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Tankless Gas Point Of Use Heater

 Smaller heaters = more efficiency
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(+1, -2) 		  [vote for,
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All of the tankless gas heaters I've found on the web are designed for whole house heating.

All of the instant undersink (point of use) heaters I've found on the web either have a tank (and are gas or electric), or are tankless electric units.

If the two types could be combined, you'd have the best of both worlds...

—goldbb, Jul 09 2009

Somewhat baked http://shop.ebay.co...=See-All-Categories
You mean like every single one of these? The L is for litres per minute [BunsenHoneydew, Jul 11 2009]

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       what ?
—FlyingToaster, Jul 10 2009
   

       May be worth clarifying that 'gas' here does not mean gasoline ...   

       -----------   

       If I understand it, this idea is simply saying:   

       - there are 'tankless gas heaters' (where water is heated up on its way to point of use, rather than being heated in a tank and then drawn off)   

       - these are already used for central heating systems, but do not appear to be used for hot water (sinks, baths, etc)   

       - why is this ... and would it not be a good idea to implement them?   

       ----------   

       I'm sure there ARE gas-based direct (non-tank) water heaters for showers etc ... I remember having one installed 20 years ago, but maybe they've stopped making them again   

       If I'm wrong on that, perhaps the reason is that in sink-based applications, people aren't prepared to wait as long for hot water as they need to with a direct heating model ... I do remember that it used to take a long time to get water back up to heat with the direct heating system. If you turn it off, even for a couple of seconds, the next time you turn it on you get cold water for at least 30 seconds before it is hot again.   

       Clearly this is less of a problem with central heating   

       So ... perhaps the idea needs to suggest a way to get direct heaters to heat water quicker?
—kindachewy, Jul 10 2009
   

       //Smaller heaters = more efficiency// why?
—loonquawl, Jul 10 2009
   

       Very baked. My grandparents house had a small gas heater directly above the kitchen sink. It was the only hot water source in the house. I believe it was referred to as a geyser, which could have been a brand name or simply a colloquial term.   

       Small, point of demand heaters are more effecient because there is very little loss from hot water lying in pipes, transient losses into and through pipework or from the surface of a permanently hot tank.   

       Widely available now are gas showers, which are exactly as described.   

       Incidentally, gas refers in the first instance to a gaseous substance and commonly to natural gas as supplied to homes and businesses. The US slang is shortened from gasoline, which is properly called petroleum spirit.
—Twizz, Jul 10 2009
   

       During the time I spent in Japan, this was the only type of water heater I ever saw - with the exception of the convection heater for the o-furo (hot tub). Just as [Twizz] described it - mounts over the sink.   

       If you adjust the water flow way down, with the fire turned up, then the water would come out boiling - spitting and blowing, I can see why someone would call it a geyser.
—lurch, Jul 10 2009
   

       well, with gas you generally need a pilot light(?) or at least have some sort of minimum flamesize... perhaps a gas-driven fuel-cell that you could use to recharge the house's batteries a little while you made hot water.
—FlyingToaster, Jul 11 2009
   

       Pilot lights are only reasonable if the burner has turn on while unattended. Which, with this unit, would not happen. Piezo works just fine.
—lurch, Jul 11 2009
   

       I'd say this is widely known to exist [link]. [marked-for-deletion]
—BunsenHoneydew, Jul 11 2009
   

       From the first item in the linked list of water heaters:   

       /Q: Will this stainless steel gas heater be able to supply a house? Or is it too small?   

       A: Yes, this heater will easily be able to supply a house with hot water. It easily supplies my bathroom and various sinks./   

       Clearly, this is a much larger device than what I'm describing...   

       Not only it's it's water heating capacity much larger than is needed, but it's physical size is larger than one could conveniently fit under a sink ... it's 47cm high, 30cm wide, and 14cm front to back.
—goldbb, Jul 13 2009
   

       i guess the problem of the (seemingly) large size is the power of gas heaters : to heat the modest flow of 1/8th liter per second from 20°C to 40°C, one would need ~ 4.2kj/kg*K*20K*0.125kg/s = 10kJ/s =10 000 Watt.   

       Generating and dissipating this kind of power via flames takes some space, while electrically, all you need is some tiny electronics, and a heating wire.   

       For 10kW, one would burn 1 litre of gas every 3 seconds - to efficiently get the heat of this to the water needs some surface area.
—loonquawl, Jul 14 2009
   


 

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