their technical helpline number is 0906 611 0005.

If you’d like to talk to me about a repair, call or text my mobile 07866 766364.