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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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Using combi in stored hot water system
Now I know I'm on dangerous ground here, and I really don't want to
unleash combi war, round 481, but I would be interested in answers to this. I have a combi which works very happily - an Ariston Microgenus 27kW. It's a perfectly good combi, but I'm toying with the idea of having a pressurised cylinder installed to provide for stored hot water at mains pressure. Before I get Mr Plumber in to suck his teeth and declare the whole system to be in need of ripping out, is there any reason why the combi can't be used to provide stored hot water in this way? My primitive understanding of combis is that they are conventional boilers, with an additional heat exchanger bolted on which provides the hot-water-on-demand function. Presumably my scheme would render the secondary heat exchanger redundant and I would just be using the primary heat exchanger to provide central heating and hot water as a conventional boiler would. Is this about right? Martin |
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In an earlier contribution to this discussion,
Martin Pentreath wrote: Now I know I'm on dangerous ground here, and I really don't want to unleash combi war, round 481, but I would be interested in answers to this. I have a combi which works very happily - an Ariston Microgenus 27kW. It's a perfectly good combi, but I'm toying with the idea of having a pressurised cylinder installed to provide for stored hot water at mains pressure. Before I get Mr Plumber in to suck his teeth and declare the whole system to be in need of ripping out, is there any reason why the combi can't be used to provide stored hot water in this way? My primitive understanding of combis is that they are conventional boilers, with an additional heat exchanger bolted on which provides the hot-water-on-demand function. Presumably my scheme would render the secondary heat exchanger redundant and I would just be using the primary heat exchanger to provide central heating and hot water as a conventional boiler would. Is this about right? Martin Yes, it is perfectly feasible to use the CH side of a combi to power both the CH *and* stored hot water. You will need some sort of zoning control (either a 3-port mid-position valve, or two 2-port zone valves) in order to have independent control over the CH and stored HW. In order to provide stored hot water, you can use a conventional indirect cylinder with a header tank, or a mains-pressure unvented cylinder (which must be professionally installed) or a thermal store/heat bank system - you pays your money . . . Many people who do this sort of thing continue to use the original HW side of the combi for providing instant hot water to the kitchen sink - and use the stored hot water for baths and (maybe) showers. -- Cheers, Set Square ______ Please reply to newsgroup. Reply address is invalid. |
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"Martin Pentreath" wrote in message om... Now I know I'm on dangerous ground here, and I really don't want to unleash combi war, round 481, but I would be interested in answers to this. I have a combi which works very happily - an Ariston Microgenus 27kW. It's a perfectly good combi, but I'm toying with the idea of having a pressurised cylinder installed to provide for stored hot water at mains pressure. Before I get Mr Plumber in to suck his teeth and declare the whole system to be in need of ripping out, is there any reason why the combi can't be used to provide stored hot water in this way? My primitive understanding of combis is that they are conventional boilers, with an additional heat exchanger bolted on which provides the hot-water-on-demand function. Presumably my scheme would render the secondary heat exchanger redundant and I would just be using the primary heat exchanger to provide central heating and hot water as a conventional boiler would. Is this about right? Martin Firstly, yes, a combi can be used as you want. Secondly, why do you want to add a cylinder? What type of cylinder? Cold tank and cylinder? Unvented cylinder? Heat bank cylinder? How many baths, showers, etc? |
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Yes, I did this a few weeks ago. The combi instantaneous hot water
supply was used only for a washing machine & a 300 litre unvented HWS cylinder was installed. If a pressurized unvented DHW storage system is to be fitted, then you need to control it's temperature with a 2-port spring-return valve. A 3-port mid position valve on it's own is not suitable. See the Honeywell S-Plan (two 2-port valves) wiring diagrams at; http://content.honeywell.com/uk/home...20S%20Plan.pdf You will get a suitable 2-port valve with the unvented cylinder package. The installer should have passed a suitable training course (CITB, IoP, etc) traing course on unvented HWS systems. |
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