Replace my gledhill pulsacoil 2000

[Ethel H]

We had a pulsacoil 2000, a vented thermal store like yours, and it was the most error prone and over complicated thing we had ever seen. It had a PCB board, flat plate heat exchanger, pump and other bits and pieces that would fail one after the other every couple of years. It was designed to fail and Gledhill must have made tons on repair call outs. And we had to remember to manually refill the overhead tank every year otherwise the whole thing would fail. The copper cylinder concealed inside ended up corroding and leaking as all copper stuff do.

In the end we replaced it with an unvented stainless steel hot water cylinder which does away with all the components I mentioned above. It is simplicity itself - fewer bits means less to go wrong, its almost maintenance free. Cost us £1300 supply and fit. Luckily the soil stack (vertical waste pipe concealed behind plasterboard) was near the cylinder so the discharge pipe from the cylinder could be cut into the stack easily. We could identify where the soil stack was by following where the kitchen sink waste pipe ended up going but we could have easily cut into the kitchen sink waste pipe itself had we not been able to locate the main waste stack.

If you do end up going unvented, you will enjoy higher water pressures too. But do not go for an Ariston cylinder, they only use copper heating elements with no option to upgrade whereas every other manufacturer uses incoloy alloy as standard with an option to upgrade to titanium that won't corrode in aggressive water areas like London.

 

[oldbuffer]

An un-vented hot water cylinder is meant to be serviced once a year.

I'm glad your plumber was able to identify that the soil pipe was capable of handling water at up to 135 degrees. Unless it was cast iron, or was of a known make and material suitable for the purpose, I wouldn't have fitted it.

 

[Ethel H]

If the pressure relief valves that are set to operate is between 90°C to 95°C, then under these controlled conditions, safety relief discharge pipework from unvented hot water storage systems can be drained to plastic sanitary pipework.

This has been proposed elsewhere on this website by G3 qualified plumbers and in Building Regulation documents. Just google "Discharge from unvented hot water storage cylinders into plastic sanitary pipework".

 

[hard-work]

The copper cylinder concealed inside ended up corroding and leaking as all copper stuff do.

This was because of neglect. If inhibitor was put in it would not rot. The same water is inside and is not constantly replaced with fresh water. There are not that many parts on it to go wrong. The tank on the top could have been converted to a normal ballcock with an overflow to your stack using a tundish. The tank tops up automatically. All you would need to do is top up the X-100 every 3 years. A DIY job, lift the tank lid.

BTW, your unvented cylinder has lots of pressure valves. When they conk you will know it pricewise. They also hold a lot of pressure and if not looked after can go bang with a big bang. To me an unvented cylinder is a last resort. I would have looked at a high flow combi first, but I assume you have no gas.

 

[Ethel H]

I can't speak for other brands, but Gledhill had a horrendous reputation with their thermal stores, you only have to see what reputable engineers say on this site including Dickie. Thermal stores and open vented systems in general are a very British thing. This UK company got into financial difficulties as a result and changed the design I believe and started moving into manufacturing unvented cylinders. It was more than just sludge and leaks, it was the various components that failed at an alarming rate of these Pulsacoils. I have not had to service my new unvented cylinder for 5 years although I am told they require a yearly service - there are several safety devices built into the design including thermostat overheat cut-out, temperature and pressure relief valve and another expansion valve so if one or more safety device fails, the other can be depended on. Unvented cylinders is the water heating system of choice in Europe and and I read that the UK are catching up with almost all flat new builds incorporating them.

 

[hard-work]

Gledhill always made every type of cylinder, including unvented. They had financial problems just after the 2008 crash, not their fault the world crashed. They reformed with a smaller range.

A friend has a Boilermate 2000 thermal store being faultless for about 20 years. All the pumps are Grundfos. He tops up the X-100 every 3 years by lifting a lid on the F&E tank pouring the liquid in. That is all he does. No maintenance or servicing ever, and no mandatory requirements for service either. When the cylinder drops to a certain temperature (I think near the bottom of the cylinder) the boiler cuts in pouring all its heat into the cylinder as the water is being drawn off adding to the stored heat in the cylinder, in effect combinig the heat output of the two. He has a simple Glow Worm heating boiler controlled by the 2000, which obviously needs servicing. This gave ignition problems once while the 2000 has not given any whatsoever. He swears by it, not ever running out of hot water. His is in the loft taking up little space in the loft, and none in house below, eliminating cold tanks. All the water is at mains pressure.

Thermal stores can be high or low pressure. The advantage is that most are low pressure. If all flats these days are installing unvented cylinders it would be because of financial incentives as that is how builders do things. The great thing about the Pulsacoils was that they could be fitted away from outside walls as no overflows or discharge pipes are needed. A great advantage for an architect for flat layouts, with Gledhill listening to these people and providing the products. Gledhill changed the design to eliminate sludge, having the stored water static and separate from the CH water. Although a lot of sludge in thermal stores was again because of neglect of maintenance not replenishing the inhibitor. Having no ferrous in the system eliminates sludge build up.

It is sad when I see these ripped out by ignorant incompetent plumbers, because maybe it needs a sensor or pcb which they can't figure out. This costs the homeowner a fortune to replace it - with an inferior system. I have seen cold tanks in lofts fitted with cheap green insulation cylinder with a power shower pump fitted. All because of ignorance and con-man plumbers.