Shore Power use

[Russ T]

2 minutes ago, Jen-in-Wellies said:

Thst's useful to know. Was hoping to get another season out of the current Midland Swindlers mild steel tube flu, but it is starting to rot out at the top. I have a thin wall 304 stainless pipe on order that, with delivery, will be cheaper than another Midland Chandlers steel one. The thermal expansion coefficient of 304 stainless steel is higher than mild steel, but the thinner wall of the pipe should keep the stress on the stove top manageable with flexible silicone sealant at the roof collar. 

I probably said this before (there's a thread somewhere). I bought a cheap, 40 quid thin bit of 304 stainless in the winter of 2023, expecting it to last one winter before I bought something better.It is only 1.5 mm thickness and still looking as good as new.

[IanD]

11 hours ago, Gybe Ho said:

 

I agree that a router would not account for anything like 0.4kWh per day. 0.1kWh tops is my guess ( the engine room is too cold to go and investigate the router input power requirement).

Or you could use measured figures instead of guessing -- typically around 8W, which is 0.2kWh/day... 😉 

[Tacet]

14 minutes ago, Jen-in-Wellies said:

 

The lesson is that you need a lot of ventilation when cooking on gas to deal with the huge amounts of water vapour produced. 

Mmm.  I suspect the water vapour produced from boiling and cooking will be greater than the vapour produced by burning the LPG.  But it all needs removal through ventilation, of course

[Gybe Ho]

10 minutes ago, Russ T said:

 

I've never used one. I can see them being beneficial at the extremities of the season, but not so much in the middle. Just learn how to drive the stove with the vents, taking into account the wind strength.

 

 

I had a 30 minute tow path chat with a liveaboard veteran the other day. Even though I was standing next to the chimney flue it took me 30 minutes to notice his stove was lit. I commented on the efficiency of the burn from his stove, he just smiled and said I have been doing it for 30 years.

 

I see a coal cage as a fuel saving device as I hope I will be able to maintain the fire with a smaller number of coals. At present fewer than 8 briquette tends to lead to a flame-out. The underlying problem is the poor draft due to the misfitted upper baffle, so perhaps the coalcage will be a temporary measure. I am also stingy, based on my sums for kgs per day I am maintaining the stove at a 2kW heat output.

[IanD]

1 minute ago, Tacet said:

Mmm.  I suspect the water vapour produced from boiling and cooking will be greater than the vapour produced by burning the LPG.  But it all needs removal through ventilation, of course

I certainly used to notice when getting up to make the tea first thing on a cold day that all the windows in the galley went from clear to covered with condensation before the kettle even boiled...

[Tacet]

1 hour ago, Jen-in-Wellies said:

Digging back over forty years to chemistry lessons. That's one litre in liquid phase. In gas phase, the volume increases dramatically. 

Propane is C3H8. So burning it in a good supply of oxygen gives four water molecules and three CO2 molecules for each propane molecule

C3H8 + 5O2 -> 3CO2 + 4H2O

 

One mole of Propane weighs 44g and is 2kg/litre density in liquid phase, or 45mol/litre.

Burning 45mol, or one litre of propane will produce 180mol of water. 1 mol of water will weigh 44g, so the same as propane and has a density of 1Kg per litre as liquid. 180mol of water from burning one litre of liquid propane translates to 4 litres of liquid water. Turn that in to vapour and it becomes 4x24* = 96litres. 

So one litre of liquid propane becomes nearly 100 litres of water vapour, so two orders of magnitude bigger. 

 

*At room temp and pressure, one mole of an ideal gas, which will include water vapour, takes up roughly 24litres.

 

Very good. I'm not sure my chemistry ever achieved that level of sophistication.  But googling suggests less water from LPG (maybe 2 litres per kg) and a greater expansion between liquid & vapour (maybe 1500x).

 

Might the latter depend on situation levels?

3 minutes ago, IanD said:

I certainly used to notice when getting up to make the tea first thing on a cold day that all the windows in the galley went from clear to covered with condensation before the kettle even boiled...

I seem to recall that evaporation occurs at all temperatures?

[Jen-in-Wellies]

4 minutes ago, Tacet said:

Mmm.  I suspect the water vapour produced from boiling and cooking will be greater than the vapour produced by burning the LPG.  But it all needs removal through ventilation, of course

Probably so. A 13kg bottle of Propane has roughly 6.5l by volume and that lasts me four months, used for cooking only, so 6.5/120, or 0.054l of propane a day, which will produce roughly 5l of water vapour a day. The amount of water vapour from simmering covered pans and boiling kettles probably exceeds the water from the propane burning. 

[IanD]

3 minutes ago, Tacet said:

Very good. I'm not sure my chemistry ever achieved that level of sophistication.  But googling suggests less water from LPG (maybe 2 litres per kg) and a greater expansion between liquid & vapour (maybe 1500x).

 

Might the latter depend on situation levels?

I seem to recall that evaporation occurs at all temperatures?

Yes but this was nothing to do with evaporation (which is negligible from a closed-in kettle anyway), it was just from burning the gas -- the windows were clouded over before it even got hot.

[Jen-in-Wellies]

7 minutes ago, Tacet said:

Very good. I'm not sure my chemistry ever achieved that level of sophistication.  But googling suggests less water from LPG (maybe 2 litres per kg) and a greater expansion between liquid & vapour (maybe 1500x).

Might be to do with the composition of LPG, which varies by country. UK LPG is entirely Propane. Warmer countries mix in more Butane and sometimes change the mix between winter and summer. 

 

Evaporation does indeed occur at all temperatures to some extent. The volume of gas will depend on pressure and temperature (Boyle and Charles laws). I picked 24l/mol as this works for 1atmosphere pressure and room temp, 21C. 

[Russ T]

2 minutes ago, Gybe Ho said:

 

I had a 30 minute tow path chat with a liveaboard veteran the other day. Even though I was standing next to the chimney flue it took me 30 minutes to notice his stove was lit. I commented on the efficiency of the burn from his stove, he just smiled and said I have been doing it for 30 years.

 

I see a coal cage as a fuel saving device as I hope I will be able to maintain the fire with a smaller number of coals. At present fewer than 8 briquette tends to lead to a flame-out. The underlying problem is the poor draft due to the misfitted upper baffle, so perhaps the coalcage will be a temporary measure. I am also stingy, based on my sums for kgs per day I am maintaining the stove at a 2kW heat output.

Interesting strategy. Mine is somewhat opposite in that I load the fire once a day,in the evening and cram in as much fuel as possible.I empty the full tray first thing in the morning before opening the fire up, and before the ash gets too hot. I have a flat faced (rectangular) coal bucket to facilitate the loading process. The bucket volume is exactly that of one load. Any flue restriction will make keeping the fire in difficult.

 

A few years back I replaced the morso grate with a hardox flat plate, that has slightly increased the gap between the ash in the tray and the bottom of the grate. The ash in the tray if left to pile up can restrict air flow. Flattening it off with a poker helps.

 

My poker is a long paint roller handle bent straightish with a bit of an angle on it.I don't mean to boast, but its very long and very comfortable to hold.

 

Not quite done 30 years yet. I would go get some pointers off the towpath vet

[Tacet]

2 minutes ago, IanD said:

Yes but this was nothing to do with evaporation (which is negligible from a closed-in kettle anyway), it was just from burning the gas -- the windows were clouded over before it even got hot.

You would have to experiment burning the gas without the kettle on the stove. 

 

Leaving a washing bowl full of water, at room temperature, results in condensation on the adjacent windows overnight.

[IanD]

23 minutes ago, Tacet said:

You would have to experiment burning the gas without the kettle on the stove. 

 

Leaving a washing bowl full of water, at room temperature, results in condensation on the adjacent windows overnight.

Did the first one (e.g heating up a frying pan, no evaporation at all), the windows steam up just the same as with a kettle.

 

An open washing up bowl will lose far more water per hour to evaporation than a closed kettle (before boiling), and still takes all night to cloud the windows -- a gas burner with or without a kettle does this in a couple of minutes.

 

Physics, innit... 😉 

Edited December 17, 2025 by IanD

[Gybe Ho]

48 minutes ago, IanD said:

Or you could use measured figures instead of guessing -- typically around 8W, which is 0.2kWh/day... 😉 

 

Ok challenge accepted. According to my Victron Connect web page the temperature sensor in my electrics cabinet in the engine room is currently 3(c) and the electrics cabinet is a good proxy for engine room temperature at this time of year.

 

I am going down to the engine room, I might be gone sometime...

 

Ok back I managed to evade the ravenous polar bears. The rated power input of the router is 7.6W, however the measured consumption is 4W. I hope to get that lower once I run an ethernet cable from the engine room to the dinette and then switch off wifi.

 

Edited December 17, 2025 by Gybe Ho

[alias]

27 minutes ago, Tacet said:

Very good. I'm not sure my chemistry ever achieved that level of sophistication.  But googling suggests less water from LPG (maybe 2 litres per kg) and a greater expansion between liquid & vapour (maybe 1500x).

 

My calculation came out around 1 kg of water per litre of liquid propane (though I had different figures from Jen for propane density and molecular mass of H2O).  Still needs a decent amount of ventilation.

[Jen-in-Wellies]

19 minutes ago, alias said:

 

My calculation came out around 1 kg of water per litre of liquid propane (though I had different figures from Jen for propane density and molecular mass of H2O).  Still needs a decent amount of ventilation.

Just realised my molecular mass for water was wrong. Had a brainstorm and used CO2, rather than water, which will be 18. Divide my figures appropriately.

[IanD]

41 minutes ago, Gybe Ho said:

 

Ok challenge accepted. According to my Victron Connect web page the temperature sensor in my electrics cabinet in the engine room is currently 3(c) and the electrics cabinet is a good proxy for engine room temperature at this time of year.

 

I am going down to the engine room, I might be gone sometime...

 

Ok back I managed to evade the ravenous polar bears. The rated power input of the router is 7.6W, however the measured consumption is 4W. I hope to get that lower once I run an ethernet cable from the engine room to the dinette and then switch off wifi.

 

Depends on the router, more advanced ones (e.g. 5G 4x4 MIMO) will probably take more -- mine (GL.iNet Spitz AX) measures 8W... 😉 

Edited December 17, 2025 by IanD

[Iain_S]

15 hours ago, Alan de Enfield said:

 

1 litre of LPG produces 1 litre of water vapour.

 

I didn't believe it when I was first told - do a Google !

Bit more, surely;

 

C3H8 + 5O2 => 3CO2 + 4H2O

[IanD]

6 minutes ago, Iain_S said:

Bit more, surely;

 

C3H8 + 5O2 => 3CO2 + 4H2O

4x as much then... (Avogadro's Law for gases)

 

But since gaseous PG has 270x the volume per kg compared to LPG, 1l of LPG does indeed generate more than 1000l of water vapour, as said earlier... 😉 

Edited December 17, 2025 by IanD

[Tony Brooks]

1 hour ago, Russ T said:

I suspect it could. Recently, I have tried putting less sealer up top than I normally would, and even a small gap at the base of the flue to collar joint.

 

When I installed our stove, I packed the top flue to collar joint with glass fibre rope (actual stove door rope) and sealed it with heat-resistant silicon. The position of the top of the flue was noticeably different between hot and cold as it expanded and contracted. I am sure that if the flue had rusted/stuck in the collar, it would exert a lot of force on the stove top and could crack a cast iron stove top plate.

[Russ T]

3 minutes ago, Tony Brooks said:

 

When I installed our stove, I packed the top flue to collar joint with glass fibre rope (actual stove door rope) and sealed it with heat-resistant silicon. The position of the top of the flue was noticeably different between hot and cold as it expanded and contracted. I am sure that if the flue had rusted/stuck in the collar, it would exert a lot of force on the stove top and could crack a cast iron stove top plate.

That's is what I have done too, but not packed it solid like I have in the past. It also make replacing the pipe easier when the time comes.

[Tacet]

1 hour ago, IanD said:

Did the first one (e.g heating up a frying pan, no evaporation at all), the windows steam up just the same as with a kettle.

 

An open washing up bowl will lose far more water per hour to evaporation than a closed kettle (before boiling), and still takes all night to cloud the windows -- a gas burner with or without a kettle does this in a couple of minutes.

 

Physics, innit... 😉 

The higher temperature of the combustion gases can carry more water vapour - until it condenses on the colder window.  If the air, window and washing up bowl are all at the same temperature the resultant condensation on the glass will be close to zero from that source.

 

But water vapour may still be increasing the humidity.

[jonathanA]

 

As pointed out earlier burning propane produces 4 water molecules for each propane molecule. 1 molar mass of propane is 44g and water 18g. So 4x 18 = 72g  so  72/44 = 1.64. 

A typical 2.5kw gas ring will burn around 180g/h of propane. This will therefore produce 180 x 1.64 = 300 (about) grams(ml) of water or about 1/2  a pint an hour.... 

 

Whether that produces 1l of vapour, 1000 or 10000 is academic there will be about a 1/3 of a litre of water in the 'air' from the propane combustion per hour.  And as Jen says probably more from the cooking...

E.G. a 3 pint kettle would easily boil dry on a gas ring in an hour so would put something like 4 to 5 times the water into the same space. 

 

That's not to say that burning propane doesn't cause condensation. Clearly it does, just trying to put some realistic and understandable numbers around it so we can appreciate the real world issues rather than some of the fanciful numbers from urban myth...

 

So 1 lire of propane is about 0.5kg which would give about 0.8kg of water when burnt. (Or put another way about 2.75 hours of gas ring)

 

I'm assuming normal calor type bottles/pressures .

[IanD]

56 minutes ago, Tacet said:

The higher temperature of the combustion gases can carry more water vapour - until it condenses on the colder window.  If the air, window and washing up bowl are all at the same temperature the resultant condensation on the glass will be close to zero from that source.

 

But water vapour may still be increasing the humidity.

As soon as the combustion gases mix into the room air their temperature drops to the room temperature -- or maybe a couple of degrees warmer since warm air rises. Condensation only happens when the moist air (raised humidity from the water vapour from burning gas) hits a cold surface, for example a single-glazed window/porthole in cold weather, as I described.

 

7 minutes ago, jonathanA said:

 

As pointed out earlier burning propane produces 4 water molecules for each propane molecule. 1 molar mass of propane is 44g and water 18g. So 4x 18 = 72g  so  72/44 = 1.64. 

A typical 2.5kw gas ring will burn around 180g/h of propane. This will therefore produce 180 x 1.64 = 300 (about) grams(ml) of water or about 1/2  a pint an hour.... 

 

Whether that produces 1l of vapour, 1000 or 10000 is academic there will be about a 1/3 of a litre of water in the 'air' from the propane combustion per hour.  And as Jen says probably more from the cooking...

E.G. a 3 pint kettle would easily boil dry on a gas ring in an hour so would put something like 4 to 5 times the water into the same space. 

 

That's not to say that burning propane doesn't cause condensation. Clearly it does, just trying to put some realistic and understandable numbers around it so we can appreciate the real world issues rather than some of the fanciful numbers from urban myth...

 

So 1 lire of propane is about 0.5kg which would give about 0.8kg of water when burnt. (Or put another way about 2.75 hours of gas ring)

 

I'm assuming normal calor type bottles/pressures .

 

All true, if you boil a kettle and the water all evaporates it will put a *lot* of water vapour into the air, far more than burning the gas will.

 

But what was being discussed was the water vapour from burning gas before the kettle*** even boils, and there is no doubt that this causes condensation on cold windows within a couple of minutes -- not an "urban myth", it's science, plus it's trivial to prove this to yourself in cold weather... 😉 

 

*** does exactly the same when not heating water, also very easy to demonstrate... 🙂 

Edited December 17, 2025 by IanD

[jonathanA]

2 hours ago, Jen-in-Wellies said:

Probably so. A 13kg bottle of Propane has roughly 6.5l by volume 

I thought it was the other way round 13kg would be 26 litres... 

 

That what I seem to recall for refilling bottles at autogas pumps.... although.my memory might be a fault...

[IanD]

1 minute ago, jonathanA said:

I thought it was the other way round 13kg would be 26 litres... 

 

That what I seem to recall for refilling bottles at autogas pumps.... although.my memory might be a fault...

Liquid propane has half the density of water, so you're correct... 🙂