Boiling Water

[ericmark]

My gas water heater, I hope it never boils the water as that would mean there is a fault, so should not call it a boiler (Am I doing a Wilson?) anyway my water heater has a quantity of water kept hot to reduce delay getting hot water to tap, so even when no central heating or domestic water is being used, it still uses some gas. It does mean there is not much delay getting hot water though.

So kettle holds 2 litres, likely need to run 1/2 litre to run out cold and warm pipes, then I boil a cup of water, 1/4 litre maybe, so by next use the warm water in kettle is cold, so what is the point?

Two kettles similar design same make, one you can stop mid flow and adjust how much water, the other is a set amount, the former takes longer to boil but will fill a large mug, I would assume the adjustment bleeds water back into reservoir, as does stop mid flow, so the larger is not as efficient as the smaller model. However both boil a cup full of water only, rest of the 1.6 or 2 litres remains nearly cold, just can't see point of filling with hot water.

Even with old kettle if boiling one cup of water you would need to run around 10 cups of water to get a cup of hot water, yes quicker as water already warm in reservoir in gas water heater, but can't be cheaper.

 

[JohnW2]

... my water heater has a quantity of water kept hot to reduce delay getting hot water to tap, so even when no central heating or domestic water is being used, it still uses some gas. It does mean there is not much delay getting hot water though.

That is obviously represents inherent inefficiency (moving partially from the concept of 'on-demand water heating' to 'stored hot water') and it is for the individual to decide whether the slight increase in 'convenience' justifies the cost.

However, if one has such built-in inefficiency in ones's gas water heating, that will presumably diminish any cost benefit to be had by using partially-gas-heated water to put into one's electric kettle.

Kind Regards, John

 

[ericmark]

In Eco mode hot water to every tap except kitchen sink, for some unknown reason boiler does not like to fire up when only kitchen sink tap used, so Eco mode is off.

I have enough not to worry unduly if inefficient, what I don't want is when she who must be obeyed demands coffee, is to miss a bit of the program I am watching because it takes too long. I use

and

size order is wrong first is larger, I have bigger cups to her so his and hers both run together and two cups of coffee in around 3 minutes anyway less time than adverts. I don't need to measure water in, it measures water out. And using a jug I can fill while it is boiling.

It is not to save money, although likely it does by only boiling right amount, it is for speed.

 

[securespark]

Are you using a hob kettle with a cap on the spout; or a saucepan for comparison?

Pan with lid.

The quantity of water in all cases was exactly the same.

 

[foxhole]

That's very true, but the question still remains as to whether it would be cost-effective to use 'as much as needed' pre-heated (by gas) water in the electric kettle.

I would assume that, given the nature of the inefficiencies of the gas heating, the cost advantage (of using partially gas-heated water) would decline as the volume of water being heated (in the kettle) reduced.

Kind Regards, John

Loss of hot water left in pipework while drawing down to kitchen in average house would negate any saving .

 

[JohnW2]

Loss of hot water left in pipework while drawing down to kitchen in average house would negate any saving .

As I've said, that is undoubtedly the case with longish pipe runs. However, we're talking combis, and with many of them there is no "drawing down to the kitchen" involved. As an example, both of my daughters have combi boilers, and in both cases they are in the kitchen, and in both cases no more than two or three feet from the sink tap.

Kind Regards, John

 

[SimonH2]

Apparently you give a brief blip of the hot tap to start the boiler, wait a few seconds and then turn the hot tap back on to get hot water

... anyway my water heater has a quantity of water kept hot to reduce delay getting hot water to tap, so even when no central heating or domestic water is being used, it still uses some gas.

It depends on the combi and it's settings. Our old non-condensing combi doesn't do it at all, I suspect some don't have the option not to, and many have some sort of "eco" mode to run it off.
As I've mentioned before, back in the cold winter of 2010/11 I was in the position to compare standing losses between the thermal store I'd just put in the flat and the combi in the house next door. In both cases the method was to allow the systems to settle for several days, read the meters, wait a couple of days, read the meters again. The combi in the house had standing losses with eco mode off (ie the "keep some water hot" mode) of the equivalent of about 160W, about twice the about 80W of the thermal store.
The reason I did this was because of all the "oh no, it's so inefficient to store hot water" arguments (c.f. the plumbing forum here) in favour of a combi instead of a thermal store - in my case an OWT debunked

 

[ban-all-sheds]

Yeah, but seriously - if I'm right:

And stored or not, MUI that hot water from a combi is not officially potable.

it's academic, as you shouldn't use hot water from a combi for drinking or cooking.

 

[ericmark]

80W and 160W seems a heck of a lot of power, same heat output or more as no light as a bulb of same wattage, if I used even a small amount of insulation then that amount of heat would soon be boiling water. The water heater in my caravan used 480W when getting up to temperature, but once there the mark/space ratio as it clicks off and on means with no water drawn it uses around 5W average to maintain the temperature, and it holds a lot more water than the gas heater in the house, enough to have a shower with. And it can also use gas instead, so if your heater uses more than 10W average to maintain heat, then it's time to get it fixed.

 

[ericmark]

Yeah, but seriously - if I'm right:it's academic, as you shouldn't use hot water from a combi for drinking or cooking.

If that were the case, then you could not use mixer taps which mix at base of tap in the kitchen, only those which mix at end of faucet, since the introduction of combi boilers we have also had kitchen taps that mix water at the base of the tap.

 

[JohnD]

Yeah, but seriously - if I'm right:it's academic, as you shouldn't use hot water from a combi for drinking or cooking.

"If" indeed.

Why do you think tap water that's been pasteurised shouldn't be consumed?

 

[JohnW2]

Why do you think tap water that's been pasteurised shouldn't be consumed?

Well, I suppose "non-potable" could relate to mineral, metallic or chemical contaminants, rather than bacterial ones, so not 'made any safer' by heat treatment.

However, in present context, whatever academic arguments or regulations there might be, I would personally be happy to drink or cook with water that had come out of a combi and then been boiled, since I really don't believe that the combi would/could have introduced any significant levels of 'mineral, metallic or chemical contaminants'.

Kind Regards, John

 

[John D v2.0]

If you had a heat pump kettle it could end up boiling more water per kw than electric. You could even use the waste heat from your fridge.
A lot of fridges have a child water facility but domestic ones don't seem to have a warm water facility.

 

[JohnW2]

... a child water facility ...

However, I agree with your point. As with most things, the 'wasted' heat (from a fridge or freezer) is not really wasted in winter, but better use could be made of it during the summer.

Kind Regards, John

 

[bernardgreen]

As with most things, the 'wasted' heat (from a fridge or freezer) is not really wasted in winter,

Including the heat from an under volted incandescent lamp with its cosy warm orange glow.