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Help me decide on the best option.
We have an ancient conventional boiler that needs replacing. We either go for a straight swap or change to a combi. Combi has its drawbacks and conventional seems inefficient as we heat a whole tank of water everyday with very little use. Kids are having less baths and more showers as they get older. Other than the occasional bath the only other need for hot water is at the kitchen sink.
So, this got me thinking of alternative options and my current thinking is along these lines.
New conventional boiler, and only fill the hot tank when needed.
Then fit a undersink hot water boiler thing to supply hot water on demand at the sink.
So questions...
Is this the cheapest, most efficient way around the new boiler question?
Are undersink hot water heaters any good?
thanks in advance
Not an under sink but I installed one of these in a flat I own. Does the bath, shower, basin & kitchen sink. Works great and reliable so far.
https://www.toolstation.com/stiebel-eltron-instantaneous-water-heater/p97614
Not an under sink but I installed one of these in a flat I own. Does the bath, shower, basin & kitchen sink. Works great and reliable so far.
https://www.toolstation.com/stiebel-eltron-instantaneous-water-heater/p97614/blockquote >
So, presumably i could fit this into the airing cupboard next to the hot tank? and it couls supply all hot taps?
Just connect a boiler to the existing cylinder, make sure it is as well insulated as possible, you have a programmer and a cylinder thermostat fitted correctly.
If your boiler is gas fired it is cheaper per kW than daytime electricity that you are proposing to use. You also haven’t factored in having to change instantaneous water heater more often than a boiler as in my experience they don’t last very long. Ok for occasional use any else seems to kill them.
Your hot water proportion of your gas bill is much smaller than the heating part, focus on reducing that usage.
Ive moved from Combi boiler house to non combi and really miss it.
Whats the drawback with a combi?
I would go Combi every day of the week !
I did exactly that. There was a large immersion cylinder which was proving uneconomical to heat for the resident.
I took that out and plumbed the heater to provide all of the hot water. Needs a well routed 10mm feed and 50A breaker.
No gas in the flat so this was the best solution
conventional seems inefficient as we heat a whole tank of water everyday with very little use
You only heat a whole tank if you use a whole tank...otherwise it's just recovering the tank's heat loss you are looking at, which is way less than heating the whole thing (and can be really, really low with a well insulated tank).
But what's the drawback with combi? This empty slogan features in every single discussion of it ever. A modern combi can deliver serious amounts of hot water so the old "big house" thing isn't really true any more. Do the sums, a combi which can deliver your likely usage will probably exist. The DHW priority over Rads can be a momentary pain (e.g. if someone showers right at the very moment you want to boost the heat and lean on a radiator on a cold day), but it's hardly a deal breaker.
Why not a combi? DHW on demand so it only fires when you turn the tap on.
the drawback of the combi is the work needed to convert our system from conventional to combi, which includes ripping up all the upstairs floorboards to run in the extra pipework needed.
As for the hot tank, i realise we do not heat up from cold every day but at the same time we can go for days and only use the equivalent of half a sink of hot water in 2-3 days.
OK the floorboards is a good answer re combi hassle @trailwagger. But direct electric water heating generally only makes sense when there's no gas, or in fancy (new) low energy houses. If you have a boiler in the house (for central heating...?), you already have the best way to heat water. And if you have hot taps, your whole house is already plumbed to take the water it heats around the house. Heat loss from a tank is surely not going to bridge the gap to fitting and using electric heaters on every sink with a hot tap. (Or even one for that matter). Especially as whenever the heating is on that heat loss directly offsets your heating bill anyway.
If you do end up fitting an instant umdersink unit fit a little air expander between the boiler and the taps
The ones we had at work started to leak sp i fitted a 6" vertical airtube between inline, seemed to help
My bro has the same issue as ypu do
Traditional boiler and hot water tank, long runs from the hw tank to some taps ad it's a town house.
He went with undersink instant for the kitchen, sucked it up for showet and bath
Sunamp do various sized heat batteries that are used for this very purpose. Can be charged on low rate mains supply or from a renewable source i.e Solar PV or solar thermal.
They work like those salt based hand warmers that you get . Pretty clever stuff actually.
A combi for a big house is often way more expensive than a boiler and invented cylinder. You end up putting a 40 kW appliance just to heat water when your heating load could be right down at 15kW. System boiler and invented cylinder would be cheaper and you have back up should the boiler break.
Modern cylinders are very well insulated so heat loss minimal, and offer the cylinder is located nearer the bathrooms so less water is wasted waiting for it to get hot. Most boilers are in the utility room of bigger houses, bathrooms often a couple of floors away.