On Mar 10, 4:56*pm, RBM wrote:
On 3/10/2012 4:16 PM, DerbyDad03 wrote:





On Mar 10, 1:52 pm, *wrote:
On 3/10/2012 12:04 PM, Al Marulli wrote:

My parents are getting quotes to replace a 30 YO oil fired boiler that
has a small "add-on" hot water tank. *He is looking into getting a gas
fired unit so that he can replace his very old electric stove with a
gas range.

AC is not part of the equation because he already has a separate
central air system.

They live in Western Massachusetts in a brick house that is not well
insulated.

Another factor to consider is that it's just the two of them, except
for a few times a year when the rest of us visit. During these visits
there could be up to 14 people in the house for 3 - 4 days. During
these visits, both showers are in use at the same time, lots of dishes
get done, etc.

I know next to nothing about boilers, so this is the best I can do to
describe their current system:

They have a thermostat that controls the boiler for the baseboard hot
water radiators and a timer switch that controls the same boiler for
the hot water tank. There is a large (1”?) pipe that runs through the
hot water tank, so I assume that the water is heated via heat transfer
from this pipe. The tank is not directly fired.

The timer has a "Hold" position so that they never run out of hot
water when the house is full of guests. *The boiler does not run
constantly when the timer is set to hold, so obviously there must be a
thermostat associated with hot water tank also.

OK, so here are the options he’s been given via a few quotes:

1 – A combo unit that will include a water heater built into the
boiler.
2 – A boiler just for heat and a separate 40 gallon water heater.

BTW…no one has suggested an instant water heater in any of the quotes,
but my dad and I discussed it and he feels the expense would not be
worth it, considering their age. He’d like to do what’s best for the
house as far as resale value, but the extra cost of the instant water
heater doesn’t seem to make sense.

The other issue is the efficiency of his choices. The quotes he has
received so far are for 85% efficiencies, but the rebates from his
utility don’t start until the units hit the 90%+ range.

So my main questions are these:

Which makes more sense in this situation:

1 - A combo unit or a boiler and separate water heater?
2 – 85% efficiency or a higher efficiency with the rebate offsets? The
rebates seem to be in the range of $1000 - $1200 but I don’t know how
much more a 90%+ boiler would cost.

Thanks for any thoughts you have on this matter.

If I were you, and assuming natural gas is an option, I would go with a
good quality "mainstream" boiler like Weil-Mclain, or Peerless in a
standard 85% +- efficiency. Definitely get an indirect water maker,
which is what you have now. Forget the timer on the indirect, it's well
insulated and will hold the heat for a long time, and make unlimited hot
water. I would also have incorporated into the system, an outdoor reset
controller. This is a device that will determine the most efficient
boiler temperature, for the outdoor temperature and boiler demand.
Unlike oil burners, you can get gas condensing boilers with a very high
efficiency rating, and you can get a rebate for them. The issue I have
with this type of boiler is it's complexity. There are a lot of things
going on inside these units, all subject to failure, which would cause a
shut down and complete loss of heat until you can get a "specialist" to
come and fix it. Your garden variety gas burner is pretty basic, so
repairs are infrequent, and easily done. The same holds true for
specialized oil burners. Your typical oil burner service company isn't
going to carry hybrid parts, or have the technical knowledge to do the
repairs, leaving you at the mercy and availability of a specialist.
Again, just my opinion. I believe reliability should be priority one,
and efficiency second.
* *I wire oil and gas heating systems for a living and have had
experience with Weil-Mclain, Peerless, Crown, Buderus, Triangle Tube,
Burnham, Biasi, Munchkin, Energy Kinetics, and Viessmann, to name a few- Hide quoted text -

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This is the OP...I accidently posted my question under a friend's
account.

First, *am I correct is saying that a "combination unit" and "a boiler
and indirect water heater" are *not* *the same thing? *If that's
correct, are you suggesting a system that has a main boiler for the
heating system and separate storage tank with a heat exchanger "piped"
to the boiler for domestic hot water? That's an indirect water heater
right?

I'm assuming that by combination unit, he's referring to a boiler with a
built in coil. It would be the least expensive option. Coils tend to
work OK when they're new, but loose their conductive properties as the
get deposit buildup on them over time







Here's why I ask:

One of the quotes Dad got was for a Burnham ES2 85% boiler. The option
for the Outdoor Reset was included and we understand how it works and
why it's good thing. (BTW If you know anything about the quality of
Burnham boilers I'd appreciate it if you'd share your opinion)

However, the quote also included an A.O Smith 40 gallon water heater,
not an indirect unit. Per the brochure, Burnham can supply an indirect
water heater with the boiler, but the company that gave Dad the quote
opted for the separate tank. At the time, we didn't know enough about
the choices so he didn't think to ask why.

Now that we know the differnce, he plans to ask them next time they
talk, but we'd like to be armed with some knowledge. Why would a
contractor suggest a separate, direct fired water heater as opposed to
a indirect unit?

Is an indirect water heater that uses the main boiler as the heat
source more or less efficient than a direct fired tank? I'm thinking
that in the summer months the main boiler has to come on in order to
heat the hot water, right? Is that burner more efficient than the
burner in a separate tank?

Thanks for your help.

I would opt for one burner, one set of controls. I just prefer to keep
these things as simple as possible. The indirect system is just a very
large coil within the tank, that operates just like any other zone on
the system. The only exception is that you usually wire an indirect zone
to have priority over heating zones.
I believe it would be less expensive during the non heating months, to
have a stand alone hot water heater, the only caveat to that is that I
believe that the boiler manufacturers recommend the boiler to be kept at
a minimum temperature to prevent some kind of flue gas damage. I'm not
sure what that's all about, and I'm trying to get some information
currently from Buderus. My interpretation, from things I've read, is
that it's not good for the boiler to be cold and damp.
You also get a wild swing on the expected savings for various types of
boilers and components. The savings achieved from using an outdoor reset
system, is anywhere from 35% down to 15%, depending upon who you're
believing. Personally, I'll be real happy with the 15. If he's going to
get a reset system. Taco makes a really nice one that integrates very
easily with their EXP circulator control panels. The thing I love most
about it, is that if anything goes wrong, you simply flip a switch, and
it acts just like any other aqua-stat controlled boiler. It doesn't go
into some humble mode like some systems.- Hide quoted text -

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Yes, indeed, the brochure does talk about the domestic hot water
having priotity over the heating system. I assume that means that even
if it's 45 degrees outside, the boiler will come on at full strength
if the hot water needs heating. Well, unless there's a way to heat
that "zone" separately, but I don't see how that could be done.

However, I need an explanation of some other things you've said:

First, when discussing combination units you said:

"Coils tend to work OK when they're new, but loose their conductive
properties as they get deposit buildup on them over time".

Then, when discussing the indirect version you said:

"The indirect system is just a very large coil within the tank, that
operates just like any other zone on the system."

So the obvious question is: Aren't the coils in the indirect system
subject to the same build up as in the combination units?

If so, why did you say "Definitely get an indirect water maker" in
your original response?

I'm not arguing, I'm just trying to learn.