Hi all this is my first post. I am a self builder looking at the options for stored hot water and have decided to go with a regular boiler heating an unvented 250 litre storage cylinder. Looking at the options there seems to be two cylinder styles available. The older style with a separate expansion vessel or the newer designs with the expansion vessel incorporated within the cylinder. Its obviously a major purchase so want to get it right. I have searching the net but cant find any comparison comment, so would welcome any views you have on the merits either systems. Thanks for your help
Although you have made the decision there is also a lot to be said for vented cylinder systems. Here the tank contains a "heat store" of hot water, heated from a system boiler with indirect coil towards the base. Hot water for the taps comes from a second indirect coil towards the top of the tank, fed by mains cold water and then after passing thorugh the tank is mixed in a blending valve with more cold before passing to the taps. Advantages? (i) easy to install with no extra qualifications needed, (ii) safer with no annual safety inspection needed, (iii) hot water to the taps is straight off the mains so "fresh", healthier and high pressure (with an unvented the hot water can remain in the tank for days before being drawn off), (iv) no sludge or scale build up in the tank - the water you filled it with initially is the water that will be there in 10 years time (give or take make up needed due to evaporation), (v) with a three port valve from the boiler as a "Y" system installation is much less complicated (no safety devices needed on the cold input etc.) diymostthings
Thanks for your reply diymostthings. I was aware of Thermal Store but possibly didn't give it the thought I should have done. I was influenced by most new builds I visited have Combi or Unvented systems but you make some interesting points worth considering. Im very tight on my SAP values so the efficiency rating is critical, any idea what the efficiency comparison is between thermal store and unvented.
Hi OSP - well I really don't know the answer to that one but I would argue that the main source of heat loss in both systems is the tank - of equivalent size in both cases and in both cases they will be well insulated to a high standard. So I would say that the efficiency would be very similar. We have an Advance Appliances heat store on a "Y" plan and it hasn't skipped a beat for over 6 years. http://www.advanceappliances.co.uk/ kind regards diymostthings
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