Symphony propex blown-air heater

Hi folks

My wife was away in the van for a couple of days recently, and ran the heater one evening for 2-3 hours 'cos it was B cold. She says that when she ran it again the next evening, it ran for about 3 minutes then cut out. She says she checked that all the gas taps were "on" and there is certainly gas in the bottles. NO problem with the electrics either. I've tried it on both butane & propane since she got back, and can't replicate the problem (but then I've only run it for maybe ten minutes -enough to produce hot air, and to show that it's not cutting out when started from cold, which was when she was experiencing the problem. Any thoughts?

Cheers

Was it on butane when it cut out. Butane won't burn at temperatures below 4 degrees. If it was on propane, thats a different matter.

Mmmm. I know. But it's a very good point, thank you. I'll check with her. I must confess I hadn't thought of that because the propane cylinder was in pole position ready for connection when she left, and when she got back. Maybe I should explain what I mean by "pole position". We carry two cylinders (one butane, one propane) all the time, one at the front of the storage cupboard ready to connect up, and the other at the back as reserve in case the one in use runs out. I've been saving money by having only one cylinder of each - but I suppose we actually need 2 propane if we're going to do winter trips.

Many thanks
W

Why not just use propane all year round?

Somebodu once told me that propane doesn't burn as hot as butane, soyou're better off with it in summer. I believed them. Is this tosh?

wallacemurray wrote:Somebodu once told me that propane doesn't burn as hot as butane, soyou're better off with it in summer. I believed them. Is this tosh?

It's true. Butane has an energy density that is just under 10% higher than propane by weight.

In theUK you are better off with Propane all year round.

Butane does have a higher energy output but its not that simple. All LPG is held in liquid form and we need to take off the gas. In our temperatures propane turns to gas easier than butane so actually the energy difference is not that much. You shouldn't really notice any difference in use, however once the temp drops below about 8c then propane is your only choice.

I know this is a slightly old thread, but ... of those of you with Symphonies, or with similar gas lockers, and running dual propane and camping gaz, what sized propane are you are able to fit in the locker alongside your, I think, 901? Do you use a T piece?

I can fit a 6kg propane and a 3.9kg propane in the locker (or a 7.5 and a 4 in butane Calor) In place of the 3.9 I sometimes carry a 907 Camping Gaz (from small to large Camping Gaz goes 901, 904 & 907). I simply carry both regulators all the time but really don't see the point of carrying butane at all at this time of year as it won't burn.

That's great, thanks, 6kg here I come. It looks to me quite an easy thing to do, but I think I'll get a pro mobile caravan engineer to do it, with a t piece, nicely, save me grovelling on the floor for hours and never quite trusting I'd done it all safely.

The Butane is ok inside the 'home but as you know, I agree real choc teapot stuff for the blown air heating, just when I wanted it most!

Paulmold wrote:I can fit a 6kg propane and a 3.9kg propane in the locker (or a 7.5 and a 4 in butane Calor) In place of the 3.9 I sometimes carry a 907 Camping Gaz (from small to large Camping Gaz goes 901, 904 & 907). I simply carry both regulators all the time but really don't see the point of carrying butane at all at this time of year as it won't burn.

Hi folks, this forum is great for little snippets of information like this.
I run Butane but will change to Propane when the bottle runs out I have a backup Camping Gaz for emergencies.
When I picked up the van in November I was asked which regulator I required but not given these reasons why so I plumped for Butane, surely the dealer should have given me this information being new at this. It doesn't matter but more unnecessary expense that is not called for.
Another nail in the dealers coffin.

Best regards Mike

Hi Mike,

If you have the Leisure Products 2000 hob/cooker fitted and are changing over to Propane, it would be worth a look at page 5 of the PDF document, supplied by Mike (VW T4) in the 'Members factsheet section'

This shows ....... 'up-ending' the brass air sleeve to change from Butane to Propane.

I will be checking mine out to see if it has been done, as we always use Propane.

Regards,

Brian

Actually this is a complex matter.

If you pay for your gas by volume then butane is better value for money having a calorific value of 102.032 btu/gallon, whereas propane has a value of 91.690 btu/gallon. If you purchase by weight then the situation reverses; butane 21.221 btu/pound and propane 21.591 btu/pound. What beautiful units btw!

But to say you lose some of the advantages of butane because it is harder to evaporate is not true. The only chemical reaction that is important, in energy terms, is that when the gas is burnt in the burner and this is shown above. Butane has a slightly higher Latent Heat of Vaporisation then propane (by mass) but this would mean than if you draw off 100ml of both then the butane tank would get colder. It does not make it less efficient in any way.

The main thing is the boiling point of the two gases; butane 0 degC and propane -42 degC, so in fact the use of butane would start to get problematical at 0 degC (or a little above even).

You often find camping books will say that butane has a much higher calorific value than propane but as we saw, this is only the case when buying by mass and then only about 11% better. My van has an under-slung lpg tank so I fill up at garages which supply a mixture I think, so these facts don't much help me.

For those of you using replaceable tanks then the facts above would tend to suggest that you are better off only ever buying propane. But to make a final judgement I think we would need to know the flame temperatures of both gases in the appliances fitted to our van. But saying this the Ignition temperatures and Max. Flame temperatures of both gases are both very similar and I doubt that propane would be sold at all if its flame temperatures were very low in practical appliances.

As a young trainee at the now defunct chemical company of May and Baker, back in the 1960s, we were very intrigued by some of the very volatile solvents that had such a low flame temperature that you could pass your hand through the flame and only just feel it. And these were liquids at room temperature!

Surely the bottom line is that with propane you can fit and forget, whereas with butane you must always have the outside temperature in mind.

Mick.

micknhilary wrote:Surely the bottom line is that with propane you can fit and forget, whereas with butane you must always have the outside temperature in mind.

Does depend on what seasons you camp and where your cylinder is installed. I only ever camp from spring through to autumn and the cylinder is inside the van, so for me butane is "fit and forget".

-mojo- wrote:

micknhilary wrote:Surely the bottom line is that with propane you can fit and forget, whereas with butane you must always have the outside temperature in mind.

Does depend on what seasons you camp and where your cylinder is installed. I only ever camp from spring through to autumn and the cylinder is inside the van, so for me butane is "fit and forget".

But one day you'll fancy a trip out in winter and then what? We used to be fair weather campers/caravanners but now we've spent two New Years in the Symphony plus some very cold spells in November and March, we have to use propane. Just might be worth thinking about next time you take your cylinder for a swop.

Paulmold wrote:
But one day you'll fancy a trip out in winter and then what? We used to be fair weather campers/caravanners but now we've spent two New Years in the Symphony plus some very cold spells in November and March, we have to use propane. Just might be worth thinking about next time you take your cylinder for a swop.

Not an issue for me - the van's got Eberspacher diesel heating as well as gas (the original owners seem to have gone overboard on the AS options list!).

I was outside working in it a few nights ago at -2 degrees ambient and the gas heater worked fine on its own, though I confess I did have the gas compartment door open inside the van, which I guess is Very Very Naughty, and not something you would want to have to do routinely.

Hi All,

Another point I had to think about (given our Clubman's appalling weight allowance) was to use Calorlite bottles ..... Propane only (as far as I'm aware !!)

Brian

I had always assumed that butane was much more efficient than propane and so you would use butane where possible and propane in the cold. But my figures show that you could use propane all year around and it wouldn't cost you any more.

Having the fixed tank in my van means I don't have a choice but it might be worth finding out the mixture values for the various suppliers - if in fact, they do vary much. But as I said in my earlier post we pay for LPG by volume, where butane has an 11% increase in calorific value over propane. Our tank is a 20l tank which is about 11kg or 24lb which is a fair old whack of gas. It works out at 70p per litre which makes a season's gas demand a not very expensive cost at all. You also get the benefit of knowing how much gas you have left. A fixed tank has many benefits then, but it does take away a bit of flexibility.

Looking around on the net a 'typical' mixture for LPG would be 60:40 propane:butane and would still have a vapour pressure at 0 degC: of 250kPa compared to propane 370kPa and butane < 5kPa. Even at -20 a 60:40 mixture has a vapour pressure of 80kPa roughly half that of propane. The interesting thing here is that butane only has a vapour pressure of 110 kPa at 20 degC, not that much more than a 60:40 LPG mix at -20 degC. That is surprising!

So do the butane tanks you mention just contain pure butane or do they tend to be a mixture? Actually looking at the Calor Gas site I think it has just butane and they recommend it for outdoor use during the milder months only. Yup guys use propane or propane/butane mixture.

footnote: Wiki answers gives the following for LPG:

Methane - 0%
Ethane - 0.20%
Propane - 57.30%
Butane - 41.10%
Pentane - 1.40%

Why state methane @ 0%? Could be that there is a trace from the manufacturing process (less than the Ethane amount) and it varies a bit. Could be for completeness, these are the first five members of the chemical group known as the Alkanes. Methane 1 Carbon, Ethane 2 C, Propane 3 C, Butane 4 C and no prizes for guessing that Pentane has 5 C.

Would some one please explain this,? we have only ever used Butane, we have been in Scotland many times when it was -4 and no problem at all with the gas, we were in a caravan, gas locker had an outside door on the locker.

Margaret

My guess would be that the rate at which heat leaked into the locker from the interior of the van was greater than the rate of leakage of heat out of the outward-facing door.

In our Comma-based A-S we had a gas cylinder locker that hung down through the floor of the van, and that was exposed to the outside air on all sides but the "hatch" in the floor. We stayed away in that in temperatures that were sub-zero (just) and we never had problems with that either.

You may have a preference for different gasses, but it is quite likely that the problem which started this thread was the use of butane at low temperature, which is not a problem with propane. 

In terms of heat output you could time the boiling rate of a kettle with both gasses for a definitive measure, but I very much doubt there would be more than a few seconds either way.

I have a Gaslow setup so use the mixture available on a forecourt. I believe the ratio of the mix is altered with the seasons, in the same way that diesel formulation changes for winter to prevent waxing problems.