gas fires that have no flue

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wrote:

Over here in the US we use a rating you probably have never heard of, BTU, British Thermal Unit. Kw, but you guys are not metric, driving on the Right side is Right.
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On Thu, 25 Feb 2010 17:12:11 GMT, "ARWadsworth"

That's pretty much what I suspected. ;-)

Yes, both "vented" and "vent-free" gas logs are available. The vent-free variety tend to have a higher output and are used for heating. The vented logs are more or less for decoration, since much of the heat escapes up the flue.
We use heat pumps for central heat. The idea of the gas fireplace logs is for auxiliary heat for the few nights where it's really too cold for the heat pumps to operate well (not enough resistive heat to maintain temperature, either). We should also be able to turn the temperature in the house down a few degrees because the gas will help recovery (heat pumps suck).
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The problem with a flueless gas fire is... - Ventilation requirements likely exceed the heat output capability - Water output is high, not unlike an LPG bottle radiant heater
In the UK there are Balanced Flue flame effect fires. - These simply require an outside wall - Drill a hole, fit a coaxial flue - Air pulled in from outside, combustion products out
It would be interesting to compare a flueless gas fire efficiency (with BG 10x10cm free air flow vent) to an electric version. Gas is abour 3p, Electric peak is about 10p (UK).
I recall Gas Inset DFE Fires can be below 35% efficient and any heat up the open flue will draw more cold air through the house so are probably 25-20% efficient in most cases. That means they are as or more expensive than an "Electric DFE" - better to get an oil radiator or fan heater and a TFT panel with flickering fire video looping on it.
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I'm not understanding this. Maybe it is our 'common language'. Is 'flueless' the same as 'ventless'? In the US a ventless has no requirement for outside air.

My 30K BTU heater has never steamed up any windows. A pot of spaghetti on the stove puts out more moisture.
For me, the moisture that is added by an LPG fire is welcome- as it is a struggle to keep the humdity as high as 38 in my NE US winters.

A ventless fire- there are wall heaters and freestanding stoves, as well as 'logs' that go in fireplaces- in the US just needs a gas line run to it. Combustion air is provided by the natural infiltration that all houses have. There is a safety switch that should turn the gas off is there is not enough oxygen for combustion.

This year- my ventless is slightly more expensive than electric. [but cheaper than my oil by about 25%] Up until a couple years ago it was cheaper than the electric.
I used 100% efficiency for electric and my ventless propane-- and 75 % for my oil furnace. It tests at 85% at the flue, and I allow for a bit lost in the ducts.

Although we both seem to have a different idea of ventless/flueless - we both agree that anything with a chimney in a living area is a losing proposition.
Jim
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wrote:

I imagine so, however secondary ventilation is often needed in the uk. A flueless gas fire in the UK has no flue or vent but there is a reqirement for a ventilation hole elsewhere in the room to allow fresh air in.

Of course. You are boiling water on the stove and creating extra moisure. Even lighting the stove with no pot on will create some moisture as a by product of the burning process.

Many house in the UK suffer from damp and extra moisture is not welcome. New build houses in the UK are often air presure tested and need to meet specific targets to stop the natural ingress of air.
A little bit of water between us makes a big difference to a common language.
Adam
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I suspect the closest we come in the US to similar conditions would be our Northwest coast. We started in the US in the 70s to make super-tight houses, and I believe that theory has fallen into dis-favor because the indoor pollution was deemed more dangerous than the monetary gains. [I might be all wet now, I haven't been in that business for 30 years, so I don't read many current trade books.]
I note on air exchanges on this page from 1997- that ASHRAE [American Society of Heating, Refrigerating and Air-Conditioning Engineers] recommended a minimum of .35 air exchanges per hour in residential construction-- but in practice most houses had 1.1. http://eetd.lbl.gov/newsletter/cbs_nl/nl13/vent.html
Do you know how that squares with UK housing?

Indeed. This is one area where it would have saved the OP some misleading info if they had named their continent, at least.
Jim
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Living Room generally 2 ACH. Living Room w/Open Flue can be 3.5-5.5 ACH.
Open Flue can really stuff up the figures for UK GCH (wet) radiator sizing, you can go from 440W to 1800W.
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wrote in message

This gives some idea on the UK recommended air changes
http://www.manrose.co.uk/fan_select.htm
We tend to rely on mechanical ventilation and not air conditioning. However I have noticed more households are installing air conditioning. (You have to realise that air con in cars has only just become the norm over here)
The daft thing is, we now make houses air tight and then add trickle vents to the windows or fans to certain rooms to allow ventilation.
Adam
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Some info here
http://www.hse.gov.uk/research/rrhtm/rr023.htm
and the report that it links to.
Adam
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wrote:

Interesting report.
They did the test on modern housing, no open flue or large number of vents, because they were specifically interested in combustion safety. The vent presence/no-presence did not affect temperatures much because the vent could not supply an open flue which will draw even without a fire due to convection (even solar :-)
For older housing the Open Flue when combined with 4in*4in free area vent can be "quite a draughty combination".
Modern houses DO have a wonderful luxury of high insulation level. Wall of U = 0.35 is so much different to U = 2.11 and the wood-inner- leaf also tends to mean very rapid heat up (problem then becomes enough thermal mass in the room, but fast warmup is great for working people arriving home as it saves on background non-resident heating requirements).
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wrote:

Nonsense.
In the winter water is goodness. It's not all *that* much water, anyway.

We have those too; ugly. Our fireplace is on an interior wall anyway.

Which is about 1/2 our cost. Electric fireplaces are even uglier. If I wanted to heat with resistive electric heaters I'd ditch the heat pumps (an incredibly *dumb* idea).

How are you measuring "efficiency"? They certainly combust more than 65% of the propane.
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No & Yes - it depends on house design: 2008 - near air tight, well insulated. 1950 - air sieve, uninsulated, 1-2 open flue chimney.
USA housing stock differs greatly from UK.
2008 house is a near air tight box. - Air tight = few Air Changes per Hour (ACH) - Adding a 4in*4in vent doesn't make ACH rocket - So comfort impact is limited
Cited H&S study found the vent didn't affect temps much. That is as expected, 2008 house has little heat loss & has *restricted* ACH.
1950 house is full of huge holes. - Air sieve = huge Air Changes per Hour - 1-2 open flue chimney with convection column from room heat & wind action. - Adding a 4in*4in vent will make ACH rocket - So comfort impact is enormous
Example. 1 - 1950s living area, flue blocked by plywood. - Heat calc: 440W required for 21oC. - Heat test: 500W heater maintained 22oC.
2 - 1950s living area, flue with outset gas fire turned OFF. - Heat calc: 750W required for 21oC based on ACH guess. - Heat test: 1440W heater maintained 19.5oC.
3 - 1950s living area, open flue. - Heat calc: 1000W required for 21oC based on ACH guess. - Heat test: 2000W could not raise temp 15oC.
UK housing is closer to 1950 than 2008. Wall hung flueless fires work well in modern air tight construction. HSE test indicates they DO thermally work in modern air tight construction, but the problem is 1) CO2 concentration 2) a poor burner hidden by a catalyst.
UK Inset Decorative Flame Effect Fire: - Inset DFE fire sits below an *open flue*. - Mimimal fire output radiates into the room. - Most fire output convects up the chimney. - Open chimney draw sucks the room cold. - Net result is you burn 6-8kW for 2kW into room. - Complaint usually "frozen & cold ankles re draughts".
Nothing to do with the burner efficiency.
Inset DFE efficiency typically quoted 28-38%. - UK thermal losses can be high re minimal Floor Wall Loft insulation. - UK ventilation can be high re numerous house wall vents. - Stick an 8kW flame below an open flue and all the heat goes up it
With older UK house thermal losses and often numerous 9in*6in ventilators, sticking a DFE fire below an open flue creates an immensely powerful heat pump up the chimney. Real world figures can be as low as 15%, so even with 8kW input people can't get warm because the draught sucks the room cold or entire house cold yet high running costs.
This is one area where UK v USA can differ enormously re installed housing construction.
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wrote:

HTH HAND
Ian.
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we have 2 vent less gas fire places. one upstairs, one down. had them for 8 years now. we also have 1 carbon monoxide meter within 10 feet of each fireplace. alerts have never gone off, though we could smell the gas. checked it two different times with a CO meter that gauged it at 2 which was in fact pretty good. what we have learned though is that these things...though very efficiant, are best run for no longer that 1 or 2 hours. in fact, the only time we really use them is for a type of instant heat when we walk in the door in very cold weather. the trick for the smell is the cleaning of the burner bar and logs. any dust whatsoever causes a distinct unpleasant smell. we use just windex to get the carbon gunk off the bars 2 times per season. roughly 25 hours of use causes a need for the burner to be wiped clean. downstairs also has a ceiling fan which really helps keeping the heat down. hope this helps.
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To get a Co meter to alarm means you are in immediate danger since the alarmed setting is very high to prevent false alarms. It has to be above a certain ppm for a period of time. You are in danger long before it alarms, in long term exposure the danger point is very low.
Does your meter have a peak memory function , is that what you check, because if not with regular meters like the Nighthawk digital your are in danger long before it alarms. Even long term exposure to about 1/10 the standard alarmed setting is real bad for you, 0ppm Co is what is healthy, 20-50 for short periods made my neighbor sick, it was her furnace, the heat exchanger was shot with cracks in most all sections, it was poisoning her, slowly. It didnt set off the Nighthawk since the furnace cycled shorter then Nighthawks time frame of alarming and her house was loose, but she was sick. It was good the Nighthawk recorded Peak Co, checking the memory proved she had a serious issue, she got a new furnace the next day. Google, Health Risks of long term low level Co exposure. Its very serious.
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Carbon monoxide is odorless, which is one of the reasons it's so deadly. You may have smelled unburned nat gas, or something else, but it sure wasn't the CO.

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From memory it is roughly that 22.4 litres - which is a bit under a cubic foot - of methane (natural gas) gives 36g of water which is about an ounce and a bit. So a fair bit of water. I would look at my gas bill and tell you how many kWh per cubic metre methane is, but I've lost it.
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wrote:

In the case of propane:
C3H8 + 5(O2) => 3(CO2) + 4(H2O)
If I've done my arithmetic properly... Water vapor output is 4x the propane input by volume or about 25% more by weight. A gallon of propane weighs something like five pounds so, if I've done my numbers right, it'll put out a little less than a gallon of water. A gallon is 93kBTU, so a bit under three hours on a 37kBTU (my 8kW, from before) logs. A extra gallon of water would be quite welcome in most houses in the heating season.
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In the UK the opposite is preferable.
Kitchen: - 75m3/hr extractor over a cooker/hob - 150m3/hr extractor if say a wall fan
Bathroom: - Similar water extraction required
UK houses very quickly suffer from damp & condensation. If you try to heat an older house via an LPG portable heater the airflow requirements for the burner and to avoid condensation will almost negate the heating effect (ie, you will need huge amounts of LPG to compensate making the seemingly cheap heating very much more expensive).
UK construction: - Double solid brick or similar (<1930) - Brick-Brick Brick-Block cavity wall (1950) - Brick-Wood cavity wall (1970) - Brick-Wood insulated cavity, airtight (2000)
It was based around cheap wood/coal open fires, huge kW output.
U values... - Solid 9in double brick - 2.11 - Cavity wall brick - 1.73 - Insulated Cavity Wall - 0.73 - 2008 wall - 0.35
Much of the UK housing stock has... - No floor insulation - No wall insulation (U = 2.11-1.73) - No loft insulation (U = 5-8 or something?) - Single glazing (U = 4 or so)
Air Changes per Hour: - 2008 is almost air tight - 1950 house with 1-2 open flue the exact opposite
To be honest there should not be free loft insulation. That should have 100 less subsidy, which should be directed towards those with solid walls. Those houses - Hard To Heat Housing - are going to become a real problem by 2020. Of course the plan is probably compulsory purchase orders of whole areas for Property Developers to ride on a free gravy train. Much of that is already happening with UKs terraced housing, much of which is ok, some of which is terrible. The problem is the people get peanuts on the Pound-Sterling and can't afford to go anywhere else; legalised theft.
UK relied on wood/coal burning 5-10kW open fires.
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wrote:

Even in Alabama it's so dry in the Winters that many run humidifiers. Anytime you heat air the RH drops. Heat air 50 degrees and lizard skin isn't unusual.

Water extraction or ventilation? That's significant air exchange right there.

That's not the point. Heating air reduces its RH. It's not unusual to have an interior RH under 20%.
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