Shore Power use

[Gybe Ho]

3 minutes ago, blackrose said:

 

Gas-free boats... I think it's a mistake but like everything else it's all down to personal choice.

 

The stove top of the Morso Squirrel is good at bringing saucepans to a slow simmer. Which reminds me I should investigate whether this stove top cooking lifestyle risks thermal shock and a crack in the stove casting. 

[Alan de Enfield]

2 hours ago, Gybe Ho said:

Meths apparently generates a lot more moisture than butane.

 

 

1 litre of LPG produces 1 litre of water vapour.

 

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

[Gybe Ho]

15 minutes ago, Alan de Enfield said:

 

1 litre of LPG produces 1 litre of water vapour.

 

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

 

Sounds scary until the calculation is done for 4 x cup of tea per day = 0.2(kWh) / 5 (kW per LPG litre) = 1/25th of a liter of water or a tiny faction of what a human breathes out in water vapour daily.

 

Providing there is decent air exchange in the cabin prior to 7pm the the humidity will have dropped back by 7pm following tea brewing, then as the cabin reaches peak evening temperature humidity drops even further. Condensation is really a factor of how much moisture is squeezed out of the air overnight as cabin temperature drops.

 

My cabin was 11(c) at 7am this morning. The diesel range raised the temp to 16 degrees by 11am before I turned it off. Went for a 6 mile walk at 2pm. The Morso was fired up at 4pm by which time cabin humidity had risen to 68% as the temp had dropped back. As I type this the cabin temp is too hot at 22(c) and humidity is back down to 43%. The opposing side hatches are cracked open 2" to keep the temp down and this has a drying effect in the boat's cabin lining.

 

There will be a frost tonight which means about 8(c) cabin temp in the morning because the Morso will have burnt out by 1am.

[NB Thistle]

4 hours ago, Up-Side-Down said:

 

I think there must be something a wee bit muddled here. The best 12V fridge I'm aware of draws 0.4kW in a 24hr period; likewise a decent router, meaning a baseline consumption of 0.8kW over 24 hours. Assuming there is no investor and everything is therefore 12V DC, it is very hard to total less than 1kW when the remaining odds and sods are accounted for.

As I write this I have one light on, the fridge and router are on as usual - I put the shopping in the fridge an hour ago - and my lad's phone is on charge. The system is showing 28W draw. I don't heat the boat when I'm the only person aboard so the fridge doesn't have to work very hard in the winter. 

2 hours ago, Alan de Enfield said:

 

1 litre of LPG produces 1 litre of water vapour.

 

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

Water expands 1,800 times when it turns to vapour so that equates to 0.55ml of water per litre of LPG. I don't know what use that information might be to me or anyone!

[Alan de Enfield]

10 minutes ago, NB Thistle said:

Water expands 1,800 times when it turns to vapour so that equates to 0.55ml of water per litre of LPG. I don't know what use that information might be to me or anyone!

 

550ml = 1 imp pint - It is a lot of water to run down the windows / walls.

[IanD]

16 minutes ago, NB Thistle said:

As I write this I have one light on, the fridge and router are on as usual - I put the shopping in the fridge an hour ago - and my lad's phone is on charge. The system is showing 28W draw. I don't heat the boat when I'm the only person aboard so the fridge doesn't have to work very hard in the winter. 

Water expands 1,800 times when it turns to vapour so that equates to 0.55ml of water per litre of LPG. I don't know what use that information might be to me or anyone!

A fridge will take a lot more than 28W when the compressor is running, the average over 24h depends what fraction of the time it runs.

 

A typical modern mains fridge consumes about 0.4kWh/day which is 17W average -- for example, this could be that it draws 100W with the compressor running, but only runs for 10mins every hour.

[MtB]

5 hours ago, Up-Side-Down said:

The best 12V fridge I'm aware of draws 0.4kW in a 24hr period

 

 

Its really disappointing when otherwise competent posters make basic technical errors like this.

 

I suspect you do actually know the difference between energy and power, and this is an accidental typo, but such carelessness confuses the hell out of people initially trying to understand the subject! 

 

 

[Gybe Ho]

44 minutes ago, NB Thistle said:

As I write this I have one light on, the fridge and router are on as usual - I put the shopping in the fridge an hour ago - and my lad's phone is on charge. The system is showing 28W draw.

 

 

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).

[NB Thistle]

33 minutes ago, IanD said:

A fridge will take a lot more than 28W when the compressor is running, the average over 24h depends what fraction of the time it runs.

 

A typical modern mains fridge consumes about 0.4kWh/day which is 17W average -- for example, this could be that it draws 100W with the compressor running, but only runs for 10mins every hour.

The compressor hasn't come on in the last 90 minutes that I've noticed.

[Alan de Enfield]

19 minutes ago, NB Thistle said:

The compressor hasn't come on in the last 90 minutes that I've noticed.

 

If you don't open the door, particularly overnight, it can be several hours between the compressor running.

[Gybe Ho]

2 minutes ago, NB Thistle said:

The compressor hasn't come on in the last 90 minutes that I've noticed.

 

I can see the fridge compressor run cycles in my Victron dashboard. Overnight as the cabin cools the compressor rests for 80 minutes by 4am. The 0.4kWh per day figure will be an average across the year, winter should be less for those who do not run their multifuel stoves non stop for 5 months.

[Tacet]

12 hours ago, Alan de Enfield said:

 

1 litre of LPG produces 1 litre of water vapour.

 

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

Buring one litre of LPG will typically produce around 2000 litres of water vapour.

[Gybe Ho]

6 minutes ago, Tacet said:

Burning one litre of LPG will typically produce around 2000 litres of water vapour.

 

Only 2000 litres. The living area of my narrowboat has about 25,000 litres of air space. 😄

 

Water vapour is only significant when it condenses out somewhere inside a boat. After my first two winter months on a narrowboat I now appreciate there is good and bad condensation. Good condensation settles on window glazing overnight and provides a useful reminder to ventilate the boat better, bad condensation comes from moist air wriggling into cupboards with poor air exchange, condensation here causes damp clothing.

[Alan de Enfield]

22 minutes ago, Tacet said:

Buring one litre of LPG will typically produce around 2000 litres of water vapour.

 

That I find even more unbelievable ...................

 

From Goil energy "Basic facts about LPG"

 

1. LPG is heavier than air. It is therefore difficult to disperse and should never be used or stored below ground level as this could result in suffocation when released in a confined space.
2. Liquid LPG is about half the weight of water and therefore floats on top of water
3. LPG is stored in cylinders under pressures approximately 7 bars (100 psi) as a liquid. It changes to gas when released into the atmosphere at room/ambient temperature.
4. One volume of liquid LPG will produce approximately 250 volumes of gas when vapourised.
5. When LPG burns it combines with air to produce carbon dioxide and water vapour. However if there is inadequate air and/or ventilation, or poor mixing of the air and gas, toxic carbon monoxide gas can be produced. As a result it is therefore necessary to open the kitchen windows when cooking to allow for complete combustion
6. For every litre of liquid LPG burnt, approximately one litre of water vapour is produced.
7. Liquid LPG freezes on contact with skin due to the rapid loss of heat caused by liquid vaporization. This results in cold burns.
8. It acts as a solvent on certain petroleum and natural rubber compounds. So hoses have to be of special resistant materials in order to prevent reaction with the LPG.
9. ‘Empty’ cylinders are still dangerous because they are NOT empty. There is still a residual amount of gas inside an ‘empty’ cylinder which can ignite and produce an explosion.

[Russ T]

14 hours ago, Gybe Ho said:

 

The stove top of the Morso Squirrel is good at bringing saucepans to a slow simmer. Which reminds me I should investigate whether this stove top cooking lifestyle risks thermal shock and a crack in the stove casting. 

The top of our squirrel is always fully loaded when it is lit. It is either heating breakfast, lunch, dinner or water for drinks. In between, it is heating water for either hot water bottles or water for washing up. We have two kettles, and two big flasks. When the water is hot enough it goes in the flasks. This way, we burn very little gas for cooking and washing up.

 

As the stove stays in all winter, it suffers less thermal shock than lighting it from cold every day. However, the top of the squirrel is on the thin size. I was worried at one stage if a heavy flue pipe rigidly fixed at the top not providing enough room for expansion could damage it. In practice, we have had a cracked collar once when heating the stove up too quickly. I think heating it up slowly from cold is very important.

 

The Baffle plate or back boiler should also protect the top plate.We have run our squirrel with neither (or fire bricks ) for the last two months, albeit on a lowish setting, without damage whilst awaiting a new boiler. 

[Lady M]

Agree that heating the Squirrel up slowly is important.

[nicknorman]

22 minutes ago, Alan de Enfield said:

 

That I find even more unbelievable ...................

 

From Goil energy "Basic facts about LPG"

 

1. LPG is heavier than air. It is therefore difficult to disperse and should never be used or stored below ground level as this could result in suffocation when released in a confined space.
2. Liquid LPG is about half the weight of water and therefore floats on top of water
3. LPG is stored in cylinders under pressures approximately 7 bars (100 psi) as a liquid. It changes to gas when released into the atmosphere at room/ambient temperature.
4. One volume of liquid LPG will produce approximately 250 volumes of gas when vapourised.
5. When LPG burns it combines with air to produce carbon dioxide and water vapour. However if there is inadequate air and/or ventilation, or poor mixing of the air and gas, toxic carbon monoxide gas can be produced. As a result it is therefore necessary to open the kitchen windows when cooking to allow for complete combustion
6. For every litre of liquid LPG burnt, approximately one litre of water vapour is produced.
7. Liquid LPG freezes on contact with skin due to the rapid loss of heat caused by liquid vaporization. This results in cold burns.
8. It acts as a solvent on certain petroleum and natural rubber compounds. So hoses have to be of special resistant materials in order to prevent reaction with the LPG.
9. ‘Empty’ cylinders are still dangerous because they are NOT empty. There is still a residual amount of gas inside an ‘empty’ cylinder which can ignite and produce an explosion.

That can’t be right. Never believe everything you read on the internet! For every litre of (liquid) LPG burnt, aprox one litre of LIQUID water is produced. Which of course as a vapour has a much, much greater volume.

[Jen-in-Wellies]

45 minutes ago, Alan de Enfield said:

For every litre of liquid LPG burnt, approximately one litre of water vapour is produced.

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.

 

[Gybe Ho]

18 minutes ago, Russ T said:

The top of our squirrel is always fully loaded when it is lit. It is either heating breakfast, lunch, dinner or water for drinks. In between, it is heating water for either hot water bottles or water for washing up.

 

 

Good to read this is common practice. Saucepans warm up very slowly hence so I am not overly concerned that a cold saucepan can thermally shock the stove top plate with a localized cold circle.

 

My Morso heats up slowly from cold because because of a draft problem, someone had previously fitted the circular chimney exit baffle under the top plate rotated 180 degrees out of position with the throat facing the rear. Apparently it should either face forward or be removed completely. At the moment the ash tray door needs to be cracked open to maintain a draft even when the stove is up to full temp.

 

Someone here recently warned that chimney flu thermal expansion can crack a stove's topplate if the top of the flu is fused to the cabintop collar due to corrosion. I will have to investigate that in the Spring while I also remove the errant internal baffle.

 

Its all a big learning curve, currently waiting for my coalcage to arrive in the post. I miss judged the temp fall last night, the main cabin was 6.5(c) this morning. Now 13(c) which means it will soon be time to climb out of my insulated offshore yachting salopettes.

[Gybe Ho]

32 minutes 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.

 

 

Small camping gas cannisters are 50% butane, so could you rerun the calc for C4H10?

[Russ T]

32 minutes ago, Gybe Ho said:

Good to read this is common practice. Saucepans warm up very slowly hence so I am not overly concerned that a cold saucepan can thermally shock the stove top plate with a localized cold circle.

Never had a problem with our cast iron pans or steel kettles. I suppose if you are really concerned, get a trivet, and leave it on the top all the time. It will not be as good as direct contact.

[Jen-in-Wellies]

19 minutes ago, Gybe Ho said:

 

Small camping gas cannisters are 50% butane, so could you rerun the calc for C4H10?

Whst is the weight of butane/propane mix in a cannister? 50% mix by molecules will be 4.5 water molecules per one of fuel on average, so slightly worse per than the straight propane you get in UK spec Calor and Flogas bottles. 

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

[Russ T]

34 minutes ago, Gybe Ho said:

 

Someone here recently warned that chimney flu thermal expansion can crack a stove's topplate if the top of the flu is fused to the cabintop collar due to corrosion. I will have to investigate that in the Spring while I also remove the errant internal baffle.

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. Having said that, we switched to a lighter stainless flue a few years back, which possibly also helps.

37 minutes ago, Gybe Ho said:

 

Its all a big learning curve, currently waiting for my coalcage to arrive in the post. I miss judged the temp fall last night, the main cabin was 6.5(c) this morning. Now 13(c) which means it will soon be time to climb out of my insulated offshore yachting salopettes.

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.

[Jen-in-Wellies]

1 minute ago, Russ T said:

Having said that, we switched to a lighter stainless flue a few years back, which possibly also helps.

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. 

[IanD]

10 hours ago, Alan de Enfield said:

 

If you don't open the door, particularly overnight, it can be several hours between the compressor running.

And then if you open the door more in the day it runs more often. That's how averages (and the data sheet energy use per year figures) work... 😉