Why is the UK always so far behind the rest of Europe, boilers have come a long way over the years, better, safer and more controllable and yet unvented cylinders have not moved with the boilers, or maybe more to the point Part G of the Building Regulations has not moved forward, my reason for bringing this up is I recently fitted a Viessmann 100 system boiler, very good boiler, now with these boilers and many other boilers on the market, you have the option of purchasing a DHW sensor to allow the boiler to control the cylinder temperature directly, this in my opinion is a far better and more accurate way to control the cylinder temperature, rather than using an old fashioned bi-metal strip as the way to control the temperature, Viessmann state that when using the DHW sensor with their boiler no 2 port valve is required, now this is correct in my opinion, the boiler management control will only heat the cylinder to the required temperature, with the old system you were relying on an external stat which could fail, so it needed to protect against the production of heat which could over heat the cylinder, now the cylinder we were installing, which was specified by the client, (otherwise this situation would not of arisen as I would of used my preferred cylinder), was prewired on the immersion and boiler overheat stat sides, I needed a port to insert my boiler sensor, but all the ports were full, I rang the manufacturer to ask which was the boiler over heat side as I wanted to remove it to install my sensor, but leaving the immersion overheat in place, they began a lecture about I MUST use the 2 port valve, I hung up, not going to listen to people who are stuck in their ways, I traced the wiring myself and removed the sensor that was not needed and placed the Viessmann sensor in, works a treat.

 

What I find most annoying about all this is this manufacturer and most other cylinder manufacturers who state Part G as a safety part of their cylinder installation, are the very same companies who when producing twin coil cylinders, for solar, provide you with two 2 port valve, one for the boiler side and one for the solar side, now the 2 port valve they supply is NOT suitable for the solar circuit, it cannot take the temperature, nor can it take the glycol, so is of no use to the installer, they also supply you with 2 x cylinder/overheat stats, now with the solar circuit you do need to run the solar pump via the overheat stat, to shut off the solar pump in the event of the cylinder reaching high temperatures, but why do they supply you with a overheat stat that is linked to a cylinder stat, so that if the stat gets adjusted the solar will stop its input early, the reason for this in my opinion is they simply want to supply what they already have, to save themselves costs, my other point is, as we all know heat rises, it’s not rocket science, so I would like to know why when they manufacture twin coil cylinders do they have a thermal cut out at the top for the boiler and a thermal cut out at the bottom for the solar, in my opinion this is wrong and is why I object to the technical of a manufacturer preaching to me about Part G safety, why have the solar cut off (overheat stat) at the bottom, if say for example the boiler stat failed and the boiler continued its input, at the set point the top overheat stat will trip, stopping the heat input from the boiler, BUT the lower stat may not of reached its trip temperature, which could allow solar input to continue which could overheat the cylinder, why do they not have the solar overheat stat and only a overheat stat at the top of the cylinder, so that it trips out at the same time as the top overheat stat, seems simple to me, but I believe the manufacturers just adapted their existing cylinders slightly to sell twin coils where they had to spend the least money and make the least manufacturing production changes to keep profits up, rather than starting from scratch with a new design, a bit like the first condensing boilers from the UK, small changes were made to try and produce condensing boilers with dire consequences, condense dripping onto the burner and causing corrosion, but then finally bigger changes were made, but only after a lot of installers switched to other brands from Europe who had already overcome these problems, the UK need to move with the times more quickly, Building Regulations need to be updated more frequently to accommodate changes in technology, we need to get rid of the old boy network who control things at the moment and are happy to cosy up to manufacturers to keep everything sweet and not rock the boat, changes are needed and if the UK ihas any chance to reach it CO reduction targets we need to embrace new technology, not sit on old school regulations that are outdated.