Showers 9.5 vs 10.8Kw

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I replaced a 40,000 BTU/r Neataheat with a 27kW combi and the warm up was real zippo in comparison - a few minutes all the rads were hot all over. Then the combi modules down. When you come after having the heating off for a week or so in winter then you appreciate a zippo warm up.
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Contact Geoff - he can sell you a new one....... .andy
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"Ed Sirett" wrote | > Surely the heat which can be dumped into the rooms is | > dependent on the size of the radiators? and having a | > bigger boiler isn't going to change anything unless | > the radiators are increased. | The case in point is that _from stone cold_ the combi boiler is likely be | able to heat the radiators up more quickly.
I can see that there could be an improvement with a combi, because if you return to a cold house and put both CH and HW on, the boiler output is divided between the two, or the HW gets priority, for the first half hour or so to heat the cylinder of cold, whereas with a combi all the heat would go to the CH ... even if you immediately started running HW through a combi (which would AIUI mean absolutely no heating) that situation shouldn't last long, after which all the heat is available for the CH. That's irrespective of the boiler power. But surely the heat to the rooms over time is dependent on the radiators/piping?
Owain
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Where I disagree with IMM is that being a combi makes any difference. Any modern system boiler does this too. In fact, they are normally exactly the same as the combi version of the boiler, but with the secondary plate exchanger, flow switch and diverter valve removed.
Christian.
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Are they? Some are, mainly system boilers, many are not, just set output rates. Heating boilers (no pump or pressure vessel) tend to be this way. Some installers fit set output rate boilers as they perceive modulated boilers to be troublesome (mainly it is because they don't understand them)
see: http://tinyurl.com/sz6l
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What do you currently have? Boiler? cylinder? tanks in loft? how many bathrooms? shower? etc?
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On Tue, 28 Oct 2003 17:21:50 +0000, Graham wrote:

The flow rates from combi for _showers_ are pretty reasonable most of the issues are to do with control and stability of temperature.
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Ed Sirett - Property maintainer and registered gas fitter.
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But while many could bring up the courage to install a shower pump, I suspect very few would install their own boiler.
Christian.
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The Nazi ones swapped hot water for Zyclon B, which I think might be considered somewhat worse than just a low flow rate, especially if your family has first hand experience of them.
Christian.
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And this is a fine site to watch a lot of pure petty bitichyness.
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snipped-for-privacy@hotmail.com (Graham) wrote in message

You can't just give a single figure for flow rate with an electric shower.
Basically, the shower will pass the amount of water that it can heat to the temperature selected, so the temperature of the incoming cold water affects the flow rate.
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grasp of engineering reality. Either quality will strongly tend to disqualify you from writing manufacturer's literature, so you'll see flow rates for various water-heating kit - combis, leccie-showers, and so on - sprayed liberally onto such literature. If challenged, they'll say "oh yes, we assume a <unrealistically-low-figure-here> temperature rise, everybody does that"; the figure they choose (maybe 25 degrees C) is relevant to warm-rather-than-hot showers taken in summer (water input temp of 15-20 degrees), rather than the less flattering "want a hot shower on a damn cold winter's day".
Me, I'm happy enough with an electric instantaneous shower - never felt the need to pretend I'm under a heated Niagra Falls. But it's a matter of taste/preference...
HTH (and apologies to the honest and clueful tech writers out there!) - S
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You can.

An instant appliance "raises" the temp of incoming water. So, if they say 5 litres/min at 35C temp rise (35C temp rise is the most common spec), and you want 45 C at the shower, then if the mains 10C you will get 5 litres/min. If the mains is 15C, you will either: reduce power to attain 45C or have a higher flow rate. The reverse applies when the mains temp is below 10C.
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The flow rate is a bit of a red herring, as manufacturers can twist it to their own advantage. Far either to just compare the actual powers. 24kW is 2.4 times 10kW and will provide 2.4 times the flow, whatever temperature rise you measure at. (Assuming the water doesn't change state!)
Christian.
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As long as they give the figures you know where you are. As combi's are becoming the traditional boiler, the government/EU should set a standard of flow rates, then everyone is looking the same way. Holland has a 1 to 4 rating for combi flowrates. This reduces confusion and householders can relate to simple figures, as with AAA in white goods. How many times have you heard, or read here, that combi's are only good for flats as the flow is so poor, etc, etc, bla, bla, rubbish, when 2 bath jobs are around and most flowrates between simple flats jobs to the 22 litres/min?
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All power is given to the DHW heat exchanger. Some combi's derate the power when in CH mode to prevent excessive boiler cycling, which still gives a hell of a lot more power than what the average house needs. This is easily overridden. The better combi's have built-in anti-cycle control anyhow.
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All power is given to the DHW heat exchanger. Some combi's derate the power when in CH mode to prevent excessive boiler cycling, which still gives a hell of a lot more power than what the average house needs. This is easily overridden. The better combi's have built-in anti-cycle control anyhow
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