On Thursday, January 28, 2016 at 10:37:11 AM UTC-5, Ophelia wrote:
> "graham" > wrote in message

> > I recently replaced my water heater with a conventional 40 gallon one. Gas
> > fired. Instant ones have been promoted here for a couple of years or so
> > but it wasn't feasible for my house. Mini, under the kitchen sink heaters
> > are often in up-market houses and have been for over 20 years.
>
> Do they run the central heating too?

Probably not. The majority of heating systems in the U.S. are
forced-air, which also allows us to install central air-conditioning,
since so much of the U.S. is hot in the summer.

I just saw a TV home improvement show install a boiler with a
heat exchanger that provided hot air to ductwork rather than
hot water to radiators, but that's very unusual. The most
common thing is a big gas flame with an air-to-air heat exchanger.

Cindy Hamilton