Propane/Butane - cold weather

[VicMallows]

Or simply because on a volume for volume basis butane requires about 30% more air for combustion than propane.

Now that's very interesting and something I hadn't appreciated. I need to get my head around it properly but I think it may be the clue to understanding how the (compromise?) of using either propane or butane at 30mb works ...... or in some cases doesn't!

I would be very interested if anyone actually knows WHAT changes have been made on modern appliances to allow either gas to be used at 30mb without adjustment/modification. ??

 

[VicS]

Now that's very interesting and something I hadn't appreciated. I need to get my head around it properly but I think it may be the clue to understanding how the (compromise?) of using either propane or butane at 30mb works ...... or in some cases doesn't!

Sorry I am not into fluid dynamics. But another factor you probably would have to take into account is the vapour density or molecular weight

I think rate of flow may be inversely proportional to the square root of the molecular weight. ?????

 

[sunquest]

Do you have one of the new 30mb 'universal' regulators? ... or did you (as I suspect) change to a 37mb propane regulator?. The symptoms you describe sound like a classic case of under aeration due to too low pressure for the size of jet fitted. (In other words the cooker was designed for 37mb).

Hi Vic. Just used the standard red propane regulator. Geoff

 

[saltylegs]

Now that's very interesting and something I hadn't appreciated. I need to get my head around it properly but I think it may be the clue to understanding how the (compromise?) of using either propane or butane at 30mb works ...... or in some cases doesn't!

I would be very interested if anyone actually knows WHAT changes have been made on modern appliances to allow either gas to be used at 30mb without adjustment/modification. ??

Very little really, as the appliances are required to perform safely within a range of pressures IIRC a propane appliance (normal operating pressure 37mbar) needed to be "stable" from 26 to 45mbar. but the appliance was always badged as for 37mbar propane and 28mbar butane, the calorific value for butane is about 25% higher than propane so less gas (due to the lower pressure) equals similar flame dynamics.
Appliances badged 30mbar are tested to a slightly different standard and range of pressures (the figures escape me at present) because the 30mbar regulators have a wider operating range than the 37 or 28mbar regulators, this is why you should only use a 30mbar regulator on an appliance that is badged for 30mbar.

One thing to note is that some LPG cookers are being produced that are not suitable for use on butane, and I have found that when some of these are used on butane the Carbon Monoxide levels were a lot higher than when used with propane (although not tested under laboratory conditions more for my own curiosity).

 

[VicMallows]

One thing to note is that some LPG cookers are being produced that are not suitable for use on butane, and I have found that when some of these are used on butane the Carbon Monoxide levels were a lot higher than when used with propane (although not tested under laboratory conditions more for my own curiosity).

That is very interesting and agrees with my findings. I have a gas fridge which is badged as '30mb UNIVERSAL LPG' . The importer, probably applying the British interpretation of 'universal', sells it as suitable for either butane or propane.

It does NOT work happily on Butane at 30mb. Flame envelope ragged and CO too high. If gas flow is restricted (effectively lowering the jet pressure) flame picture improves and CO becomes minimal.

My research suggests that the term 'Universal LPG' is only commonly used in Aus/NZ and in fact refers to 'Auto-Gas' which is predominantly propane.

(in case anyone gets worried, my gas fridge has an external flu anyway)

 

[saltylegs]

That is very interesting and agrees with my findings. I have a gas fridge which is badged as '30mb UNIVERSAL LPG' . The importer, probably applying the British interpretation of 'universal', sells it as suitable for either butane or propane.

It does NOT work happily on Butane at 30mb. Flame envelope ragged and CO too high. If gas flow is restricted (effectively lowering the jet pressure) flame picture improves and CO becomes minimal.

My research suggests that the term 'Universal LPG' is only commonly used in Aus/NZ and in fact refers to 'Auto-Gas' which is predominantly propane.

(in case anyone gets worried, my gas fridge has an external flu anyway)

'30mb UNIVERSAL LPG' as you say is likely to apply to Aus/Nz, any modern CE approved appliance badged LPG 30 mbar will work ok on both Propane and Butane through a 30mbar regulator but you will find that the actual pressure supplied by the regulator will differ slightly depending whether you are using Propane or Butane (but will still be within the performance curve for that regulator and a 30mbar badged appliance)

 

[laika]

Now discovered the GasBOAT range and it is wonderful...

I fitted a gasboat regulator and can confirm that both propane and butane work through it with my nelson spinflo cooker. I have the manual changeover thingy so I can hook up 2 cylinders and just change a switch to go from one bottle to the other, so no mucking about with changing regulators over when I run out of gas in lumpy weather (that's the theory, but in the couple of years that I've had it I've only run out of gas while moored). Not 100% convinced by the manufacturing quality of all the adapters. My first regulator stopped working after a few months (Mr Hayward the distributor sent me a new one immediately with no argument) and whilst the propane/butane adapters seem nice and solid (and work well), the one which should have worked for a BP gas cylinder I couldn't get to work without leaking (I reverted to the original regulator then did some horse trading at the dump for a calor cylinder I could trade up at the chandler's).

With an installation similar to mine, all Ru88ell would have to do would be to swap an empty butane for a full propane when he runs one down then he could just switch to the propane cylinder on cold days. Having said that I've got 2 propanes because I don't like like having 2 part- full bottles on board.