The Woodland House
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Posted By: SteamyTeaIt is an interesting problem and is really to do more with how the system is used and the rate at which the flat uses DHW and looses heat.If the heat rate loss is very low/slow and the hot water is used in one go, typical for one occupant, then the maximum may be more important than the minimum. Think mornings when the flat is being heated and a shower is taking place.But if the place is constantly occupied and showers/baths happen at different times then the minimum may be more important.
Posted By: JSHarrisIn general it's better to run a combi at the lowest flow temperature you can, but that needs fairly large radiators in order to get a reasonable flow/return temperature differential.Larger than normal radiators can help if the boiler is slightly too large, by giving a buffer whilst the boiler stays in the anti-short cycling time delay phase. This then limits the oscillations in the room temperature around the set point that you might otherwise get from an over-size boiler with short cycling protection.
Posted By: JSHarrisMy experience says yes, increase the radiator size and lower the flow temperature setting on the boiler. The result should be better condensing performance (as this is directly proportional to return temperature) and hence higher efficiency from the boiler.I found that increasing the insulation level of the house (CWI, decent DG, thick loft insulation, improved airtightness) meant that most of my existing radiators were then oversized, so worked well with a much lower flow temperature, even in pretty cold conditions.Hard to be definitive about one big versus two smaller, but in general I'd opt for two rather than one just to get better heat distribution in the room and to increase the volume of water in the system. Although greater water volume means slower heat up response time, it also acts as a fairly effective buffer, helping to maintain more stable room temperatures. Heat output is proportional to radiator surface area and temperature, rather than volume.
Posted By: SteamyTeaDo you have any solid internal walls you can put radiators against?
Posted By: DamonHDFor us last year (so, mild winters at either end) gas consumption ~3936kWh, so with approx baseline (DHW+cooking) ~5kWh/day that leaves 2111kWh for space heating, ie nearly 50:50 in a mild year with improving insulation (etc).http://www.earth.org.uk/saving-electricity.html#meter2011" >http://www.earth.org.uk/saving-electricity.html#meter2011Maybe allowing for cooking, DHW is somewhat over 25% of the total, ie 1MWh out of the 4MWh, but we've been cutting both baseline and kWh/HDD numbers.RgdsDamon
Posted By: alecthe important thing for reliability, efficiency and comfort is the compensation controllers...not the on-off controls we are so used too
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