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Recently on my website
discussion board at www.FiredragonEnt.com we started talking
about the operating benefits or lack of them regarding a
principle called ‘cold-start.’ Now although most of us
know that refers to system operating temperatures I’m
going to define the term and its opposites for the sake of
the newbies and greenies out there. After that, I’m going
to tell you why I don’t like it and throw a curveball on
another cold-start problem.
Heat-only unit: This is any
unit that just runs for heat, no domestic hot water of any
kind. A furnace meets this description to a ‘tee.’
Cold-start unit: This is any heating appliance that does not
maintain temperature, but does produce domestic hot water.
The concept is most successful with an oversized indirect,
proper piping and control applications and ideally with a
low-mass, low-water content boiler. The circulator and
piping must also be properly sized and pumping toward the
coil. Hot-start unit: This is any heating appliance that
maintains a high temperature (160°F to 210°F) to produce
domestic hot water.
The concept is most
commonly used with undersized, poorly applied internal
tankless heaters. Warm-start unit: This is any heating
appliance that maintains some temperature (100°F to 120°F)
and produces domestic hot water. The concept allows the
boiler to remain cleaner throughout the operating year and
actually accelerates recovery during extended periods of
domestic hot water draw. It also reduces maintenance costs
for a minimal amount of energy used.
After a recent move I was asked if I still believed in the
concept of warm-start over cold-start while buying my oil at
$3.35 a gallon. My answer? “Yup, I believe it should be
done across the board. My former residence was a horizontal
multipass, this one is a pin-type. I think they all need it,
JMO!” Why did I say that, simple because it makes sense
and I’ve seen the effects of both, here’s the rest of my
posting; “Here’s a shocker though. I don’t believe
that 350°F Gross is a hot enough operating temperature
anymore.
With what I’m seeing on CO
lawsuits and malfunctions across the board, 350°F doesn’t
seem to be cutting it. At 350°F in the breech you ain’t
getting **** at the top of a 35 foot oversized chimney.
TRUE, liners would stop all the BS, FACT, but the industry
has been too slow to go and the problems are increasing
daily. Back in 1981 with the introduction of low-mass,
horizontal, multipass boilers the Euros told me that 350°F
Gross - 285°F Net was minimum to operate.
Story
continues below ↓
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were the same people who convinced me of cold-start, another
principle I no longer believe in. But, unlike cold-start
they were basing the info on standards that are not accepted
here, properly relined (retroffited) chimneys. Cold-start
was based on inspection of the unit twice a year by
government officials with immediate service, if required.
Homeowners here get serviced much less frequently and the
quality of the service work is deteriorating quickly, too
quickly, JMO! We need to seriously look at our outdated
policies in regards to venting, chimney design, retrofit and
operating temperatures. We have now not only killed people
with oilheat, we are making a lot of people sick.
TRUE, faulty installations,
carelessness and lousy service procedures heaped on top of a
general lack of
education is mostly responsible, but when will this BS stop?”
Although that answer is a bit long, and it opened the door
to another subject, it was my way of also showing that
things aren’t always as they appear and that no matter
what, time and technology move on. I was once a great
believer in cold-start. I put it in my home, I taught it
like a religion and I truly thought that it was the way to
go. What the heck, an oilburner is 100% efficient only in
two modes, it burns 100% of the fuel going through it when
on and it doesn’t burn any when it’s off.
The problem with cold-start
is that it was based on only using it with an indirect,
preferably oversized, and with a lowmass, low water content
boiler. It also depends on the burner being set for true
zero smoke and the boiler being properly cleaned once a year
or more. I’m a lazy tech, but in my opinion that also
makes me a good one. I don’t work hard, I work easy. When
I saw the debris building up in my boiler I knew something
was wrong. I don’t like to clean my boiler, but when I do
I scrub it right down to the bare metal with a brush and
water. Then, it dawned on me. What do most guys like to
clean, a hot boiler or a cold one? Which one is easier to
clean? That’s also a no-brainer and the answer to the
question, is cold-start worth it?
Well, if you follow all of
the rules, yes, but since I try to go 3 or 4 years between
tuneups it just doesn’t cut it for me. Then there’s the
production of domestic hot water and the weak spot,
recovery. We tear the subject of domestic hot water (DHW)
apart in our book The Hot Water Handbook, but here’s the
skinny facts. To make and supply adequate DHW you need one
of two things or both; recovery and storage. One of the
biggest problems you can create is an undersized indirect
with an oversized (water quantity) boiler. Are you really
buying this? Can’t you believe that if you have a coil
that holds half gallon of water and a boiler that holds 14
gallons that you must turn over the 60 degree water into the
hot indirect 28 times before you start recovering
temperature.
You’re pumping cold water
into a warm vessel and that just doesn’t work. The
Europeans who came up with this figured the same coil, but
with a boiler that holds 3 gallons of water, that’s a 6 to
1 turnover as opposed to the 28 to 1 that many try to
do.
With wall-hung,
modulatingcondensing (mod-con) gas boilers that hold a
couple of quarts of water, cold-start will generally work,
but they don’t make them for oil and we may never see one
in this country in our lifetime for oil. It’s important to
note right now how these boilers are piped too. Then we have
to look at temperature. Not just the temperature of the
water in the boiler and water heater, but what’s happening
during start-up to the flue gases. Again, I think cold-start
has ruined lots of jobs.
If the boiler is warm
throughout the year, not only is the production of DHW
faster, but the flue gases are in better shape. With
cold-start you have a tough ignition sequence since there is
no latent heat to help vaporize the oil and assist with
igniting the atomized oil. Most of today’s boilers have no
lined combustion chambers and so you’re trying to fire
into this cold black hole. Venting is tough except maybe in
the dead of winter because the chimney cools during cycles
and there is little to no thermal draft present on
start-up.
Tight combustion heads have
helped with off-cycle losses over older oilburners, but they
also do their job and reduce the flow of air through the
chimney causing the oilburner to have to reheat the chimney
every cycle increasing condensation. In the warmer weather,
cold-start boilers can wreak havoc with service again due to
draft problems. Cold-start, high efficiency boilers, in my
opinion, also lead to a lot of damage being done to chimneys
and masonry chimney liners that is called spalling. Spalling
of a chimney allows deposits to build up and block the flue
opening and that can lead to carbon monoxide (CO)backing up
into the home. In addition, low temperatures in the flue may
never properly heat up and then condense on the top of the
chimney, causing the condensation of flue gases and the
resultant freezing of the condensation. Until last year I
knew of these theories, but had no proof. Due to some very
quick action on the part of a fire department who
took pictures of a chimney after a CO incident I now know
these theories are absolutely true and have the pictures to
prove it, Figure 1, Figure 2 and Figure 3. The pictures show
quite clearly ice build-up and spalling of the masonry
chimney liner.
The photos were taken as
the occupants were rushed to a hospital and later placed
into a hyperbaric chamber. These occupants did not die, but
in New Hampshire in 2007 three people died from a similar
event. I have begged this industry to investigate metal
liners to no avail for over 20 years. If you don’t want to
do them, fine, as they say, ‘see you in court.’ But if
you don’t want to use liners, then make sure the chimney
is clear and in good condition and that the chimney base is
open as far down as you can go. Keep in mind that a chimney
inspection is probably in your service contract and that an
NFPA Level Two Inspection is required by code in every
oilheat state either by code or the manufacturer’s
instructions with a new install.
Make sure that first
tune-up you do after the new install is very thorough. The
greatest damage to the chimney and masonry chimney liners
will be right after new equipment is put in. The lawsuits I
work on for CO problems are on mostly new equipment.
Finally, on the subject of flue gases I am beginning to
believe that our industry standard of maintaining a minimum
of 350°F Gross and 285°F Net stack temperature is not
adequate for most chimneys in the Northern United States and
Canada. These chimneys are for the most part too tall, too
big and don’t warm up quick enough. In addition, we use a
lot of outside chimneys and the 350°F Gross is supposed to
be with a maximum of 10 feet of fluepipe.
In many cases flue pipes
are longer and just add to the cooling
process along with improperly installed and simply not
needed draft regulators. I am now recommending that we
maintain a minimum of 400°F Gross at the breeching and that
we run a slightly higher temperature to prevent problems and
enhance operation. If you line the chimney with stainless,
fine; 350°F just may do it, but if the chimney is masonry
and masonry lined I would go to 400°F. In conclusion let me
offer another option for those who are determined to do
coldstart. The solution, in my mind, is piping. If I could
be assured that beginning tomorrow everyone would only pipe
boilers with a by-pass pipe or do them in a
primary-secondary configuration I would have to shut up and
go away on this subject.
The bad news is, it just
isn’t going to happen. In my opinion that’s why
coldstart works with the mod-con gas boilers, they are only
supposed to be installed with primary-secondary piping.
Interesting, huh? Many of us do things because we were
taught to do them the way the guy who taught us did them. In
most cases he was taught by a guy in 1938 who was taught to
do it following the anthem “but we always did it that way.”
Technology has progressed a long way and yet many in this
industry think that our outdated traditions make more sense
than following the manufacturer’s recommendations and that
won’t hold up in court because it just doesn’t make
sense. See ya.
*George Lanthier is the
owner of Firedragon Enterprises, a teaching, publishing and
consulting firm. He is an industry trainer and the author of
over 25 books on oilheating and HVAC subjects. He can be
reached at 608 Moose Hill Road, Leicester, MA 01524. His
phone is 508-421-3490, fax at 508-421-3477 and his web-site
and chat room can be found at www.Firedragon Ent.com
Copyright 2010 George Lanthier - HVAC Insider - First Serial
Printing.
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