I just installed a 30K Btu/h natural gas vent-free radiant heater in
a house near Allentown, PA, where kerosine now costs $3.50/gallon
and natural gas costs about $1.50/therm (roughly equivalent).

Empire Comfort Systems (Enerco) makes this "Mr. Heater." Tractor Supply
sells it for $229.99 as sku #2151954. It comes with a thermostat and
a blower and a digital temperature display. It has an oxygen depletion
sensor, and it can work without grid power, but there have been some
problems since installation.

The thermostat only has 5 temp settings, as well as "pilot only." It is
supposed to make the room about 55 F min, with 5 F steps above that, but
the temp sensing bulb is on the back near a cold floor under a cold single-
pane window. When the first setting heats most of the room to more than
70 F, the owner turns the thermostat back to pilot before the heater
turns itself off, while the temperature display still only reads 58 F, ie
the thermostat isn't doing much. The owner says with the knob between
the lowest and pilot settings, the heater emits interesting flaming blue
gas footballs instead of the usual red glow. And it makes condensation
on the indoor window surfaces.

We might fix the first 2 problems by putting a 25 watt light bulb near
the temp sensor with a $15 line-voltage thermostat on the wall that
turns the bulb off when the room is warm enough.

This old house seemed drafty enough to avoid window condensation, but
it also has a damp basement, with puddles of water after rain. Keeping
water out of the basement might help a lot. Indoor storm window shrink
films could also help. Allentown is 31.8 F on an average December day.
An R1 window with a 1.5 Btu/h-F-ft^2 still airfilm indoor conductance to
70 F room air and (70-31.8)1ft^2/R1 = 38.2 Btu/h-ft^2 of heatflow would
have a glazing temp (dew point) of 70-38.2x1ft^2/1.5 = 44.5 F (504.5 R),
with indoor RH = 100e^-(9621(530-504.5)/(504.5x530) = 40% at 70 F (530 R).
Basement puddles at 55 F could condense on window surfaces.

If indoor film makes the windows R2 and raises the film temp to 70-19.1/1.5
59.4 F (519.4 R), the a max indoor RH = 100e^-(9621(530-519.4)/(519.4x530)
= 69%, with no condensation from basement puddles.

NREL says Allentown has an average humidity ratio wo = 0.0028 pounds of water
per pound of dry air in December, with Pa = 29.921/(1+0.62198/0.0028)
= 0.1341 "Hg. Air at 70 F and 100% RH has Psat = e^(17.863-9621/(460+70))
= 0.748 "Hg, approximately, so merely heating the outdoor air to 70 F
with no basement puddles would make the indoor RH = 100Pa/Psat = 18%.

The ASHRAE HOF says pure methane (vs a different natural gas mixture) has
a high heating value (HHV) of 23,875 Btu/lb, when we condense the water vapor
from combustion and a low heating value (LHV) of 21,495 (11% less) when we
don't, and 1000 Btu can evaporate a pound of water, so a vent-free heater
that makes 20K Btu/h also makes 0.11x20K/1000 = 2.2 lb/h of water vapor.
With window films and no basement puddles, we could keep a 50% indoor RH
(wi= 0.016) by moving in C cfm of fresh air (at 0.075 lb/ft^3), where
2.2=60C0.075(wi-wo), so C = 37 cfm, with a heat loss of about 37(70-31.8)
1420 Btu/h, which lowers the heater system efficiency to 93%, compared to
an HHV- 100%.

We might move outdoor air into the room with a $30 humidistat and a muffin
fan, or (more efficiently) use a homebrew HRV with condensation outside
and fresh air inside Coroplast (plastic corrugated sign material) plates,
or run a dehumidifier or an $80 low-airspeed window AC inside the room.

If the $1275 DV-20E 81.5%-efficient direct vent and $3268 93%-efficient
Mantis condensing gas heaters are measured with LHV-based efficiencies
and we subtract 11% to compare apples to apples, the $229 vent-free
heater is more efficient, as well as a lot cheaper.

Kiddie's 900-0113 plug-in CO and explosive gas detector with battery backup
($48 from Amazon, with free shipping) would go well with this.

Nick

wrote:
I just installed a 30K Btu/h natural gas vent-free radiant heater in
a house near Allentown, PA, where kerosine now costs $3.50/gallon
and natural gas costs about $1.50/therm (roughly equivalent).

Empire Comfort Systems (Enerco) makes this "Mr. Heater." Tractor Supply
sells it for $229.99 as sku #2151954. It comes with a thermostat and
a blower and a digital temperature display. It has an oxygen depletion
sensor, and it can work without grid power, but there have been some
problems since installation.


I have never seen one of those style heaters that didn't have the same
slightly acrid odor that is really annoying in a confined space such as
a house. Is this one any different?

On 18 Dec 2007 08:46:13 -0500, wrote:
the temp sensing bulb is on the back near a cold floor under a cold single-
pane window.

Not an ideal location... I wonder if the bulb could be relocated a
bit, and perhaps some insulation could be added on two or three sides of
the bulb to prevent cold drafts from the window above and perhaps allow
more effect from the radiant transfer of the warm room to the bulb.
Might could even put insulation on up to 5 sides of the sensor.

We might fix the first 2 problems by putting a 25 watt light bulb near
the temp sensor with a $15 line-voltage thermostat on the wall that
turns the bulb off when the room is warm enough.

Hmm, I prefer a passive solution if possible. And if that second
thermostat is plugged into an outlet on the exterior wall, it is likely
to have the same problems as the thermostat built into the heater.

If the $1275 DV-20E 81.5%-efficient direct vent and $3268 93%-efficient
Mantis condensing gas heaters are measured with LHV-based efficiencies
and we subtract 11% to compare apples to apples, the $229 vent-free
heater is more efficient, as well as a lot cheaper.

The 93% and 81.5% already account for the 11% loss in non-condensing.
It is erroneous to subtract it again. Never the less, the non-vented
heater is nearly 100% efficient, and the price looks very good in
comparison.

Kiddie's 900-0113 plug-in CO and explosive gas detector with battery backup
($48 from Amazon, with free shipping) would go well with this.

Absolutely.

sdb

--
What's seen on your screen? http://PcScreenWatch.com
sdbuse1 on mailhost bigfoot.com

sylvan butler wrote:

If the $1275 DV-20E 81.5%-efficient direct vent and $3268 93%-efficient
Mantis condensing gas heaters are measured with LHV-based efficiencies
and we subtract 11% to compare apples to apples, the $229 vent-free
heater is more efficient, as well as a lot cheaper.

The 93% and 81.5% already account for the 11% loss in non-condensing.

I finally heard from the manufacturer, who tested all of them with gas
with a heating value of 1035 vs 930 Btu/ft^3, ie the HHV.

Nick

[reading this on alt.home.repair]

On 18 Dec 2007 08:46:13 -0500, wrote:

I just installed a 30K Btu/h natural gas vent-free radiant heater in
a house near Allentown, PA, where kerosine now costs $3.50/gallon
and natural gas costs about $1.50/therm (roughly equivalent).

In how big an open area? I like my unvented gas stove & have never
had a bit of odor, nor has it ever registered more than the slightest
amount of CO on my detector----- But I remember when I bought it
10[?] years ago the main concern was whether or not it was too big.

My house is pretty open downstairs & the stove is in a 12x20 room with
an outside door and 5 windows. We [my gas supplier & myself]
decided that 30K would be doable.

Mine is just used as supplemental [and on the odd occasion that my
furnace goes out or we lose power. But it has never fogged windows.
-snip-
The thermostat only has 5 temp settings, as well as "pilot only." It is
supposed to make the room about 55 F min, with 5 F steps above that, but
the temp sensing bulb is on the back near a cold floor under a cold single-
pane window. When the first setting heats most of the room to more than
70 F, the owner turns the thermostat back to pilot before the heater
turns itself off,

I'd ask him/her to leave it alone until it can even itself out.

-snip-
And it makes condensation
on the indoor window surfaces.

That could be poorly insulated windows, high humidity in the house- or
excess humidity from the gas. [LP adds water to the air- I think
natural gas does, too]

-snip a whole lot of ASHRAE gobbledygook-gook-

We might move outdoor air into the room with a $30 humidistat and a muffin
fan, or (more efficiently) use a homebrew HRV with condensation outside
and fresh air inside Coroplast (plastic corrugated sign material) plates,
or run a dehumidifier or an $80 low-airspeed window AC inside the room.

Call your local fire department and ask them to invite you clean out
the next house they get called to remove a body that succumbed to CO
poisoning because some gadget failed.

-snip-
Kiddie's 900-0113 plug-in CO and explosive gas detector with battery backup
($48 from Amazon, with free shipping) would go well with this.

It [or a similar alarm] 'goes well' with any combustion device in your
house. With a ventless stove you're a damn fool for not plugging
it in before you cranked up the stove. Especially one as big as
you're running there. spend a little of the time you've invested
poring over ASHRAE charts and read what your local building department
suggests in regards to those stoves.

Jim

On 18 Dec 2007 08:46:13 -0500, wrote:

I just installed a 30K Btu/h natural gas vent-free radiant heater in
a house near Allentown, PA, where kerosine now costs $3.50/gallon
and natural gas costs about $1.50/therm (roughly equivalent).

Empire Comfort Systems (Enerco) makes this "Mr. Heater." Tractor Supply
sells it for $229.99 as sku #2151954. It comes with a thermostat and
a blower and a digital temperature display. It has an oxygen depletion
sensor, and it can work without grid power, but there have been some
problems since installation.

The thermostat only has 5 temp settings, as well as "pilot only." It is
supposed to make the room about 55 F min, with 5 F steps above that, but
the temp sensing bulb is on the back near a cold floor under a cold single-
pane window. When the first setting heats most of the room to more than
70 F, the owner turns the thermostat back to pilot before the heater
turns itself off, while the temperature display still only reads 58 F, ie
the thermostat isn't doing much. The owner says with the knob between
the lowest and pilot settings, the heater emits interesting flaming blue
gas footballs instead of the usual red glow. And it makes condensation
on the indoor window surfaces.

We might fix the first 2 problems by putting a 25 watt light bulb near
the temp sensor with a $15 line-voltage thermostat on the wall that
turns the bulb off when the room is warm enough.

This old house seemed drafty enough to avoid window condensation, but
it also has a damp basement, with puddles of water after rain. Keeping
water out of the basement might help a lot. Indoor storm window shrink
films could also help. Allentown is 31.8 F on an average December day.
An R1 window with a 1.5 Btu/h-F-ft^2 still airfilm indoor conductance to
70 F room air and (70-31.8)1ft^2/R1 = 38.2 Btu/h-ft^2 of heatflow would
have a glazing temp (dew point) of 70-38.2x1ft^2/1.5 = 44.5 F (504.5 R),
with indoor RH = 100e^-(9621(530-504.5)/(504.5x530) = 40% at 70 F (530 R).
Basement puddles at 55 F could condense on window surfaces.

If indoor film makes the windows R2 and raises the film temp to 70-19.1/1.5
59.4 F (519.4 R), the a max indoor RH = 100e^-(9621(530-519.4)/(519.4x530)
= 69%, with no condensation from basement puddles.

NREL says Allentown has an average humidity ratio wo = 0.0028 pounds of water
per pound of dry air in December, with Pa = 29.921/(1+0.62198/0.0028)
= 0.1341 "Hg. Air at 70 F and 100% RH has Psat = e^(17.863-9621/(460+70))
= 0.748 "Hg, approximately, so merely heating the outdoor air to 70 F
with no basement puddles would make the indoor RH = 100Pa/Psat = 18%.

The ASHRAE HOF says pure methane (vs a different natural gas mixture) has
a high heating value (HHV) of 23,875 Btu/lb, when we condense the water vapor
from combustion and a low heating value (LHV) of 21,495 (11% less) when we
don't, and 1000 Btu can evaporate a pound of water, so a vent-free heater
that makes 20K Btu/h also makes 0.11x20K/1000 = 2.2 lb/h of water vapor.
With window films and no basement puddles, we could keep a 50% indoor RH
(wi= 0.016) by moving in C cfm of fresh air (at 0.075 lb/ft^3), where
2.2=60C0.075(wi-wo), so C = 37 cfm, with a heat loss of about 37(70-31.8)
1420 Btu/h, which lowers the heater system efficiency to 93%, compared to
an HHV- 100%.

We might move outdoor air into the room with a $30 humidistat and a muffin
fan, or (more efficiently) use a homebrew HRV with condensation outside
and fresh air inside Coroplast (plastic corrugated sign material) plates,
or run a dehumidifier or an $80 low-airspeed window AC inside the room.

If the $1275 DV-20E 81.5%-efficient direct vent and $3268 93%-efficient
Mantis condensing gas heaters are measured with LHV-based efficiencies
and we subtract 11% to compare apples to apples, the $229 vent-free
heater is more efficient, as well as a lot cheaper.

Kiddie's 900-0113 plug-in CO and explosive gas detector with battery backup
($48 from Amazon, with free shipping) would go well with this.

Nick

Vent free heaters produce COPIOUS amounts of water vapour - a much
more serious issue in most cases thanoxygen depletement or CO
concentration.

--
Posted via a free Usenet account from http://www.teranews.com

wrote in message
...
I just installed a 30K Btu/h natural gas vent-free radiant heater in
a house near Allentown, PA, where kerosine now costs $3.50/gallon
and natural gas costs about $1.50/therm (roughly equivalent).

Empire Comfort Systems (Enerco) makes this "Mr. Heater." Tractor Supply
sells it for $229.99 as sku #2151954. It comes with a thermostat and
a blower and a digital temperature display. It has an oxygen depletion
sensor, and it can work without grid power, but there have been some
problems since installation.

The thermostat only has 5 temp settings, as well as "pilot only." It is
supposed to make the room about 55 F min, with 5 F steps above that, but
the temp sensing bulb is on the back near a cold floor under a cold single-
pane window. When the first setting heats most of the room to more than
70 F, the owner turns the thermostat back to pilot before the heater
turns itself off, while the temperature display still only reads 58 F, ie
the thermostat isn't doing much. The owner says with the knob between
the lowest and pilot settings, the heater emits interesting flaming blue
gas footballs instead of the usual red glow. And it makes condensation
on the indoor window surfaces.

We might fix the first 2 problems by putting a 25 watt light bulb near
the temp sensor with a $15 line-voltage thermostat on the wall that
turns the bulb off when the room is warm enough.

You could use a small "computer" fan to circulate room air to the thermostat
better. Or, add insulation behind the heater.

In article ,
clare at snyder.on.ca wrote:

Vent free heaters produce COPIOUS amounts of water vapour - a much
more serious issue in most cases thanoxygen depletement or CO
concentration.

--
Posted via a free Usenet account from http://www.teranews.com

That would depend on the Relative Humidity of the area you live in....
if your RH is very low, you may just want a bit of humidity enhancement
in your house....

You wrote:
clare at snyder.on.ca wrote:

Vent free heaters produce COPIOUS amounts of water vapour...

Exactly 2.2 pounds per hour, with 20K Btu/h of heat.

That would depend on the Relative Humidity of the area you live in....

No, but removing it does... 37 cfm of fresh air will keep the indoor RH at
50% at 70F on an average 31.8 F December day in Allentown, PA. In a perfectly
airtight house (vs an average US house that naturally leaks 224 cfm), we
might do that with a humidistat and a muffin fan, or open a 2'wide x 3'tall
window with an A ft^2 gap at the top and bottom with A = cfm/(16.6sqrt(HdT))
= 37/(16.6sqrt(3'(70-31.8)) = 0.21 ft^2, ie a 2'wide x 1.25" gap at the top
and bottom. In a non-airtight house with a window 24' below a leaky upstairs,
the gap might be 37/(16.6sqrt(24'(70-31.8)) = 0.074 ft^2, ie a single 0.44"
max gap at the bottom of a first-floor window.

Nick

On Tue, 18 Dec 2007 22:06:57 -0500, clare at snyder.on.ca clare wrote:
Vent free heaters produce COPIOUS amounts of water vapour - a much
more serious issue in most cases thanoxygen depletement or CO
concentration.

Except my humidifier (on a humidistat) runs nearly all winter long
anyway. So added humidity from unvented gas heater would not likely be
an issue. I'm thinking in climates where heating is needed (not just to
take the chill off, e.g. southern C.A.) lack of humidity is frequently
more of a problem than too much humidity.

sdb
--
What's seen on your screen? http://PcScreenWatch.com
sdbuse1 on mailhost bigfoot.com

sylvan butler wrote:

clare at snyder.on.ca clare wrote:

Vent free heaters produce COPIOUS amounts of water vapour - a much more
serious issue in most cases thanoxygen depletement or CO concentration.

Except my humidifier (on a humidistat) runs nearly all winter long anyway.
So added humidity from unvented gas heater would not likely be an issue.

It would a help...

I'm thinking in climates where heating is needed (not just to take
the chill off, e.g. southern C.A.) lack of humidity is frequently
more of a problem than too much humidity.

An average 2400 ft^2 US house leaks naturally leaks 0.7 ACH, ie 224 cfm,
much more than ASHRAE's standard of 15 cfm per full-time occupant (which
used to be 5 cfm.) This makes house air very dry in wintertime and makes
the system efficiency of a vent-free heater higher than any vented heater.

A good (IDEAS) Canadian house only leaks 2.5 cfm. With people and green
plants evaporating water inside, it needs DEhumidification (eg mechanical
ventilation) in wintertime.

Nick

daestrom wrote:

I just installed a 30K Btu/h natural gas vent-free radiant heater in
a house near Allentown, PA, where kerosine now costs $3.50/gallon
and natural gas costs about $1.50/therm (roughly equivalent)...

... Why does it have the sensor low to the floor

Dunno.

... and why did you install it in front of a window?

That was sort of an accident. It might possibly change.

2.2=60C0.075(wi-wo), so C = 37 cfm, with a heat loss of about 37(70-31.8)
1420 Btu/h, which lowers the heater system efficiency to 93%, compared to
an HHV-based 100%.

70 degF air at RH 50% is about 25.5 Btu/lbm and 31.8 degF air at RH 100% is
about 11.7 Btu/lbm. So the heat loss from 37 cfm is
37*60*.075*(25.5-11.7)=2298 Btu/hr, more like 88.5% efficiency.

Ah yes. I was just thinking about the sensible loss. Then again,
we might build that Coroplast condensing air-air heat exchanger.

So with ventilation to control the humidity, you'll get efficiencies
comparable to a conventional gas furnace.

Higher, I'd say, in this drafty house.

It'll be nice and humid in the house, but with single pane windows you'll
have a lot of condensate and mold growth on the frames.

The owner seems reluctant to add window films or fix the basement puddles...

Nick

wrote:

ASHRAE's standard of 15 cfm per full-time occupant
(which used to be 5 cfm.)

300% upward revision.... I'm wondering why this spec change occurred.

The original (19th C?) standard was based on productivity. Somebody noticed
that coal mine workers with less than 5 cfm fell asleep :-)

The newer version is based on odors and other pollutants.

Nick

daestrom wrote:

2.2=60C0.075(wi-wo), so C = 37 cfm, with a heat loss of about
37(70-31.8) = 1420 Btu/h, which lowers the heater system efficiency
to 93%, compared to an HHV-based 100%.

70 degF air at RH 50% is about 25.5 Btu/lbm and 31.8 degF air at RH 100%
is about 11.7 Btu/lbm. So the heat loss from 37 cfm is
37*60*.075*(25.5-11.7)=2298 Btu/hr, more like 88.5% efficiency.

Ah yes. I was just thinking about the sensible loss. Then again,
we might build that Coroplast condensing air-air heat exchanger.

As long as you stay above freezing to avoid frost I suppose...

Maybe we need 2 fans, with a Thermocube and a relay to turn off the outdoor
fan if the outgoing airflow is less than 35 F. With equal capacity fans and
outgoing condensation, freezing seems unlikely. One $9 sheet of Coroplast
and a tube of 3M 4693 H adhesive could make a 2' wide x 6" high x 8" deep
box that sits in a window with about 64 ft^2 of heat transfer surface and
Cmin = 50 cfm and NTU = AU/Cmin = 64x1.5/50 = 1.9 and E = 1-e^-1.9 = 0.85.

Nick

Too_Many_Tools wrote:

... believe me when I say you do need to deal with the moisture.

... Excessive moisture will destroy a house.

This one's pretty much already destroyed :-)

Lately I'm thinking a natural convection air-air heat exchanger might be nice,
with more airflow than a sensible heat exchanger, since humidity adds bouyancy
and the outgoing air would be warmer, with condensation.

Nick

Lately I'm thinking a natural convection air-air heat exchanger might be nice,
with more airflow than a sensible heat exchanger, since humidity adds bouyancy
and the outgoing air would be warmer, with condensation.

Something like this sensible calc, with poly film plates...

20 H=4'hx height (feet)
30 W=2'hx width (feet)
35 NP=8'number of hx plates
40 A=2*NP*H*W'hx area (ft^2)
50 U=1.5'hx conductance (Btu/h-F-ft^2)
60 CFM=37'hx airflow
70 NTU=A*U/CFM'Number of heat Transfer Units
80 E=NTU/(NTU+1)'hx effectiveness
90 TCI=31.8'cold inlet temp (F)
100 THI=65'hot inlet temp (F)
110 TCO=TCI+E*(THI-TCI)'cold outlet temp (F)
120 TCA=(TCI+TCO)/2'average cold temp (F)
130 THO=THI-(TCO-TCI)'hot outlet temp (F)
140 THA=(THI+THO)/2'average hot temp (F)
150 DT=THA-TCA'average temp diff (F)
160 AV=CFM/(16.6*SQR(H*DT))'vent area (ft^2)
170 S=12*AV/((NP-1)*W)'min plate spacing (inches)
180 DS=4/25.4'Coroplast spacer depth (inches)
190 NS=INT(S/DS+.5)'# Coroplast spacers
200 D=(2+(NP+1)*NS)*DS'hx depth (inches)
220 PRINT E,D,S,NS
230 PRINT THI,THO,TCI,TCO

effectiveness depth (in) spacing (in) # spacers

0.838428 4.566929 0.4124437 3

Thi Tho Tci Tco

65 37.16419 31.8 59.63581

To avoid freezing, a $13 TC-3 Thermocube might turn on a small
room air exhaust fan when the room air outlet temp drops to 35 F.

Nick

On Mar 18, 8:29*pm, "Stormin Mormon"
wrote:
Winter time in northern states of USA, humidity is rather low. We northern
folks often use a humidifier to add water to the air. so, a vent free heater
adding humidity is good.

--
Christopher A. Young
Learn more about Jesus
*www.lds.org
.

"You" wrote in message

...

That would depend on the Relative Humidity of the area you live in....
if your RH is very low, you may just want a bit of humidity enhancement
in your house....

Yea adding more pollutants you dont need, smart, unless your house
leaks like a sieve vent free are not a healthy choise. I believe many
areas in Canada they are banned.