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C & E
 
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Default Computing electric costs

Would one of you electron benders please tell me how I go about computing
cost of operation of an appliance if I know that it operates on 220vac at
2,000 w and 'y' is the cost of electricity/ Kwh. Is there a time factor tied
to the 2,000 (- too many years)? I'm thinking of supplementing the shop's
LPG heat with electric thinking that it would be cheaper than just using the
gas alone. I only heat on an as-needed basis but the last fill up nearly
cost me a good internal organ!


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Edwin Pawlowski
 
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"C & E" wrote in message
news
Would one of you electron benders please tell me how I go about computing
cost of operation of an appliance if I know that it operates on 220vac at
2,000 w and 'y' is the cost of electricity/ Kwh. Is there a time factor
tied to the 2,000 (- too many years)? I'm thinking of supplementing the
shop's LPG heat with electric thinking that it would be cheaper than just
using the gas alone. I only heat on an as-needed basis but the last fill
up nearly cost me a good internal organ!


Multiply the watts of power consumed (at any voltage, it does not matter)
time the kW rate your utility is charging.

2000 watts (2 kW) at .15 kW = 30 per hour


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Bob
 
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Depending on where you are, electric is usually more expensive than l.p.
Find out what the cost of both are, and then go here to calculate
http://energy.cas.psu.edu/energyselector/


"C & E" wrote in message
news
Would one of you electron benders please tell me how I go about computing
cost of operation of an appliance if I know that it operates on 220vac at
2,000 w and 'y' is the cost of electricity/ Kwh. Is there a time factor
tied
to the 2,000 (- too many years)? I'm thinking of supplementing the shop's
LPG heat with electric thinking that it would be cheaper than just using

the
gas alone. I only heat on an as-needed basis but the last fill up nearly
cost me a good internal organ!




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Default Computing electric costs

Edwin Pawlowski wrote:

Multiply the watts of power consumed (at any voltage, it does not matter)
time the kW rate your utility is charging.


NO! Multiply watts of power by hours to get kilowatt hours of energy!

2000 watts (2 kW) at .15 kW = 30 per hour


Learn the difference between power and energy!

Nick

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BobK207
 
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Default Computing electric costs

chill...........

Ed's final answer is correct...............note the units in his reply

30 per hour

but his calc needs a slight correction to be dimensionally correct

2000 watts (2 kW) at .15 kW = 30 per hour

S/B

2000 watts X 1 kW /(1000 watts) X 15 / kWatt hr = 30 / hr

giving the cost to operate an electrical device in or $ per hour
makes the most sense, that way the user can easily determine the cost
since he has a good idea of the total time of usage.

cheers
Bob

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George E. Cawthon
 
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C & E wrote:
Would one of you electron benders please tell me how I go about computing
cost of operation of an appliance if I know that it operates on 220vac at
2,000 w and 'y' is the cost of electricity/ Kwh. Is there a time factor tied
to the 2,000 (- too many years)? I'm thinking of supplementing the shop's
LPG heat with electric thinking that it would be cheaper than just using the
gas alone. I only heat on an as-needed basis but the last fill up nearly
cost me a good internal organ!



Watts is an instantaneous figure; no time factor.
So w/1000 x y = cost per kWh.
E.G. 2000 W heater, cost is $0.10 per kWh.
So 2000/1000 x $0.10/kWh =
2kW x $.10/kWh = $0.20/h

That probably doesn't tell you much because you
won't know how many hours the 2Kw heater will run
in a month. Nontheless, heating with electricity
is likely to be less costly than heating with LPG.
Somebody could tell you the BTU per gallon of LPG
and the BTU for a kilowatt of electricity and then
you could apply your local cost per gallon of LPG
and per kWh of electricity to see which would be
cheaper.
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Robert Barr wrote:

Learn the difference between power and energy!


Learn the difference between giving advice and being a horse's ass.


With 7 horses, I know the difference. Do you? :-)

Nick

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m Ransley
 
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Compare cost of your gas price to your electric price by btu. for me in
the midwest electric is stlll apx 50% more expensive than Ng, only you
know your costs. Btu comparisons or for Lp are online. In other words
how much is your cost for 100000 btu for each. You likely will see Lp is
best, but it depends on your area.

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Edwin Pawlowski
 
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wrote in message
...
Edwin Pawlowski wrote:

Multiply the watts of power consumed (at any voltage, it does not matter)
time the kW rate your utility is charging.


NO! Multiply watts of power by hours to get kilowatt hours of energy!

2000 watts (2 kW) at .15 kW = 30 per hour


Learn the difference between power and energy!

Nick


And your answer to the original question is??????????????




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Jeff Wisnia
 
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m Ransley wrote:
Compare cost of your gas price to your electric price by btu. for me in
the midwest electric is stlll apx 50% more expensive than Ng, only you
know your costs. Btu comparisons or for Lp are online. In other words
how much is your cost for 100000 btu for each. You likely will see Lp is
best, but it depends on your area.


How efficient is a typical "LPG heater"?

I presume they must vent the exhaust outdoors, so what's a reasonable
number for the percentage of BTUs in the gas that actually heats the
workspace?

Does it vary significantly with the design (and era of manufacture) of
the LPG heater?

I expect that electric heat must be near 100% efficient, huh?

My inquiring mind wants to know...

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."
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Bob
 
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The original question of "tell me how I go about computing cost of operation
of an appliance" can only be answered by knowing how many BTUs he needs.
Then he can figure out how long an electric heater will have to run.
All that calculating isn't necessary. All he has to do is multiply his gas
usage by his heater's efficiency, then divide that by 3,413 to find out how
many KWs he needs.

"Edwin Pawlowski" wrote in message
m...

wrote in message
...
Edwin Pawlowski wrote:

Multiply the watts of power consumed (at any voltage, it does not

matter)
time the kW rate your utility is charging.


NO! Multiply watts of power by hours to get kilowatt hours of energy!

2000 watts (2 kW) at .15 kW = 30 per hour


Learn the difference between power and energy!

Nick


And your answer to the original question is??????????????




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m Ransley
 
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Right OP didnt say what his lpg heater is so how can you figure a
comparison without knowing its efficiency. Im sure its as efficient as
Ng and there are many types and ratings so he could have junk running
40% efficiency or a ventless 99% or furnace at 60-94.5% eficiency
Electric is 100% efficient.

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m Ransley
 
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He is talking to supliment heat thinking electric is cheaper, so cost
comparing the 2 sources is all he needs to know if its worth looking
further

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George E. Cawthon
 
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m Ransley wrote:
Right OP didnt say what his lpg heater is so how can you figure a
comparison without knowing its efficiency. Im sure its as efficient as
Ng and there are many types and ratings so he could have junk running
40% efficiency or a ventless 99% or furnace at 60-94.5% eficiency
Electric is 100% efficient.

One thing that bugs me about gas furnace/heater
efficiency is how they calculate it.

My gas furnace is 80 percent which I assume means
that the 80 percent of the BTU's in the gas end up
in the house side of the heat exchanger, i.e,
useable heat.

But I don't think they ever consider the heat loss
from the the vents. How many BTU's are lost
through the the two openings of 100 square inches
each, one at the floor and one at the ceiling.
The flow of air through these vents is continous
24 hours a day. The furnace may put 80 percent of
the heat into the house, but how much heat is lost
through those vent openings? The greater the
difference between inside temperature and outside
temperature, the greater the total heat loss.
Maybe that is why they don't estimate that loss.

I could imagine that at 0 degrees, as much as 50
percent of the heat could be lost. In other
words, at 80 percent AFUE furnace would actually
result in only 40 percent of the heat retained in
the house compared to Electric heat which would be
100 percent since no vents are used.


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Edwin Pawlowski
 
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Default Computing electric costs


"Bob" wrote in message
...
The original question of "tell me how I go about computing cost of
operation
of an appliance" can only be answered by knowing how many BTUs he needs.
Then he can figure out how long an electric heater will have to run.
All that calculating isn't necessary. All he has to do is multiply his gas
usage by his heater's efficiency, then divide that by 3,413 to find out
how
many KWs he needs.


But he does not know how to figure the operating cost of those kWs. He
seems to know what he needs, (thus the 2,000 watt figure) just not the cost
of operation compared to propane.


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m Ransley
 
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When you say vents do you mean exuast up the chimney, Im sure its
calculated in in Afue rating. The big increase in condensing units is
the powered vent, exterior air, and of course second exchanger.

But an interesting fact is the efficiency difference between an 80% and
95% furnace is not 15 % its an 18.75% increase, time to think again.

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George E. Cawthon
 
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m Ransley wrote:
When you say vents do you mean exuast up the chimney, Im sure its
calculated in in Afue rating. The big increase in condensing units is
the powered vent, exterior air, and of course second exchanger.

No, what goes up the chimney is part of the AFUE.
The vents are for combustion air and ventilation.

But an interesting fact is the efficiency difference between an 80% and
95% furnace is not 15 % its an 18.75% increase, time to think again.

Standard math. 95-80 =15. 15/80 is .1875 or an
18.75 percent increase in efficiency.

If you go the other way, i.e., drop from 95 to 80,
it is 95-80 = 15, and 15/95 is .1666, or a drop in
efficiency of 16.66percent.
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m Ransley
 
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If vents are in attic or in walls that leak out the attic or a cold
crawlspace yes, you loose a bit yes. Dont run it 24x7 and insulate , I
insulated ducts and blew in foam in the walls above in wall registers, I
blew out a few walls too with the expanding foam.

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Bob wrote:

The original question of "tell me how I go about computing cost of operation
of an appliance" can only be answered by knowing how many BTUs he needs.
Then he can figure out how long an electric heater will have to run.
All that calculating isn't necessary. All he has to do is multiply his gas
usage by his heater's efficiency, then divide that by 3,413 to find out how
many KWs he needs.


Kilowatt-HOURS!!!

Nick



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Bob
 
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Seeing as electric heat is 100% efficient, all he has to do is multiply the
KW times the rate his electric company charges.

By doing it this way, he will be able to arrive at an accurate figure on
total operating costs of l.p. vs. electric.





"Edwin Pawlowski" wrote in message
t...

"Bob" wrote in message
...
The original question of "tell me how I go about computing cost of
operation
of an appliance" can only be answered by knowing how many BTUs he needs.
Then he can figure out how long an electric heater will have to run.
All that calculating isn't necessary. All he has to do is multiply his

gas
usage by his heater's efficiency, then divide that by 3,413 to find out
how
many KWs he needs.


But he does not know how to figure the operating cost of those kWs. He
seems to know what he needs, (thus the 2,000 watt figure) just not the

cost
of operation compared to propane.




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Bob
 
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Heaters have two different types of efficiency ratings. One is called steady
state efficiency, and one is called seasonal efficiency.


The only way to rate a heater is under laboratory conditions. If you take
the exact same heater, and install it in two different homes, the season
efficiency will change, depending on run time. Natural draft through a
vented heater will cool it down when it isn't running.

The draft you are talking about is considered "infiltration", and is taken
into account during a heat loss/gain calculation. It has little to do with
the efficiency of the heater.



"George E. Cawthon" wrote in message
...
m Ransley wrote:
Right OP didnt say what his lpg heater is so how can you figure a
comparison without knowing its efficiency. Im sure its as efficient as
Ng and there are many types and ratings so he could have junk running
40% efficiency or a ventless 99% or furnace at 60-94.5% eficiency
Electric is 100% efficient.

One thing that bugs me about gas furnace/heater
efficiency is how they calculate it.

My gas furnace is 80 percent which I assume means
that the 80 percent of the BTU's in the gas end up
in the house side of the heat exchanger, i.e,
useable heat.

But I don't think they ever consider the heat loss
from the the vents. How many BTU's are lost
through the the two openings of 100 square inches
each, one at the floor and one at the ceiling.
The flow of air through these vents is continous
24 hours a day. The furnace may put 80 percent of
the heat into the house, but how much heat is lost
through those vent openings? The greater the
difference between inside temperature and outside
temperature, the greater the total heat loss.
Maybe that is why they don't estimate that loss.

I could imagine that at 0 degrees, as much as 50
percent of the heat could be lost. In other
words, at 80 percent AFUE furnace would actually
result in only 40 percent of the heat retained in
the house compared to Electric heat which would be
100 percent since no vents are used.



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George E. Cawthon
 
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Yes, but my understanding is the furnace
manufacture calculates the heater efficiency
without taking required ventilation (draft) into
account. So when you compare a gas furnace which
requires a certain amount of ventilation to an
electric furnace which requires no ventilation,
The results are skewed in favor of the gas furnace.

Bob wrote:
Heaters have two different types of efficiency ratings. One is called steady
state efficiency, and one is called seasonal efficiency.


The only way to rate a heater is under laboratory conditions. If you take
the exact same heater, and install it in two different homes, the season
efficiency will change, depending on run time. Natural draft through a
vented heater will cool it down when it isn't running.

The draft you are talking about is considered "infiltration", and is taken
into account during a heat loss/gain calculation. It has little to do with
the efficiency of the heater.



"George E. Cawthon" wrote in message
...

m Ransley wrote:

Right OP didnt say what his lpg heater is so how can you figure a
comparison without knowing its efficiency. Im sure its as efficient as
Ng and there are many types and ratings so he could have junk running
40% efficiency or a ventless 99% or furnace at 60-94.5% eficiency
Electric is 100% efficient.


One thing that bugs me about gas furnace/heater
efficiency is how they calculate it.

My gas furnace is 80 percent which I assume means
that the 80 percent of the BTU's in the gas end up
in the house side of the heat exchanger, i.e,
useable heat.

But I don't think they ever consider the heat loss
from the the vents. How many BTU's are lost
through the the two openings of 100 square inches
each, one at the floor and one at the ceiling.
The flow of air through these vents is continous
24 hours a day. The furnace may put 80 percent of
the heat into the house, but how much heat is lost
through those vent openings? The greater the
difference between inside temperature and outside
temperature, the greater the total heat loss.
Maybe that is why they don't estimate that loss.

I could imagine that at 0 degrees, as much as 50
percent of the heat could be lost. In other
words, at 80 percent AFUE furnace would actually
result in only 40 percent of the heat retained in
the house compared to Electric heat which would be
100 percent since no vents are used.




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George E. Cawthon
 
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m Ransley wrote:
If vents are in attic or in walls that leak out the attic or a cold
crawlspace yes, you loose a bit yes. Dont run it 24x7 and insulate , I
insulated ducts and blew in foam in the walls above in wall registers, I
blew out a few walls too with the expanding foam.


I think you miss the point. A gas furnace requires
1 square inch of opening for a certain number
of BTU's depending on the exact installation. If
you have a furnace siting in the open in a very
large space you don't have to have this
ventilation because infiltration would be
sufficient. But in normal situation you need the
ventilation. In my case it is per 4000 BTU but
not less than 100 square inches each for
combustion and ventilation. The combustion air
opening is required to be within 18 inches of the
floor and the ventilation air is require to be
within 18 inches of the ceiling. These vents are
passive, you may not open and close them, they are
open all the time as safety measures to prevent
build up of CO and to eliminate build up of gas
from leaks.

There is essentially nothing you can do to reduce
the infiltration through the combustion opening
and not way to reduce the heat loss through the
ventilation opening. My contention is that this
heat loss is never calculated in comparing
electric heat with gas heat. The result is a bias
in favor of gas heat because the electric heat
will not have these losses. If you live in an
especially cold climate, and the cost calculated
for electric and gas heat are about equal, the
real world cost of the electric heat will be lower
than for gas heat.
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m Ransley
 
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OK you are right to a point I think, Thats why I put in a condensing
unit with cold air intake outside, but I would not have optioned or
considered a window open type set up logical or necessary. To be sure I
understand you every time the furnace runs you are sucking in cold air
on a regular unit, but you say through a vent is necessary, or as in a
window open. If your chimney won`t draw this could be nessecary right,
but then the option is powervent exuast only. Or to be sure a blower
door test is done to calculate air exchanges per hr. I had to go direct
power vent everything after I put in new windows and all tyvek. unless
its a million or 2m btu commercial boiler in a small room I dont see
having a vent open to air as being an idea id even consider and I dought
you could get a house tight enough to not draw in air through
infiltration, it comes in every where, even the attic. Real tight houses
need fresh air recirculators for good oxygen and reducing humidity, but
heating systems through negative pressure generated by exuast get makeup
air through everywhere even closed windows have infiltration ratings,
because they leak. Direct vent condensing furnaces with outside air
intake are common I think all condensing furnaces offer this option
standard.



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m Ransley
 
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Who requires this opening of venting 18 " off the floor and ceiling, not
my furnace lennox. Ive never heard of a house having this open vent to
outdoors set up. My apt building with a 1.6 million btu boiler has a
window cracked 1" and the flame is adjusted by a tech with a Bachrach
set up and he says oxygen, color and burner efficiency are tops. boiler
is in a small room, heats 16 units steam heat. Infiltration does the
rest.

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Edwin Pawlowski
 
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"m Ransley" wrote in message
...
My apt building with a 1.6 million btu boiler has a
window cracked 1" and the flame is adjusted by a tech with a Bachrach
set up and he says oxygen, color and burner efficiency are tops. boiler
is in a small room, heats 16 units steam heat. Infiltration does the
rest.


I wonder how much, if any, difference it would be with a larger vent
instead of infiltration. I run a large boiler in one of our buildings and it
has a motorized louver. You need a winter coat if you stand in front of the
boiler when the blower is running for combustion. The boiler room is
otherwise closed off by a door. This is in an old building with plenty of
drafts and infiltration, but spread out over four floors and distances of
200 feet or so.


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m Ransley
 
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Yours is cold, I packed a foot of insulation and its still real warm,
Yes I need a vent but now I use a window 15 ft away .The proper way is
exterior air or like what you have a motorised air set up is better than
a window, its a Kewanee 2 pass

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George E. Cawthon
 
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m Ransley wrote:
OK you are right to a point I think, Thats why I put in a condensing
unit with cold air intake outside, but I would not have optioned or
considered a window open type set up logical or necessary. To be sure I
understand you every time the furnace runs you are sucking in cold air
on a regular unit, but you say through a vent is necessary, or as in a
window open. If your chimney won`t draw this could be nessecary right,
but then the option is powervent exuast only. Or to be sure a blower
door test is done to calculate air exchanges per hr. I had to go direct
power vent everything after I put in new windows and all tyvek. unless
its a million or 2m btu commercial boiler in a small room I dont see
having a vent open to air as being an idea id even consider and I dought
you could get a house tight enough to not draw in air through
infiltration, it comes in every where, even the attic. Real tight houses
need fresh air recirculators for good oxygen and reducing humidity, but
heating systems through negative pressure generated by exuast get makeup
air through everywhere even closed windows have infiltration ratings,
because they leak. Direct vent condensing furnaces with outside air
intake are common I think all condensing furnaces offer this option
standard.

I don't know how the most efficient furnaces are
set up, mine is down a bit as are most peoples.
And I'm not going through the whole Installation
Instruction.

But lets just take the water tank which has an
unpowered flue and a pilot light. The tank has a
hole in the center above the burner, there is a
gap between the tank the funnel which is the
bottom of the exhaust flue which is about 2-1/2 in
diameter. There is a louvered vent in the ceiling
to the attic and a louvered vent in the floor to
the crawlspace. When the burner is on, air is
sucked from the adjoining rooms but mainly from
the crawlspace in to the burner and goes up the
exhaust pipe. Now what do you think the air flow
is like when the burner is not on. Warm air
naturally rises so warm air goes through the
burner area but probably mostly through the gap at
the funnel and goes up the flue to the outside.
In doing this, it pulls air not only from the
living space but also from the crawl space. Of
course warm air also rises through the vent in the
ceiling and it is much larger than the flue. All
of these areas are much warmer than the outside so
heat is lost and cold air from the outside is
pulled in. BTW, the furnace is essentially the
same except that it is a higher efficiency unit so
it has an inductor fan.

Now if the system were completely sealed, and
maybe high efficiency units are but I don't think
they are, you wouldn't have these losses.
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George E. Cawthon
 
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m Ransley wrote:
Who requires this opening of venting 18 " off the floor and ceiling, not
my furnace lennox. Ive never heard of a house having this open vent to
outdoors set up. My apt building with a 1.6 million btu boiler has a
window cracked 1" and the flame is adjusted by a tech with a Bachrach
set up and he says oxygen, color and burner efficiency are tops. boiler
is in a small room, heats 16 units steam heat. Infiltration does the
rest.


Ok, my furnace is an Amana my water heater is a
Brad ford White. The requirements are from the
National Fuel Gas Code NFPA 54/ANSI Z223.1 Section 5.3


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George E. Cawthon wrote:

... A gas furnace requires 1 square inch of opening for a certain number
of BTU's depending on the exact installation.


More precisely, 1 ft^3 of gas has a heating value of about 1000 Btu, and
burning it takes about 9.6 ft^3 of air, so a 50K Btu/h furnace burns about
50 ft^3 per hour with about 9.6x50 = 480 ft^3/h or 8 cfm of combustion air.

If you have a furnace siting in the open in a very large space you don't
have to have this ventilation because infiltration would be sufficient.


An average 2400 ft^2 US house leaks about 0.5x2400x8/60 = 160 cfm, 20 times
more than 8 cfm, so vents for combustion air or gas leak dilution seem
completely unnecessary, unless you install the furnace in a tight closet.

Nick

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George E. Cawthon
 
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wrote:
George E. Cawthon wrote:


... A gas furnace requires 1 square inch of opening for a certain number
of BTU's depending on the exact installation.



More precisely, 1 ft^3 of gas has a heating value of about 1000 Btu, and
burning it takes about 9.6 ft^3 of air, so a 50K Btu/h furnace burns about
50 ft^3 per hour with about 9.6x50 = 480 ft^3/h or 8 cfm of combustion air.


I'm not going to go through all the calculations,
so I will assume they are correct, but see below.


If you have a furnace siting in the open in a very large space you don't
have to have this ventilation because infiltration would be sufficient.



An average 2400 ft^2 US house leaks about 0.5x2400x8/60 = 160 cfm, 20 times
more than 8 cfm, so vents for combustion air or gas leak dilution seem
completely unnecessary, unless you install the furnace in a tight closet.

Nick


I don't think 2400 square feet is the average
house. Besides average means nothing, the median
size house tells a lot more and I am sure it is
well below 2400 square feet. Anyway my house is
1500 square feet and I don't think that it leaked
anywhere near that amount of air (before
installation of the gas furnace and water heater.

The rules as I read them are for a confined space
and an unconfined space. Mine furnace is in fact
in a closet, but even if it were outside the
closet or the closet door was removed, it would
still be categorized as a confined space and has
to follow the confined space rules. That is
because unconfined space is defined as that part
that directly communicates with the furnace and is
not equipped with doors. Much of my house would
be behind those doors even though they are
normally all open. It doesn't matter what the
actual air flow facts are or what I think of the
rules, the installers apparently followed the
rules and the result is a lot more air
infiltration and passive heat loss than before the
electric furnace and water heater were replaced
with gas appliances.

Just as a side note, I also would never again have
a gas water heater because the thermostat has way
too much range compared to an electric water
heater. My electric water heaters always held the
water within a very narrow range of temperature
(say 3-4 degrees). My gas water heater can't keep
water within a range of less than 10-15 degrees.
  #33   Report Post  
Posted to alt.home.repair
m Ransley
 
Posts: n/a
Default Computing electric costs

Close your exterior air intake vents, im sure you will be fine. Air
would not go up and out the chimney if there was not enough make up air,
it would cool and downdraft. it will save you alot.

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