Showers 9.5 vs 10.8Kw

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There's some things you can validly suggest people have a go at DIYing. Hanging doors, building walls, changing taps, adding sockets etc. And there's some things you shouldn't suggest people DIY unless they're really sure about it. I would include fitting boilers and Live Working in this list.
D
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do
A man is enquiring about his shower. he must know about pipes.
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You need some logic lessons. It implies no such thing. It merely states that having a shower is insufficient reason to replace a boiler with a combi. I agree. It is a lot of work and expense for something that could be achieved by a pump.
At the end of a day, a pump is cheap (100-250 quid) and quick and simple to install. Keeping the poor electric installation is even cheaper. A combi is expensive (400-1200 quid) and requires a large degree of expensive expertise to install, especially if a new water pipe has to run from the boiler location to the shower room.
Christian.
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A decent one is 250 plus fittings. Anything less than the best in power shower pumps is not worth it, for points I have already outlined.

The Nazi solution.

Can be got for less than 400. I have seen them going for 360, that will do a shower very well. I have highlighted the pros of spending about 150 more than installing a pump.

Not really. boiler out, boiler in, run the shower only from the water section.

The only real uheaval is that is one, that's if it is one.
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snipped-for-privacy@hotmail.com (Graham) wrote in message

Not a lot. It'll be slightly better but probably not so's you'd notice.

Say you are looking for a 30 degree rise in temperature from mains. with a 9.5KW shower you should see something like
Flow = 9.5*60/4.2*30 = 4.5 l/min
Upgrading to a 10.5 KW unit:
Flow = 10.5*60/4.2*30 = 5.0 l/min
whoopee.

On a 25m run you can probably expect a noticeable voltage drop- you'd be better using heavier cable, even if the 6mm would be safe. You may find that the detailed installation notes say 6mm is OK for short runs but you should use 10mm for longer ones. I reckon 25m counts as "longer".
Cheers, W.
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snipped-for-privacy@ed.ac.uk (William Warburton) wrote in message

Thanks for all your comments. I guess electric showers are sort of "they are what they are". I have a four bed/two bathroom/six+ person house and the idea was to have a instant hit with a shower regardless of other CH/DWH requirements with hundreds of other bodies floating round the house as normal. It was disappointing. I was nervous of combi as flow rates seemed so poor in houses I've been to with them. Perhaps I'll look closer.
Thanks
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snipped-for-privacy@hotmail.com (Graham) wrote

That's pretty much it. Performance is "adequate", if you're not too fussy, and they are extremely convenient.

Yup. We have a 9.8KW shower which is fine in summer but pretty poor in winter, when it would be nice to have plenty of hot flow. It is tank fed, with an integral pump, as our mains supply is inedequate, and consequently gets quite high input temperatures in summer. I have in mind to feed it warm water through a thermostatic valve some day, which would provide a good shower all year, as long as there was hot water available, without precluding a shower if the hot water supply has failed for some reason. OTOH, a gravity mixer might be a better solution... havn't decided yet.

I won't be going for a combi any time soon, I don't think. I don't have mains gas, have a poor mains water supply and expect I would need to replumb most of the house to accomodate it.
I'm sure combis are a good solution to some problems, but I have a hard time seeing them as a panacea for all ills. Perhaps it would be appropriate for some of their more outspoken proponents to balance their proposals?
Cheers, W.
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If your mains can't cope then they are not the ideal solution as they are mains fed. And that goes for any mains fed system like Megaflows and thermal stores. Although with poor mains pressure you can run a combi off a tank and pump in the loft and save cylinder space in the tiny house below - sorted. This may be an interim solution until your mains is updated.
They can go up to 22 litres/minute if you want. For "most" households they the best solution in simplicity and importantly, far less space taken up in tiny British homes. Around 550,000 fitted per year says it all. For the majority of British homes combi's are a panacea. They also heat the house up "real fast". They are the ideal choice for DIYers when selecting a fully specced idiot proof job like the Ariston Microgenus. BTW, A Microgenus 2 has just come out with 3 outputs of 24kW, 27kW and a 13+ litres/minute 31or 32kW job .
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IMM wrote:

Please explain "real fast". Why would they be any faster than a conventional boiler?
Don't blather on about heating the water first. This can be dealt with with the timer.
Ben
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Most are 85,000 to 100,000 btu/h, when the heating load is usually 40,000-50,000 BTU/h, so zippo warm up.
Our know-it-all continues...

You don't have a timer for DHW with a combi.
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IMM wrote:

Is this true for the CH exchanger? I thought this was lower than the hot water exchanger?
Ben
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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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On Wed, 29 Oct 2003 17:01:17 +0000, Ben Harrington wrote:

Most combis have just one gas/water heat exchanger. For once I'll support IMM on this claim. Because the boiler is rated typically at 24 or 28 kW this is usually far in excess of the space heating requirements so then boiler is cabable of heating the radiators up 'zippo' or 'real fast'. In fact it might do so too well and not give the wall thermostat or TRV's time to respond until after the rads have been filled with very HW whcih subsequently overheats the house - things settle down and the boilers invariably have the ability to moderate the gas rate and have other gadgets/features in the control systems to operate more efficiently.
HTH
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Ed Sirett - Property maintainer and registered gas fitter.
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I you don't support me on al my claims you little of this business. :)

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"Ed Sirett" wrote | >> > > For the | >> > > majority of British homes combi's are | >> > > a panacea. They also heat the house | >> > > up "real fast". | >> > Please explain "real fast". Why would they be any faster | >> > than a conventional boiler? | >> Most are 85,000 to 100,000 btu/h, | > Is this true for the CH exchanger? I thought this was lower | > than the hot water exchanger? | Most combis have just one gas/water heat exchanger. | For once I'll support IMM on this claim. | Because the boiler is rated typically at 24 or 28 kW this is usually far | in excess of the space heating requirements so then boiler is cabable of | heating the radiators up 'zippo' or 'real fast'.
I may be missing the point here but ...
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. If the radiators stay the same (ie undersized compared to the boiler) then the return temp of the radiator water will be higher and the boiler will shut down or go bang.
Owain
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Yeah, but from cold, an oversized boiler can get them hot in no time at all. After the radiators are hot, it makes no difference (assuming it can modulate down to be equivalent to the fixed rate and thus avoid short cycling).
Christian.
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"Tony Bryer" wrote | Owain 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 | You're thinking about the steady state situation. It takes | energy to get the temperature of all that water and steel | up to working temperature, and the bigger the boiler the | faster this happens. A BMW 316 and a BMW 328 will both do | 70 on a motorway but one gets there a lot faster from a | standing start.
But that makes little difference to the overall journey time between London and Edinburgh?
I can understand that the rads themselves will get hotter quicker, but that happens quite quickly in most cases anyway. That's not the same as heating the house up "real fast". My rads get hot within a few minutes. I have a boiler which could heat a 3-bed house but the flat takes an age to heat up from cold, because the radiators are undersized (and wired in microbore). They are the limiting factor, not the boiler.
I still don't understand therefore how 'combis are a panacea. They also heat the house up "real fast"'
Owain
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London
that
A few simple explanations have been given, after that well....
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On Thu, 30 Oct 2003 15:57:27 +0000, Owain wrote:

I was only supporting this claim in the quite common case of where a medium sized conventional boiler has been replaced with a combi boiler.
Heating the radiators is one thing heating the house happens later, but clearly the radiators have to heat up first so if that happens quicker then the eventual process is quicker.
Of course, there are plenty of cases where this might not be true, such as the one you have outlined.
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Ed Sirett - Property maintainer and registered gas fitter.
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On Thu, 30 Oct 2003 01:32:17 +0000, Owain wrote:

The case in point is that _from stone cold_ the combi boiler is likely be able to heat the radiators up more quickly.
Of course if you compare a 24kW system boiler (eg. Vaillant T/max 624e) with the combi model (824e) then there will be no difference at all. However if you were to have a stored hot water system you might realistically install 15kW system boiler (eg. Vaillant 615e). In this case there might be a difference in the warm up times. However we are really picking nits here as we might be talking about a few minutes difference.
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