View Full Version : External Hot Water Tank

09-15-2005, 05:15 AM
I have a Weil-McLain oil fired boiler that is 14 years old. Was never in love with the manner in which it produced our home hot water, with that internal coil method. Never seemed to be enough HOT water. Was thinking of having some sort of hot water tank installed but am not sure what system is best. It is just my wife and myself in the home now. The fella that services and cleans my burner says he can install an external 40 to 50 gallon stainless tank on its own zone for around $1300 dollars. Would this be the best type of system at a fair price or are there better alternatives? What about indirect hot water heaters or a booster tank? Thank you.

master plumber mark
09-15-2005, 05:20 AM
I dont know what it costs to run an oil boiler
year round and dont know how trouble free they are either...

I am pretty sure you could just install a 50 gallon electric
water heater for about 600 plus the cost of a 220 volt electrical run
It will cost about 470 per year to heat the water..

they are pretty much trouble free with SS elements in them
for about 10 years

so do the math and decide

09-15-2005, 06:57 AM
I had the same system (even worth - with little external heat exchanger).
Hot water was a BIG problem. About 8 years ago I replaced the entire system.
Now I have Burnham cold start (no need to keep it warm when there is no
demand for heat) oil fired boiler with 82.2% efficiency, 1.02 GPH
fuel consumption and indirect SuperStore 40 gallons water heater (this heater
came with life time warranty and should last forever) on its own heating zone.
I am very happy with this system – so far never ran out of hot water even
wile taking two showers simultaneously at winter time.
At summer time boiler turns on no more then twice a day (usually only once).
This translates into fuel consumption about 2/3 gallon per day or about
250 gallons per year. Coast of course depend on fuel price (who knows
what it will be this year). Until recently I did not know, I had a very high
(90+psi) city water pressure. So, I installed PRV to reduce house water
pressure down to 50psi. This way I’ll have far less water wasting (hot and
cold) and less money should fly out the chimney.
Another words,
I have very good experience with indirect water heating system.

- Vitaliy

master plumber mark
09-15-2005, 04:09 PM
it really depends on what it cost per gallon
during the summer time to heat that hot water..

winter time is NA ---but from april through septermber
about 6 months of the year

someone else do the math.

09-15-2005, 05:47 PM
Hi Mark,

Why Winter time is NA (Not Applicable?)
There is nothing to do with season, it does not matter.

Ok, here is some math.
BTU is amount of heat energy required to raise one pound
of water one degree Fahrenheit.
Gallon of water is 8.33 pounds;
10min shower required about 20 gallons of water
(assuming shower head rate is 2Gallons per Minute)
or 20x8.33= 166.6pounds.
Assuming inlet water temperature is about 40F and
temperature, comfortable for taking shower is about 100F.
So, one 10minutes comfortable shower required
166.6(100-40)=166.3x60=9996BTU (~10,000BTU)
regardless of energy source (Gas/Oil/Electric/Solar/etc.)
and regardless of season (Winter, Spring, Summer, Fall).
Assuming heat conversion efficiency is 80%, energy source
must supply 10000/0.8=12,500BTU
One gallon of heating oil could produce about 140,000BTU
The above shower will need about 12,500/140,00=0.089
gallons of heating oil. And finally if price per gallon is $3.00
then cost of one 10 minutes shower is 3x0.089=$0.269
So, just a shower for 4 people per day is a bit more then $1.00
or about $400 a year.

Electricity versus oil:
Or 1KWH= 3600000/1055=3412BTU
or Energy from burning of 1 Gallon of Heating Oil is equal
to 140,000/3412=41Kilowatt*Hour of Electric Energy.
If price for 1KWH is about $0.15 then the same energy
from electricity is about twice expensive then from burning
oil 41x0.15=$6.15
Well, I am not surprised: Most of the Electricity is coming from
burning oil/coal plus overhead.

- Vitaliy

master plumber mark
09-15-2005, 06:16 PM
It looks like you did some homework here,

wether its fuzzy math or not is beyond anything
I want to figure out tonight...

but it looks pretty legitimate, and thats all that counts.
throw a bunch of numbers at me and I am convinced..

the reason hot water is not factored in in the winter
is because the boiler is being used already and its probably
minimal to heat the water at the same time...so its basically
hot water for free rideing piggy back on the heating needs.

I was just looking at the time during the
non heating months
when the only reason the boiler
is comming on was to heat the hot water
figured about 6 months... it probably balances itself out.

someone out there has the answer to this question
and they most likely work for a boiler distributor or company

they could probably throw a few graphs and bar charts at me
and really get my head to spinning.

if the hot water from the boiler is pretty much low maintaince and
trouble free, and gives you good hot water when you
want it, then it appears to be a cheaper way to go.

as long as oil stays low its the way to go

09-15-2005, 06:43 PM
Hi Mark,

From your post:
“the reason hot water is not factored in in the winter
is because the boiler is being used already and its probably
minimal to heat the water at the same time...”

This is absolutely wrong assumption!
It takes the same amount of energy to heat the same amount of
water (well at winter time it will take even more energy because
of supply water is colder) to the same temperature regardless of
other energy consumers (house heating system in this case).
However if boiler is not a “cold start boiler” and required to be
hot all the time (I had that monster before) then yes, at summer
time it will waste a lot of energy to keep himself warm and at
winter time relative energy waste will be less because of high
demand for house heat.

- Vitaliy

09-16-2005, 03:46 AM
Maybe I didn't explain myself well because you are getting away form the point. I'm really just wanting to know the different systems i may use in heating my domestic hot water and the way in which those options work. i.e.....indirect heating storage tank, booster tank, etc. It's looking like I may go the indirect storage tank heating method. Any recommendations on what brand tank to use and ballpark figure of parts and installation? Thanks again.

master plumber mark
09-16-2005, 04:48 AM
we just got off the track and started debateing
about the cost and economy of a few different approaches.

I dont know wether Vitality is right or wrong, we are really
cutting hairs here and neither of us are experts....

its best to find an oil boiler man and ask that guy to get the facts.

do whatever you feel is the best for you...

personally I feel the most simple way to do something is the best.
the less complicated the better ,

and I personally despise all boilers, and refuse to work on them..

some guys just love them, they give great heat ect... except you
usualy have to add teh AC system separate...ect..ect..

but for me they only seem to break down

on me on X-mas day...or on Sundays, so I have had my fill of them.

I just would rather install something that anyone can work on
and repair quickly instead of being dependent on your boiler man,

even if the electrical water heater cost more in the long run
its ok with me.

09-16-2005, 05:57 AM
Here are my unprofessional comments:

You already have a boiler. Check what kind of boiler it is.

If it is “cold start boiler” (i.e. does not have to be worm if there is no
demand for heat) then indirect water heater will add less installation
complexity then all other options and it is virtually maintenance and
trouble free (if it is installed correctly).
I am 100% with Mark – simplest system is the best.

Don’t even think about indirect water heater if you boiler must be kept
worm all the time – system still will work fine but a lot of your money
will be flying out through the chimney and contribute to global warming.

The final decision is yours but my approach for all my projects is to
minimize maintenance/service/troubles in the future instead of minimizing
initial installation cost (which also must be very reasonably priced).

- Vitaliy.

09-16-2005, 06:19 PM
Enough of the talk.
Just put in a 40 or 50 gal gas w/h and be done with it..........

09-16-2005, 06:42 PM
Hi Plumber1,

Why you are so aggressive?

JKON has OIL fired heater!
He may not have GAS supply at all and your very
aggressive advice in this case is absolutely useless.

- Vitaliy

09-17-2005, 09:24 AM
Sorry Vitaliy.

All I meant was that it seemed there was too much technical talk just to chainge a w/h. Wheather it be oil, gas or electric.
He said he had an oil fired boiler. but there could be gas in the house...