Electric water heater in line with combi hot supply

[Cymrukid]

We have a gas combi boiler for water and heating and are also on a water meter. To get hot water for washing up in the kitchen means running the tap for a minute or so, wasting lots of water each time. I am thinking about an electric water heater under the sink, such as the Ariston 2kW 10l model. It seems, from reading the manual, the heater is thermostatically controlled rather than flow controlled. So I am thinking could I plumb this into the hot supply? By the time the water from the combi reached the heater I would have drawn sufficient hot water from the heater's tank and it would fill will water from the combi saving on heating purely cold water. Could this be done?

 

[dancinplumba]

need to know if heater will accept incoming hot water, which it will be sometimes

 

[Rob Foster]

There are devices which claim to reduce or even solve this problem with combi systems, but I have no trade names to,pass on, others on here might know
centralheatking

 

[Welder]

OP. Really sorry, but as laudable as your motivations might be, the cost of water vs the electricery to heat that small amount of water, the cost of kit, its installation and its limited life (aka start the whole cycle again) means you'll actually be doing a far greater dis-service to the environment than the current wasted water. The cost of kit and electricity is going to rise far faster than water too.

Depressing but true

How about making sure you use as much of the run-off for other purposes? Kettle, filling the car washer, dogs bowl, bathing a child in cold to toughen 'em up, washing your hair to thicken it, putting into a water filter to save on bottled water etc etc

 

[Cymrukid]

OP. Really sorry, but as laudable as your motivations might be, the cost of water vs the electricery to heat that small amount of water, the cost of kit, its installation and its limited life (aka start the whole cycle again) means you'll actually be doing a far greater dis-service to the environment than the current wasted water. The cost of kit and electricity is going to rise far faster than water too.

Depressing but true

How about making sure you use as much of the run-off for other purposes? Kettle, filling the car washer, dogs bowl, bathing a child in cold to toughen 'em up, washing your hair to thicken it, putting into a water filter to save on bottled water etc etc

You make great points, but it's not all about saving water, it's the convenience too. I have thought about a diverting a sink waste to a water butt for use on the garden, which would be fine if it was just me, but you can imagine the cr*p going down it from other people in the house.

 

[Last Plumber]

We have a gas combi boiler for water and heating and are also on a water meter. To get hot water for washing up in the kitchen means running the tap for a minute or so, wasting lots of water each time. I am thinking about an electric water heater under the sink, such as the Ariston 2kW 10l model. It seems, from reading the manual, the heater is thermostatically controlled rather than flow controlled. So I am thinking could I plumb this into the hot supply? By the time the water from the combi reached the heater I would have drawn sufficient hot water from the heater's tank and it would fill will water from the combi saving on heating purely cold water. Could this be done?

Which Combi is it?

 

[Cymrukid]

Which Combi is it?

15 year old Worcester 28CDi

 

[Last Plumber]

15 year old Worcester 28CDi

Here's a thought!
New Vaillant ecotec with pre-heat.
A lot of new Combi Boilers have a pre-heat option.
I personally think Vallant are the best but everyone has an opinion.
If it's 15 years old, even if you don't do it right away then you could have it in mind for the near future.

 

[Last Plumber]

Pre-heat keeps the Boiler up to temp where the delivery of Hot water is concerned. On some boilers you can time that to come on and off so you are not wasting Gas whilst you're out or asleep.

Good idea?

 

[Rob Foster]

We have a gas combi boiler for water and heating and are also on a water meter. To get hot water for washing up in the kitchen means running the tap for a minute or so, wasting lots of water each time. I am thinking about an electric water heater under the sink, such as the Ariston 2kW 10l model. It seems, from reading the manual, the heater is thermostatically controlled rather than flow controlled. So I am thinking could I plumb this into the hot supply? By the time the water from the combi reached the heater I would have drawn sufficient hot water from the heater's tank and it would fill will water from the combi saving on heating purely cold water. Could this be done?

Why not put the cold mains water through a pressurised cylinder with a solar coil in it
This will save energy as the combi will only have to lift the water temp,up the last little bit.
We did get close to this set up a few years ago for Senyab Ltd
Rob Foster aka centralheatking