I have a oil boiler with a very small reserve for the hot water. I don't
take long showers and I have never been able to get a good full very warm
shower with this boiler. For years I have seen various sizes of Point of
Use eletric water heaters that all show they can be used solo or inline with
boilers or other hot water so I figured why not just do this with a 30
gallon electic unit.
A few years ago I interupted the line for the hot water and in line I added
the 30 gallon water heater. Showers have been very good for the whole
family, but I am now wondering if I am throwing money away by having this 30
gallon reserve instead of just installing one of those 4 - 6 gallon mini
units at Home Depot.
the mini unit tankless cant supply enough hot water for a shower. the
electrical power needed for a proper tankless will require yyou to get
a service upgrade. this will cost a fortune.
feel your existing hot water tank. does it feel hot? probably not new
tanks with foam insulation have very low standby losses.
your best solution is the one you have. you might check on a oil fired
hot water tank, operation would likely cost less than electric,
Well, you are wasting any money that you spend at Home Depot,
but that is another thread.
The small water heaters are not for the purpose that you want.
They are just enough to service a small bar sink or hand
washing sink, or something along those lines. They have been
in use in RVs for a long time.
What you are probably thinking about are true tankless water
heaters. They just heat the water that you use, as you use
it. Endless hot water without having to keep it hot all day
or while you are away on vacation or all night while you sleep.
The installation is very high compared to standard water
heaters, and they take a while to recoup their value. They do
however waste less energy and you never run out of hot water.
If you decide to go with one of the tankless, get a good one.
You should also invest in the cleaning kit (the good ones
offer the kits as an option) so that you can descale it every
year or so. This increases the life of the units
dramatically, especially in hard water areas.
But, don't buy it at home depot. Or lowes.
Unless you are trying to run two showers from a unit designed to supply
Are there tankless oil fired units? The OP was talking about replacing
oil heat with electric heat and in that case he could well be cheaper
wasting the oil supplied heat vs far less wasted heat that was supplied by
I don't know if there are or not. Why would he want one? It
was my impression from the OP that he had this installed
inline between the boiler and the fixtures. If so, then it
would be the perfect place for an electric tankless water
heater. If he wants endless hot water, then he would have it.
The boiler preheats the water and the water temp entering
the tankless unit is one of the determining factors in their
efficiency and capability, especially in electric models.
This one would work:
Instead of adding half assed add-ons after the boiler water heater
that he already has, why not just fix the real problem. Any decent
boiler can supply plenty of hot water. If his isn't, it's likely
because there is a problem, like the water heating coils are packed
with mineral deposits. You could fix that for a lot less than
buying new water heaters of any type.
I could have mineral deposits. My water is a little hard, but I do know for
sure that the water reserve in the tank is small. I got the 30 gallon tank
for exactly what each of you have the impression. To supliment the low
performance of the boiler and just use the boiler as a preheater.
I believe I will look into Robert A's suggested electric tankless heater.
That one looks like it might do the job and is easy to install
I just used that one as an example of one that would work in
your situation. I am not recommending it. (As a matter of
fact, I don't even remember which one it was.)
I would advise you to look online at the various models and
brands available, then find a local supplier or find one
online. You can get significant savings if you shop around.
We have found some of the best prices at this site:
I have only bought gas models, however, so you are on your own
In many places, electric heat is far more expensive than gas, oil, or
propane. I'd be thinking some other fuel source than electric.
The only wasted heat is either up the chimney, or heat escaping into the
Please consider to put the electric heater after the boiler. That way, the
electric is only used if the demand exceeds what your boiler can supply.
And where does the wasted heat from electric go if not into the room?
Isn't the insulation around an electric water heater at least as good
as a gas or oil? Plus there is no chimney going up the middle of it,
like a gas or oil water heater, so there is actually less heat loss.
This is misleading. The electric unit is always going to have
electic usage to make up the heat loss while the water is sitting
there unused, ie standby losses. It's main function is to give him a
30 gal reserve of hot water. Once that is used up, with tepid water
coming into it from the furnace, it's not going to be able to
instantly heat that up much to supply a never ending amount of hot
What about an indirect oil fired water tank. Usually a 30 gallon tank
can well supply a family. It has a coil that is supplied from the
boiler and is very well insulated. I think they are now at the point
of losing only 1/2 degree F per hour. SuperStor is a well known
one. I have a different setup that is great. A Weil-McClain
tankless boiler. It has 2 coils, one for hydronic heat and another
for domestic hot water. When demand is pulled for a shower, the
boiler kicks on as needed. Family of 7 has been well served by this
setup and NEVER run out of hot water even when all 3 bathrooms are in
use and lots of showers.
I don't think I can do anything more to "fix" the problem with the boiler.
I get it tuned up every year and the oil company says it is old (20 years)
but fine. I can check more on scale build up, but I don't think that it
will help much because that boiler just does not look that large to me.
What we're reading is what the OP wrote, which was that he has a 30
gal conventional water heater installed after his furnace, not a
tankless. I was replying to Stormin's post, where he never
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