Combi Boiler in - Shower Fully Electric or off the Combi?
Discussion
Jonny_ said:
Top-end electric shower: ~11kW output
Most basic of combi boilers: ~25kW hot water output
If you like your showers hot and powerful, combi is the way to go
Doesnt work like that from what I can see, the issue with combi and really hot water is there is a trade off for water flow i.e time to heat water up as you shower and have a good flow rate - I have a 3okw combi and and electric shower - the temp on the electric is constant where as the combi was a bit hit and missMost basic of combi boilers: ~25kW hot water output
If you like your showers hot and powerful, combi is the way to go
is it possible to provide hot water for a place exclusively using electric on demand heating? A retrofit combi is horrifically expensive even before you consider running costs and replacement. I hope I am not hijacking but at Casa Del Paolow where we have huge water pressure I have considered an electric unit rather than gas for on demand water. this would provide hot water for the kitchen sink, shower and even a bath! (in theory).
I know many would crow about the expense but at the mo a hot water cylinder is used for all hot water so an on demand system would cost the same? no? IS that doable?
I know many would crow about the expense but at the mo a hot water cylinder is used for all hot water so an on demand system would cost the same? no? IS that doable?
_dobbo said:
If you need hotter than an 11kW shower puts out, you must have skin made of asbestos.
I can't turn mine up past half way!
What I meant was in terms of the flow rate - any flow heater (even one of those little 2kW handwash water heater things) will, with a sufficiently low flow rate, produce scalding water. But I've found that most electric showers need the flow rate to be quite low to achieve a decent temperature (unless you like cold showers!).I can't turn mine up past half way!
Whereas my combi, despite being about 10 years old, a bit rattly and probably the most basic/puny model that Worcester made at the time, gives a good strong torrent of hot water even in the middle of winter when the incoming water temp is only just above freezing
Yes a combi is the way to go. A modern combi will have a flow rate better than 12 litres p/m at a constant rise of 35c. Now given our water temperature in the winter is probably about 5c that give a shower of 40c at that rate - not bad i'd say. The more powerful combis would give a much better flow rate and still achieve the same temp. I have seen flow rates up to about 15 litres a minute.
We used to have an electric shower & had no problems with it at all. Then we got the bathroom redone & even though I'm the only person who ever uses the thing (my mum & dad have their own Ensuite & everyone else has moved out), the new 1 is 1 powered off the boiler despite me wanting another electric 1. The day the arse falls out of the boiler & I've got to have a cold shower I'm going to be fuming, I don't mind having no heating at all but I need a hot shower at least once a day
Road2Ruin said:
Yes a combi is the way to go. A modern combi will have a flow rate better than 12 litres p/m at a constant rise of 35c. Now given our water temperature in the winter is probably about 5c that give a shower of 40c at that rate - not bad i'd say. The more powerful combis would give a much better flow rate and still achieve the same temp. I have seen flow rates up to about 15 litres a minute.
15 litres a minute is fine for one outlet, but run two at a time and this is where the combination boiler shows it's failing. Vented or correctly installed unvented cylinders will be capable of 25-30 litres a minute. Boiler manufacturers have responded to pathetic flow-rates with ever increasing inputs, but more heat equals bigger gas supply pipes and (in hard water areas) plate heat-exchanger problems.
paolow said:
is it possible to provide hot water for a place exclusively using electric on demand heating? A retrofit combi is horrifically expensive even before you consider running costs and replacement. I hope I am not hijacking but at Casa Del Paolow where we have huge water pressure I have considered an electric unit rather than gas for on demand water. this would provide hot water for the kitchen sink, shower and even a bath! (in theory).
I know many would crow about the expense but at the mo a hot water cylinder is used for all hot water so an on demand system would cost the same? no? IS that doable?
I'm not a plumber, but I'd have thought on demand heating will be much more expensive than a hot water cylinder. I know many would crow about the expense but at the mo a hot water cylinder is used for all hot water so an on demand system would cost the same? no? IS that doable?
Hot water immersion cylinder 2kw heater.
Basic shower 8kw (guess)
The heater for an on demand electric would need to be probably 20+Kw. Running for as long as it takes to fill the bath, then on again for washing dishes, then on again for a shower, etc etc.
An immersion can be used overnight (low rate) to heat all or at least most of the water you will need all day.
It might be worth while considering a heat pump to heat your stored water.
thebullettrain said:
Aren't mixer units going against the grain here-isn't it agreed that you don't want the shower to lose hot or cold water flow when other water points are used?
In some houses there just isn't enough mains pressure so a thermostatic mixer is required so that you don't get fluctuations is temperature when other outlets are used, just a drop in pressure.Road2Ruin said:
thebullettrain said:
Aren't mixer units going against the grain here-isn't it agreed that you don't want the shower to lose hot or cold water flow when other water points are used?
In some houses there just isn't enough mains pressure so a thermostatic mixer is required so that you don't get fluctuations is temperature when other outlets are used, just a drop in pressure.Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff