On Jul 25, 6:09*am, ransley wrote:
On Jul 24, 6:30*pm, Rick-Meister wrote:





The biggest problem with tankless water heaters is that DIY'ers and
many plumbers don't bother with the size calculations. Sizing a
tankless requires estimating usage and combining that with water
pressure. The higher the water pressure, the larger the BTU's required
to handle the same usage.

Also, remember that tankless water heaters are not energy efficient
across the entire range of use. Sure you save the energy of storing a
huge tank of water. But if you run a dishwasher, for example, that
uses only a few gallons per cycle and you have high water pressure and
high BTU's, you'll get very INEFFICIENT energy use for those few
gallons. The burner will have to light up like crazy and then shut
down fast after only a few gallons.

Tankless heaters are most efficient for bathing and that's where their
energy calculations are made.

If they're sized right, they're a great improvement over atmospheric
vented tank heaters.

Doesnt a dishwasher use alot of water, well if it was not efficent why
am I getting a 4 yr payback, and why am I now paying 45$ for Ng where
I now have a tank, where was just paying 7-9 in summer with the
tankless, you have theories, and no numbers, I have numbers I dont
need unproven theorys- Hide quoted text -

- Show quoted text -


Yes, I'd like to see a reference for how and why a tankless is
supposed to be very inefficient in supplying water on demand to a
dishwasher. That makes no sense to me. It fires up and instantly
starts heating the water. All the heat goes into the water and into
the dishwasher, except for the heat in the water left in the pipes at
the end when the use stops. The latter happens exactly the same with
a tank type unit. Nor do some of the other comments here make sense:


"1. We're concerned that it might not always give us as much hot
water as
we want. If washing machine and dishwasher are running, and someone
is
taking a shower, it could be stretched to its limit, and, if someone
else
turns on a hot water faucet, the shower might suddenly get cold
bullets or
whatever. "

You presently have a 25 gallon conventional unit and need a
replacement that will fit in an 18" space, which would be more of a
problem in that regard than a tankless. I don't see how anyone
suddenly gets cold bullets with tankless. As more water is drawn,
the outgoing temp of the water just drops following a smooth line.


"2. The supply of cold water to our house might not always be high
enough
pressure. We get the vague impression that our water pressure
varies,
possibly depending on usage by neighbors. It's probably not a
problem, but
it's one more minor worry. "

If you don't have sufficient pressure, then how are you going to
deliver so much hot water to the washing machine, dishwasher, shower,
etc that the tankless can't keep up in problem #1?


"3. We're thinking of putting in new insulated hot water pipes,
running
through our access-only attic, to all of our hot water faucets etc. A
tank
water heater would keep those pipes partly warm, so we wouldn't have
to
wait as long for hot water after turning a faucet on. "

Any type of hot water heater isn't going to do anything different with
regard to keeping those pipes warm. Conventional hot water heaters
have devices in them specifically to prevent hot water from rising out
of them because it wastes energy. So they aren't going to keep those
pipes warm either, unless you put in a circulating pump. I thought
you wanted high efficiency? The only thing insulation will do is:

a - prevent some heat loss for the water on it's trip across the
house

b - allow the water in the pipes to cool more slowly, so that if it's
used again within an hour or so, it will still be warm.

Both those work exactly the same without regard to how the water gets
heated


"5. If it turns out to have problems, the problems are most likely to
be in
our pipes or whatever, and not the fault of the manufacturer.
Therefore,
such problems would not be covered by the warranty. A lot of people
regret
getting a tankless for that very reason, and feel stuck with it,
because it
would cost them too much to replace it with a tank, having already
spent
their budget on the tankless. "

This I don't understand at all and sounds like FUD.


"6. When such problems happen, the plumber often can't figure them
out, and
spends too much time on them, then starting thinking of that customer
as a
problem customer. "

Certainly FUD. If a plumber can't figure out a tankless, you don't
want that plumber around anyway.


"7. If energy prices keep going up, I want to consier other options,
such
as solar etc., and/or maybe get a geothermal heat pump for heating and
air
conditioning, and get hot water from that same system. If I spend a
lot on
a tankless now, that reduces my budget for that. "

If you go to geo, the difference in cost you would pay now of a tank
vs tankless is going to be a tiny percentage in cost of that overall
system.