Been doing some research and could use the help of the experts on a
couple of things. I had 5 HVAC companies come to my house for
estimates on replacing my 50 year old 90,000 btu furnace for my 1500
sq. ft. ranch in N.W. OH. The estimates where similar in terms of
cost for most, so I am going with the installer that I trust the most
and received good feedback on from references ( BTW - none of the
installers did a manual J calc, most where just concerned with how to
get the exhaust out). My questions for the group are these.
1) Do I go with a Trane or Armstrong, both are the 90 plus percent
efficient, but the Trane cost an extra $425. What does an extra 425
2) The contractor I am going with recommended a flue liner for $210
for the hot water heater exhaust. Is that necessary/recommended,
would it be better to skip the liner and route the water heater
exhaust throught the same PVC that is being run out the roof for the
furnace ( the furnace and water heater are next to one another)
3) Is it ok to run the PVC exhaust through an unheated garage to the
roof. It will be hugging the wall, but do I need to insulate the
4) One installer recommended replacing the coil, while this guy said
to wait. Why would I replace the coil, is it recommended?
5) As far as sizing, all the contractors quoted something different.
The guy I trust the most said 60,000 btu but I had others that
recommended 90,000. What are the implications of undersizing/
oversizing. Is a manual J calc absolutely necessary or is a trained
eye who is familiar with the neighborhood construction able to tell
Any feedback is appreciated.
Look at the labels inside your current furnace. There should be a BTU
rating somewhere. A close BTU match for your new furnace is what you
atre looking for.
I just posted this in the follow up to a "no burner flame" problem in
this newsgroup. Go to a major HVAC parts supplier in your city. Ask
all the questions you have and also get a pricing for the equipment
they charge everyone. Take a good look at their display model and get
a good idea of the work involved. The dispaly model I inspected had
an installation manual. Read that. That's all the required
installation work the installer can do. Anything more or less can be
a code violation.
I don't know enough to tell if one manufacturer has >$400 worth of
technology over another. If you look inside to inspect how the
furnace is constructed its hard to discern where one manufacturer
could have make significant design differences to warrant that price
premium. I'd go with the lower priced one.
My game plan was if the estimate from a repair guy exceeded $500 I
would toss out the existing furnace and install one of those high
efficiency ones myself. Mine looks new (well maintained) but its
already 28 years old thereabouts. When the heat exchanger tubes give
out, as they must some day not too far into the future, they will no
longer be replaceable . By law the stores are not allowed to to stock
them as replacement parts or sell any. Same with that $183 regulator.
If faulty, replace only, no repairs.
Now if you HVAC guys can say this nicely, that your hands are tied by
law (be prepared to show printed copy to customer) and give a best
effort to do the simple fixes first, then perhaps you will get a much
less hostile reaction from your customers. Explain what you did in
repairs and why they didn't work. Gas fitting is not brain surgery
that only HVAC guys can understand. Explain the problem solving
procedures so that the customer knows they were something he could or
could not have done. We all want to save a few bucks and this
knowledge will satisfy the homeowner that its better to call you for
fixes he'd realise as beyond his abilities.
Then give them the "bad news" a $3000 replacement or some equally
shocking figure. Give them the name of your supplier so that they can
check on prices. And also the opportunity to select a particular
model. The customer expects to pay you something extra and reasonable
as a markup for you to order and deliver the hardware for them. And
to get rid of the old one. You charge service fees accordingly. The
dollar amount won't be pleasant. But an honest breakdown of the costs
that the customer can check on avoids a lot of unwarranted suspicions
and bad impressions.
I went to a major appliance parts supplier store and they had a number
of furnaces on display including the high efficiency ones. The panels
had been removed so it was easy for me to make a close inspection of
its assembly modules and installation requirements. To install a high
efficiency furnace is a lot easier than to service one. Specified PVC
ducting for the air intake and burner exhaust. The gas connection and
the electrical connection. That's it.
The new furnaces are shorter than the old gas furnaces. A transition
plenum will be needed to connect the shorter) new furnace to the
existing hot air plenum. My intended adaptation will be to instead
make a steel stand to raise the furnace to the existing plenum. That
way the bottom of the furnace will be off the floor and free from any
dampness or standing water. My existing furnace is resting on spare
aluminium bath door tracks and its free from rust and grime.
I chatted with the store personnel and they didn't bat an eye on my
intent to do the installation myself. In fact they gave a lot of
pointers on things I should do, such as resizing the hot water heater
exhaust vent (to a 4 inch liner) as my existing stack will be too
large. I found the same information in the installation manual. But
I still appreciated the information as it gives me the right
information to make my installation plans in the meantime.
The basic high efficiency furnace model is $1300. I can budget for
That's true if the old one isn't oversized, but a lot of them were,
especially if the insulation was upgraded since 50 years ago.
I think an experienced HVAC pro who was familiar with similar houses
in the neighborhood, especially if it's a development of almost
ones, could have a pretty good idea what furnace to use, but I'd still
to see calculations done. My feeling is that somebody who just won't
do the math either doesn't know how, or else is too proud to admit
a guess might be wrong, and I can't say I like either of those
I'm not a furnace man, but in other areas I am always finding out that
experience is something that needs sanity checking.
OP, a furnace is something you won't have to buy for 20 years or so,
and Trane is a good furnace, so if you can afford the extra cost I'd
say to go for it. I think I would like to see some kind of heat-loss
calculation done, however.
As for the water heater, I don't know what kind it is. I don't think
can vent it through the same PVC, even if it's a power-vent type, and
if it's an ordinary heater it will need to use the chimney, not PVC.
Is the contractor you are using, who recommended the liner, the one
you "trust the most", as mentioned below?
On Fri, 19 Oct 2007 09:55:04 -0700, firstname.lastname@example.org wrote:
Should the high efficiency furnace be installed then the PVC pipe
intake and exhaust for this furnace must be entirely separate runs and
nowhere near the hot metal flues. I am convinced about the high
efficiency claim because the waste gas coming out at the furnace
plenum is cool enough to put one's hands around them. In the old
style furnaces that will be too hot to touch and that's waste heat
going up the flue. In fact keep the PVC piping as far away from the
current exhaust's stack on the roof to avoid the PVC intake sucking in
poisonous exhaust gasses. My preference will be to run the PVC
through a side wall to reduce the run length and the convenience of
just making two holes through the floor joist instead of running them
through the first floor, the ceiling and roof. And I will have to do
this in a way that the PVC pipes won't intrude into the decor of the
house insides, keep a respectable distance from the hot water exhaust
flue........ too much of a hassle all round.
My hot water heater's 4 inch flue is connected into the main 6 1/2
inch flue for the furnace. This is made of galvanized steel sheet and
too hot to touch when the burners fire up. The now disconnected
from the old "no longer there" furnace 6 1/2 inch flue will certainly
be too large to vent just the heater waste. It will likely risk
having hot water heater exhaust gas blown back into the basement (or
the rising hot exhaust may drive a convection current up the flue thus
drawing useful heated air from the basement??). The installation
manual recommendation is to run the 4 inch flue all the way up through
the roof as a liner inside the 6 1/2 inch pipe. That way you don't
need to do any major work cutting through though the ceiling, roof,
flashing, etc. You cannot run the PVC piping up the same 6 1/2 flue
as the hot 4 inch flue will melt the PVC pipe. I have a high and very
steep roof and the run is equivalent to two floor lengths. It worth
to me the $250 asked for the labor and materials. The material cost
is minimal. The other contractors may have included this in their
quote without identifying it as a separate item. This modification
should be mandatory. It would be a negligent for a installer to omit
it and force the homeowner to correect the omission at a later date.
As for BTU calculations it takes only a grade 8 qualification to enter
a Trade Apprenticeship program. Doing math is not a strong skill. I
can understand their reluctance to provide the math. The current
furnace should give a strong feel as to whether its undersized or
oversized. Go from there.
Yes, but he did say the old one is 90,000 BTU's and 50 years old.
And he said absolutely nothing about what the duty cycle of it has
been in typical winters. If he has one that's already over size, and
he's getting a new one that's maybe 25% more efficient, why should he
over size it even more by going with the same BTU?
On Oct 19, 5:32 pm, email@example.com wrote:
Size it by a load calculation , you may only need 40000 BTU, who
knows, who cares,. New high efficency units waste less and give more
heat . I cut my btu from 110, 000 to 47000 and its still to high, a
new load calc put it at 35000 , R 110 attic helped............
This post is more to show homeowners how to debunk trolls like kipro
than as a reply to him.
Okay, I missed mentioning this item since its not an immediate task
(installing the furnace) for me to keep in mind. The condensate
hookup is in the installation manual. More to the point the label
right beside the condensate collector in the furnace tells whoever is
reading it what must be connected and why. Its just a tube into run
to a drain to get rid of the water condensate.
As for the rest, after self installation, get it inspected by the
appropriate authority and be certified as correctly installed. There
isn't any secret magic stuff that only HVAC trolls can do.
In my Province I can do my own electricals and plumbing too. If I got
myself maimed or killed, tough. Its not a crime. My neighbor, should
I damage his property in the process, can sue me. The insurance
company can refuse to pay for self inflicted damages. Otherwise I can
do anything I want to and inside my house short of buring it down and
endangering the neighborhood.
Had I not been in such in a hurry I could have repaired my furnace
regulator (already done) and saved myself $138 bucks. But I had
already installed the new one. It would be unethical for me to
uninstall it, put back the repaired one and return the new regulator
to the store for a refund.
I can certainly replace the heat exchanger tubes too should I be able
to get my hands on some new ones. By law the appliance part store
cannot stock or sell any. I took a look and (mine) the tubes should
be good for another ten years at least.
However, if you work in the trade the Provincial laws clearly state
that you can only replace the gas regulator and cannot do any repairs.
You also cannot replace heat exchanger tubes. If our Kipro from Hell
insists on doing that in my Province he will lose his license and I
can sue the pants off him for, in law, endangering my life and
As a general rule, for modern day equipment, that is anything 20 years
old or younger, they are no longer designed for parts repairs. All
the service technician does is to swap modules. The main
consideration is will a complete new piece of equipment cost
significantly more than the cost of parts and labor for a repair. If
fixing the old one is half the cost of a new one a better option is
to toss out the old one. The new one will give you more years of
trouble free service than the hassle of recurring small problems with
the old failing one. This module swapping design philosophy also
means that fixing a faulty piece of equipment something you can do
yourself without having to master some complex skill and special
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